Vehicle is a 98 camaro ls1 automatic. Mostly stock, headers back exhaust slp intake. we bought a comp cams camshaft and the matching pushrods and valve springs.
Cam Info:
224/224 duration .563 lift with a 112LSa. Very Mild
Problem, at idle when first started it will missfire, and thats all. But, as it warms up, it will begin to backfire badly. the backfire is consistent with the miss at cold idle. hit the gas and it bogs right out. Been working on this a while now, has 6 people totally confused right now.
No visible damage to cam or components. Timing set, coil packs are in right. video available from you tube, i will try to attach it.
any help is greatly appreciated.
-chris
Thanks in advance
The sound quality in the video is fairly poor so it is not helping me much unfortunately. I will say from what I could hear it sounds like maybe it is firing will there is still an exhaust valve open. Have you done a compressiont test or leak down test? Do you know how much preload you are getting in the lifters? Do you know what part number pushrods you ordered?
__________________
Aaron Mick
Comp Performance Group
Technical Consultant
The engine backfires through # 3 carb venturi at an idle and continues backfiring while the engine is reved up. Putting a load on the engine by driving it causes the engine to run really poorly. I initially thought that this indicated an ignition problem due to the noticable deteriation in firing under load. I have read quite a bit about Type 4 lifter and cam problems. I had assumed that if a lifter was losing its face, the valve lash would be increasing. I have checked the valves several times and I have only reduced the clearence in # 3 Intake and exhaust by 1 or 2 thousanths total.
Cam Problem Massive backfire 
Linear Mode
