has anyone ever had a problem with the motor backfiring under a load. but it runs great in neutral. i think pushrods are to long. i am going to measure them tonight and see what size i need but i just want to make sure this is the cause.

 

tell us more about your setup! why do you think pushrod?
if the pushrods were too long it wouldn't run right at all, not just under load. I am guessing you just did a rebuild?
either way tell about what you have and what you've done recently to get a better idea how to help you. Otherwise you'll get nothing or more than you wanted to hear!

 

its is a old lloyd elliot set up. i ran this set up on my stock short block for a couple of years, then i wrecked my car and sold the motor to a friend. he then had a shop take my top end and put it on a 355 forged(zero decked) bottom end. well the shop didnt do a very good job and it leaked oil from everywhere and turned out they didnt use thread sealer on the headstuds. so it was leaking coolant from there also. so yes i took the heads off and found they used multi layes steel head gaskets(dont know which brand). and i went back with impala gm headgaskets. other than that i installed a double roller timing chain in place of the stock one the shop put back on. no it idles perfect and revs up fine neutral but in gear under a load it backfires. the reason i think the push rods are to long is because, well the roller rocker tip is sitting on the back part of the valve not the center. they didnt seem to fit like that on my stock bottom end. would the block being zero decked call for a shorter pushrod. also i just put back a stock length pushrod and it still backfires. doesnt seem to be as bad though. please let me know what you think.

 

The incorrect push-rod length is a minor issue, but still needs to be corrected. Too much lifter preload can cause the lifters to "pump-up" and hold the valves open off the seat (don't close completely), resulting in a back-fire.

WD