so i did my head swap not too long ago, about 3 weeks, and i noticed about 3 days ago, my coolant started to dissapear...where you may ask...IN TO THE CRANK CASE! I checked my oil, and instead of oil, i got milk. i thought to myself, where did i go wrong, and it was the MITCHEL ON DEMAND 5 computer repair/estimation program. it gave me the correct sequence for torquing head bolts, but it said to have them at 42 ft lbs....when today i found they should be at 70 ft lbs!! just letting others to be wary of what info they use, so they dont have to do a job twice, especially head gaskets.

 

this is when a haynes manual is pure gold, gives all proper torque specs

 

I gave him the spec from the factory service manual.

FSM > Holy book Haynes

 

My GM book says 40lbs, plus 1/4 turn. Plus has the pattern in which your to tighten it.

6a2-19

 

could be a miss print. sometimes they say go up to like 40 then step up to the next level so the bolts stretch right. Then recheck after 100 miles if your smart and reusing old hardware/ studs, bolts nuts.........

[bolts studs n what not do stretch some, its meant to. Makes it hold torque better. Some of the real fancy brands can only be used once. When the stretch is gone, it wont hold as well. ]


Haynes says

Head Bolts

2.8 70ft lbs

3.1
Step 1 40ft lbs
Step 2 tighten an adtional 90* degrees

Intake to heads

2.8 23ft lbs

3.1 19ft lbs



Both of those being off would lend to the use of a different head gasket, thicker, thinner, steel, copper, paper....... dunno which but only reason I can think of for different specs like that.

on some engine they run them very thick, some thin as paper.

 

Please say that you used NEW Head Bolts...

 

The head bolts on these engines are re-usable. No requirement to use new ones.


redbird8628, if you haven't torn it down yet, try torquing the head bolts to spec. If the head gaskets aren't damaged it will probably seal back up.

RBob.

 

I reused my head bolts and had no problems. Torqued to specs then went up another 4 ft lbs. so I don't have to retorque.

 

RBob, are you sure? I could've sworn i read in my GM service manual that the head bolts stretch and must be replaced. Or is this another 3.4 thing that's different than the 2.8? But, I still don't think I'd reuse head bolts (unless it was 5 am and no place was open)...

On that 2.8/2.8 swap I helped with, when the guy was putting the heads back on, some of the bolts wouldn't thread into the holes. He started to force them but I stopped him! I had kept some head bolts at my house from a junkyard trip and brought 'em over... we'd spin each one by hand into the block- if it went all the way in, we'd use it. We found quite a few that had stretched and would've stripped the block if we forced it. Those got thrown out.. and the ones that "did" screw in easily got checked in another head bolt hole as a double-check.

In fact... there was a guy on here once, he had a Fiero... he stripped his block out by reusing the old head bolts... I think it was 82T/A (username)?

 

I know the 2.8's use stretch bolts, I'm assuming 3.4's use stretch bolts also. The ez way to know, is when torquing the bolts does it require a 1/4 turn more (as the 2.8's do). If it does then they are stretch bolts and should be replaced. Can you re-use them of course, will you get a proper torque, NO. That's why they sell a head bolt kit...

 

Re-used head bolts here my 3.4, and re-used twice on a friends 2.5 s10.

 

Yes it's recomended to use new head bolts, as some of us have done, we've re-used teh head bolts. I try to only re-use them once.

I re-used head bolts on my turbo 3.2L and it ran fine for 20000 KMs, and when I pulled the heads (upgrading to 3400 top end from 3100), the surface was perfect, no sign of anywhere that a leak or seap would have started.

 

If you can afford it, change em.
You just gotta weigh the risks right.

Sometimes your the bug, sometimes your the windshield.

 

The '92 GM service manual states that 'fasteners that are not reused, and those requiring thread locking compound will be called out.' The head bolts are not called out as 'non-reusable' items.

In the 3.1 head R&R guide the only call out on the head bolts is to apply a thread sealing compound. There is also a notice that the bolt and block threads need to be clean. This is to avoid an improper torque.

Bolt torque is spec'd at 40 ft/lbs + 1/4 turn.

In the case of what TomP ran into, yes, I too would have used a different set of head bolts. I have a 327 (SBC) that was 'rebuilt' at one time. Didn't know it at the time I was tearing it down. But found the head and mains way too difficult to remove. Obvious case of someone assembling an engine without a torque wrench. Once I figured out what was going on those bolts went in the trash.

It never hurts to purchase new bolts for any build (as long as they are GM bolts). But sometimes it really isn't required.

RBob.

 

The 2.8 bolts are NOT stretch bolts, to my knowledge (hence the torque to 70 and call it a day, but do it in 3 passes, still, please )

The 3.1 bolts, I know are. The aftermarket FelPros, are.

Get a set of ARP studs, and never worry again

 

could i use 2.8 non stretch bolts on my 3.4, the 2.8's are $17.50 per bank and the 3.4 is like $22 for one bank and $55 for the other??

 

WOW at least you agree that they use stretch bolts... Fel-Pro part# ES72857 full set is about $30... I gave up trying to convince some members that they these engines use stretch bolts...

 

Are you certain that you have the original 2.8 bolts in there? The originals from the factory are not stretch, to my knowledge, but the 3.1s and the FelPros are... I'd put new Felpros in there myself, unless you can spring for ARPs (my personal choice)

 

haynes has this for the 4th gen f-bod 3.4: torque to 41ft-lbs, then rotate 1/4 turn (90*)

......Chase the threads before installing bolts.....

....keep in mind there are two different legnth bolts......

....use sealant on threads & underside of bolt heads.......

nothing about using new head bolts.

it does mention using NEW bolts for the 3800 II, but reuse origonals for teh v-ate

 

So anyone seen the head gaskets or compared parts???

That is still an awful low torque for a head. Lawn mowers use more. Has to be some physical reason for the low torque, besides just bolts. I would want to know for sure you got all the right matching parts for that low torque. has to be something different, besides bolts. Has to be more of a reason.

 

Even worse would be the thought of using 70lbs on a 40lbs engine and ya get piston to valve contact in the hi rpms.

 

no, you either get stripped threads, or something cracks.

 

Are you stating that GM 3.1L RWD engine head bolts are stretch?

Or stating that Fel-Pro head bolts for the 3.1L RWD engine are stretch?

Please note that the GM service manual for the '92 3.1 f-body engine does not state that the head bolts are stretch. It is implied that they are re-usable, by not stating that they need to be replaced

RBob.

 

AFAIK, BOTH are stretch... : / I'll double check if I happen to think of it tomorrow.

Gumby, the 2.8 and 3.1 use the exact same heads and block - you can torque the 3.1 to 70lbs/ft as well, and it will be fine - that is what I did, reusing my stock 2.8 bolts.

 

Is there an official GM reason for the 40lbs?

 

40 lbs/ft, then a 90 degree turn = preloading stretch bolts.

 

I don't see why this is even an issue. I think that if you're going to do something, do it right the firt time and just buy the new bolts...regardless. I don't think it'll be worth trying to figure out if head bolts are reusable when you can get a full set for <$100 to save a possible $700 rebuilt motor.

As long as you double check all your information and follow instructions exactly, you can't screw it up. The important thing to remember is that if you're in doubt about something, check it against another source. I use Mitchell OnDemand5 all the time at work, but yes, sometimes stuff is wrong, but if I don't think something is right, you can always give them a call and they'll look it up in a book and fax it to you if you want.

 

well, today my unlce( mechanic for 30yrs) said that since i was doing such big job, i probably got some coolant in the crankcase upon dissasembly. the oil was on the pcv / and diptick, but he saw the oil i drained out and said it looked ok. im thinking at most its an intake gasket, and maybe i had a few air pockets in my cooling system. i have the upper and mid. intake off, so im gonna put new intake gaskets on it if they looked f****d and retorque the heads, if they look ok, ill do head gaksets and bolts too, i have the parts soo...here we go again.