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Main jet?

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Old Hutcho Officially Full-On Dubber

281 posts · joined Jan 2004 ·

#961609
Can anybody tell me at what revs the main jet kicks in on a stock 1600TP engine with a ICT34 carb? I dont need guesses folks, I need to know as precisely as possible. Surely that is documented somewhere in the VW lieterature?

regards

Old Hutcho

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 ·

#961611
It's as much throttle possition as it is rpm, so no actual figure. Air speed through carb is totally rpm based, jets though are actuated by vacuum which varies with throttle position. At 3000 rpm with your foot off the gas, as you apply throttle the main will begin to work at a lower rpm than in a similar situation but at 1000 rpm. Get a gas anyliser and DIY or go to a specialist....beware tho, I've seen crazy jetting come out of some specialised dyno tuners !!!
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

Old Hutcho Officially Full-On Dubber

281 posts · joined Jan 2004 ·

#961612
I appreciate your reply. I have a PICT carb, not the mumbo jumbo I typed above. I also now have a gas analyser which measures through a lambda sensor (oxygen) and I am doing it on a hard stand, not in the real world on the road. The instructions are telling me to go to 2500 rpm and measure there. I did that and I got good readings, however, in the real world it feels doughy and I am thinking about a smaller main jet. Problem is I dont know where to look for the point the main jet kicks in. Once I get it right on the apron, I will put it on the road and see what its like in the real world of driving. Motor is a 1776 stocker.

regards

Old Hutcho

matberry Moderator Go hard or go home

8,114 posts · joined Mar 2006 ·

#961618
doughy sounds rich, lean will be crisp BUT too lean gets hot, then way lean is back-fire through the carb. If the engine is still relatively stock, heads and cam, no jet changes will be necessary. I hear so often that a different engine combo needs rejetting....bollocks.
The carb is a metering device, it adds fuel to the air stream. It should be always around 14:1 Air:Fuel (I actually aim richer for increased cooling like 13.5:1) A bigger engine draws more air....so more air travels thru the carb, but this doesn't mean the jets need to be inlarged, as the carb is purely adding fuel tu the volume of air that goes thru it.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE

68AutoBug Beetle Restorer - Experience over 138\% - YIKES --

11,654 posts · joined Aug 2002 ·

#961620
Old Hutcho wrote:Can anybody tell me at what revs the main jet kicks in on a stock 1600TP engine with a ICT34 carb? I dont need guesses folks, I need to know as precisely as possible. Surely that is documented somewhere in the VW lieterature?

regards

Old Hutcho
Hi

SOLEX 34 PICT 3 ?

I have many VW manuals and none of them give that info..
some of the books give great drawings of the carbies working in each application and how they work.. etc including 34 PICT 3 etc

but I don't think they CAN actually tell You at what revs etc as the distributor has a large bearing on it too, especially where vacuum advance is used..
I;ve been fiddling with a new BROSOL [Brasillian solex] H30/31 carby for months now .. and You can vary the way the carby works by the adjustments..
Its slowly getting better to drive, and doesn't stop or have a huge flat spot anymore.. accelerator pump is working great but its not accelerating up hills as good as it should. so more adjustment..

Mat knows all about it.. lol wish he lived closer.. lol

Best of Luck

LEE
- Helping keep Air Cooled VWs on the road - location: SCONE in the Upper Hunter Valley - Northern NSW 320 kms NNW of SYDNEY---

13bwagon Officially Full-On Dubber

316 posts · joined Nov 2006 ·

#961662
😂 don't we all ! he is dreamy 😍
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