How to jet a 30 pict 1

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hapnastyracing
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How to jet a 30 pict 1

Post by hapnastyracing » Tue Mar 26, 2013 10:17 pm

My brother and I are picked up a short track race car minus motor and are trying to get it set up to race on may 11 at miller motor sports park. We just bought a race ready 30 pict 1, it will be going on a freshly rebuild 1600 SP motor that I build myself, but it will need to be jetted for our altitude. We will be racing at about 5000 feet above sea level. I'm sure it will run out of the box but I would like to learn more about jetting and I would like to get maximum performance as well as help the motor last as long as possible. I've never jetted a carb so be gental. What suggestions do you have for jetting sizes?

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Marc
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Re: How to jet a 30 pict 1

Post by Marc » Tue Mar 26, 2013 11:11 pm

Stock jetting for a 30PICT-1 on a 1500 Beetle is a 125 main, and a 125x air correction jet. Air density at 5000' is about 17% less than at sea level (for the same temp and humidity) so a 150 A/C would be indicated to compensate. It's hard to find an A/C that size in a VW carb (look in 28PICTs, where 145 is fairly common), but a 105-110 main would be in the same ballpark with a 125 A/C - at WOT, anyway.
Hard to say exactly what a race-prepped 1600 is going to need, but the factory 125 over 125 probably isn't a bad place to start - step up on the air and/or down on the main from there to see if top-end power improves...if you notice any fall-off back up a step. Any barking back through the intake at high RPM (sounds a lot like valve float) means you're way too lean, jump a couple steps richer. As a rule of thumb, 5 on the main (say from 115 to 120) is roughly comparable to 10 or 15 the other way on the A/C (145 to 135 or 130 in this example) when you're close.

Do you know the jet sizes of your "race ready" carb? Stock venturi diameter is 24mm...if they bored that out, disregard the specific numbers mentioned above...but the principles should still apply.

hapnastyracing
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Joined: Tue Jan 22, 2013 9:31 pm

Re: How to jet a 30 pict 1

Post by hapnastyracing » Tue Mar 26, 2013 11:29 pm

Thanks marc, if it helps the motor is not built for racing. It was build as a back up motor for my 67 DD so it's pretty mild with a stock cam. The only reason we are using it is we have a limited budget and it's what we have. We just want to get to car going for the season with hopes to upgrade later on. I hope this info helps on how to jet correctly.

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