Moparts
reusing head bolts
FOR THE RECORD: I have new head bolts for my 318 I am currently putting back together.
I was wondering; we have been told to not reuse head bolts, they stretch, etc.
Who has actually resued head bolts and seen a failure from doing this? This is just a question, not an argument starter, just curious.
eightlitermopar
Posted By: RapidRobert
Re: reusing head bolts - 11/29/12 11:04 PM
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Who has actually resued head bolts and seen a failure from doing this?
no failures from reusing here & on a 318 I wouldn't give it a seconds' thought
Posted By: MoparforLife
Re: reusing head bolts - 11/30/12 12:30 AM
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Quote:
Who has actually resued head bolts and seen a failure from doing this?
no failures from reusing here & on a 318 I wouldn't give it a seconds' thought
Have reused head bolts for years and never had a problem or given it thought.
Posted By: robertop
Re: reusing head bolts - 11/30/12 12:32 AM
The head bolts on any engine should be torqued to factory specs that are well below the yield point, i.e. the point at which they permanently stretch, so follow the engine specs and put your mind at ease.
Bolts behave essentially like springs: you can stretch them up to a point and they will return to the same length as many times as you want, but if you pass a certain point (yield point) they will take a permanent set, as a spring would. All manufacturers specify a certain torque that should not be exceeded; if you do that you will be OK.
Posted By: ahy
Re: reusing head bolts - 11/30/12 12:36 AM
Re-using is generally OK as long as they are not the torque to yield type used on some newer engines. Re-using torque to yield is a no-no because stretching them the first time changes their properties and a second stretch may overload the bolt and joint.
For standard head bolts, a thread guage is a good way to check for stretch. I was working with an experienced mechanic on a 60+ year old flathead. Those bolts had been re-used who knows how many times. He checked each one before re-installing and had to use some spares to replace those that had stretched in the threads.
These were the stock bolts that were installed from Ma mopar.
Hmmm...maybe I'll return my head bolt set then and get my 33 bucks back. Where this is a budget build, I could use the money.
Acutally, I already opened the new box of bolts so they are non-returnable now. I am putting '96 magnum heads on this old 318 so I wanted to be sure they were the right head bolts. However, this is good information to know for the future!
Thanks!
Posted By: 1_WILD_RT
Re: reusing head bolts - 11/30/12 03:27 AM
Quote:
Re-using is generally OK as long as they are not the torque to yield type used on some newer engines. Re-using torque to yield is a no-no because stretching them the first time changes their properties and a second stretch may overload the bolt and joint.
For standard head bolts, a thread guage is a good way to check for stretch. I was working with an experienced mechanic on a 60+ year old flathead. Those bolts had been re-used who knows how many times. He checked each one before re-installing and had to use some spares to replace those that had stretched in the threads.
Posted By: RapidRobert
Re: reusing head bolts - 11/30/12 03:25 PM
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I am putting '96 magnum heads on this old 318 so I wanted to be sure they were the right head bolts.
I believe the mags take a unique bolt (P4876759). I have a set for a Magnum swap also & I'm not sure if they are torque to yield or not. You have used ones that you were considering reusing? If not TTY then the thread gauge check sounds excellent & I'd just lightly wire brush em clean & good visual for nicks that would screw up your torque readings.
I have built several engines over the years 440s along with many pontiacs,never have I bought new bolts,I just used the factory ones.Most of the motors were pretty healthy,the only new bolts that I invest in are the rod bolts.Save the money and return them.
Posted By: 70Cuda383
Re: reusing head bolts - 11/30/12 04:14 PM
Magnum headbolts are NOT torque to yield, and I've re-used them several times without any problems. however, on a high compression performance build, I would suggest going with new ARP hardware anyway.
but for a mild build, stock bolts are fine. mine has re-used stockbolts, and it's about a 350-ish hp engine. (285 RWHP)
However, Magnum head bolts ARE different than LA head bolts. I found this out when I ordered a set of ARP hardware for edelbrock heads off Mancini. They arrived with 3 different length bolts. The Magnums use 2 length bolts, 5 long ones down the middle of the head, and 5 short ones for the base of the head below the exhaust ports. When I called Mancini they confirmed that the LA heads use a different bolt set than a Magnum bolt set, and took the opened set of LA bolts back without any problem, and sent me the correct head bolts instead.
Posted By: RapidRobert
Re: reusing head bolts - 11/30/12 06:00 PM
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Magnum headbolts are NOT torque to yield,
Thank you
Posted By: patrick
Re: reusing head bolts - 11/30/12 08:13 PM
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I am putting '96 magnum heads on this old 318 so I wanted to be sure they were the right head bolts.
I believe the mags take a unique bolt (P4876759). I have a set for a Magnum swap also & I'm not sure if they are torque to yield or not. You have used ones that you were considering reusing? If not TTY then the thread gauge check sounds excellent & I'd just lightly wire brush em clean & good visual for nicks that would screw up your torque readings.
magnum INTAKE bolts are supposed to be TTY, IIRC, not the head bolts. and there's 1 or 2 that are different length for an LA, so LA head bolts won't work.
I reused mag head bolts when I put mag heads on an LA 318 roller, didn't have any problems.
thanks for the info. My brand new head bolts ARE for magnum heads. I was curious if they were different, and now I know.
I'll let you know as I progress.
eightlitermopar
Posted By: 70Cuda383
Re: reusing head bolts - 12/01/12 01:11 PM
Quote:
Quote:
Quote:
I am putting '96 magnum heads on this old 318 so I wanted to be sure they were the right head bolts.
I believe the mags take a unique bolt (P4876759). I have a set for a Magnum swap also & I'm not sure if they are torque to yield or not. You have used ones that you were considering reusing? If not TTY then the thread gauge check sounds excellent & I'd just lightly wire brush em clean & good visual for nicks that would screw up your torque readings.
magnum INTAKE bolts are supposed to be TTY, IIRC, not the head bolts. and there's 1 or 2 that are different length for an LA, so LA head bolts won't work.
I reused mag head bolts when I put mag heads on an LA 318 roller, didn't have any problems.
Are you sure about that? D0 they really TTY at just 12 ft lbs?!
I've always replaced the stock bolts regardless though, because they are always corroded and look like 75 year old junk that sat at the bottom of the ocean when I pull them out.
Posted By: dogdays
Re: reusing head bolts - 12/03/12 05:52 PM
KUDOS to robertop for the correct answer. Straight out of Strengths of Materials.
I have never bought a new head bolt and as they are inside the engine I haven't seen any that were corroded badly. Oily, yes.
If you have a few thousands invested in an engine it is nice to spend a few dollar$ and have new bolts. But on a 318? only if you are running forced induction or something like that.
R.
Posted By: 70Cuda383
Re: reusing head bolts - 12/03/12 10:02 PM
Does anyone know if there are engines out there that DO TTY the bolts that hold on the heads? Seems like there HAS to be a few of them, otherwise there'd be no myth about having to replace them every time
and just for the record, I was talking about the intake manifold bolts when I said that I replace them. the originals always look like junk because of the galvanic reaction taking place between the 3 different metals (whatever alloy the bolts are, the cast aluminum of the intake, and the cast iron of the head.)
head bolts NEVER look bad when taking apart an engine.
Posted By: dogdays
Re: reusing head bolts - 12/04/12 12:03 AM
Thank you.
I would assume that some of the newer engines using the torque-plus-angle tightening method actually do torque to yield.
However, I have been hearing the same old story since before TTY bolts were thought of in automotive applications. It seems that it is easier to spend someone else's money telling them to goldplate a project, than telling them where the $$$ can be saved. And of course, rod bolts are a different story.
BUT, as I said earlier, if you have a few thousands stuck in a motor, then a couple of hundreds for new bolts doesn't seem out of line.
R.
Posted By: ahy
Re: reusing head bolts - 12/04/12 01:49 AM
I had to pull heads on a couple of water cooled VW's while living overseas. A 1600 cc and a 1043 cc. Both were torque to yield. They would have been late 80's, early 90's builds. The FSM, dealer and parts store all said the same thing... change them!
So what would the downside be:
to getting the right size intake bolts from a local hardware store in a grade 5 or 8 so that they can be reused in the future? Do they HAVE to be replaced with a TTY bolt?
Also, what is the torque spec on these magnum intake bolts? TTY or otherwise?
Posted By: MowP4rsn
Re: reusing head bolts - 12/04/12 05:33 AM
Quote:
Does anyone know if there are engines out there that DO TTY the bolts that hold on the heads? Seems like there HAS to be a few of them, otherwise there'd be no myth about having to replace them every time
and just for the record, I was talking about the intake manifold bolts when I said that I replace them. the originals always look like junk because of the galvanic reaction taking place between the 3 different metals (whatever alloy the bolts are, the cast aluminum of the intake, and the cast iron of the head.)
head bolts NEVER look bad when taking apart an engine.
I'm stretching my brain a little trying to remember this (see what I did there? 
) but I seem to recall the Neon 2 liter had TTY head bolts.
Posted By: RoadRunnerJD
Re: reusing head bolts - 12/04/12 05:41 AM
The used original bolts are probably better than new aftermarket bolts in many cases. Are your new bolts made in USA?
Posted By: None2Slow
Re: reusing head bolts - 12/04/12 07:39 AM
Ford has used them on their 3.8 v6 supercharged and n/a. Their 6.0 and 6.4 Diesels are also TTY. Several manufactures use them. No, you do NOT have to replace them with TTY when you buy new. When doing a head swap on the 3.8 fords, Fel-Pro sells the head kit with or without the head bolts. The bolts they include are TTY. Just go to autozones website and browse there parts and see what vehicles need them.
Posted By: dogdays
Re: reusing head bolts - 12/04/12 04:59 PM
If you use Grade 5 bolts they might very well be "torque to yield" bolts!
I can't remember seeing anything other than Grade 8 on my disassemblies. That is 6 marks on the bolt head.
R.