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Re-Torque small block heads or not?

Re-Torque Poll

6K views 46 replies 20 participants last post by  Duntov 
#1 ·
Should we Re-torque small block heads? Yes or NO
 
#3 ·
Still having tech problems

Hey AirBoat :welcome:

Are TTY bolts available for early V8s? If so I think that would save a lot of bacon.

Still having tech problems getting the correct link to send people to the poll, Can someone fix it?

I'm not very good on a keyboard, Thanks Duntov
 
#10 ·
I'm learning a lot from this poll

curtis73 said:
The first 20 or so engines that I built I retorqued only to find they were all in spec.

However... I have never built one with head gaskets that said to re-torque. I've always used Cometic, Fel-Pro and ROL - all of which were a one-torque type gasket.

I've never heard anyone say that before.. So it brings up the question; "What kind of sealant did you use on the head bolts?"

One comment though. A lot of people mark the bolt and the head, then break the bolt loose and retorque. People who do that almost always say the bolts traveled 3 hours on more on the clock position past the mark. Maybe they're breaking a combination of thread sealer and engine paint. I don't know.. Glad you participated in the poll.
 
#12 ·
Jake_Dragon said:
Do you torque them to the full amount or do you stage it?
I torqued mine in 3 stages 30 - 45 - 65 and let them rest between stages.
I have had no problems at all.

We stage in a similar way as you do. Do you ever go back and check a couple hundred miles down the line?

I should have ask in the poll what thread dope people are using also. Thanks for the comment..........Duntov
 
#13 ·
Duntov said:
We stage in a similar way as you do. Do you ever go back and check a couple hundred miles down the line?

I should have ask in the poll what thread dope people are using also. Thanks for the comment..........Duntov
Sounds silly, but I use teflon tape on my head bolts. An old engine builder told me this was the best method.
 
#14 ·
that seems like that is the real question, if you retorque what do you seal the headbolts that go into the coolant passages with that isn't going to leak when you retorque.

The problem with this question is that when you tighten a bolt and let it sit it "sticks" so you need a break away torque to overcome that before it will turn. If you just walk up to the engine with your clicker torque wrench set to the proper torque even if the gaskets did compress some, the break away torque will be high enough that you won't overcome the sticking and the wrench will click without tightening the bolts. The only way that you're going to tighten the bolts to the same torque setting is if you back them off first, then retorque.
 
#15 · (Edited)
Duntov said:
Should we Re-torque small block heads? Yes or NO
I re-torque, because, I suppose repetition builds a false sense of security if for no other reason.

For bolts, I use non hardening sealant either Permatex #3 or Hylomar, or non-hardening plumbers Teflon pipe joint compound such as Otay 31230. Since this stuff doesn't harden, it allows the fastener to be re-adjusted without loosing a coolant or oil tight seal.

Studs are set with a hardening sealer such as epoxy or some cyano-acrylic (superglue) compound so the stud will not move to break it's seal when the nuts are adjusted.

Re-torquing is a bigger issue with engines where iron blocks and aluminum heads are used with composition or multi-layered steel gaskets. This is for several reasons:

1) Aluminum expands and contracts more than cast iron, so the fastener has not only to deal with operating loads of the combustion cycle but also with the greater material expansion of aluminum. So the fasteners see actual loads that may equal or exceed their stretch (torque) loads.

2) Aluminum is soft and deforms plastically to escape loads. Which is to say that the area under the fastener will try to escape the force applied to it. You can see this on disassembly where there will be a depression under the fastening device head be it bolt head or a nut. A hardened washer helps but doesn't eliminate the condition. Related to this is the abrasion action of the soft aluminum rubbing the underside of the fastener's "head". Both actions place a loose dimension between the parts allowing the fastener to lose its grip. Tension To Yield fasteners work better in this situation as they are in a what one could call a spring (plastic) state and they will adjust to these movements to a degree that pretty much eliminates re-torquing. But these are one time use items, once pushed to their yield limit, unloading and reloading them is an invitation to failure.

3) In a reaction to #2 above, aluminum deforms along the gasket surface and will "bend" with gasket deformation (crush) and block deformation that warps the deck surface. Things like zero decking, large over-bores, extreme compression, detonation events, solid engine to chassis mounting, and most certainly overheating and in engines with paired exhaust valves super heating the center of the head all result in movements of the aluminum part to chase these events which will loosen the head bolts as the head deforms.

I'd say how often I see this depends a lot on the use of the engine. Easy street use doesn't seem to require re-torquing, I still do it for checking purposes but mostly everything is fine. Race motors are more problematic, the harder and hotter they are run the more I find that chasing proper torque is needed. This is especially true where aluminum heads have been welded on and not re-tempered to a T4 or T6 condition. The heat of welding removes the tempered hardness which resists these deforming forces. When that is removed the actions of deformation and abrasion in the weld's heat affected zone substantially increase.

Bogie
 
#16 ·
Duntov said:
I've never heard anyone say that before.. So it brings up the question; "What kind of sealant did you use on the head bolts?"
It depends on the engine and what I have in my toolbox :) I almost always use teflon paste since it lubes well and seals pretty well. Its also pretty easy to clean up if you have to get back in there for repairs. I have used black RTV for more permanent applications, but it makes a rubbery mess in the threads.

I always torque in three steps: first by hand to about 20, then with a torque wrench to 2/3 of the final torque spec, then final torque.

Another little myth about TTY bolts (since someone asked earlier)... it has nothing to do with the bolt, its simply the method used to torque them. The point is to get the proper bolt stretch for maximum clamping. Bolts are like springs - not enough stretch and they don't clamp enough. Too much and they fail. Using a torque setting to determine that stretch is marginal. A burr on the threads, friction under the head, and a few thousand other factors mean that you can reach your torque value long before the proper stretch has been achieved. The other huge factor is that friction increases exponentially as you increase torque value. Using a TTY method is much more accurate since you go to a smaller torque value and then use degrees to set stretch. Since thread pitch is known, a specific degree of rotation provides a more accurate amount of stretch.
 
#17 ·
I can wholeheartedly agree with the head bolts staying torqued. I just like making sure they stay there after a few miles. It's just like aluminum rims. they say to retorque after 100 miles or so, but it's really to cover their butts if it does come off. I've never seen any fall off.

If it's my pocket the money comes out of, i'll retorque only to check and varify. if not, screw it.
 
#18 ·
PTFE teflon pipe dope/paste

Silverback said:
that seems like that is the real question, if you retorque what do you seal the headbolts that go into the coolant passages with that isn't going to leak when you retorque.

The problem with this question is that when you tighten a bolt and let it sit it "sticks" so you need a break away torque to overcome that before it will turn. If you just walk up to the engine with your clicker torque wrench set to the proper torque even if the gaskets did compress some, the break away torque will be high enough that you won't overcome the sticking and the wrench will click without tightening the bolts. The only way that you're going to tighten the bolts to the same torque setting is if you back them off first, then retorque.
Exactly Silverback!

I'm sure a whole lot of people were waiting to hear that said, because it's been true for fifty years.
That's why we use the PTFE pipe dope from a professional plumbing supply outfit. Learned it from a hydraulics engineer in the Eighties. It acts like a medium grease on first torque. to 65 ftlbs. but will hold 3500 psi of hot hydraulic fluid, on a half inch pipe thread.backhoes ect.

When heat cycled it tends to become or better said "react" as a viscious liquid, while warm. It mimics a thick grease then.
It is the only substance I've experimented with which reconstitutes it's viscosity/integrity when disturbed, even multiple times. getting a little thicker every time.

So when on re-torque I don't have to break the bolts' "seat" << that the right word?, in order to have it turn, even with a clicker.

Sometimes though it takes a beam type to get it to move, but once it does move, set a clicker to 70 and it will move several degrees before it clicks again, sometimes 90 Degrees if you don't push to fast. I like a beam wrench for final really. And of course once a bolt turns it's neighbor tends to become loose and it spreads like a disease. I go over a couple of times. When I walk away I feel really good about it.. And there is still only 70ftlbs of stress on the threads... Duntov
 
#19 ·
curtis73 said:
It depends on the engine and what I have in my toolbox :) I almost always use teflon paste since it lubes well and seals pretty well. Its also pretty easy to clean up if you have to get back in there for repairs. I have used black RTV for more permanent applications, but it makes a rubbery mess in the threads.

I always torque in three steps: first by hand to about 20, then with a torque wrench to 2/3 of the final torque spec, then final torque.

Another little myth about TTY bolts (since someone asked earlier)... it has nothing to do with the bolt, its simply the method used to torque them. The point is to get the proper bolt stretch for maximum clamping. Bolts are like springs - not enough stretch and they don't clamp enough. Too much and they fail. Using a torque setting to determine that stretch is marginal. A burr on the threads, friction under the head, and a few thousand other factors mean that you can reach your torque value long before the proper stretch has been achieved. The other huge factor is that friction increases exponentially as you increase torque value. Using a TTY method is much more accurate since you go to a smaller torque value and then use degrees to set stretch. Since thread pitch is known, a specific degree of rotation provides a more accurate amount of stretch.
:thumbup: :thumbup: DITTO ALL DAY LONG :thumbup: :thumbup:
 
#21 ·
I am no more than a weekend mechanic. Built a handfull of small blocks and watched a handfull being built. So, no valuable input here but I have to ask ...


What was the reason for this poll ? You must have had some past experience that made you ask this question ?


I am not an engine builder but understand 95% of what is posted in these threads and thank all of you for sharing your wisdom. And thanks for putting up with us "weekend warriors" and OUR silly questions. :D

Matt

BTW I was taught to use ARP sealer
 
#22 ·
oldbogie said:
Studs are set with a hardening sealer such as epoxy or some cyano-acrylic
(superglue) compound so the stud will not move to break it's seal when the
nuts are adjusted.

The people that have their heart set on re-torquing should go this route, this
would work a lot better that trying to re-torquing a bolt that has been sealed.

I never seem to find time to go through the work it takes to get to all the
nuts with headers and rocker arms in the way. I'm not blowing head gaskets
so it must be OK.
 
#23 ·
I knew some of the bigger dogs were in this forum!

Now the Pros are speaking up and it's getting down to the details that provoke more consideration than appears on the surface of the matter.

:D I suspect the Big Dogs who send their work to the Super Speedway consider the details endlessly. :D
 
#24 ·
automotive breath said:
would work a lot better that trying to re-torquing a bolt that has been sealed.
I doubt there are many who will use a hardening sealer for sealing the threads of a head bolt they intend to retorque- I know I don't. So there is zero issues w/"breaking" any seal- the sealer never hardens- certainly not within the time frame involved for retorquing the heads.

I never seem to find time to go through the work it takes to get to all the nuts with headers and rocker arms in the way.
Yes, to retorque heads more work is involved. I do not let that stand in my way, however.

The details involved in building an engine differ between every builder, some more than others. Go w/what works for you.
 
#25 ·
Re-torque?

I already gave my opinion in the original post but I figured I'd give my vote in the poll. ;) Back in the day when you could still get high octane pump gas I was into real high compression engines. When pump gas octane went down, so did my build compressions, I mean you can't run around on race fuel.

Steel shim gaskets were normally used along with domed pistons, yes back then I used all the layers of coppercoat I could build up and re-torque more than once and still occasionally blow a leak in a head gasket. Then you pull in down and go through the head gasket replacement.

The Fel-Pro performance head gaskets have been my favorite, since I got away from building for big compression stuff. I have rechecked torque on at least six engines before I decided it was a waste of time, using the Fel-Pro gaskets. You might give up a little quench with the thicker gaskets, but then you can build a drop in engine with no further adjustment necessary. At my age, I like pushing the Easy Button.

Todays gasket materials are a far cry better than the stuff I sold in auto parts in the '70's. Back then, even composition gaskets required a re-torque. Today, I spend the extra bucks and buy the Easy Button, PermaTorque gaskets.

Why work your butt to death doing extra work when you don't need to? ;) olnolan
 
#26 · (Edited)
I agree it's the details that make the difference. Abnormal combustion will kill
a head gasket quicker than anything; light ping cycle after cycle, pre-ignition,
high combustion temperatures and pressure spikes. I spent all the time
it takes to eliminate these completely. We race every weekend and run our
engines two to three years before freshening up, never find loose bolts
or blown gaskets.
 
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