Popping up thru carb - Team Camaro Tech
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post #1 of 2 (permalink) Old Apr 21st, 06, 07:06 PM Thread Starter
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Join Date: Apr 2004
Location: yonkers, new york
Posts: 33
Unhappy Popping up thru carb

Aluminum head, solid roller,poly locks, stud girdles, 468 ci, comp 294 cam, Valve lash had not been done fo 5000 miles. car ran great alll along. Started getting popping up thru the carb at about 3500 rpm and then popping thru carb down to 2200 rpm. Did a cold valve lash at .022 like the cam card says. Buttoned it all back up and took it for a ride,, ran like a smooth sewing machine, very strong, took the rpms smoothly up to 3500 rpm, temp got to about 160. Brought it home waited a few minutes, started back up took it for another ride,, temp was about 180, ran smooth for a few row through the gears. Then it started running alittle rough at idle and started
popping up through the carb all over again at abt 2500 rpm????
Can't do a hot valve lash, cranking the engine by hand with all I've got to tear down,,, valve covers, plugs, wiper motor, msd box, fan blades( radiators got to come out), to take the rad out I've got to take out the battery tray!! By then the motor will cool off?? What should I do?
Should it pop through the carb just because the valve setting changes because of the aluminum
heads? or could there be something else wrong in the heads? Doesn't look like a broken spring( or inner spring) that I can see. The plugs do have a little oil on some of them. Compression test showed 190-193 every cylinder.
Ploy locks snap when I break them loose but no snap( crick) when I tighten them??
Can anyone help??

69' SS 396 L78/468 /71' RS/SS 4 spd nev silver/66' SS L78 triple blk chevelle sold

Last edited by dougie fresh; Apr 21st, 06 at 07:08 PM. Reason: wrong mileage
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post #2 of 2 (permalink) Old Apr 26th, 06, 10:22 AM
Senior Tech
Join Date: Oct 2005
Location: Rhode Island
Posts: 1,356
Re: Popping up thru carb

Are you getting good up/down rocker movement? Sometimes cam lobes will wear out, but not as much with roller cam. How about maybe bad rocker arm?

My primary suspects would be:

* cracked cap
* bad wire(s)
* broken valve spring
* poor fuel delivery causing lean condition (clogged filter maybe)
* vacuum leak (intake manifold or hose)


Dave F. in Rhode Island
'68 Camaro SS Accel DFI 454 (SOLD - I'm a boring Corvette owner now)
Bought my first big-block Chevy in 1970
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