Can I use a slightly smaller head bolt head size than stock?

(2010-05-30 10:58:54)

1. jeremy Says: Puttin on new gaskets on a 1951 flathead engine. I have a set of headbolts (grade 8, 5/8 head). Should be ok to use a slgihtly smaller head than the stock grade 5 11/16 head right? Other than the size of the head, the bolt is the same dimension. Cast iron heads.

2. Kevin Says: no you cant use a smaller bolt, there will be slop side to side up and down, just spend the money and get a set of bolts that are right

3. Infinitrium Says: I wouldn't do it. There would be less than optimal clamping force to hold the head down due to the smaller bolt head size.

4. JB Says: I doubt you'd have any problems with it.

5. Wesley Says: If your too tight to go get the correct bolts, just put a hardened washer under the head. Make sure you use engine oil under the head of the bolt and on the thread.

6. Steve Says: I would use it as long as there is a spacer washer under it, This should help transfer the torque.
Be sure to oil the threads and let only the residual remain on the threads.

7. thundercats Says: I don't know about the head size but the grade needs to be the same or the bolt will snap.
http://www.boltdepot.com/fastener-information/Materials-and-Grades/Bolt-Grade-Chart.aspx