retorquing head bolts - how often and what are the benefits?

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Just wondering how often folks retorque their head bolts? Is there a performance benefit or is it more to protect against a gasket failure?
 
When a head and block get hot, the bolts can stretch and gaskets can squeeze a little thinner. Not always, but it's possible. Checking the torque on head bolts is just a precautionary thing. One of those things you don't want to guess about.
 
We haven't had any issue with head gaskets but we pull the head mid season to touch up the valves. Maybe others have and we have just been lucky. I gave had good success with reusing the gasket when we do this. Input a new one on in the off season. Ymmv..
 
We haven't had any issue with head gaskets but we pull the head mid season to touch up the valves. Maybe others have and we have just been lucky. I gave had good success with reusing the gasket when we do this. Input a new one on in the off season. Ymmv..

Have you measured your head gasket for compliance after the second use? Curious as to how much more crush you are seeing. While the gaskets are not coming from the factory as close as they once were, if they compress as much the second time as they do the first, I am concerned they are very close to non-compliance and I don't want to take the chance.
 
From what I have heard is you are ok to reuse them once. Of course this is assuming you torque the head bolts to a reasonable limit. I personally have not measured them. They are cheap anyway so change it if your worried.
 
^^ Yes, be careful reusing head gaskets.
They compress down too much and can get you tossed in tech -- that is another reason that I tell customers to never re-torque the head bolts while the engine is hot.
 
Just wondering how often folks retorque their head bolts? Is there a performance benefit or is it more to protect against a gasket failure?


It's good practice to check them occasionally. I see no harm in doing that. Just be sure you have a quality torque wrench and that it is reading correctly.

I've seen engines come in our shop that have run a full season and the upper left head bolt (closest to the exhaust) was only fingers tight when pulling the head. These heads typically leak between the top two head bolts over time due to the corners of the head pulling down (especially the upper left corner near the exhaust.) That bolt will lose torque first. It's also the toughest to get to. You will pretty much have to remove the exhaust pipe to get on it straight with a socket.
As preventative measure, you can break the bolts loose 1/4 turn, then creep up on them 10 inch pounds at a time until you achieve your desired torque value (220"# is a good place to end up.)

In my opinion, if you're going to take your maintenance seriously, it's a good time to swap out heads to a spare fresh one, and send the old one off to be touched up. Have the correct head gasket on hand, replace, and you're golden.


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Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
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31 years of service to the karting industry
Linden, IN
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We did this. It was kind of a pain - as Brian points out for a little more work one could swap out for a fresh head which - which is what we will probably do next time.
 
The head bolt next to the header pipe WILL get loose over time.
The reason it gets loose is that the head gets so hot in that area that the aluminum will actually get soft and compress.
The reason for the heat disperser under that head bolt is to HELP prevent that from happening. It does really help!
If you mark that head bolt on a new engine and check it mid way through the season (depends on how many races) you will find that it hasn't moved at all. It hasn't actually turned or loosened.
Hear's what i'd recommend. Mark the head bolt and a corresponding spot on the head with a sharpie. Use a rachet or breaker bar and loosen the head bolt 1/2 turn and then use a good inch pound torque wrench and re-torque it to 210" pounds. Next check to see if the marks you made with the sharpie line up again. Most of the time they won't line up because things have compressed a little bit.
Before Briggs installed the heat disperser we would see the flange on the head bolt distort and the aluminum under the head bolt get distorted / dished.
My suggestion for those that have the proper tools and ambition is to remove the header pipe, mark the bolt and head with a sharpie, then loosen the head bolt 1/2 turn and re-torque that head bolt 1/2 way through the season. While your at it put a new header gasket on also.
If for any reason you have to remove the header pipe i's suggest checking the head bolt also.
Good luck
Jim
 
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