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Hypatec pistons 351 Cleveland clearance issue

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Hi all, I have started dummy assembling a 351c together and have noticed once I installed pistons I have very little clearance between the bottom of the piston skirt and the crank counterweight. In one case it actually touches. Just wondering if anyone has ever encountered this or used these hypatec cast pistons before.

The engine has just been balanced So I want to take off as little material as possible. My next question is, would taking off material from just one side of the piston skirt be a bad idea and would taking material off from that area weaken the piston at all. Hard to see in the pictures but it is directly under the piston pin.

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It's not that unusual to run quite close, but hitting?

My initial thought was there's a mismatch of parts - the FORD Cleveland engine had at least three different stroke engines that I'm aware of - 302, 351 and 400 which was sometimes designated M400, or similar (not a FORD engine chap), and obviously they had different strokes but I have no idea of pin heights and connecting rod lengths to accommodate the deck heights - are those heights in the correct range?

Could you have been supplied 302 pistons, maybe with matching connecting rods if bought as a set, as they may have had more counterweight clearance. Something to talk to your supplier about as if it isn't as described?

Regardless, it doesn't help in your case, as you will need to either relieve the piston skirts - shouldn't affect their strength or wear characteristics - or use pistons with more clearance. Either way, talk to your engine balancer and see what they think - I suspect you will need to re-balance and it's a reminder to us ALL, not to assume something and make balancing one of the last things to do, at least after the initial dummy builds.

Thanks for the reply. I did try reaching out to the supplier but haven't had a response. All the piston/rods measure up the same weight so I will try just taking away the same amount on all pistons. Was more worried about weakening the piston somehow. My machine shop has said it will be fine however i wanted another opinion.


Hi Jeremy i have found this issue also and have machined just that side to maintain a 2-3mm clearance

the effect on the overall balance of the engine didn't seem to be affected at all

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