Oil pan clearance to crank bolts

Old April 21st, 2019, 09:36 PM
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Oil pan clearance to crank bolts

I am assembling a 455. My machine shop fastened the crank using studs rather than bolts. But now the oil pan hits the studs before sealing against the block. My question is what is the big difference using studs instead of bolts? Obviously, these studs will need to be cut down, but I'd rather just use bolts--much easier. I do know you get "truer torque readings" using studs. But this is a daily driver that I'll never race. 5,000 rpm is the max this engine will ever turn.

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Old April 22nd, 2019, 12:10 AM
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Are the studs screwed all the way in ?
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Old April 22nd, 2019, 04:45 AM
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Take the engine back to the machine shop and tell them to reassemble the bottom end with the original hardware. There's no reason to use studs on the main bearing caps of a street driven engine. In fact, I would consider that engine suspect now. Why would a machine shop spend extra money for main bearing cap studs when assembling an engine that the owner never asked or payed for? Chances are they cut corners and used hardware store studs. Even Grade 8 studs are too weak for main bearing caps. The OE hardware was engineered correctly when the engine was built.
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Old April 22nd, 2019, 06:45 AM
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The line bore may have to be re-done as it is affected by the type of hardware. I agree that there is nothing wrong with the stock bolts for your application.
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Old April 22nd, 2019, 07:07 AM
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Yep
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Old April 22nd, 2019, 07:08 AM
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Actually, it's a really good shop. They build racing engines. I think he was wanting to use "the best" stuff. But you're right, it's overkill for a daily driver.
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Old April 22nd, 2019, 07:10 AM
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Yeah, you're right. I just talked with the shop. Can't switch to bolts now because the stresses are different and might affect the housing bore. I don't want to take it apart again, so I'm going to (carefully) cut down the studs.
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Old April 22nd, 2019, 07:14 AM
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Studs are stronger than bolts & offer more clamping force due to the fine thread on the nut side.

If they changed the fasteners, they should have line bored/honed the engine to keep everything straight... the main bore distorts from the clamping force of the bolts/studs.
If they didn't you need to take it back & get things done correctly.

The studs should be installed finger tight in the block. You can easily remove them & cut off the excess length for better clearance.
FYI, I have the studs sold by Mondello in my 442 & they clear the factory pan with no issues.
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Old April 22nd, 2019, 07:26 AM
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Dimple the oil pan with a suitable motivator (hammer) as necessary. Not terribly uncommon on the big blocks.
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Old April 22nd, 2019, 08:35 AM
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Tap the main stud holes until the studs are able to bottom out or close to it (do not bottom them out).
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Old April 22nd, 2019, 11:05 AM
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Originally Posted by Lonnies Performance View Post
Studs are stronger than bolts & offer more clamping force due to the fine thread on the nut side.

If they changed the fasteners, they should have line bored/honed the engine to keep everything straight... the main bore distorts from the clamping force of the bolts/studs.
If they didn't you need to take it back & get things done correctly.

The studs should be installed finger tight in the block. You can easily remove them & cut off the excess length for better clearance.
FYI, I have the studs sold by Mondello in my 442 & they clear the factory pan with no issues.
Yes, they did all machining with the studs torqued. I was able to remove them one at a time and cut them down--success! The reason they're so close is because I'm using reinforcing straps on the crank.
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