Do I need to replace headbolts when I do a valve job

[seabreez]

Originally Posted by Valmika

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.

There are other variables... on some engines you must use special torque wrenches. You torque the head bolts and then you have to turn additional so many degrees that the torque wrench will measure. At this point the head bolt uses elasticity to pull down on the head. In this engine service manual they recommend to replace the head bolts... then I would replace the head bolts...

[Lepke]

I've done many engines in my life, mostly marine diesel, but also racing gas and piston aircraft (original training). Even on racing engines, head bolts don't get changed every time. Westerbeke isn't the only source for new bolts. They add marine components to basic engines that other companies built. Westerbeke is known for price gouging.
A decent auto parts store or tractor supply should be able to supply head bolts, but I doubt you need them. The price should be well under $10 each. More like $25 a set.
Inspect the threads and run a cleaning tap down the holes.

[a64pilot]

Originally Posted by seabreez

There are other variables... on some engines you must use special torque wrenches. You torque the head bolts and then you have to turn additional so many degrees that the torque wrench will measure. At this point the head bolt uses elasticity to pull down on the head. In this engine service manual they recommend to replace the head bolts... then I would replace the head bolts...

Known as the wrench arc torque method, it is supposedly more accurate than simple torque as it measures bolt stretch.
Bolts stretch, that is how they work, many high strength, high stress bolts should not be reused. Guy I think spoke of rod bolts as an example, and it's a good one. If the manufacturer recommends bolt replacement, then maybe you ought to.
I believe Mercedes and others have for a very long time, although US engines almost always reuse of the bolts is fine.

Steel is more elastic than rubber, hard to believe but its true, but steel fatigues too.

[Valmika]

Just so everyone knows, Westerbeke wants $42 a piece for the 10 12 MM * 120 MM bolts and $24 for the 4 10 MM ones. I like the idea about checking the threads. What is a DNT check? Dye?

[model 10]

It's NDT ( non destructive testing.) The only worth while test is going to be Magnaflux. An good automotive maching shop uses this equipment to check crankshats and connecting rods etc. Trouble is, these days they often use just a powder and black light like the Zyglow process and that is not so hot for what you need. Zyglow only finds surface cracks where Magnaflux can detect cracks below the surface.

[Kita]

Originally Posted by Valmika

Just so everyone knows, Westerbeke wants $42 a piece for the 10 12 MM * 120 MM bolts and $24 for the 4 10 MM ones. I like the idea about checking the threads. What is a DNT check? Dye?

Don't know anything about prices,but that's steep for bolts I think, shop , but at that price & with them saying to replace,tells me those are most likely a one time use bolt..they kinda stretch at tq. Then next time they may stretch easier, so bottom line inconsistent tq. May be a problem, may not be ...but if it was in an airplane..I am not that lucky......done to many heads...all that work, risky......I would definitely be shopping

[hellosailor]

Valmika-
A friend of mine had an engine rebuilt. And having grown up in the Depression, he kinda still practiced being very tight about money. So he told the shop to re-use some bolts (holding the pistons to the bearings) that the shop said should not be re-used.
A little over a year later, guess what failed? And he had to rebuild the engine a second time.

Same thing with head bolts. MANY engines specify that the bolts are used once, torqued once, and REPLACED if they are removed. Some do not. The reason may be that there are different metals used, and the bolts are not all the same. Whatever it is...you can check with the manufacturer or the maintenance manual for what is right for THAT ENGINE and the bolts from THAT MAKER. Or, you can expect the bolts will be improperly torqued and you may blow a head gasket a year or three from now.

It doesn't seem right to throw away perfectly good bolts, but "penny wise pound foolish". Follow the factory advice for that particular engine, because they are NOT all the same.