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I've been waiting to post an update until I get this issue sorted but basically I encountered an issue with the hypermax kit:
They provide 9/16 ARP studs to attach the bedplate to the block and instruct you to drill and tap the existing M12 holes for that thread.
In threaded joints the first thread sees more stress than any other thread so the holes in the stock block are counterbored. This puts thread engagement deeper in the web such that there's a bunch of meat above that first thread: Pic from a YouTube video
After drilling and tapping for the larger studs the holes in the register are now bigger and therefore closer to the bearing cradle:
The problem is the threads are to the top so the weakly supported threads right next to the bearing cradle will see the most stress, potentially leading to a fatigue induced crack.
The auto machinist who did the work said the holes shouldn't be counterbored because that would bring edge of the hole right up to the bearing cradle and a crack would eventually form. He recommended grinding threads off the fastener to get the desired thread engagement.
We talked with an engineer at ARP who recommended just turning down the stud shank and undesired threaded portion because it will create a stronger fastener vs just grinding the threads off (which would concentrate fatigue on that portion). So the studs have been sent off to a machinist to be modified to be reduced shank like this:
This will put thread engagement deeper in the block where it should be without having to do a risky counterbore. Once the studs are done in a few weeks, can get back to reassembling.
So lack of update is because I had to do a mini crash course on bolted joint design to figure the best solution to this issue. In retrospect, I would have just bought the bedplate without the studs and bought M12 ARP studs of appropriate length.
In the meantime I've been doing a complete file deburring of the deck's coolant and oil passages and chamfer of the head stud holes. Also the cap registers and pan rails. Will make it easier to wipe clean without snags, reduces chances of cracks forming.
Have also been practicing my lapping process on an old head. Doing this to the deck and heads will allow me to get the best finish possible for Cometic MLS gaskets.
Will also be using a sand paper process on the cam lobes to achieve a low RA finish. This will result in a lobe surface that will better support the increased lifter roller contact pressure from the beehive valve springs.
Just don't remove too much or the elasticity will change thus screwing up your torque specs. Should not be a problem for decent machinist. Mic the diameter and look for consistency.
Just don't remove too much or the elasticity will change thus screwing up your torque specs. Should not be a problem for decent machinist.
We're going to turn the shank and the unwanted threads down to the minor diameter of the coarse thread (5 thou tolerance on that diameter is the goal). It's not a lot but it's enough to require recalculating torque... I should be able to hit the same preload as before without getting into yield territory.
We're going to turn the shank and the unwanted threads down to the minor diameter of the coarse thread (5 thou tolerance on that diameter is the goal). It's not a lot but it's enough to require recalculating torque... I should be able to hit the same preload as before without getting into yield territory.
If the machined bolts are a few thousandths different than nominal diameter I would not worry about it.
But a tenth? Then ya gotta do math. Math that is beyond me. Look up Young's modulus and despair.
For a while I did tensile testing of half inch steel test bars. ASTM testing to qualify cast steel parts. Nominal diameter of the test bars was .500". Each test bar diameter was measured and the computer factored that into final tensile/yield strength. A few thou did not really make much difference. But .005 was noticeable, and a tenth out was cause for rejection.
Surely ARP can tell you what the new torque value to achieve the same preload with the turned shank studs, can’t they?
Maybe they can. The problem is there's a bunch of unknowns. Tightening via torque has an uncertainty of maybe 25% in ideal conditions. Using ARP studs, washers, lubricant helps make things more consistent but even the burnishing of the threads from one tightening can drastically effect the resultant torque on the second tightening. If I can reach the engineers again, will see what they have to say. Using stretch would be best but not so easy to measure on a blind hole stud.
Originally Posted by aawlberninf350
If the machined bolts are a few thousandths different than nominal diameter I would not worry about it.
But a tenth? Then ya gotta do math. Math that is beyond me. Look up Young's modulus and despair.
Figuring 215KPSI uts, with a min tensile strength area of 0.1626in² (tolerance is 5 thou on diameter, which means ~2% variance on area) I get a max of ~35,000 lb force. I just need to find the right percentage of that to replicate the unmodified stud's clamping force (which I think can be ballparked using the standard formula and the K factor of the lube Hypermax provided which is 0.16).
Anyway, first stud from machinist friend looks great:
I would want the same clamping force as was exerted during the line bore.
Why are the fasteners different than when the machine work was completed?
Did they not have these studs available during the machining timing?
Why not use the same fasteners at the same condition as was set (torque I assume) during machining?
I would want the same clamping force as was exerted during the line bore.
Agreed, that's the goal.
Originally Posted by RacinJasonWV
Why are the fasteners different than when the machine work was completed?
Did they not have these studs available during the machining timing?
Why not use the same fasteners at the same condition as was set (torque I assume) during machining?
