bog/stumble - Team Camaro Tech
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post #1 of 4 (permalink) Old Nov 22nd, 05, 10:37 PM Thread Starter
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bog/stumble

I have noticed over the last few day that my engine has devloped a slight hesitation if you stab it into WOT but if you ease into it it takes off like crazy. Also if i just floor it it will bog and sometimes give a little backfire throught the exhaust but then takes off like crazy. I was thinking that it might be a timing issue because sometims when I shut it off it desials alittle bit.. IT just started doing this on its own but this is a new motor with about 1000 miles on it now and it is just starting to get broke in.. Any Ideas?

69 Camaro RS, 383ci,10.5-1 AFR 195's ported, Comp 286HR, 4340 forged Crank & Rods, JE Pistons, RPM Airgap, Holley 750 HP carb, 350 turbo w/ shift kit, 3000 Coan, Be cool, caltracs,12bolt 355 eaton posi..Best E.T. 12.22 @ 112

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post #2 of 4 (permalink) Old Nov 23rd, 05, 05:46 AM
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Dave
 
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Re: bog/stumble

Your sig says you got a Holley 750, so my main suspect would be the accelerator pump circuit. Holley carbs are easy to tweak the pump shot. Look down carb and work the throttle. You should IMMEDIATELY see two strong shots of gas, one into each venturi.

There are typically two check valves, one is a silver ball under the pump diaphragm (held in place by peened-over tabs) and the other looks like a small upside-down rocket located under the pump squirter (removed with a philips driver). Make sure both of those are good. A piece of dirt anywhere in the accelerator pump circuit will cause your symptoms. Also check the pump diaphragm and linkage.

Of course, make sure your tune is good too.

Dave F. in Rhode Island
'68 Camaro SS Accel DFI 454 (SOLD - I'm a boring Corvette owner now)
Bought my first big-block Chevy in 1970
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post #3 of 4 (permalink) Old Nov 23rd, 05, 06:19 AM
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Re: bog/stumble

When you remove the squirter to check the ball, replace the screw with Holley's hollow screw, both pri & sec. squirters. Allows less fuel flow restriction.

I would advance initial timing and turn down curb idle.

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post #4 of 4 (permalink) Old Nov 23rd, 05, 02:28 PM
 
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Re: bog/stumble

I had the same issues with my brand new 383 a few weeks back. I know that my carb needs to be tuned so i was waiting until the motor had 1000 miles on it or so to have some shop put it on the dyno and tune it. Anyway a couple weeks back i changed the timing slightly about 6 degrees initial and now it's like night and day. You may want to check the timing and try tweaking it but definetely have the carb tuned if it hasnt already been tuned.
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