Head bolt replacement.

[534BC]

Why is it recommended to replace head bolts on the 3.4 venture when doing head gaskets?

In fact does anyone know why it's recommended exactly to replace the intake bolts too?

Does the deck or head surface need resurfaced frequently when doing the head gasket?

I guess another way of asking is to ask what makes the gaskets fail commonly.

I did the intake and conclude that it was loose bolts, but the head bolts were tight.

Thanks for ideas,answers.

[534BC]

I forgot another question about head gasket.

Do we want them to move/slide or is it best to keep them sealed in between the aluminum and iron surfaces.

[merc81]

Head bolts are no longer designed as solid fasteners. Instead they are intended to stretch a bit when in use so that the tension they apply between the block and the head remains fairly constant despite different expansion rates of block and head. They are tightened to spec, then turned an additional amount given in degrees so that the bolt is stretched beyond its first clamping pressure.
You can't or shouldn't rely on a bolt that's been in constant stress under heating and cooling conditions to be removed and then used again. The metal is not the same as a new bolt. Bolts cost almost nothing compared to the damage a bad bolt would cause--toss 'em out and use new.

As to head gaskets sliding about--it can't happen. There are guide pins the gasket fit over very snugly--no motion is possible, and the gasket has a metal center layer which precludes any movement throughout the entire gasket.

[534BC]

Thanks, bolts are ordered along with gasket set and parts. I still can't quite figure out why the gasket leak.

[534BC]

Head gasket job just got done (122,000) and pistons and bores looked good so we did a valve job soda blasted stuff and resurfaced heads too.

Used fel-pro severe duty gaskets (?) and all fel-pro bolts. Went pretty well. About $600 plus labor.

Which anti-freeze shall I use? there's some universal stuff nowadays I think.

green glycol, red/orange dexcool, universal from napa?

[merc81]

Originally Posted by 534BC

Head gasket job just got done (122,000) and pistons and bores looked good so we did a valve job soda blasted stuff and resurfaced heads too.

Used fel-pro severe duty gaskets (?) and all fel-pro bolts. Went pretty well. About $600 plus labor.

Which anti-freeze shall I use? there's some universal stuff nowadays I think.

green glycol, red/orange dexcool, universal from napa?

I went with Canary from walmart - - cheap cheap green.

[534BC]

Thank you. There sure is a lot of info on green/red,ect.

It seems the most important thing is to not mix them. We used to buy by the drum, it doesn't sem that easy anymore.

I think I'll try to get some fluch and some universal AF so all my vehicles can use it.

[534BC]

Originally Posted by 534BC

Why is it recommended to replace head bolts on the 3.4 venture when doing head gaskets?

In fact does anyone know why it's recommended exactly to replace the intake bolts too?

Does the deck or head surface need resurfaced frequently when doing the head gasket?

I guess another way of asking is to ask what makes the gaskets fail commonly.

I did the intake and conclude that it was loose bolts, but the head bolts were tight.

Thanks for ideas,answers.

Here's my guess after doing this job and seeing how stuff is made. The head gaskets fail because of weak bolts and going UP one grade of bolt may help tremendously. That is in addition to the gasket sliding during heat cycling. Some lube may help them on the top surface. The block deck is very weak/thin and gets wavy/warped especially at the ends right around the cyclinder. There's no strength between deck surface and bore , but the gasket is right on the money for size (sealing at top or cylinder where it ought to)
A re-tourque of bolts may help them from leaking (like we did in old days) I found one bolt was looser than the rest where the gasket was leaking. The intake bolts are fine, just need loctited and/or retork may help them as well. To do it right perhaps the intake bolts can be removed one at a time and re-loctited.

I wish I had more time to experiment and document differign techniques, I'd do many things differently and see how each one went.