# Backfire through carb & cold exhaust



## The Patchwork Tiger (Apr 8, 2009)

Hello group,

Just installed a new set of stamped rocker arms. Set also includes the fulcrum ball and retainer nut. Since there is no formal rocker arm "adjustment" for Pontiac, The retainer nuts are brought to the base of the stud then backed off a 1/4 turn. A few nuts were able to be loosened by finger at this, so they were tightened to base. Top end is oiling fair to good.

OBSERVATION
Engine starts fine but now idles rough.

Next, listening to the exhaust pressure which "sounds" off. I feel both sides of the pipes, driver side is hot, passenger side is cool. . . . . .? 

DRIVING
Backfiring quite a bit upon throttle.

Anyone have thoughts on this? All was running strong until now. Reason for new components was to quiet excessive top end chatter.

Thank you for your insight,
Alex


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## GTO JUDGE (May 14, 2005)

How's the timing and dwell? How are the idle mixture screws set in conjunction with the proper air gas mixture? All this could have changed with work on motor. I know mine did and it all had to be reset and dialed in.


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## Mr. P-Body (Jan 20, 2011)

What rockers? Brand name, please.

"Stock" Pontiac rockers are torqued to 20 lb. ft. If the new rockes are made to stock specs, that should "work", assuming a stock (or at least stock base circle) camshaft. 

It sounds, based on your description, some of the intakes are too "tight". 

Still have stock exhaust system? If so, many have a "flapper valve" in the right-side (passenger) exhaust manifold that has a bi-metallic spring, holding it "closed" for warm up, forcing all the exhaust across the intake to the driver's side. This would explain the difference in "sides" and temps. If it's still "cold" after warm-up, there may be a restriction or collapsed pipe. I doubt the two issues are directly related.

Jim


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