Engine is my newly rebuilt 454, 4bolt, GMPP Sig Series Aluminum healds, HD stock type rockers, Stealth 8019 intake, Holley 3310, stock GM dist, Mallory coil. CompCams XE-282-S straight up, M-77 oil pump.

I've got a miss starting @2500rpm's and only when in gear. At idle and increasing the rpm's----no problem. Only under load. Plugs and plug wires are new as is fuel pump and filter. Only pieces not new are the dist cap & rotor.

I've got timing @14degBTDC--reduced from 18, vac = 21, oil pressure =35, temp 190, valve lash @0.022 as per CompCam'c.

idle ~850rpm's, dwell 30. I'm gonna swap carbs today to a 4150.


Here's a sound clip at idle(was about 900 for this video) and reving thru ~4,500rpm---no miss. Yeah, it's a Vette but I know how much you guys like a little diversity. :D Reving to 4,500rpm. (http://65corvette.nonethewiser.net/posts/sounds/BB%20idling%20@900%20reving%20to%204%20500.mpg)

Typically characteristic of a vacuum leak, as it leans out under load. Check it out when you swap carbs. Pull the PCV out of the valve cover, and see if there is any suction on the breather side, as this would indicate an intake not sealing internally.

Thanks.

I switched carbs and the stumble is gone.

You could probably increase the primary jets by a step or two and the stumble would be gone. Your symptom is showing lean on transistion.

Originally posted by d1_bradley:
You could probably increase the primary jets by a step or two and the stumble would be gone. Your symptom is showing lean on transistion. The carb I switched to is a 4150 with all 82 jets. I think it's running rich now.

850? For sure I'd try and back down the primary to 78-79. Also, if idle vacuum is acceptable, while you do that, might wnat to put a quicker opening power valve in, such as 85, 95, or even 105. It usually compensates the leaner cruise setting well for part throttle.

Likely you could have had a vacuum leak or the other carb was very poorly calibrated. Anyway, glad its solved.

Originally posted by 427L88:
850? For sure I'd try and back down the primary to 78-79. Also, if idle vacuum is acceptable, while you do that, might wnat to put a quicker opening power valve in, such as 85, 95, or even 105. It usually compensates the leaner cruise setting well for part throttle.

Likely you could have had a vacuum leak or the other carb was very poorly calibrated. Anyway, glad its solved. Thanks Gene. It's a 1000+cfm.

I know how you corvette people are, graemlins/clonk.gif but come on now. This is 2004. Lets try and get a electronic dist. in that thing. ;) AKA...GreatWhite Shark

Very Very Nice Vette! :D

Originally posted by Fathom Chevelle:
I know how you corvette people are, graemlins/clonk.gif but come on now. This is 2004. Lets try and get a electronic dist. in that thing. ;) AKA...GreatWhite Shark I'm accepting donations. ;)