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H22A with ARP main studs, how much is too much out of round?

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Old Feb 18, 2025 | 06:32 PM
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Default H22A with ARP main studs, how much is too much out of round?

I know there are a lot of threads covering the gist of using arp main studs on this forum, but I wanted to get a little more nitty gritty with measurements, specs, and what's in tolerance. The FSM for the H22A doesn't talk about main cap measurements with bearings and crankshaft out so I've come here to see if someone has any experience with this particular topic. I threaded the ARP studs in finger tight and torqued them down using the pattern in the FSM

I first torqued them to 22 ft lbs, followed by the factory final spec of 54 ft lbs.
I took measurements of the main caps and they were all less than .001 out of round.

I then torqued them down to 80 ft lbs and this distorted the main bores quite a bit more with the measurements almost being .002 out of round.
It also pulled the top/bottom side of the main cap down about .001 across all 5 journals, but it didn't change too much on the breaking left/right line.
If anything I think it made the measurements more consistent left/right.

Here are my measurements below:


So I guess my question is for ARP main studs, how out of round is too much? How much distortion is okay?

Last edited by lube_n00b; Feb 19, 2025 at 08:21 AM.
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