Rod side clearance
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Rod side clearance
Building my 421 shortblock, got everything mocked up to grind clearance on the rods for the cam lobes and I checked my rod side clearance and it is at .026" on the two journals that I checked. Does this seem excessive? I assume there is nothing that can be done about it short of buying another crank or different rods.
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Re: Rod side clearance
thats .026" divided over 3 points of clearance, about .008" and a bit per clearance point you have no problems. This is oil exit area for the big end bearings, there needs to be enough area to allow enough flow.cgarb wrote: ↑Sun Apr 22, 2018 8:08 pm Building my 421 shortblock, got everything mocked up to grind clearance on the rods for the cam lobes and I checked my rod side clearance and it is at .026" on the two journals that I checked. Does this seem excessive? I assume there is nothing that can be done about it short of buying another crank or different rods.
Craig.
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Re: Rod side clearance
I found a spec online somewhere for factory type SBC specs and it was .010-.020" my .026" was out of that spec so I was just asking to be sure I wouldn't have any issues with that. Taking my time, checking all my clearance's so I can hopefully have an issue free racing season...well late start to a racing season...lol.
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Re: Rod side clearance
Have you ever heard the saying---a little loose, nobody knows. Too tight, everybody knows (when she self destructs) ? David Reher of Reher Morrison Racing engines stated, my feelings on engine clearances in pretty simple i would much rather it be a little loose than on them tight side. Mark H.
Re: Rod side clearance
Yes, I have heard that before...I'm a machinist by trade and a bit OCD when building engines. I can't help it... Thanks for the advice. Do you think I could make a .008" thick shim to put between the rods?....just kidding.
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Re: Rod side clearance
I remember that thread and the issues about excessive oiling...that's not my issue here. I was just concerned about the mechanical ability of excessive clearance keeping the rods 90 deg to the crankshaft. My pistons are not guided at the top so I was worried about one of my rods deciding to take a stage right outside the block. That seems to be not an issue with the general consensus so I'm going to continue on with the build.
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Re: Rod side clearance
The old rule of thumb for connecting rod side clearance is 4 times the bearing clearance, minimumcgarb wrote: ↑Sun Apr 22, 2018 8:08 pm Building my 421 shortblock, got everything mocked up to grind clearance on the rods for the cam lobes and I checked my rod side clearance and it is at .026" on the two journals that I checked. Does this seem excessive? I assume there is nothing that can be done about it short of buying another crank or different rods.
I don't think you will see any issue.
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