Poor throttle response

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kocuda

kocuda

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Portage, WI
Need you guys suggestions.
I have
30 over 440, 12.5 to 1, reworked eddy rpm heads, team G intake, quick fuel 850 carb,2" primary tube headers, 4500 stall converter, 456 gears
solid lifter cam, H&S roller rockers (see cam specs)
Problem engine runs great mid and high range, off idle I have to feather the gas. I want to be able to just nail the pedal and go.
Some of you suggested I need to go to a eddy rpm manifold. I think I'm in agreement with that.
Do I need to change cams as well?

Camshaft.jpg
 
It all sounds like a carb problim.Not enough shot to get her going.Try the 50cc pump you will need to change the pump nozzel and maybe the pump cam.sounds like you have a holly on there.The pump cam will give a longer shot the 50cc will keep it from running out of gas and the nozzel will give it more flow.Sounds like tuning time.Good luck.Kocuda
 
I've tried different pump cams but only on the primary, It is a quick fuel carb, maybe 500cc pumps and bigger nozzels would be the way to go.
Would I go to 50cc on both primary and secondary?
 
Secondary should have a 50cc already. Can you take some cylinder presure readings? What is your timing setup like? That thing should snap.
 
I'm pretty sure secondary is only 30cc, if it was 50 it would be a deeper pump housing right?
 
Yes if it were 50cc then you need the bigger houseing sorry forgot that one.A little tip is cut the rubber out of two houseing gasgets stack them that work for me once until i got the 50cc houseing.Is it going flat when you nail the throttle if so not enought fuel is still my guess.That beast wants more fuel try more tricks to the secondaries.
 
You said this was an off idle problem? Before changing the accel pump, you might try going up 3 sizes on the primary "shooters". Which pump cam are you using and have you verified instantaneous squirt upon cracking the throttle?

My 850 on 440 hesitated bad until I upped the squirter. I did change the pump cam too. Verify that your float levels are dead on.
 
Thanks 70Duster440
Any suggestions on squirter size since I'm going to buy some?
 
Carefully remove the front squirter (without losing the screw or washer :) ) and you'll see a number stamped on it. Add at least 3 to that number. Any less isn't a significant enough change. In theory you would keep going up in size till performance drops or you note black soot from the tail pipe on acceleration - then back off a couple sizes.

If, for some reason, you have to go larger than a 39 (.039") shooter, then you'll need to change the squirter screw to the hollow style.

If your car still has a lean stumble with the biggest cams and the biggest nozzles, you might then try a 50cc pump and the corresponding cam. The black cam is required on 50cc pumps to get the full shot of the 50cc pump.

FYI, the pump cam determines the volume of fuel the accelerator pump delivers (up to 30 or up to 50 cc's per 10 strokes) and the profile of the cam determines how this volume is spread out over the angle of travel.

The nozzles or "shooters" determine the rate of discharge. The smaller the orofice, the longer the shot will be spread out.
 
You need more initial timing.I would say it will probably like close to 20*
 
Can I assume that Quick Fuel is basicly a Holley and all the same principles apply?
 
Always start with timing. It's free, and in your case, needed. I'd go 20° initial, ad I'd bring it in faster than 2200. as a first step. My thoughts on upping the squirtor size... You cannot add fuel volume without it being over a shorter time. So that shot ends earlier in the throttle's travel. I've never had to use a squirtor larger than 31. I tried 35 and 37 on a couple cars. The 37 slowed the 60' down by .03. They come with 28s IIRC. I'd start with the timing, because once you change the timing, the carb will be affected. Carb wont affect timing.
 
Agreed. FWIW, I have a distributor recurved by Don at FBO. Initial's at 16 with total of 34 @ 3400 rpms.
 
Thanks guys, as soon as the snow melts some here in WI. I'll be trying your suggestions, starting with timing.
 
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