Originally Posted by hotboy454
hello, I have a sbc 400 that i had rebuild 2 years ago it sat in a project now that I'm building a 468bbc for. I took the motor out and put it in my 73 c-10. This motor had 0 miles on it. far as i took it was around the block Since it been in my truck. I started to drive it to iron out all the bugs one day it backfired through the carb. then started sputtering upon acceleration idling it does fine but runs rich. I cant seem to get idel dialed in without it shutting off. 1100 rpm its where its comfortable at in gear 400rpm something weird there.
Hopefully it IS the timing
The cam has to be broken in correctly or it can fail. If a lobe has worn off (along w/the bottom of the lifter in most cases), it can act how you are describing.
So, did you use cam break in lube on the lifters and lobes as well as break in oil or oil additive like ZDDPlus? At least 2000 rpm w/NO IDLING for the first 15-20 minutes? Details here
If you suspect this may be the problem you can measure the lift at the retainer. Sometimes it can be seen by just removing the valve cover and checking for excessive looseness of the rockers. This is often (but not always
) accompanied by a loud or ticking valve train, and it tends to not hold the lifter adjustment- it will keep loosening up on you.