Alright. Here's the deal. I just rebuild the motor. buttom block is GE 83.5mm sleeved (oringed and blah blah blah) w/ JE 9:1 pistons and eagle rods. Top was off a race car that only ran once on the dyno (pratically new). During the dyno run...the radiator fluid kicked back to the canister when its under boost (7psi). It has no signs of overheating, compression's good (170 all across), and good vacuum. Ralphy said that it's building up boost in the water jacket under boost. Does anyone ever encounter this problem before?

Jeff-

 

When you do the compression test, the motor's not running, correct? So is it possible the headgasket only leaks under boost like when on the dyno?

 

You may be lifting the head slightly in boost. Check the torque on your headstuds to make sure they haven't backed off any.

 

Maybe the head was only on a race car on a dyno once for a reason

Did you bother checking to see if it was flat before you built the motor?

 

Id say maybe yer head is lifting under boost also, just my $0.02

 

Your head is def. lifting in boost. I had the exact same problem when my arp studs came loose. The coolant would shoot out of the overflow tank.

 

under boost and the radiator fluid goes into the revesouir sounds like a headgasket or your head lifted...Either, or, will cause that problem

 

well, we thought it was the headgasket that's why we replaced it w/ OEM headgasket from golden eagle. So you think the head's lifted huh? gonna have to look into that tomorrow to see if it needs to retorque.

thanks fo rthe help guys. we'll see what's up tomorrow!

Jeff-

 

hahahaha..it was checked by a machine shop along w/ my short block to make sure it's flush

Jeff-

 

i have arp head studs as well. gonna ask ralphy tomorrow to see if they can retorque it

Jeff-