Quote:
Originally Posted by steve25
I don't like that ARP replacement bolt!
That reduced head size concerns me .
That extended top pad on the factory bolt was engineered there to better releve the bending forces trying to widen that upper part of the rod out to each side because the the rod will tend to go Egg shaped.
I mean for a street rebuild I would use the ARP bolt but other wise I would chance a 3rd or even 4th torque up of the stock bolt.
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I do like the flat, square head of the OE bolts better. It does provide a larger landing area on the rod. Unfortunately, I do not know the full history of the OE bolts. I believe this may be the third time this engine has been apart. Not sure how many stretch cycles it went through on the last rebuild or before that. Typically, three stretch cycles would be the minimum for a single rebuild. 1. to assemble the rods to hone them. 2 to assemble the rods with the bearings for measurement of oil clearance. 3 for final assembly. My guess on the head design by ARP is they looked at their existing dies for 7/16" rod bolts and chose a die that fit the rods with adequate clearance not creating a stress area near the beam. Then made a couple thousand bolts on a short run of bolts. They are so oddly shaped and so specific, they didn't want to start from scratch with new dies for just a few thousand fasteners. Probably the same reason they went with regular 7/16-20 fine thread. I have little doubt the ARP bolt is made of premium material. They also fit nice and snug in the rods. About half the OE bolts just fell out of the rods. Another possible indication they have been overstretched at some point. If I have a chance to dyno this engine, I will certainly take it to the RPM range where the power drops off. I assume around 6000 RPM. No plans to race it or anything like that. But if I want to run it hard on the street some, don't want to be worrying about connecting rods coming loose.