Engine Bogging at full throttle

RAREBIRD

MEMBER
PONTIAC FIREBIRD

1978 Trans Am, Rebuilt engine and carb. New fuel pump, wires ohm out great, dist cap and rotor sufficent, timing on the mark as well as plug gap.
At full throttle enging stumbles as if low on fuel. Let of the throttle it regains untill RPM range is met again. RPM is about 4500. Fuel float actually slightly jigher than spec.

4 Replies

MERLIN2021

MECHANIC
17,250 POSTS

Check the secondaries. Butterfly opening and fuel being pumped at full throttle? Also on the back of the carb, if it's a Rochester, pull the vacuum hose off the back and push a piece of wire in thers to clean out any carbon!

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Thursday, November 8th, 2007 AT 3:41 PM

MERLIN2021

MECHANIC
17,250 POSTS

What type carb? Rochester or holley? Check carb baseplate, if you have a dwellmeter, check dwell, raise RPM to 2000-3000 and dwell should not change, if it does, distributor is bad.I still think it's the carb tho! New filter in that carb?

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Friday, November 9th, 2007 AT 2:31 AM

RAREBIRD

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2 POSTS

Rochester Quadrajet 800cfm, new fuel filter and pump, less than 1200 miles on complete overhaul on engine and carb, No dwell capability in a HEI. Timing set at 18*BTDC, cam timing straight up, manifold vaccum 17psi. Fuel pressure 18 psi.

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Friday, November 9th, 2007 AT 5:45 PM

MERLIN2021

MECHANIC
17,250 POSTS

If you have a dwell meter with battery hook-up, and third clip, you can read the dwell! Hook third to tack. Read dwell.I know it's a carb or timing issue! Advance timming till it pings, then back off a wee bit.

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Friday, November 9th, 2007 AT 6:50 PM