Dead Lifters and Cylinders
We had an interesting issue with Cadillac Northstar heads. We did a normal blast, dye check, valve job, stem height adjustment, and surface as requested. We also did our normal vacuum test before sending the heads back. We were then surprised when the repair shop tech called and told us that our valve work was incompetent. It seems that they had a few cylinders misfiring and blamed us. He said a leak down test was performed and our valve job was indeed “junk.” Since most of the misfiring cylinders were near the back of the engine, we suggested loosening the cams and replacing the lifters that could be gotten to easily. Some of the misfire coded cylinders changed position. OK, it’s probably not our fault, but what was it? Some of the “name brand” lifters had less chamfer on the bottom than the original factory lifters. The problem was that some of the lifter bores in the heads had more of a bottom chamfer than others and because of that, some of the lifters were sitting up on the bore and not fully seating on the bottom. This was holding some of the valves open and causing the misfire. Solution? We chucked up all of the lifters in our valve grinder and ground a larger chamfer on the bottom using the side of the wheel. You could probably do this on a bench grinder. We put blue layout fluid on the lifters before installation and spun them in the head to verify they were indeed fully seated. Problem solved. There are more engines out there with “dead” lifters, and we now check them all.

Timm Jurincie
Tuf-Enuf Auto & Marine Performance
Avondale, AZ
July, 2015