Re: holley tuning advice
[Re: ohiodemon]
#440148
08/16/09 06:46 PM
08/16/09 06:46 PM
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Joined: Mar 2005
Posts: 1,373 Rancho Cucamonga, CA
D_C
pro stock
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pro stock
Joined: Mar 2005
Posts: 1,373
Rancho Cucamonga, CA
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Agree with above. Stumble at Cruise sounds like Float level induced fuel starvation or problem with secondaries. Stumble off start or acceleration from cruise is the Accelerator-Pump circuit (or sometimes, secondaries coming in too soon or late.) This from Holley.com: Quote:
ANSWER: The most common cause of a stumble is not having an adequate accelerator pump shot. The first thing to do is to look at the discharge nozzle and make sure you are getting a good strong pump shot. If not then you need to inspect the pump diaphram for a hole or tear. You will also need to make sure that the pump passage is clear from any trash or debris.
First you will need to check the adjustment on the pump. To do this you will open the throttle all the way (WOT). Push the pump arm lever down and then adjust the pump override spring to obtain .015" clearance between the pump arm and lever.
If you are having a stumble and no black smoke out the tailpipe then you will need to increase the shooter size. If it stumbles and you are getting black smoke from the tailpipe then it will be necessary to decrease the shooter size.
Final fuel-level setting is made at operating temperature, engine running, sight-plug out, by adjusting the needle-seat / float height with the adjusting-nut / screw.
Holley has a good Tech Section, lots of easily understood topics, plus "Holley TV" and you can view videos from Holley on YouTube.
Holley Tech Section
Choosing the best/correct Power-Valve for your engine, plus cracking the secondary throttle plates open a bit (secondary idle set-screw) often helps get Idle speed down to "Normal" range (like 700 - 800 RPM) even with a moderately big camshaft.
Getting the Accelerator-Pump circuit (Squirter Size, Pump-Cam, Lever-Adjusted) helps with instantaneous throttle-response (no Bog from a stop or sudden acceleration.)
Invest some time in the Holley website. Doesn't take all that long to learn a lot.
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Re: holley tuning advice
[Re: b body dreams]
#440151
08/16/09 07:54 PM
08/16/09 07:54 PM
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Joined: Mar 2005
Posts: 1,373 Rancho Cucamonga, CA
D_C
pro stock
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pro stock
Joined: Mar 2005
Posts: 1,373
Rancho Cucamonga, CA
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Yes, there is a 50 cc upgrade kit. It includes a deeper pump housing, deeper diaphragm, taller spring, larger pump-lever and pump cam. Holley 50 cc Pump There is a point (squirter-size) at which this upgrade is recommended by Holley. I have 50 cc pumps on my 850 CFM Dual-Feed, Double-Pump Holley List# 4781-2.
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Re: holley tuning advice
[Re: mopars4ever]
#440153
08/16/09 08:34 PM
08/16/09 08:34 PM
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Joined: Nov 2004
Posts: 2,495 Oregon City, OR
Baxter61
top fuel
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top fuel
Joined: Nov 2004
Posts: 2,495
Oregon City, OR
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Quote:
I just went thru a similar problem. Maybe this will help you with yours. First thing I did was make sure the timing was good.
This is where I would start.
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Re: holley tuning advice
[Re: mopars4ever]
#440154
08/16/09 08:35 PM
08/16/09 08:35 PM
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Joined: Mar 2005
Posts: 1,373 Rancho Cucamonga, CA
D_C
pro stock
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pro stock
Joined: Mar 2005
Posts: 1,373
Rancho Cucamonga, CA
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with mopars4ever, Adding a 50 cc pump may be unnecessary, waste fuel and hinder rather than help performance. IIRC, it is not needed or required until you use either it was #31 or #36 size squirters. Something on that order. That, and the hollow squirter-screws. Excessively rich (too much fuel) can hurt performance as can excessively lean.
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