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Author Topic:   help with carb question
Dirt Maniac

Total posts: 121
posted October 19, 2004 01:55 PM  
ok guys needing alittle help . never ran a 4412 holley . needing advise on what jetting an power valve might need.

ok on engine , 327 60 over set of 58cc heads
flat tops pistons . with i think a 550 lift cam .

got motor all together , an running , but im way to fat on fuel . fouled 2 sets of plugs already
so i know i need to stick smaller jets in but done want to go to small to hurt power

be running on a small 1/4 mile semi bank stays dry slick most of time .

im also working on a 350 60 over . so anyone got any ideas to go with . let meknow

Dirt Forum Champ
Total posts: 1019
posted October 19, 2004 02:01 PM  
What jets and power valve have you got in there now?

It's a safe bet that you should start in the ballpark that the 4412 comes with off the shelf. And that would be a 73 jet and a 4.5 power valve.
The power valve should be chosen based on your manifold vacuum at idle (2 #'s lower than the idle vacuum reading for starters).

You're also going to have to dial in your idle circuit before the thing will run properly at idle without fouling plugs, stalling, etc, no matter what jet size you're using.


Dirt Maniac

Total posts: 121
posted October 19, 2004 02:05 PM  
ok just looked got 67 jets in it now .

also got questions on idle screws , how many turns in or out should i be . looks like either 1 1/2 or 1 3/4

Dirt Forum Champ
Total posts: 1019
posted October 19, 2004 02:23 PM  
If you're down to 67's and still fouling plugs, then there are other issues, most definitely.
1.5 turns out from lightly seated is a good ballpark starting point.
Where is the float level set? What's your idle fuel pressure? No great need for anything higher than 6lbs.
Is your ignition system working properly and delivering enough spark? What's the plug gap at?
Verify that isn't your problem by just gapping the plugs at about .025" and see if it helps it a lot. That'll tell you if it's electrical.
Are you sure you're not oil-fouling the plugs? Are the rings seated?

That's just for starters, but if you're down to a 67 jet (too small, really, unless you're running a stock 4cyl), I'd say the problem isn't in jetting...
Then there's the distinct possibility that your power valve is blown and dumping raw fuel thru the baseplate at idle and fouling up everything.
Or simply that your power valve gasket is twisted and not sealing....

Hope that helps.

[This message has been edited by KPLugnut (edited October 19, 2004).]

sc1 racing
Dirt Freak

Total posts: 419
posted November 07, 2004 02:18 AM  
hey man i found you here..go with a p/v block and get a set of 78 jets. set timming, then you have to go be ear and throttle response on adjusting screws. if you want give me a call and ill come by see what we can get going..

Dirt Forum Racer

Total posts: 81
posted November 08, 2004 07:43 PM  
Id say you've got trouble if you're fouling with 67 jets in it. make sure it has the right gasket in it for the metering block. I always set the float level flat with bowl sight plug,
change discharge nozzle to a 31 size and jef it between 75-78 jets with a 6.5 p/v to start. you may need to go with a 5.5 or 4.5 p/v after you test it out. Also depending on your cam duration @ .050, you idle screw turns will vary. I usually find 1 3/4 to 2 turns seems to yield the best results


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