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Old 19-09-2017, 09:48   #1
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Do I need to replace headbolts when I do a valve job

I have been told I should replace my headbolts due to possible stretch while I am replacing my headgasket on a 42 Westerbeke. I have rebuilt the head since it was out anyway but they want a bloody fortune for the bolts ($42 apiece) and I have never done on any other engine. I never rebuilt a diesel though. Please any expert opinions on this.
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Old 19-09-2017, 10:05   #2
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Re: Do I need to replace headbolts when I do a valve job

No need. Steel "stretches" a lot before it takes a permanent deformation. Every time you tighten them they stretch elastically.... meaning they bounce back when you remove them. To create permanent deformation would take a lot more than that. Depending on the alloy and heat treatment, they may not take any permanent deformation until just before they actually break!
It's always good procedure to make sure the threads are clean and free of debris.
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Old 19-09-2017, 11:03   #3
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Re: Do I need to replace headbolts when I do a valve job

If the last person really over torqued them maybe, but how could you know? You could have them magnafluxed for a lot less than new bolts. There is no way to know for certain unless there is a spec for the length and there ain't. I've never heard of buying new head bolts for no known reason. Rod bolts are different deal.
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Old 19-09-2017, 11:23   #4
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Re: Do I need to replace headbolts when I do a valve job

Replacing the head bolts sounds like the standard service manual instructions that assume a perfect world, failsafe precautions, and an unlimited bank account.

According to the shop manual, I'm supposed to replace the gasket on the oil drain bolt on my 2000 Ford Ranger. Never seen that done unless it's actually leaking.

New bolts (and any other part) can be "bad" out of the factory package as well. I would tend to trust an undamaged, unworn "used" part as much or more than one that is brand new.
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Old 19-09-2017, 11:35   #5
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Re: Do I need to replace headbolts when I do a valve job

I reused my Westerbeke (Mitsubishi) bolts when I put the head back on my Westerbeke 44B. I can't remember if the service manual called for it or not but there were 13ish bolts and I'm not doing that $$. Or if it bothers you find the actual manufacturer of the engine and buy them from a tractor supply.

Only thing I've ever seen for torque to yield was a Ford truck diesel.
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Old 19-09-2017, 11:48   #6
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Re: Do I need to replace headbolts when I do a valve job

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Originally Posted by sailah View Post
I reused my Westerbeke (Mitsubishi) bolts when I put the head back on my Westerbeke 44B. I can't remember if the service manual called for it or not but there were 13ish bolts and I'm not doing that $$. Or if it bothers you find the actual manufacturer of the engine and buy them from a tractor supply.

Only thing I've ever seen for torque to yield was a Ford truck diesel.

Thanks, Mine is a 42B but probably the same Mitsu K4F block as yours. How many hours since the top end was done? Any issues I should look for?
Did you use an OEM Head Gasket?$226 vs $96

Thanks
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Old 20-09-2017, 08:25   #7
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Re: Do I need to replace headbolts when I do a valve job

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Originally Posted by Valmika View Post
Thanks, Mine is a 42B but probably the same Mitsu K4F block as yours. How many hours since the top end was done? Any issues I should look for?
Did you use an OEM Head Gasket?$226 vs $96

Thanks
My engine is based on a Mitsubishi S4L2 so I think the blocks are different.

I had the valve work done by an excellent local machine shop this spring. Maybe 50 hours at most? Runs like a top.

I bought a complete gasket kit and I mean COMPLETE for my engine. It was a factory Mitsubishi gasket set and had everything (rear main seal, valve seals etc). Which was handy for reattaching the exhaust manifold, thermostat etc. I bought on ebay from England it was about $120 shipped.

Since you'll probably have to remove various cooling systems, it would make sense to have every gasket in one kit. Who knows when you may need another. I did have to buy a couple specific gaskets from Westerbeke like the exhaust manifold but that wasn't too bad.

I don't think there is anything I would say to look out for, but I don't know your mechanical skill set. I used expandable rubber test plugs from Mcmaster to seal up the bores while it was exposed. I also took great care in carefully cleaning everything before opening it up lest debris fall down the oil galleys. I used lots of clean plastic wrap and would cover up the exposed engine when done for the day or even if I was not working on it for a moment.

I used my high quality Snap On torque wrench and torqued the bolts in 3 stages following the guidelines. I also loosened in 2 steps.

Setting valve lash is simple, you just need feeler gauge set.

One thing I do which I find very helpful is I buy a large box of 1 quart and 1 gal zip locks heavy duty. I first write with a Sharpie on the baggie say THERMOSTAT, and then when disassembling I put everything in the bag and seal it. Then I put baggie in a cardboard box and move to the next component. Course your hands will be all grubby so this is a quick way to make sure you don't lose parts. If I have a random bolt that doesn't have a "name", say holding a bracket or something, I will remove the bracket, then loosely thread the bolt back in. Saves the inevitable "now where does this bolt go?"

Should go without saying to download and print the factory service manual from Mitsubishi which I found to be excellent and easy to follow. I hole punched mine and put in a binder.
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Old 20-09-2017, 09:46   #8
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Re: Do I need to replace headbolts when I do a valve job

Ok guys,some engines are designed to replace them & some are not,alot of smaller 4 cly are..so bottom line check with a builder,if it's mine & they call for it then yeah,do it,,,they do stretch more than you might realize. Some of them is stretch just a bit when you torque the bolt down under assembly, as someone said torque to yield...the ones that do stretch usually will not torque correctly when reused,as they approach torque they give a bit easier & you wind up with incorrect torque & open yourself up later to cooling problems from head gasket issues. ..all this from a guy that did a bunch of valve jobs,& have tried to cheep out & had to go back & do it again!.... also learned that if I pull the head even if nothing wrong with it & try to replace gasket & go....2 out of 3 failed, every one I had the head cut slightly worked 100%......not worth the work of a failure, pull it & if nothing else resurfacing min cut helps to bond new headgaskit
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Old 20-09-2017, 10:52   #9
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Re: Do I need to replace headbolts when I do a valve job

Having worked in aviation, head bolts should be inspected and NDT'd prior to re-installing. When torqued properly, all bolts will stretch and can be reused that is, of course there is no corrosion, cracking, and the plating is in good condition. Proper torque is inportant!!
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Old 20-09-2017, 12:30   #10
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Re: Do I need to replace headbolts when I do a valve job

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Originally Posted by P3sailor View Post
Having worked in aviation, head bolts should be inspected and NDT'd prior to re-installing. When torqued properly, all bolts will stretch and can be reused that is, of course there is no corrosion, cracking, and the plating is in good condition. Proper torque is inportant!!
I have never seen a head bolt on an aircraft engine. Maybe something from the 1920's? Aircraft cylinders use studs and through bolts which also hold the crankcase halves together. Airplane and boat engines are an apples an oranges thing.
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Old 20-09-2017, 13:48   #11
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Re: Do I need to replace headbolts when I do a valve job

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Originally Posted by Valmika View Post
I have been told I should replace my headbolts due to possible stretch while I am replacing my headgasket on a 42 Westerbeke. I have rebuilt the head since it was out anyway but they want a bloody fortune for the bolts ($42 apiece) and I have never done on any other engine. I never rebuilt a diesel though. Please any expert opinions on this.
Lots of variables, if the engineers that specified the bolts think they should be replaced then they should be replaced. Not replacing them doesn't mean it won't run. If you particular model engine is not know to have head gasket issues and your particular engine is a lower horse power version of that model engine you would be less likely to have a problem from reusing your bolts. Manufacturers often have higher horsepower versions of same cubic inch engine, They achieve more power by increasing combustion cylinder pressures by adding more fuel and air. Higher cylinder pressure = more likely to have a problem reusing bolts. Bottom line is "Do ya feel lucky".
I would agree with previous advice about looking for cheaper source of quality new head bolts, both OEM and quality brand of aftermarket. I've spent from $11 to $15 per bolt for OEM 6 cylinder diesel. Don't look for a cheap head gasket, look for a cheap high quality gasket. The last engine I worked on, Cummins wanted over $300 for the head gasket set, with some research I discovered that Fel Pro makes that gasket set for Cummins but Fel Pro sells it for about 1/3 the price.
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Old 20-09-2017, 13:56   #12
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Re: Do I need to replace headbolts when I do a valve job

Right, no "head bolts" on an aircraft reciprocating engine, pays to proof-read but, we always performed NDT on the hardware during the rebuilding process. When in doubt, like the originator of this thread, either replace or have them NDT'd. Chances are, if there is no corrosion, they are probably good to go.
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Old 20-09-2017, 14:49   #13
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Re: Do I need to replace headbolts when I do a valve job

I would bet that a high quality supplier like ARP would be able to supply quality US made cylinder head bolts:

ARP | The Official Web Site
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Old 20-09-2017, 15:47   #14
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Re: Do I need to replace headbolts when I do a valve job

are the head bolts torqued down or angle twist type ?
if they are angle tightened you will need new but if touqed then maybe no ,,,
Have a look at the vid ,, motors like the new ford diesel (marinised) need new ,,, I dont know of your motor sorry

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Old 20-09-2017, 16:39   #15
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Re: Do I need to replace headbolts when I do a valve job

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Originally Posted by Valmika View Post
I have been told I should replace my headbolts due to possible stretch while I am replacing my headgasket on a 42 Westerbeke. I have rebuilt the head since it was out anyway but they want a bloody fortune for the bolts ($42 apiece) and I have never done on any other engine. I never rebuilt a diesel though. Please any expert opinions on this.
I rebuild engine, gas and diesel and the first thing I check are the head bolts. To do this, (before cleaning the bolts), count the number of threads that were actually in the block when the head was installed. You will see this by the dirt demarcation. Then wire wheel clean every bolts. Then check beyond the number of threads you counted and check for deformation. If the treads are waving or not uniform then change the bolts. If the Threads are uniform I would not replace them. Before reinstalling the head bolts, I always clean the threads in the block by cleaning by chasing a tap in the block. Then where you counted the number of threads I always put a sealer around the bolt and lightly oil the first thread and then torque to the appropriate torque, no more no less. Never had one go wrong.
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