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Author Topic:   Need help KP
speedyd1
Dirt Maniac

Total posts: 170
posted June 07, 2004 06:47 AM  
i fighting the holley blues on my modified 4.
i dont know why on earth i put this carb back on but heres what i have. i bought one of the keith dorton 500 holleys. i hoped it would not have the same pullover problems that are associated with the stock units. i'm running 70 mains / 3.5 PV / 21 pump discharge nozzle / the new metering block of course. runs great up to 7000 then it starts the pullover and is killing me going in the corners. i tried restricting the PV passages - no help. i tried a block off and went with more mains - no help. i tried the hollow pump discharge screw with a couple of bearings hoping i could increase the weight enough to stop it but it only helped some.i am sitting on a 38 dgas weber that i am really considering but wanted your input first. my flow bench shows that it flows as well if not better than the holley. i measured it at around 475 cfm.

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted June 07, 2004 01:01 PM  
some of the issues are because of the new style pump check diaphram in the pump well in the bowl. Harmonics cause that to "flutter" and actually pump fuel out the squirters in the 4cyl motors.
Try installing an old style bowl that doesn't have the orange umbrella seal under the pump diaphram, but has the old style check ball.
And install an anti-pullover squirter, not just a small orifice standard one.
The Dorton carbs, like standard off the shelf ones, are NOT set up for use on a 4cyl.

Another thing to do (if the Dorton carb came with it) is get rid of the 50cc pump and go with a 30cc one and either a black, white, or pink pump cam, depending on your motor's specific needs.

Also, double check to see if maybe your float level can be safely lowered so that at higher rpms, the boosters aren't "asking" for raw fuel direct from the bowl, but yet there is still enough fuel level not to pull air thru the PV channel restrictions. BTW< those PV restrictions should be about .040", and make sure your PV choice is at least 2 below what your idle vacuum reading is.

Other things to look into are idle restrictions smaller than what comes in that carb, to try and cut back on the pullover thru the idle circuit at high rpms (if there is any there).
Also, another thing I've done that helps if you don't have an anti-pullover squirter is to use a tin "shield" similar to what came in the oem Motorcraft 2bbls over the squirters. It shields the squirter orifices from the low pressure signal.

Hope that helps.

KP

racerman707
Dirt Freak

Total posts: 374
posted June 08, 2004 09:44 AM  
KP.....Sorry to but in but how much would you charge to fix a sorry running 500 holley or should I go with a Motorcraft?

KPLugnut
Dirt Forum Champ
Total posts: 1019
posted June 08, 2004 10:42 AM  
$150 plus shipping

b4racing
Dirt Forum Champ
Total posts: 626
posted June 08, 2004 10:52 AM  
one more thing you can do is lower your fuel pressure a holley only needs 3 lbs of fuel pressure and this should help. BObby

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