HT4100 4.1, 4.5, 4.9 Discussion, Question when torquing headbolts 4.9L in Cadillac Engine Technical Discussion; My dad's Cadillac (92 DeVille) was leaking antifreeze into the exhaust, so we checked to see if the overflow was ...
My dad's Cadillac (92 DeVille) was leaking antifreeze into the exhaust, so we checked to see if the overflow was bubbling. You guessed it, bubbles.
So we pull the top of the motor, pull the head gaskets, and you can see where the antifreeze was leaking past the head gasket. New gaskets and we start to button up the top end. #1 headbolt end up spinning and pulls the threads out. Heli-coil does no good. So we find another 4.9L from a parts recycler. Pulled the top end to make sure everything was peachy (including the heads), now we are putting it back together. We have the head bolts tightened to 68 lbs, but my brother doesn't want to go to 90 in fear of stripping the threads in this motor.
Are we asking for trouble if we don't go to 90 lbs on the top 3? He said he read somewhere in the Haynes manual about threads being stripped out with 75 lbs of torque pressure in these motors.
Automobile(s): Cadillac 78 Seville, 78 Coupe de Ville, 92 Sedan de Ville
Re: Question when torquing headbolts 4.9L
Dude, you need to do some reading up on that by searching the archives here. From what I have heard, whenever you take the heads off a 4.9 you need to put helicoils in the block. I always said if the head gaskets went in mine that I would buy another engine and put it in without touching the heads. I think I would take my chances with 75 ft/lbs because I think they are almost guaranteed to strip and 75 is adequate for old chevy V8's. Good luck.
The head bolt torque sequence in graduated levels of foot pounds is essential on the 4.x series mixed metal engines. You should always use new GM head bolts. I think the time-sert kits are only required for Northstars, but ask. You'll save a lot of headaches buy purchasing a GM factory shop manual, or maybe somebody can post the 4.9's torque pattern chart for you here.