Hello, I had to take the head off my car to do a repair. I had to heat the head bolts up to get them out, but none of them broke and all the treads look good with minimal pitting on the heads.
Would it be ok to reuse these bolts, or since I heated them would it be safer to replace them with parts vendor reproductions?
I'm torn because I hate to throw out perfectly good stuff.
Me I would reuse. You only need to torque the head bolts to about 40-45fp anyway. Be sure to re-torque a couple of times after the engine has come up to temperature. Read my 10:40 posting and some that follow it.
How hot did you beat them? Red?
I quit re-using my head bolts. Over the last 12 years, I've had the head off my 15 two different times. Each time, a head bolt snapped. Fortunately, I was able to get the threaded end out without issue. In any event, it seems after 100 years of heating and cooling, the metal has crystalized. So, I replaced them.
I like to replace stuff like that when possible!! Just my opinion... Tim
Most important is to run a bottoming tap into the threads in the block and clean out any dirt, carbon, rust by blowing with compressed air. Then if you get new bolts, put the head on without a gasket and turn in the bolts until they stop. Don't torque them just bottom them out. If the tops of the bolts are not snug against the head, grind off enough to be able to turn them in. Make all the bolts the length of the shortest one, so that you won't have this happen in the future. When you know that all the bolts are the right length, you will then remove the head and install the gasket.
Thanks for the info guys. I read Mark's post before I posted, good info. I heated them until they were a dull red. I guess it's not worth the hassle if one should break just because of age. I'll just replace them. I'll make sure I clean out the holes good.
As far as the bolt snugness, do you mean grind a little off the head where the head of the bolt contacts if need be?
I will be searching for a good used head. I have two in storage, I need to get them magnafluxed to see if they are cracked. The one on the car has an old JB weld repair to the center where the water circulates. It has never leaked but I'd rather not chance it, this is the time to replace it.
Bryan - I'm sure Norm doesn't need me to answer for him, but I happened to notice your question, and I'm sure that Norm meant that if a new bolt bottoms out, to grind off a bit of the threaded end of the new bolt which in effect, shortens the over all length of the bolt.
Yes, What Harold says. You see many heads and blocks have been resurfaced which makes a good gasket seal, but also in that case the bolts are too long. What I mean is when you tighten the bolts with no gasket, the bolts should turn all the way down to the head. If the head of the bolt is raised from the top of the head, the bolt is too long and you should take out the bolt and grind off a bit from the threaded end, then try again. The reason for making all the bolts the same length is so that you can place them in any order without having any too long.
By using bolts the correct length, you will be able to compress the gasket when you torque the head. If the bolts are too long, they will bottom out and although they feel tight and the torque wrench reads tight, they will be tight against the bottom of the bolt holes and not at the top where they contact the head.
I hope this longer explanation will help you.
These guys are probably more knowledgeable than me-
Norm touched on it well, in that using a bottom tap and cleaning up the threads/hole properly, will make all the difference. Les I am guessing is addressing the idea of altering the metal/grain structure with putting too much heat in them thus "weakening" them beyond there purpose. If reusing the old, using a die to chase the bolt as well will get the threads back into shape to transfer the load/clamping properly for a T's purpose. You can get into spot facing the head so the bolt does contact at the surface flat/perpendicular, but in my opinion this is more a "racing" extreme worry and probably not as big of concern for a T. A suggestion if you wanted to fool with it would be to check out a site like ARP an learn to be dangerous with some basic information better than I could give concerning the engineering behind fasteners in general. It is a fascinating engineering field all its own. I now on anything off road that I race, tap and dies keep things sort of in line as we constantly are take things apart and it puts a beating on the threads and there ability to clamp properly as well as stay in place. Head bolts are probably one of those "put new in after a certain number of uses" or an unusual event. Again judgment on our 90 year old engines allows us to be a little more loose about reusing hardware as opposed to modern things. Just a few opinions. Hope it all gets back together well. TS
For a slightly higher price you can buy aviation grade bolts. The metallurgy is far superior than anything made a century ago and that has been exposed to possible intergranular corrosion and has stress cracks from thermal swings and tension.
It would be interesting to do die penetrant or magnaflux tests on old bolts to see what shows up.
Make sure to clean out the steam holes while the head is off. KGB
Let us know how it went and any tips you learned. I would like to make a checklist before I start on mine, so I don't get excited and leave my wrist watch inside a cylinder or anything silly like that.
Also, is it safe and advisable to use a wire brush to clean out The carbon deposits I see on my system tops and valves? I peeked into each cylinder with a camera when cleaning my 3 week old plugs. The carbon is so thick that it looks almost like crystallized lava on the pistons.
I've purchased the reproduction bolts several times. They are always too long. It is absolutely critical to install the head bolts with no head gasket first to make sure they do not bottom out. Again this is the same thing that you would do if working on a lawn mower or any other kind of engine.
As far as a checklist Chris I don't think there is a checklist for being a good mechanic.
Well they are old and at best only Class 2 bolts, the new ones are Class 8 as I've been told and cheap enough. Many people have them break when torquing up to 50lbs. Be sure to clean out the bolt holes. I found all kinds of junk in Derrick Pangs engine.
$10 for a full set from Langs
Most of those bolts that break are due to bottoming out in the hole. The advice to clear the holes with a bottoming tap and blowing the trash out with compressed air is sound advice. Also, follow Royce's recommendation to ensure the bolts aren't too long by temporarily installing without gasket.