What steel grade in engine bolts

[Roberto]

What steel grade has been (should be) used in Perkins engine bolts/nuts?
I am looking for some replacement bits (head, injector bolts/studs, etc), some of them have been replaced by metric so no longer OEM, can for example 8.8 be considered ok, or should I look for higher grades 10-12?

 

[DownWest]

I would think 8.8/ high tensile would be good enough.

 

[vyv_cox]

I would think 8.8/ high tensile would be good enough.

I agree. I can think of no automotive bolting applications that would need to be stronger. I do know, from someone else's bitter experience, that the big-end bolts in a Volvo D2-40 are nowhere near as strong as that, more like 4.6 I would guess. Brittleness increases with strength grade, making the risk of snapping them greater.

 

[Roberto]

thank you both DownWest and Vyv
8.8 it will be; besides, stronger bolts are increasingly difficult to source, especially in small quantities

regards
r

 

[DownWest]

One comment:
The flywheel single use bolts on a 1600 Ford were 10:8 or something and I had to get some sent out from UK. Fine thread too.
Luckily, my local tractor shop has a good stock of 8:8 metric and AF bolts. Even 8:8 threaded rod in I mtr. lengths.