Quote:
Originally Posted by Joey Soul
So I'm more of a over head cam guy, first time putting together a pushrod engine. I recently rebuilt my engine with forged pistons and a BTR 225, Caddie race lifters and btr valve train. Non-decked head and stock head gasket I assumed to stay with the 7.850 rods. On start up engine ran like crap, I went back into it and noticed it was hanging the valve open a bit. Talked to btr and they recommended going 7.80s with ls7 style lifters in the lt1. I went ahead and measured the valvetrain at 7.750 and zero lash and the race lifters call for .05-.1 preload which lands me back at 7.80s. So here is the problem, I run the rockers down by hand until they stop with the 7.80s, then Torque them to 22lb which is abot 3\4t turns and its still pushing the valve down by just a bit which is hanging it open even on the heel of the cam.  So the question is what am I doing wrong? The lifters don't seem to take any of the preload. |
If your camshaft/lifter is not on base circle (when the roller is not on the cam lobe), then it will open the valve based on where its at. You need to check on a cylinder that is set to base circle to accurately measure pushrod length.
Once you verify you are at base circle, take your pushrod measurement at 0 lash (rocker should be stocked down by hand, with the ability to move the rocker side to side, but not up and down. Add .075 to that number and round to the nearest size.
If you are at base circle already, and it is still hanging a valve open, you are unfortunately not measuring correctly, or there is something fluky going on.