Torque to Yield Head Bolts

[Kristang]

I replaced a head on my 95 Gt with a P1SC Procharger. I used new head bolts(FelPro)when I re-assembled and followed their torque specs. A short time later I blew the head gasket. I believe the torque spec was 55ft. lbs. and a quarter turn. I am not sure why the gasket let go, I am only pushing 8 lbs. of boost, and the other head is working just fine. When I removed the head from the block, I noticed it didnt take much effort to break them loose. When I removed the original head, it took ALOT more effort to break them. Should I torque them higher, or do something different? Thanks

[1moretoy]

55ft lbs. seems alittle low to me

[Stormwalker]

80 ft lbs for a 302.

[Roast'em]

Did you use use lube on the head bolts when you torqued them down? There are different torque specs for different types of lube. Installing them dry is a bad idea in my opinion, since friction can affect your torque reading.

[Southern]

55 cant be right. Maybe that is the first torque setting to go to, and then you go up to 80 ft lbs? I have never heard of 55 ft lbs???

[Stormwalker]

Almost anything and everything I've read for bolting heads onto a 302 state that the top head bolts should be dipped in motor oil (i.e. 10w-40) and ultimately torqued to 80ft/lbs, and the bottom head bolts should have thread sealer on them and ultimately get torqued to 75ft/lbs.

[Southern]

Almost anything and everything I've read for bolting heads onto a 302 state that the top head bolts should be dipped in motor oil (i.e. 10w-40) and ultimately torqued to 80ft/lbs, and the bottom head bolts should have thread sealer on them and ultimately get torqued to 75ft/lbs.

You are correct. Not sure where 55 came from?

[LES]

That is if you still have 3/8" head bolts. MY 1/2" studs are 80# lower and 90# upper. And that is for studs with nuts not bolts , so I will shut up now as it doesnt apply .. As you were.

[Kristang]

Thanks for the information. I have always torqued my small block ford bolts to 80 lbs., that is why I thought it unusual that the FELPRO instructions say 55 lbs. That is probably why it let go. Thanks!

[RustyLX]

So you've poped the same headgasket twice. I would have that head check to see if it's still flat.

[Chrm97PI]

also see if the block is flat, and you dont want to soak the head bolts, u just need to spray em with a lil lube, if you lube them too much it will throw your torque specs off

[onewickedstang]

That is if you still have 3/8" head bolts. MY 1/2" studs are 80# lower and 90# upper. And that is for studs with nuts not bolts , so I will shut up now as it doesnt apply .. As you were.

not that it matters to this post, but Edelbrock recommended dropping 10# when using the 1/2" studs due to the extra clamping force provided by the studs and fine threads. when my motor was assembled the shop that did the assmebly tightened them to the 105# that fel-pro had listed on the install sheet for the gaskets. they ended up cracking the water jacket on both heads near the lower studs. they did however take credit for the mistake and pay to have them welded.

[LES]

not that it matters to this post, but Edelbrock recommended dropping 10# when using the 1/2" studs due to the extra clamping force provided by the studs and fine threads. when my motor was assembled the shop that did the assmebly tightened them to the 105# that fel-pro had listed on the install sheet for the gaskets. they ended up cracking the water jacket on both heads near the lower studs. they did however take credit for the mistake and pay to have them welded.

I hear what you are saying ,but will be quick to point out 2 things

1) 105# is 15% more then 90# And is incredible THAT ANY ENGINE BUILDER WOULD DO THAT!

2) My TFS TW heads are ALOT thicker thne Edelbrock.


But I do hear what you are saying.

[mustang cobra93]

You are correct. Not sure where 55 came from?

On a torque-to-yield head bolt I believe he is correct, 55 ft. lbs. i believe and a 1/4 to a 1/2 turn, but he should dip those bolts in oil at least, or use a moly-lube on the underside of the head bolt to get the correct #'s. Personally i would go buy ARP head bolts and go 75 ft. lbs. lower(thread sealer also) & 80 ft. lbs. uppers and ditch the torque-to-yield bolts!!! Still use the moly-lube on the underside of the bolts.....7/16th of an inch bolts BTW.

Torque-to-yield head bolts are factory type replacements and are supposed to stretch when torqued, unlike ARP bolts or studs.....

[Kristang]

I put the head back on tonight. Thanks for all the opinions and advisement! I ended up torqing them to 70#. When I took the head off it was obvious the gasket let go on the top edge near the lifter valley and the water escaped there. There were 3 definitive areas leading from the water jacket holes in the gasket right up to the lifter valley. Hopefully the 70# torque wont be an issue.

Thanks again!