MY UNCLE HAS A 1974 LS4 454 THAT BOGGS DOWN WHEN FIRST STARTING OUT FROM 0 MILES TO 15 MPH. HE HAS A 3/4" CAM STOCK PISTONS, STOCK HEADS, A NEW HOLLY CARB AND HOLLY MANIFOLD ALSO HE GOT A NEW DISTRIBUTOR (POINTS)ALSO IT HAS 411 GEARS AND A 4SPEED TRANNY. IT HAS ABOUT 2000 MILES ON THE ENGINE. IT WAS ALSO GIVIN A COMPLETE TUNE UP AND THAT DID'NT SOLVE IT. IT IS NEVER RACED OR EVEN FLOORED. ANY IDEAS WHAT THE BOGGING COULD BE? THANKS IN ADVANCE.
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Re: 1974 454 BOGGING DOWN WHEN FIRST PULLING OUT
I FORGOT TO SAY THAT IT HAS BEEN RECENTLY DOING THIS. IT WAS NOT LIKE THIS BEFORE. -
Re: 1974 454 BOGGING DOWN WHEN FIRST PULLING OUT
If this is both a hot/cold engine situation, I'd start by checking for vac leaks.... Remove air cleaner and carefully/selectively spritz carb cleaner around the base of carb corners of intake--most any place where you could be losing intake vac under accel. You're looking for the engine's idle to jump 100-200 RPM in response to the extra fuel sucked in by the source of the vac leak. Be careful not to get carb cleaner into the carb's airhorn, not to spritz too much cleaner at one time to artficially enrichen all the underhood air or you'll create a false diagnostic.
If she's tight/sound all around, it's probably time to question the integrity of the Q-Jet--it's idle mixture and 'shooter' operation.
If the problem is only during intial start and cold drive away, that's another story altogether. The 'usual suspects' are choke setting, pull off operation and/or choke stove operation.Comment
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Re: 1974 454 BOGGING DOWN WHEN FIRST PULLING OUT
I would suspect the Holley carb's power valve from the information you have given. If the Holley valve is not working as designed, and when you start out the carb's accelerator pump is pumping extra fuel which really richens the mixture. I am no Holley carb expert but I have used Holley carb's for about 20 years and have replaced a fair amount of power valves. Replacing a power valve is really pretty easy and not very expensive if you do it yourself.Comment
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Tweren't no Holleys in '74--all Q-Jet.... *NM*
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Re: Tweren't no Holleys in '74--all Q-Jet....
Jack I know there were not any factory Holley's on Corvettes in 74. Eric first post says the 74 has a new Holley carb and Holley intake.Comment
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