rke_011

Head Bolts For 5K

11 posts in this topic

Hey,

About to start building my 5k with 4k head.. but need head bolts seeing I can't get my hands on studs.. any one got an idea if I would have to buy 5k or 4k bolts? Or are they the same length?

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If you have both heads there you could measure the bolt length required for both heads and compare.

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When you are mixing heads & blocks, which may or may not have been skimmed or decked respectively, the best way is to measure the length required. It's not hard, but is important. If the head bolt is too long, it will bottom out in the threaded hole in the block, with all sorts of problems. If the bolt is too short, then not all the thread in the hole is used, with also possible ramifications of thread failure.

 

Clean the block threaded holes to make sure there is no rubbish in there. A tap helps. Measure the precise depth of the hole & note. Lay the head on its side & put a head bolt through the head, not forgetting to fit the hardened thick washer, under the bolt head. Put an old head gasket up against the head, & measure the length of thread sticking out beyond the head gasket, & note length.

 

This length should be approximately the depth of the block hole, previously measured, less the thickness of 2-3 threads of the head bolt.

 

I've always used this technique without problems.

 

It would be advantageous to use new bolts. The bolts you have are probably 30-40 years old & you never know how many times they have been tensioned. Head bolts stretch, each time they are tensioned, which is why manuals always suggest replacing them.

 

Hope this assists.

 

Cheers Banjo

Edited by Banjo
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Cheers.. seems there is no bolts in Australia.. well there are 2.. so I'll be looking into studs.. if anyone can point me in the right direction

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Your predicament is not unknown. It's been mentioned on here previously.

 

Here is a previous post with a few ideas & P/Ns, from about 3 years ago.

 

http://www.rollaclub...7-in-australia/

 

Cheers Banjo

Edited by Banjo
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I found in my adventure when building my 5k that the 5k headbolts are torque to yield bolts, meaning they cannot be used again once they are torqued down, and the 4k ones are not. However i myself believe that the 4k head bolts would also stretch, you could try finding an unopened 4k (there are a few getting around) and steal the head bolts out of that. My 5k was high high compression so it kept lifting the head and blowing the headgasket so i ended up going to Boltmasters (my local bolt shop) giving them my stock 4k headbolts and asking for some similar, they hooked me up and theyve been holding my head down ever since.

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Well guys...thanks to this topic and Dregs answer, it suddenly occurred to me that there is a Fastenal store not two blocks behind me. I've been considering ordering new bolts from RockAuto but they are $200. I'm about to bore and rebuild my 3K.

After reading this, I just looked and I can get SAE Grade 8's for about $2 apiece. Hmmm....$20 vs $200....what will I do? As long as these originals don't turn out to be some funky thread pattern. Gotta wait til after Christmas to find out though.

 

Thanks and Merry Christmas!

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Well it's after Christmas...and he can't get them. I brought one of the Toyota head bolts with me, it has no marking except some kind of symbol but this guy thinks they are grade 11 or 12. I don't know these things. Do any of you?

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