235-261's use 1/2 inch main bolts in two different sizes, the rod bolts are 3/8
You never know where bolts have been in over 50 years, more likely than not ,over tightened by a past hack.New bolts are cheaper than running over your own crankshaft.
You can't mike a bolt unless you know the length of each one when it was new.GM didn't machine each bolt to an exact length like ARP does.
The 351 Cleveland rod bolts were suggested to my friend by ARP themselves as the diameter of the machined shank is exactly the same as 235 rod bolts.The grade 9 bolts from the industrial supplier are 170,00 psi, same as the "economy" bolts from ARP.
If you're doing a low cost re ring and bearing job, the old bolts are probably Ok.But today ,with the cost of parts and machining for these old engines on a first class rebuild,it's cheap insurance to replace bolts.
