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Author Topic:   4412 Holley
BIGDADDYBOZ
Dirt Freak

Total posts: 466
posted February 09, 2005 07:23 PM  
I've got a 4412 that I'm gonna be running on a 11to1 358. what size Power valve and jets should I start with? Thanks

leapinlizard
Dirt Freak

Total posts: 402
posted February 09, 2005 08:11 PM  
gas or alky?

What gas?

I would block the power valve. They only do thier job at thier rated vacuum and less. At wide open you'll only use the main booster circiut. It'll give you better adjustability of the fuel mixture if you don't have to contend with the PV.

waltonjr1
Dirt Forum Champ
Total posts: 516
posted February 10, 2005 04:26 AM  
Actually with the PV blocked you cant tune your carb for maximum performance, you will either be to fat on bottom end or to lean on top end. With your car in gear and your foot on the brake check your manifold vacuum, whatever your reading is subtract two and thats the size PV you should start with. Ex, if your vacuum reading is 8" you need around a 6.0 PV.


waltonjr1
Dirt Forum Champ
Total posts: 516
posted February 10, 2005 04:30 AM  
Oh for jets I would start at around 85 and go from there. More than likely you will jet down but that should put you close.

[This message has been edited by waltonjr1 (edited February 10, 2005).]

BIGDADDYBOZ
Dirt Freak

Total posts: 466
posted February 10, 2005 06:00 AM  
Sorry i will be running Cam2. In a stock car Thanks.

ss99
Dirt Maniac

Total posts: 120
posted February 10, 2005 07:43 AM  
Your jet and PV selection will depend on much more than the information you've provided so far. For the PV, take your manifold vacuum reading at idle and subtract 1.5 - 2. Most find that a PV between 4.5 and 6.0 work well.

I think a lot of racers run too rich with their 4412s. I think if you're in the 80s, you're running too fat. You'll have to jet depending on the climate in your area and your motor combo, but generally something between 74 and 78 will work well. I run primarily 76s in texas.


leapinlizard
Dirt Freak

Total posts: 402
posted February 10, 2005 08:28 AM  
waltonjr1,

The power valve's(PV primary job is to enrichen the Air Fuel(AF) mixture under high load/lows engine speed conditions. This creates a very low vacuum in the manifold and reduces booster signal to the point of stalling. Same reason you get a hesitation if your accelerater pump is too small/short/low volume/out of tune. While it is partially true you will lose the low speed high vacuum throttle response(cruise mixture)a race car seldomly experiances these conditions. I recommend blocking the PV and jetting up two numbers. I also increase the power valve channel restriction and redirect that fuel through the main jets so even more control of the AF can be achieved. You can also drill out the low speed air bleeds to introduce more emulsion into the cruise circiuts to lean if plug fouling should occur. But that rarely occur's with normal timing event's.

BIGDADDYBOZ, I like 72-78 depending on temps and humidity, weight or vehicle, gear, top speed manifold vacuum ect...

stockcar5
Dirt Forum Champ
Total posts: 578
posted February 10, 2005 10:58 AM  
ask any carb builder...do NOT block the power valve. i've seen what a carb with a pv blocked does on a dyno...not good....a/f ratio is all over the place.

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BIGDADDYBOZ
Dirt Freak

Total posts: 466
posted February 10, 2005 11:16 AM  
I will be running a Performer Manifold, turning around 68-7000 rpms.Headers and will be weighing about 3150. The track is a 1/2 mile with tight corners and long straights.
The carb has 80 jets in it now and the power valve has a 4 and 5 on it. Thanks for all the info everyone.

stockcar5
Dirt Forum Champ
Total posts: 578
posted February 10, 2005 04:14 PM  
on a similar motor we ended up with 74 jets and a 6.5 power valve

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sbc350
Dirt Full Roller

Total posts: 59
posted February 13, 2005 06:58 AM  
I run about the same combo also with 70-72 jets with a 6.5 power valve. If its a stock Holley 4412 with no work done to the metering block the a/f ratio is really going to fatten up at top end so you're not going to want to run it too rich.

[This message has been edited by sbc350 (edited February 13, 2005).]

waltonjr1
Dirt Forum Champ
Total posts: 516
posted February 13, 2005 07:03 AM  
It all depends on the head and intake combo you have, if I would run 72's I would melt the pistons for sure. My motor likes 80 to 85's.


RangeRover
Dirt Freak

Total posts: 279
posted February 13, 2005 09:13 PM  
I thought I was the only one with bigger jets around here, walton. To get my plugs looking good, I've got to run between 89 and 92. When I first got my new 4412 I was told to resist putting my old jets in it and run it straight out of the box first. Reluctantly, I did run the stock 72s or 74s or whatever it had and I freakin' overheated in about 5 hot laps; the plugs came out scary white! I stepped the jetting up until I got the color, temperature and performance I wanted and it turns out I needed right about the jet numbers I had before, 89 through 92ish.

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