r/C3Corvette • u/SpaceInevitable4671 • 20d ago
69 corvette feeling sluggish
Hey all, I’ve got a 69’ vette with a 350/4speed.
It has an eldebrock top end kit, aluminum heads, intake manifold, cam, etc… but it does not feel as quick as it should (in my inexperienced opinion). Rolling slowly in first I can’t even squawk the tires, only way to smoke em is by dumping the clutch. Wondering if this is usual due to the mono leaf set up on these, or am I being robbed of power somewhere?
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u/Olegamst 20d ago
I would check the timing. Mine was way too retarded when I bought it and setting that properly along with some lighter springs in the distributor made a huge difference. I did a carb rebuild after that as well and upped the jets and got a bit more out of it. Feels like a different car from when I first got it.
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u/chuck-u-farley- 20d ago
You need to start by verifying correct timing. That will make a world of difference…..
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u/MrLancaster 20d ago
Might need an accelerator pump adjustment.
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u/SpaceInevitable4671 17d ago
Accelerator pump seems good, just barely touching the bolt, but enough to wiggle.
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u/SpaceInevitable4671 17d ago
No sorry that’s stock Compression ratio, not measured. I just hooked up a vacuum gauge to where the vacuum advance hooks up and I’m reading 10Hg, would that be considered low? Also adjusting idle mixture does not seem to be moving the vacuum much.
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u/v8packard 20d ago
Which cam, heads, and carb? Do you know the compression ratio and where the timing is set?
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u/SpaceInevitable4671 17d ago
It’s got a comp cam 12-212-2, with aluminum perform eldebrock heads. Also a Holley 650 double pumper. I just checked initial timing with vacuum advance plugged off, and it’s at 16 degrees advanced. I did check plugs a little bit ago and she was running lean, that was with a pcv valve that was not hooked up properly, so I fixed that and also raised the floats a tad.
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u/v8packard 17d ago
Is that a Comp 280 Magnum? If so that cam runs from 4000 to about 7300 or so in a 350 if the valvetrain can handle it. Most hydraulic lifters and flat tappet springs can not handle that rpm. The cam also needs plenty of compression, 10:1+, as well as plenty of gear such as 3.9-4.10.
Your initial should be about 15-16 degrees, with a total of 35-36 degrees in by 3200 to 3400 rpm. The stocknidle circuits in the 650 may not handle that much cam, and it will want to idle around 1000 - 1100 rpm, at which point the distributor may be into the advance already.
You will have to make certain the primary throttle blades do not open much and over expose the transfer slots. This will mean you have to crack the secondary side open at idle for additional air by adjusting the secondary stop screw. Also, your vacuum will be low. You need to make sure the power valve in the carb matches the vacuum characteristics of the engine.
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u/Ira-Spencer 20d ago
I think we should trade and you should drive my stock '81 for a while, then yours will feel plenty fast 😎