Need some advice for a car that seems to stumble under heavy acceleration (this only appears once the engine has been running and warmed up). The issue is new this year after the car sat in storage for over a year.
It will idle fine and runs ok for the first 20 minutes or so, but once warm, the car seems to stumble and misfire under heavy acceleration. This persists for a few seconds then smooths out, regardless of whether I keep accelerating or feather the gas. It does not happen under light acceleration, nor when revving the engine in neutral. So far Iāve checked the following:
Drained and refilled fuel tank with fresh fuel and seafoam fuel treatment. Installed inline fuel filter
I confess I am not as familiar with Edelbrock carbs, so I canāt tell you precisely how to fix this, but it sounds like an issue with the accelerator pump.
The pumpās purpose is to enrich the mix when you step on the gas, and dump a bunch of extra air in. When youāre in Neutral and rev, the amount of fuel required is trivial, as the time it takes to rev and start drawing enough fuel out of the boosters is also trivial. You donāt notice hesitation.
But at full throttle under acceleration, you get the āsquirtā - throttle still wide open, flow is still low, and not able to draw enough fuel yet. Because the engine cannot quickly get to higher RPMs where thereās enough flow to draw fuel effectively (unlike a Neutral rev), you get a stumble/bog when the squirter is empty, and the mix gets lean. Slowly, the fuel/air mix catch up with each other from the boosters and the car accelerates at a more normal pace.
You may need to raise your floats so the carb can draw fuel easier? Or find some way to achieve āmore squirtā. With Holleys, they have different sizes of squirters, so you can just add a slightly bigger reservoir to deal with this kind of problem.
Hopefully someone more knowledgeable about the Eddies/Carters will chime in!
It sounds like the engine isnāt getting the timing advanced when it should-Check the action on the vacuum advance at the distributor. Make sure the diaphragm hasnāt become solid, and the plates are still movingā¦Unless you have a non vacuum advance distributor. Also, along the same lines check and make sure both ends of the vacuum line from the distributor to the carb arenāt split. For some reason fuel vapors are a lot more damaging than they used to be, or at least so it seemsā¦
I donāt have any suggestions but just a question/comment; how does the symptom that is, this only happens after 20 min warm up, how to explain that? Iām assuming he can start it up, back out of the drive and mash the pedalā¦ and it accelerates without hesitation. But 20 min later mash the pedal and this problemā¦ ?
I will have to double check what the timing is set at, as I had a family member assist me with that previously. Fairly certain its around 10-12 degrees.
The car has a Petronix ignitor 1. It was running a stock coil when these issues began (Iāve since replaced it with a 1.5 ohm flamethrower).
With no insult intended here at all, if you are not SURE what your timing is, this is a very good place to start. Verify TDC on your #1 piston too, to make sure the weight ring on your damper hasnāt slipped. They get brittle, fail, move around, and then you have no idea what your timingās actually at.
Once you verify TDC, set your initial timing, then rev the engine to see where it stops advancing.
Most of these stock engines seem to like about 10-12 degrees initial, with around 34-36 degrees of timing āall inā by 2900 or so.
Once you have it set, you can reconnect your vacuum advance, and go take some test drives! Ideally, youād get your car nice and warm, then go drive uphill into the wind and listen for ping. If youāre getting any signs of detonation, back it off a degree or two and repeat. When you find the very edge of what your car likes, back it off a tiny fraction if you can (to account for varying temps and fuel quality) and you should be good to go.