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 Post subject: mk1 carb setup (help)
PostPosted: Mon Feb 15, 2010 12:46 am 
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Joined: Tue May 20, 2008 2:02 am
Posts: 9
Hello guys

I am planning to run my Suzuki gti mk1 on 40 DCOE Weber Carburetor, I would like to ask if it is a good idea to shave the head by 0.5 mm or 0.25 mm and just polish the head as it has done 200,000 km and where can i except the power band to shift from 6500 rpm???. I am also planing to to have three angle valve cut would it be safe for an engine which has done 200,000km????

what would be the best tuning setup for carb as i intended to participate in autocross and drag races????


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PostPosted: Mon Feb 15, 2010 1:34 am 
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Joined: Tue Sep 09, 2008 2:34 am
Posts: 367
Location: Roumania
You can shave the head but that will give you increased torque with a minor shift in the rpm band. The most important thing you can do is to find a very good manifold , polish it, polish and enlarge your head intake and exaust and don't forget to match the manifols to the head once you enlarge it.
You can run 34 mm venturi for maximum power .

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G13B 1.3L 16v 115hp


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PostPosted: Mon Feb 15, 2010 3:48 am 
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Joined: Tue May 20, 2008 2:02 am
Posts: 9
you mean 34 mm venturi for drag races and 30mm for autocross

I have question for you,by how much should i enlarge the intake and exhaust ports because by enlarging them u loose low end power and should i stick to stock valves and as far as manifold is concern i have to make a custom manifold

but over here in our country we don't get higher octane then 96 then how much should i shave the head 0.25mm or .5mm


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PostPosted: Mon Feb 15, 2010 4:12 pm 
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Joined: Tue Sep 09, 2008 2:34 am
Posts: 367
Location: Roumania
You can run "true" octane boosters . Try to find lead tetraethyl. Naphtalene.

Truth is that none of my engines ping , there was one time when my renault 1.4 8 valce with 11.5:1 comp ratio ran with old 95 gasoline.
Back to your problem ...

Running carbs isn't easy ,parts for the carbs are a bit expensive and to tune them you need to swap jets and venturis.
First , you have to buy a manifold , i would suggest my friend John in Greece aka Motorman . From my research others make crappy intakes in terms of alu composition and design. After buyin that you have to clean and replace worn parts on your carbs.
If you allready have webers they'r ok although i prefer dellortos .
Next , venturi size , the books tell you that 32 mm if optimum for the gti engine but from my experience you can run 34 easily.
I ran 130 mains with 50 idle and 35 pumps on 32 venturi and 118 mains with 45 idle and 35 pumps on 30mm venturi. I will probably run 148 mains with 50 jets and 35 pumps on 34 venturis.
You will find usefull info on the web on how to set your float bowls and sync your carbs...i do it by touch and sound , a specialist will tune them without using tools if it's a must.
Also get the biggest needle valve you can get your hands on , because you need to feed the carbs with a large volume of fuel at a low pressure.

Next, you will have to buy a facet red top fuel pump and put new fuel lines from your tank to the carbs, or you can use your gti pump to fill a surge tank from where the facet red top pump will get the fuel. I run 3.5 psi of fuel pressure on normal driving and 5 psi when racing. 5psi will most likely richen the mixture due to the excess fuel entering the carbs.

About shaving the head...your pick 0.2 or 0.5 won't make a difference. 1mm will make a difference.
You can enlarge the ports as much as you want, also cut the valve guides. If you autocross or drag race the car you probably won't be going less than 4000 rpm so ...low end torque isn't an issue unless it's a daily driver.

These are my suggestions and you can use them on your own responsability. The things i've written i've also tried and worked.

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G13B 1.3L 16v 115hp


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PostPosted: Wed Feb 17, 2010 4:07 am 
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Joined: Tue May 20, 2008 2:02 am
Posts: 9
thanks for detailed answer

I wanted to ask

what air correction jet,emulsion tube and auxiliary venturi are u running on 30,32,34 mm venturi????

If i disconnect the original gti intank fuel pump and put the facet red top fuel pump under the hood in series with gti pump will it work without having the surge tank???? as i have read that facet pump will easily pump through original gti fuel pump.


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