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PostPosted: Wed Sep 10, 2008 12:18 am 
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I recently took my standard '93 3-cyl motor in for a rebuild as part of a conversion to an XFI.
Had the block bored out and the cam sent to Delta Cam in Tacoma WA for a regrind to XFI specifications. (In the process I also acquire an XFI transmission and a model B8 'XFI' ECU from the wrecking yards to complete the XFI conversion).
Rebuilt motor, tranny and ECU go back into the car, but it idles and runs rough where my son's 1992 tired Metro idles smooth as silk.
Shift light comes on so early, I'm lugging the motor every time I shift up because the RPMs are so low in the next higher gear. Occasionally it comes on when I shift into neutral on the way up/down to the next gear.
The car goes back to the machine shop where the shop owner determines a valve isn't completely closing - possibly from grit or maybe a hydraulic lifter. Per instructions, I take it to the limit on the highway a couple times to try to blow out any grit... no difference... motor still misses and is extremely lethargic while accelerating.
At a highway on-ramp, the car does 35 to 60mph on the flat in zero-point-five miles...(!)
I consider myself fortunate not to get run over while merging with the traffic!!

I continue the break in, varying the speed as I'm supposed to. During the break-in I take the car back in to the machine shop where the compression measures 125, 135 and 150 PSI respectively.
New PCV valve, spark plug coil, O2 sensor, plugs, cap and wires... no difference.
Reamed out the EGR channels... no difference.
I take it in to my trusted import auto repair shop (of 9 years) for an independent diagnostic... pretty much the same compression readings as the machine shop. They're thinking like I am, that I've got a bad cam regrind, given the compression pattern and low vacuum line readings - like there's a vacuum leak even though they couldn't find one.

I swap my son's ENTIRE 1992 intake manifold, throttle body, EGR, and all, into my car... no difference... it misses EXACTLY like it did before. No performance improvement... nothing changes.

Brand new EGR at the repair shop's recommendation... no difference.
Machine shop owner puts a variable-delay timing light on what is now the 4th throttle body injector. It's not completely misting like it should - we see dripping and a little bit of a stream of gas underneath the injector. I swap one of the other throttle body injectors onto the car and we see the same thing again.
Shop owner wonders if the un-misted gas was sufficient enough in quantity to wash out the rings during the break-in (which is complete by this time).

I take these two throttle bodies in to another shop and have the injectors overhauled... still no difference.

The machine shop finally agrees to swap my son's cam onto my engine (by this time the kid has burnt a valve, and even though all the plugs are fouled by the time he gets home, after cleaning them as much as possible, it STILL idles smoother then my motor!!!). With the kid's cam on the head, the shop checks, and the compression has now evened out at 152 PSI on all three cylinders. The shift light also waits to come on until the motor reaches higher RPMs and doesn't flip on in between gears.

On the freeway now, if I go over 57mph, eventually (not immediately) the engine crank will case will suddenly over-pressurize, blowing oil out the valve cover through the PVC tube where it gets sucked into the bottom half of the air filter housing (there's oil everywhere inside it and all over the top of the throttle body) and then down into the motor where it is burnt and blown out the tailpipe - so thick that I will almost loose site of any cars unfortunate enough to be following me (My son followed me to verify it's blowing out the tail pipe and not from the engine compartment). When I back off to 50 mph the billowing smoke quickly diminishes and disappears.


My theory is that the rings in the cylinders that were at 125 & 135 PSI during the break-in can't handle the increased compression that comes with my son's cam, especially at the 58+mph RPMs.

The oil pump over-pressuirzation (bleed-off?) valve doesn't seem to be an issue while revving the motor RPMs up in 3rd gear while going 50+ mph down the road, so that's not the source of the smoke.

Any thoughts? Am I correct in my assessment? Could the nozzle spray have played a factor in the lopsided compression readings during the break in?

Enquiring minds want to know!


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PostPosted: Wed Sep 10, 2008 4:23 am 
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G-Whiz wrote:
On the freeway now, if I go over 57mph, eventually (not immediately) the engine crank will case will suddenly over-pressurize, blowing oil out the valve cover through the PVC tube where it gets sucked into the bottom half of the air filter housing (there's oil everywhere inside it and all over the top of the throttle body) and then down into the motor where it is burnt and blown out the tailpipe - so thick that I will almost loose site of any cars unfortunate enough to be following me (My son followed me to verify it's blowing out the tail pipe and not from the engine compartment). When I back off to 50 mph the billowing smoke quickly diminishes and disappears.





On the smoking problem,

viewtopic.php?f=11&t=24773


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PostPosted: Wed Sep 10, 2008 5:27 am 
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155 psi is "minimum allowable" according to the factory service manual. Your freshly rebuilt engine should have around 200, that's your problem. When they take it apart to measure the cylinders and determine if the new rings are bad or a bore job is necessary, make sure the oil check valve is there and the holes in the gasket line up. I don't think that's the problem though, you've got so much blowby going past the rings it's overwhelming the PCV system.

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PostPosted: Wed Sep 10, 2008 7:52 am 
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G-Whiz wrote:
The machine shop finally agrees to swap my son's cam onto my engine (by this time the kid has burnt a valve, and even though all the plugs are fouled by the time he gets home, after cleaning them as much as possible, it STILL idles smoother then my motor!!!). With the kid's cam on the head, the shop checks, and the compression has now evened out at 152 PSI on all three cylinders . The shift light also waits to come on until the motor reaches higher RPMs and doesn't flip on in between gears.

Any thoughts? Am I correct in my assessment? Could the nozzle spray have played a factor in the lopsided compression readings during the break in?

Enquiring minds want to know!


Right there - that points to the "lopsided" compression issue as being caused by the cam.

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PostPosted: Wed Sep 10, 2008 9:06 am 
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OK, so with low compression, that would explain why the engine constantly misses?

The smoke screen didn't appear until the kid's cam was swapped onto the head, so I'm not sure the smoke was from an oil channel problem. However, I'll be printing and taking the posts (with pictures) in to the machine shop when I take the motor in for tear down and re-ringing.

Delta swore there's no way their regrind could have gone bad (maybe it's automated?). The machine shop owner is going to be taking the reground cam back to them. Before he goes up there, are there any things he should look for on the cam? Are there any insights as to how a regrind could have gone bad?

I've already decided Delta doesn't get a second chance. I have econo cams and stainless steel valves on their way here from superfly for both my Metro and my son's motor (His will eventually have the head, valves, and piston tops coated so I can experiment with HHO systems without worrying about hydrogen embrittlement - which I realize is a whole different topic).


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PostPosted: Wed Sep 10, 2008 10:36 am 
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after my rebuild i have the same problem. im going to do the bottem end now.

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PostPosted: Wed Sep 10, 2008 10:29 pm 
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Ok on the low compression numbers and the smoke
DOES IT USE ANY OIL..??
(a) the new rings groove were not staggard...low compression..!! (btdt) compression should be 200-210 on rebuilt
unless you shave the head
(b) posabably the oil ring scraper was installed upside down...excessive smoke

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PostPosted: Wed Sep 10, 2008 11:11 pm 
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jaguar,vettes&sprints wrote:
Ok on the low compression numbers and the smoke
DOES IT USE ANY OIL..??
(a) the new rings groove were not staggard...low compression..!! (btdt) compression should be 200-210 on rebuilt
unless you shave the head
(b) possibly the oil ring scraper was installed upside down...excessive smoke



At 1200 miles since the initial oil change it's still 2/3rds of the way up between the two holes in the dip stick.

(a) Don't believe the head was shaved. However, the top of the block was. This is because because the G10 steel cylinder sleeves are known to "float" after yanking the head off, and this ensures the surface for the block is completely even for the head gasket when the engine is reassembled, otherwise you can end up with oil/water leaks according the the machine shop owner. Interesting point though. Could that cause the rings to break their seal at high RPMs?

(b) They are probably installed properly otherwise I would expect to have seen billowing smoke from day one, and not just in sudden high-rpm bursts. Just after the break-in period with the XFI cam still on the head I took the car up a long uphill stretch of highway at 78mph. The engine was wound up all the way and the RPMs were so high that the car never showed signs of slowing down on what must have been almost a 2 mile uphill grade. No smoke the entire time. Again, it never billowed smoke until the cam swap.


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PostPosted: Thu Sep 11, 2008 12:14 am 
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2-Stix wrote:
after my rebuild i have the same problem. im going to do the bottem end now.


Good luck and please let me/us know what you find. I'm especially curious about the ring orientation relative to each other (are the ring gaps on opposite sides of the piston, at 90 degree angles, etc...) and if you see any telltale clues with them, the pistons or the cylinder walls. :)


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PostPosted: Sat Sep 13, 2008 5:06 pm 
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2-Stix wrote:
after my rebuild i have the same problem. im going to do the bottem end now.



What kind of gas mileage were you getting?
I was hovering just shy of 35 mpg until I swapped the kid's cam on. Since then I have calculated 50 & 45(mixture of city & highway driving) mpg when filling up the tank.


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PostPosted: Sat Oct 25, 2008 3:37 am 
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G-Whiz wrote:
jaguar,vettes&sprints wrote:
Ok on the low compression numbers and the smoke
DOES IT USE ANY OIL..??
(a) the new rings groove were not staggerd...low compression..!! (btdt) compression should be 200-210 on rebuilt
unless you shave the head
(b) possibly the oil ring scraper was installed upside down...excessive smoke



At 1200 miles since the initial oil change it's still 2/3rds of the way up between the two holes in the dip stick.

(a) Don't believe the head was shaved. However, the top of the block was. This is because because the G10 steel cylinder sleeves are known to "float" after yanking the head off, and this ensures the surface for the block is completely even for the head gasket when the engine is reassembled, otherwise you can end up with oil/water leaks according the the machine shop owner. Interesting point though. Could that cause the rings to break their seal at high RPMs?

(b) They are probably installed properly otherwise I would expect to have seen billowing smoke from day one, and not just in sudden high-rpm bursts. Just after the break-in period with the XFI cam still on the head I took the car up a long uphill stretch of highway at 78mph. The engine was wound up all the way and the RPMs were so high that the car never showed signs of slowing down on what must have been almost a 2 mile uphill grade. No smoke the entire time. Again, it never billowed smoke until the cam swap.


After more than a month since the previous post, I finally pulled the motor and yesterday, the machine shop had me come down for the "Big Reveal".

My only regret was that I didn't have my camera with me. I did go home afterward, retrieve it, and return, but by then it was too late for some of the shots I wanted to get... the cylinders had already been honed and the rings were off the pistons.

What follows are observations. There was no hard evidence involving a smoking gun (i.e., the Delta cam regrind being the culprit), only the symptoms of a rebuild gone terribly wrong.

The first thing we noticed when we pulled the head was that the chamber and valves on the underside of the head for the #2 cylinder were mostly dry while the #1 and to a lesser extent, the #3 were moist from excess oil.
Attachment:
Underside of head and gasket-1.jpg
Underside of head and gasket-1.jpg [ 670.14 KIB | Viewed 4710 times ]



The second thing we noticed were two dark rings running all the way around the the cylinder walls just below the top of the cylinders. The rings were about a quarter inch tall and were spaced apart about a quarter inch from each other. The shop owner said the existence of two rings rather than one was because I had driven the car with two different cams, each causing the spark plugs to fire at a different piston position before TDC. While there's some possibility it could have been a result of not setting the ignition timing the same on the distributor after having them swap my son's cam in place of the stock cam that was reground by Delta, I recall ensuring (with a timing light) that the engine was set to fire before Top Dead Center according to the repair manual. The shop owner said there was no way to know which ring was created by the reground cam. If the Delta regrind and my son's cam were both stock cams, I would NOT have expected to see two separate rings... maybe a single 1/3 to 1/2 inch tall ring... The point I'm trying to make is, that with the ignition firing that close to TDC, most of the piston travel has already taken place and the piston has slowed to a crawl (relatively speaking). So there shouldn't be all that much travel left in the piston before it hits TDC, even if the distributor timing varied 4 to 5 degrees as a result of swapping cams.

The bottom end bearings and the piston skirts all looked good, but then they should have - I hadn't even reached the first regular 3000 mile oil change when I pulled the motor.

In regards to item (a), well... sorry... but I screwed up, forgetting to verify that the rings were staggered. I remember looking at the rings on one of the pistons when it first came out, but I was looking for breaks, cracks or gashes in the sides of the rings. I remember one of the crew spinning the rings around the piston and there was no sign of the ring gaps being lined up with each other when he started to do that.
Recall the the compression readings on cylinders 1, 2 & 3 were 125, 135, and 150 PSI after the motor was broke in? Well all 3 pistons had carbon buildup on the top surface, seeming a little thick for a motor with only about 2500 miles on it. Although the pictures don't seem to show it, it seemed like the number 1 piston had a lot of oily carbon crud - and lacquer, if you will - on it, around the sides between the top of the pistons and the first (compression) ring. There was less crud on the second piston, and even less than that on the sides of the 3rd. When the shop employee pulled the first piston and looked at the rings, the first thing he said was that he could tell they had *tried* to seat properly. The center section of the outside edge of the compression ring was shiny from rubbing against the cylinder walls while the top and bottom of that edge were still dull - it was as if the outer edge wasn't perfectly flat top-to-bottom, but rather, slightly rounded.

Looking at the close-up, you can see that there are indeed, no sharp edges... they are rounded as I first thought. Not sure why the flat, shiny surface came out dark in this photo:
Attachment:
Outer face of Compression ring.jpg
Outer face of Compression ring.jpg [ 53.68 KIB | Viewed 7650 times ]


Regarding item (B), the oil ring scraper, well I assume you are talking about the second (thicker, ring) since the shop owner called it by that term also. Being thicker, it was easier to see what was going on. What we saw was the top half of the outer edge was polished from rubbing against the cylinder walls while the lower half was still dull.

In the picture of two of the oil scraper rings, notice how the width of the shiny (worn) area varied around the outer edge of the ring. Sorry, the auto focus didn't want to cooperate, focusing on the shop crew's thumb instead:
Attachment:
uneven wear on 2 oil wiper rings.jpg
uneven wear on 2 oil wiper rings.jpg [ 252.83 KIB | Viewed 4703 times ]


Oh, and one other thing... I wasn't aware of the possibility that there could be a right-side-up scenario for the scraper rings.

The third thing we noticed was that while there were no signs of... trauma... to the head gasket, there was a problem with it restricting flow down through two oil drain back holes. These were only 1/4 inch holes (if even that) provided in the gasket for what were obviously much larger drain channels in the block. These oil drains are located on the firewall-side of the motor and as a result of the tilt as it sits in the engine compartment, these holes:
1) sit lower than the radiator-side of the head
2) sit below, and to either side of the exhaust blow-by tube on the valve cover (which runs to the PCV valve and air filter housing). These small little holes puts them in a prime position for allowing oil to back up on the head and then be sucked into the blow-by tube (This subject was covered elsewhere on this message board).
Attachment:
Head gasket drain back holes-1.jpg
Head gasket drain back holes-1.jpg [ 395.39 KIB | Viewed 4973 times ]


Last edited by G-Whiz on Sun Oct 26, 2008 11:32 pm, edited 7 times in total.

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PostPosted: Sun Oct 26, 2008 5:44 pm 
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i got like 40+ mpg. shoud be more. toe it apart after 75 miles of driving since bought. dont have time for the bottem untill december time.

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PostPosted: Mon Oct 27, 2008 4:02 pm 
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Note to self *Don't take my car to the shop you did"

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PostPosted: Tue Oct 28, 2008 12:09 am 
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Justintoxicated wrote:
Note to self *Don't take my car to the shop you did"

Ha! Yeah right!!!
It's not about the shop. It's about the one non-standard, non-stock part that I put on this motor: the reground cam.

I stand by my machine shop.
My neighbor - who runs his own auto repair business - and many of his customers stand by this shop and it's crew (one who has been driving his own little green Metro for over 10 years now).
The shop and it's crew stands behind their work and are rebuilding the motor, eating the cost, other than for the extra work I'm having done. I'm sending the pistons, valves (including 3-tech's SS exhaust valves) and the head to California for a protective coating before the shop puts it all back together with 3-tech's econo cam and advanced timing cam sprocket. The only thing is, the shop has to remove the rods before I can ship the pistons, and there's a risk to the pistons while pressing out the wrist pins. But since this is "above and beyond" what the shop would normally be doing to the motor I plan to reimburse the shop for the extra work.

Anyway, re-read the thread and you will see where my trusted local car repair garage of 9 years (who is familiar with this machine shop & didn't have any criticisms of their work), and even fordem agrees with my conclusion:
We **all** believe Delta Cam screwed up the regrind and blew the engine rebuild - and there was nothing I saw during the motor tear down last week to indicate otherwise. If anyone can tell me different based on the pictures I've posted, well... I'm all ears!

Justintoxicated, maybe your comment was meant to be just joking around, but my hope for this thread is for it to be educational (in the spirit of this web site), not cynical... that it will help others who may find themselves in this same unfortunate position.

With that said, I'm now waiting for the head to be prepped and the pistons to be removed from the rods. Then the head, pistons and valves will be shipped to California for what will probably be a 3 week round trip.

Just what I'm looking forward to - doing an engine installation in November or December... in an open carport rather than a heated garage... grrr.

I'll take pictures and post them so everyone can see what the protective coating looks like before the shop slaps it all back together.

When it's back in and broke in with Superfly's econo cam & +6 cam sprocket, I'll post the compression readings and MPG results before I start fitting it with an HHO electrolyzer system.


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PostPosted: Tue Oct 28, 2008 5:58 am 
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All the evidence here points to rings not seating or installed wrong. How could the cam grind cause oil to get up there?

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PostPosted: Tue Oct 28, 2008 9:46 am 
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I think the rings not seating properly are a symptom - not the cause - of too low a compression (remember the 125, 135 & 150 with the reground cam and the 151 PSI all the way across all 3 cylinders when I replaced it with with the kid's stock cam?).

With the compression ring not seated properly - or seated for a lower compression - when the compression went up with kids cam on the head, gases started blowing by the rings.
This blowby had to go somewhere, and that somewhere was out the vent tube on the valve cover and into the throttle body, picking up excess oil splashing around on the back side of the head, most of it from droplets being slung around by the cam, but very likely it also included oil pooling at the drain back holes because of the tiny head gasket holes I circled in the picture. Those holes restricted the oil from freely draining back down into the oil pan.

The increased amount of blowby gasses flowing to the throttle body picked up more of the oil droplets, coating the top of the throttle body with oil as it was sucked into the cylinders.


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PostPosted: Tue Oct 28, 2008 10:57 am 
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So the rings where not seated correctly? If that was the case that would be the CAUSE of your problems. 150psi is low period. What was the ring spacing like? Where the ring gaps set properly and spaced per spec? What do the cylinder walls look like?

You said it was bored out? How much? are you running oversized rings? What sahpe are your pistons in? You where running the stockers correct? Well if your rings are rounded so badly your ring grooves might be/probably are bad? Have you checked them out?

Seems to me like alot of steps where taken to do the job right, but a few major little things where forgotten. Now for that reground cam you know all you have to do is mic all the cam lobes and see if they are consistent across the board for the intake/exhaust. Then you can rule out the cam or not.

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PostPosted: Wed Oct 29, 2008 2:33 am 
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thinkmoto wrote:
So the rings where not seated correctly? If that was the case that would be the CAUSE of your problems. 150psi is low period. What was the ring spacing like? Where the ring gaps set properly and spaced per spec? What do the cylinder walls look like?

You said it was bored out? How much? are you running oversized rings? What sahpe are your pistons in? You where running the stockers correct? Well if your rings are rounded so badly your ring grooves might be/probably are bad? Have you checked them out?

Seems to me like alot of steps where taken to do the job right, but a few major little things where forgotten. Now for that reground cam you know all you have to do is mic all the cam lobes and see if they are consistent across the board for the intake/exhaust. Then you can rule out the cam or not.


If you're saying piston rings are *not necessairly* ready to go into a bored-out cylinder straight out of the box then that's news to me. I had never considered the possibility.

I admit it, I don't understand what you're asking here: Where the ring gaps set properly and spaced per spec?
I thought they either fit because they were properly "gapped" at the manufacturer, or they didn't. What does spaced per spec mean? Are you talking about staggering the gaps on the pistons?

Somewhere in my younger days I was told that PSI plays a part in the break in, just like varying the speed of your motor does. I don't even know where I heard it, but the logic was that the outer face of the rings would seat differently against the cylinder wall based on the PSI pressure that's pushing against them.

Fact? Fiction? Old Husbands tale? I honestly don't know.

The most extreme example I can think of is what the sudden PSI increase can do to old, worn rings when a freshly rebuilt head is slapped on the motor. ("Bummer dude. You rolled the rings.")

It's been my understanding that the rings are going to flex more the greater the PSI is. For a given PSI, it's going to flex the ring to a certain point which in turn, impacts how the outer surface seats during the break in period. So, take a ring that broke in (seated) at 125 PSI, increase it to 151, rev the motor up on the freeway at 60 MPH, and suddenly you're looking at a slightly changed angle between the outer face of the ring and the piston wall. Your ring faces are no longer flush (perfectly seated) against the cylinder wall, the rings start to... uhm... break wind, and the next thing you know, you're blowing out a smoke screen. This is why I believe the rings that broke in at 125 & 135 PSI have had problems breaking their seal against the cylinder wall after the kids cam increased the compression to 151.

There's a few questions here that I do not have answers for, simply because I didn't perform the rebuild. With as many rebuilds as they do in their shop I wouldn't expect them to remember the details of what they did on this motor at the beginning of last Summer. (Sigh)

Yes, I agree... 150 PSI seems low based on other posts on this site.

No mention was made as to whether they had to adjust the ring gaps but they did say the gaps had been properly staggered. Again, I failed to check when the pistons were pulled... my bad, although my son informed me the reason so many engines come with 3 or 4 rings is because the ring gaps tend to drift around the side of the pistons. Hmm... that's another new one for me...

The block was bored out to the next size up (20 thousandths?).
I didn't closely examine the cylinder walls - and even then, I wouldn't have known what detail to look/feel for. How do I describe the cylinder walls... partly polished, but the angled hone (bore?) marks were still visible - again, the motor only had about 2500 miles on it.

Yes, they installed brand spanking new oversized pistons & rings.
Stockers? Not sure what you're saying, but it's safe to say they are just your run of the mill pistons.

What would I look for as far as damaged ring grooves are concerned?
Sorry I don't have better pictures of the grooves at the moment so these will have to do...
Attachment:
Piston1 side.jpg
Piston1 side.jpg [ 592.39 KIB | Viewed 4696 times ]

Attachment:
Piston2 side.jpg
Piston2 side.jpg [ 517.18 KIB | Viewed 4691 times ]

Attachment:
Piston3 side.jpg
Piston3 side.jpg [ 591.27 KIB | Viewed 4692 times ]


Based on what I've read elsewhere on this site, it sounds a little more involved than simply doing a mic job. Duration and angle on the cam of the lobe's opening and closing of the valves also comes into play. Open (or close?) a valve at the wrong part of the piston stroke, and you'll lower your vacuum and/or compression. This is why we all think I got the lopsided compression readings with the reground cam. Remember too, my local car repair garage stated that the whacked regrind was causing what originally looked like a vacuum leak.


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PostPosted: Wed Oct 29, 2008 10:33 am 
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Location: Palm Springs: Too hot from June to Oct.!
I just did an engine like yours for my wife:
viewtopic.php?f=2&t=40445
viewtopic.php?f=14&t=39927

You check out Geo racer's thread:
viewtopic.php?f=22&t=40391

Most of the time, people don't do compression tests on a new engine, unless it doesn't run right.
Consistently low compression tests in a fresh engine, steady miss, plus your sluggish performance might point to a misinstalled cam.
Maybe your shop lined up the marks, but it was still off a couple of teeth. That would explain most of your problems.

A simple trick is to try the cam at different positions, like Geo racer did. :wink:

You spent close to $1300 on an engine, you expect it to perform like new. As close as you were, you should have had them try different cam timing positions, especially with those compression readings. Point is probably moot.

Most shops are afraid to move the belt a tooth in either direction, as they are used to dealing with 'interference engines' and think the valves will hit the pistons. :shock:
Your engine, as you've probably read, is non-interference and it won't hurt a thing. I'm talking about a 3 NOT a 4 cylinder engine, in case you just jumped in on this thread.

Did the reground cam have the same gear on it when you reinstalled it?


Ah, in hindsight, armchair mechanics can do no wrong...

Just my 2 cents.

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PostPosted: Thu Oct 30, 2008 2:25 am 
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You have my admiration on balancing the pistons and connecting rods. Well done!! :D

Phil N Ed wrote:
You check out Geo racer's thread:
viewtopic.php?f=22&t=40391

Ah yes! Thank you!
It was fordem's explanation on the valve/piston stroke timing that was what I was referring to in my previous post.

Geo Racer's post about the mismarked cam sprocket and having to retard it 3 teeth... WOW!!! That could explain the low 151 PSI compression.

Phil N Ed wrote:
Most of the time, people don't do compression tests on a new engine, unless it doesn't run right.
Consistently low compression tests in a fresh engine, steady miss, plus your sluggish performance might point to a misinstalled cam.

The machine shop said that the PSI readings don't start to stabilize until you have a minimum of 75 miles on a motor. Some stabilize at 75 miles, others take 100 or more miles. After that, your engine is pretty much in "the zone" and you shouldn't see much, if any change after that.
Prior to the repair garage and the machine shop both getting the lopsided 125/135/150 PSI readings, my son and I did a compression check and got 128/150/160PSI. I believe it was immediately after we had the motor up and running and first realized we had a problem... before I even had a chance to start the break in.

What are some examples of a misinstalled cam? Are you talking about the sprocket being off a tooth or two?

Phil N Ed wrote:
You spent close to $1300 on an engine, you expect it to perform like new. As close as you were, you should have had them try different cam timing positions, especially with those compression readings. Point is probably moot.

Let's put aside the fact that the regrind had lopsided compression and the kid's stock cam had even compression for a moment...

If the cam sprocket was off by one or two teeth in either direction, then all of the cam lobes would be equally off by the same amount on each cylinder. With all things being equal(ly off), how do you account for the lopsided compression in this scenario?

Phil N Ed wrote:
Did the reground cam have the same gear on it when you reinstalled it?

Yes, the shop used the same original cam sprocket for the reground cam. As for when they swapped in the kid's stock cam? I don't know, but I would think they just went with the sprocket that was already on his cam. It was the shop's engine rebuild so I didn't get involved and wasn't there when they did the swap. I stood back and let them do the swap to my kid's old stock cam.

The fact that there were two dark rings at the tops of the cylinders and that the reground cam was originally just another stock cam, well, it gives credence to the idea that the install of the kid's cam was off by a tooth or two (resulting in the 151PSI).

However, since the reground cam had the lopsided compression, let's assume:
a) Delta did NOT screw up the regrind and that the lobes were properly reground
b) The reground cam was the one that was off by a tooth or two

As I asked above, how do you account for the lopsided compression in this scenario?


In response to the previous post with the question about the ring gap... I talked to one of the shop crew members this afternoon. He said after boring out the cylinder, they put the rings in the cylinder and check the ring gap at 3 different positions, using the piston to push the ring down further for each measurement. He said he calculated the allowable gap to be 11 thousandths of an inch for a G10 cylinder that was bored out, 20 thousandths of an inch over. He didn't understand the "ring spacing" terminology either.

Also, while I was there, I took a close look at the grooves on two of the pistons now that they have been cleaned up. I didn't see any signs of damage.


Since the shop owner still suspects the injector could have ruined the break in, I'm still hoping to hear from someone who actually had their rings washed out during the break-in period by an improperly functioning throttle body injector - even if it happened to something other than a Geo Metro!


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PostPosted: Thu Oct 30, 2008 2:33 pm 
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Phil N Ed wrote:
Ah, in hindsight, armchair mechanics can do no wrong...

Just my 2 cents.


Is that is in reference to my post? If so fuck off I'm no arm chair mechanic. I'm a Journeymen Millwright Engines don't even compare to the complexity of the machinery I work on, on a day to day basis. Yes I've rebuilt motors and no I've never had problems with the rebuilds. I'm asking honset questions to help him get to the bottom of this problem. he never mentioned honestly if the rings where gapped or the grooves properly staggered before. That is a critical thing to do in engine assembly.....or am I wrong :roll: I understand he stands by his shop and others do too, but you know what people have off days, we make mistakes, we are human. if someone fucked up the assembly and they know, they may not own upto it. I'm not saying they are, but no one really knows for sure.

As for you Phil N ED thank you for putting more piss into my vinegar today.

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PostPosted: Thu Oct 30, 2008 2:33 pm 
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Phil N Ed wrote:
Ah, in hindsight, armchair mechanics can do no wrong...

Just my 2 cents.


Is that is in reference to my post? If so fuck off I'm no arm chair mechanic. I'm a Journeymen Millwright Engines don't even compare to the complexity of the machinery I work on, on a day to day basis. Yes I've rebuilt motors and no I've never had problems with the rebuilds. I'm asking honset questions to help him get to the bottom of this problem. he never mentioned honestly if the rings where gapped or the grooves properly staggered before. That is a critical thing to do in engine assembly.....or am I wrong :roll: I understand he stands by his shop and others do too, but you know what people have off days, we make mistakes, we are human. if someone fucked up the assembly and they know, they may not own upto it. I'm not saying they are, but no one really knows for sure.

As for you Phil N ED thank you for putting more piss into my vinegar today.

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Just when I thought I was about to get back on my own 2 feet life kicked me in the shorts.

94 GEO METRO PARTS FOR SALE EVERYTHING MUST GO!!!!
94 XFI rust bucket
96 Honda Accord


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PostPosted: Thu Oct 30, 2008 4:03 pm 
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G-Whiz

Assuming the remainder of the engine to be in reasonable shape - as evidenced by the compression with your son's cam - incorrect timing does not explain the lopsided timing with the Delta cam - the compression should have been low but even.

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PostPosted: Thu Oct 30, 2008 9:29 pm 
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Ack!
thinkmoto, I'm sorry but I see nothing in Phil N Ed's post addressing anybody but me!!
It was left the next morning, immediately following my post where I asked "Fact? Fiction? Old Husbands tale? I honestly don't know."
I put the cylinder PSI issue out there not as absolute proven fact, but as theory as best I understood it, at least as it applied to the engine blow by at high RPMs, hoping to learn from anyone willing to share what they have been taught, or have learned from personal experience.

Phil N Ed's post was very thoughtful, insightful, and I'm actually thankful for it since it got the gears turning in the old noggin. The ribbing about the armchair mechanic actually brought a smile to my face...


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PostPosted: Sun Nov 02, 2008 4:09 am 
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Paid a visit to my machine shop Saturday morning.
I had hoped to bring the rings home so I could take better shots. Only Paul, the owner, was there and I was told they may have been tossed since there's no sign of a box that might have contained them.

As you are aware by now, I've been thinking that if the compression was 125/135/150 PSI, then the number #1 cylinder should be saturated with the most oil while #3 should be the least, since I was assuming the oil was being sucked up past the rings when they lost their seal with the cylinder walls.

However, my photo of the underside of the head did not support this theory, and it's been bugging me for some time now.

At the shop, Paul said he had been thinking about the head gasket restriction issue and how it could cause the motor to blow smoke at sustained speeds over 56 mph.
Well, he was close... right cause but wrong symptom. He didn't explain the smoke screen (that was explained elsewhere on this site - but I think it only addresses 1 of the drain back holes!). Instead, Paul explained the photo showing the presence of all that oil in the #1 and #3 cylinders...

Out on the freeway over 56mph, the oil was being delivered to the head faster than it could drain through the small gasket holes, eventually flooding the two restricted drain back channels on either end of the head. It then flooded the top of the head in the area around the valve stem oil seals, especially around the #1 and #3 cylinders. From there it was seeping down the valve stems and into the cylinders, creating the conditions seen in the photo of the underside of the head.

Again, at the same time the oil was flooding the top of the head, it was splattering oil droplets up into the valve cover baffle from all the engine vibration and these droplets were then being sucked through PVC vent tube, and into the cylinders creating the smoke screen.


Here are a couple pictures of the top of the head on the #1 end of the engine, showing the proximity of the restricted drain back channel to the valves. The yellow rectangle shows it's location behind the head bolt hole and the underside of the outer wall of the head.
Attachment:
Oil drain back hole next to cylinder 1.jpg
Oil drain back hole next to cylinder 1.jpg [ 171.16 KIB | Viewed 4688 times ]


The circled area in this shot is intended to show where there is a gap between the top of the head and the underside of the hydraulic lifter housing (if you want to call it that). This gap is where the oil can reach the valve stem oil seal.
Attachment:
Oil drain back hole next to cylinder 2.jpg
Oil drain back hole next to cylinder 2.jpg [ 207.92 KIB | Viewed 4690 times ]


Ah hah!!!
Discovered this during the Saturday visit. Notice the damage caused to both sides of the sprocket positioning hole by the rounded shoulder of the positioning peg on the end the the Delta cam. The sprocket is toast - it rotates slightly on the end of the cam now! Paul said the peg will have to be pulled and reseated so it sticks all the way through the positioning hole in 3-Tech's +6 cam sprocket.
Attachment:
Metro cam sprocket positioning peg hole.jpg
Metro cam sprocket positioning peg hole.jpg [ 182.51 KIB | Viewed 7210 times ]



Notice that the positioning pin on the Delta regrind cam (on the right) does NOT stick out as far as the spare stock cam (on the left). If it managed to booger up my old sprocket, I can't help but wonder what kind of chaos it could have caused during the regrind at Delta!
Attachment:
Stock cam on left and Delta cam on right.jpg
Stock cam on left and Delta cam on right.jpg [ 236.62 KIB | Viewed 4683 times ]


I have brought the kid's head, the Delta cam, and a spare regular cam home from the shop. Paul didn't know where the crew put the kid's cam.

I don't know how to mic these cams. I certainly don't have any equipment to mic them with. Tomorrow I was thinking taking pictures of the position of the sprocket where each input lobe:
-first touches the hydraulic lifter
-is positioned straight down against the top of the lifter
-last touches the hydraulic lifter

3 shots for each input lobe on each cam... 18 shots.

Anybody got a better idea of how to compare these two cams to see if Delta really did screw up the regrind?


Last edited by G-Whiz on Sun Dec 07, 2008 4:36 am, edited 1 time in total.

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