I hear different practices. Some guys replace them every time, and some guys re-use them once.

Some guys say it makes no difference with the iron head.

Does anybody know?

Arn

They are not Torque to yield bolts, so it doesn't matter how many times you use them as long as they are not pitted and the threads are in good shape. Make sure the threads are clean also. If they are dirty or hard to screw into the block replace them because it will affect your ability to properly torque them.

Thanks,

Just one more little detail eh?

Arn

ONCE would be the correct answer.
There is a reason why, NEW head bolts come with the top end gasket set, and they are not to be used as paper weights.
yea, yea, yea, just because the guy next to you jumped off the bridge, are you going to follow ?
Those people that say they re-use there head bolts, may be doing so, but it doesn't mean they are doing it right.
CHANGE THOSE BOLTS OUT.

i agree. replace them every time you pull them. if anything, it's cheap insurance. those bolts go through serious stresses from heating and cooling. i personally would replace them every time. no question.

quote Originally posted by CYNFIERO: ONCE would be the correct answer. There is a reason why, NEW head bolts come with the top end gasket set, and they are not to be used as paper weights. yea, yea, yea, just because the guy next to you jumped off the bridge, are you going to follow ? Those people that say they re-use there head bolts, may be doing so, but it doesn't mean they are doing it right. CHANGE THOSE BOLTS OUT.

If they're not TTY and are in good shape, why should someone replace them? Could you explain why the old ones would be no good once used? I'm not trying to say I think you're wrong, this is just a topic I don't know too much about and you have me curious.

thanks
Dave

All the information I have seen says they are torque to yeild, so the should only be used once and replaced when ever they are removed.

Steve

All I work on is... 2.8's (ok, mostly)

As already stated - these are not torque to yield bolts. If they're in good shape, reuse them (with proper cleaning, sealant, etc).

I have *never* had a failure in all the engines I've built from reusing them. A lot of the engines I do are getting WAY up there in mileage, so of course I *do* replace them. But that's from a damaged threads point of view. Make sure to tap/clean the threads in the block out as well.

TTY type bolts - YEAH, replace them! They're easy to spot. If the specs say torque to "X" ft-lbs, then go "X"* (degrees) more turn, then they're TTY.

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87/88 V6 5spd "FormulaGT" Turbo
85 Bright red GT 4spd (with matching 1:18 diecast and 1:24 plastic models!)
86 SE (custom body in progress)

My pages:
http://www.fieroclub.com
http://www.fierohut.com

anytime your tq a bolt down you stretch it... however small you DO stretch it... would you rather spend a little cash on some headbolts now or have to replace some more stuff if one fails and you get coolant in your oil.... i know id rather replace them plus its cool to have ARP stuff in your motor

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'86 Fiero GT

My Fiero XoticRydz Mid-Rear Madness

Be Excellent To Each Other" - Bill S. Preston Esquire Ted Theadore Logan

I agree. You can reuse them if they are in good shape. Done it a billion times also.

Bolt stretch is only a real factor in rod bolts.

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1984 Indy Fiero 3.4L 4spd
www.cardomain.com/id/donk_316

Like I said, there are differing opinions.

So, does anybody know what the shop manual says about torquing headbolts? Is is TTY or not?

I am open to doing it any way right now. I just want to do it right the first time.

Arn

BTW thanks guys for all the responses.

1986 GM Manual says:
Recommendations for fastener re-use:
1.Clean, unrusted prevailing torque nuts and bolts may be re-used as follows:
a. clean dirt and other foreign material off nut or bolt.
b.Inspect nut or bolt to make sure there are no cracks, elongation, or other signs of abuse or overtightening.If there is any doubt, replace with a new prevailing torque fastener of equal or greater strength.
c. Lightly coat the bolt and nut with engine oil. Assemble parts and handstart nut or bolt.
d.observe that before fastener seats,it develops torque per chart in fig.10( if there is any doubt, as above)
e. tighten fastener to torque specified in appropriate part of this manual.
2. Bolts or nuts which are rusty or damaged should be replaced with parts of equal or greater strength.
fierofetish

[This message has been edited by fierofetish (edited 11-08-2004).]

I would personally reuse them if new ones are expensive or ARP ones are too expensive but If I was doing them for someone else i would tell them they need to be replaced just incase so it doesnt come back. on my Honda I took the head off a dozen times to check out the pistons and always reused the head bolts, last time I put in ARP studs though because I got them for only 85$ used on ebay

Kyle

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1988 Fierhoe Formula 2M6 5 Speed - CRX Intake, NOS dry kit, ZEX Ejector Air Amplifier, Taylor Wires, NGK UR5 plugs, MSD 6AL Ignition /w 2 step rev control, MSD Blaster 3 coil, WCF dog bone, WCF engine mount, Autometer Ultra-Lite guages (A/F,Vac.), KYB GR2's, Sequential turn signals, Rapid 3rd brake light.... Anyone want to buy my engine/tranny?
Recurring donator
1995 Honduh civic EX - turbocharged B18B1 13.2 @ 107 on stock internals and junk yard turbo set up with PVC pipe
www.cardomain.com/id/integrab18ls

Arn,
In the '88 GM / Fiero service manual it says nothing about use once, or TTY. The torque spec in the cylinder head replacement section states 66 ft.lbs. In the engine bolt torque chart at the end of the 2.8 V6 engine section, the cylinder head torque is listed as 65 - 90 ft. lbs.

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Tim
Red 88 Formula Auto 2.8 100K+ Miles

Logic is a systematic method of coming to the wrong conclusion with confidence!

The headbolts in question are not torque to yield, as has been stated. What is the difference? Some basics on metal properties. We all know that you can bend a piece of metal a certain amount and it will pop back to its original shape, and if you bend it too far it stays bent. These two amounts of bend can be referred to as elastic deformation (pops back completely) and plastic deformation (stays bent to some extent). The point where the elastic turns to plastic is called the yield point. These properties also apply when stretching metal as well, and the amount of stretch is referred to as elongation. Now that you have a basic grasp of these concepts lets look at bolts in general. Whenever you tighten a bolt two main kinds of stress are put into the bolt. Elongation as the threaded end of the bolt is pulled further into the threaded hole while the head is held back, and torsional as the head of the bolt is twisted against the friction of the threads. Torsional stress can be ignored for this discussion, though it's a big problem when the head breaks off of an exhaust bolt because the thread friction is so high from rust.

Now for head bolts there are a couple main ways the engineers designed the engine's head to be held on, more specifically how to determine the amount of clamping force of the bolt so as to ensure proper gasket compression (not too little, not too much). Controlling clamping force with regular bolts uses a torque wrench to measure the increase in bolt tightness as an indirect indicator of bolt tension. This relies on thread friction in a known state, that is clean threads with light oil, which is fine in most cases as variations in tightness of 20-30% aren't really relevant. Bolts that are used this way never stretch beyond the elastic stage, so as a result they are reusable as long as the threads stay in good condition.

Many modern engines, however, require much more accurate control of the clamping forces, particularly in engines with aluminum heads and/or blocks. Enter the TTY, or Torque To Yield bolts. Since all bolts stretch elastically when tightened and when tightened to yield and plastic deformation will stay permanently stretched in a very predictable way, engineers designed bolting systems that relied on the permanent stretching of the bolt to set the clamping force. That's what TTY bolts do, they permanently stretch since they are tightened beyond their yield point. When the tightening process is completed, usually as turning the bolt x number of degrees after a certain amount of preload by turning to torque, the residual elasticity of the bolt clamps with a very predictable and controllable force. That's why TTY bolts can't be reused, at least not in that application. The next stretch operation will not yield the same clamping force.

As far as I know, no top end set for any Fiero comes with new head bolts, you have to buy those separately. There's no reason to replace them unless they're damaged, or you're FieroX and you torqued them down to a 150 ft-lbs because your torque wrench was faulty.

JazzMan

[This message has been edited by JazzMan (edited 11-08-2004).]

I always replace them, for the $65 CAD it is worth the piece of mind

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86 SE 2.9L
Best ET : 14.9 @ 90 MPH

The last time I looked up a set of headbolts (two weeks ago) at the parts store I work at, the Felpro part number specifically list the new head bolts for a 88 2.8 V6 as being TTY bolts. It is very specific in its description and highlights it in bold italic print in the Felpro parts book.

This does not necessarily mean that the OEM bolts are TTY, but any new ones bought and installed in your engine may in fact be TTY bolts.

With that said, unless you are the original owner of your car it may have been fooled with at some point. What is the chance that the heads haven't been pulled before? Most would agree that the almost all of our cars have been worked on at Uncle Bob's Garage and Bait shop at some time.

Your car may have been produced with re-usable bolts, but manufacturing and design has changed since out cars were being built.

They 35 - 40 bucks, piece of mind goes along ways.

88Ironduke

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Pilots with out maintainers are just pedestrians with a cool jacket and sunglasses.
I.Y.A.M.Y.A.S.

Okok, so I have a '88 V6 which has the original head bolts. Are you saying I have to buy new head bolts?? The Haynes manual says nothing about buying new head bolts, and it DOES say so for my '95 Escort, which uses TTY head bolts.

AFAIK no Fiero V6 uses TTY bolts. If I am wrong, tell me now! I'm going to start my rebuild next week!

Thanks

Ed

PS I don't mean to hijack the thread but I don't see the point to starting another thread for my own question when there's already one here.

Thanks to all, and special thanks to Frugalfiero for the most correct answer.

The manual will not lie on this and I was able to confirm.

The bolts look good and I'm using them. The fact that suppliers are saying to use TTY bolts does not mean the original factory requirement was TTY as the manual indicates.

Moreover, if the OE GM grade of bolt does not have 'stretch' built in, why would I change the engineering specs?

Thanks again guys.

Arn

quote Originally posted by JazzMan: Many modern engines, however, require much more accurate control of the clamping forces, particularly in engines with aluminum heads and/or blocks. Enter the TTY, or Torque To Yield bolts. Since all bolts stretch elastically when tightened and when tightened to yield and plastic deformation will stay permanently stretched in a very predictable way, engineers designed bolting systems that relied on the permanent stretching of the bolt to set the clamping force. That's what TTY bolts do, they permanently stretch since they are tightened beyond their yield point. When the tightening process is completed, usually as turning the bolt x number of degrees after a certain amount of preload by turning to torque, the residual elasticity of the bolt clamps with a very predictable and controllable force. That's why TTY bolts can't be reused, at least not in that application. The next stretch operation will not yield the same clamping force.

It's at least partly driven by economy. GM accountants want to save $2.00 per vehicle by using smaller cheaper fasteners. The torque to yield sequence brings these smaller bolts to the exactly to the yield point every time, whereas with a torque only specification, they could be overtorqued.

Also, modern engine designs tend to require even clamping force across the surface being bolted down, and the TTY bolts help do that.

Not all TQ + angle bolts are TTY. The Northstar head bolts call for three 60 degree angles in sequence, for a total of 180, but this is just to crush the head gasket properly. The bolts can be reused if the factory thread lube/locker is brushed away and loctite used on the threads.
The N* main bolts also call for TQ+>, but they're reuseable as well. The only fasteners that are not are the factory rod bolts. The difference is that the main bolts are very long and call for 50 or 60 degrees and the rod bolts are very short and call for 120 or 135 (don't remember which).

In short, 2.8 head bolts are reuseable.

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Turn the key and feel the engine shake the whole car with its lope; Plant the gas pedal and feel in your chest neither a shriek nor a wail but a bellowing roar; Lift and be pushed into the harness by compression braking that only comes from the biggest cylinders while listening to music of pops and gurgles. Know that you are driving an American V8. There are finer engines made, but none of them are this cool.

Luck, Fate and Destiny are words used by those who lack the courage to define their own future

[This message has been edited by Will (edited 11-09-2004).]

You can reuse the stock headbolts if they are in good condition.
If you are increasing compression or plan on adding boost, New ones would be recommended. When I built my 3.4L, since I increased compression slightly, I went with the ARP head studs. These turned out to be better for a few reasons. First, since the studs are installed first, There is less chance of having excessive sealer bleed between the head gasket and the mating surfaces. (This could lead to a weak seal and a blown head gasket later.) Second the torque specs have less tolerence than the factory specs. Factory manual states 65-90 ft/lbs ARP head studs state 76 +/- 2 ft/lbs. I know that everyone uses the same torque for all the bolts, But there is a chance that you could mis-torque the bolts which could lead to a warped/damaged head.
Finally, I found the headstuds made it easier to install the head evenly where if placing the head on the block, where the other way, You could accidently damage the head gasket opposite the head guides.

I thought most TTY style headbolts were used on heads that were a different material then the block? (I.E. aluminum heads on a cast block) This was due to the difference in thermal expansion of the different materials.

Last summer, I got coolant in the oil/overheating/missing/white smoke/etc, all the classic blown head gasket symptoms. When I tore the engine down, I discovered the gaskets didn't blow.....a bolt snapped right at the thread on the front head. This I discovered AFTER I had all but the last three bolts out of the second head. I recalled that when I put the 3.4 in the car last year (64K on the block) I replaced the head gaskets (to be SAFE, right?) but DIDN'T replace the bolts...

Moral? SAVE YOURSELF THE HEADACHE, SPEND THE $22 (Murray's) AND GET NEW HEAD BOLTS!!

That's my 2 cents.