Head bolts

T

tarawa

Active member
Can standard off the shelf bolts be used as head bolts? There is a slight difference in length, but not enough to matter in my opinion. I used off the shelf grade 8 bolts, but used a washer. I don’t know if it was a good idea to use washers.
 
I have read that it is ok to use washers under head bolts, provided the washers are hardened steel. You could cut the bolts to length, but should use a nut installed on the bolt to protect the threads. The lower half inch of the bolt threads should be coated with a non-hardening, PTFE sealer, because the bolts extend into the water jacket.
 
some of my cub motors have washers under head bolts ----some dont--- they were that way when I bought them.
 
tarawa":15rz9zit said:
Can standard off the shelf bolts be used as head bolts? There is a slight difference in length, but not enough to matter in my opinion. I used off the shelf grade 8 bolts, but used a washer. I don’t know if it was a good idea to use washers.
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You could cut them to length?
 
My concern about cutting them is that you remove any protective coating there might have been and may make the bolt end more susceptible to rusting. Probably not a problem except for the guy 25 years from now trying to remove the head.
 
Bob McCarty":7lvsp4fl said:
My concern about cutting them is that you remove any protective coating there might have been and may make the bolt end more susceptible to rusting. Probably not a problem except for the guy 25 years from now trying to remove the head.
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On the other hand, exposed threads sticking into the water jacket may have their own rust in 25 years. When you are ready to remove the bolt, I think I'd rather have a rusty end than rusty threads. I'd cut off the excess.
 
Jim Becker":1eba7cru said:
Bob McCarty":1eba7cru said:
My concern about cutting them is that you remove any protective coating there might have been and may make the bolt end more susceptible to rusting. Probably not a problem except for the guy 25 years from now trying to remove the head.
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On the other hand, exposed threads sticking into the water jacket may have their own rust in 25 years. When you are ready to remove the bolt, I think I'd rather have a rusty end than rusty threads. I'd cut off the excess.
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i certainly understand Jim's point. Would there be any corrosion if quality coolant was used?
 
I think it is important to have the bolts the correct length more than the risk of corrosion from the coating being removed. The original bolts were a lower grade and not coated. What about the risk of corrosion of having more of the bolt in the coolant, or having a washer in a location where one is not specified?

The coating is extremely thin. The coating does provide protection but the main concern could be surface corrosion in the tread area which should not be impacted by taking a little coating off. Also, a high-grade bolt is made out of a better material which will have corrosion resistance as well

The general suggestion on this site is to use a Head Bolt and Water Jacket Sealant like permatex thread sealant or Loctite 1158514 Head Bolt and Water Jacket Sealant to seal and reduce corrosion. You want a sealant in this application that stays pliable and does not harden.
 
tnestell":2cnzi8lu said:
i certainly understand Jim's point. Would there be any corrosion if quality coolant was used?
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inairam":2cnzi8lu said:
I think it is important to have the bolts the correct length more than the risk of corrosion from the coating being removed. The original bolts were a lower grade and not coated. What about the risk of corrosion of having more of the bolt in the coolant, or having a washer in a location where one is not specified?
. . .

The general suggestion on this site is to use a Head Bolt and Water Jacket Sealant like permatex thread sealant or Loctite 1158514 Head Bolt and Water Jacket Sealant to seal and reduce corrosion. You want a sealant in this application that stays pliable and does not harden.
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I think there is more coolant-specific risk from coolant that isn't regularly changed rather than the original quality of the coolant. I know I'm guilty of this.

I also think (no proof) that if adding a high grade washer will keep the end of the bolt out of the water jacket, it is a completely acceptable approach. Asking about choice of sealer is a little like asking about motor oil brands. In this application, it needs to be non-hardening to allow for retorquing the bolts (okay, cap screws). If you use something like RTV, the seal will be compromised by the retorquing. My current inclination is to use Teflon pipe sealer, even though it is more of a lubricant than an actual sealer.
 
Many automotive applications use washers on cylinder head "cap screws", they are always of the ground and hardened variety. I see no issue in using them, either, as long as they are hardened washers.
 
I purchased a set of grade 9 head bolts from FASTENAL, and used a grade 8 washer to make them the correct length for the block. Not sure but seems the price was less than $50, picked up at the local store.
 
I also ordered replacements from Fastenal several years ago, but cut the few slightly longer ones to length. (I ordered 2 sets while I was at it)
FYI, Hamilton Bob (site sponsor) offers a set for $28. They don't list the sizes, but their price is very attractive vs. many options available.
 
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