.0032 Main Bearing Clearance?
.0032 Main Bearing Clearance? Got my shortblock from Thompson this week. Clearances for the blueprint are:
Piston to wall - .005"
Rod bearing clearance - .0021"
Main bearing clearance - .0032"
At first glance, the main bearing clearance seemed pretty large? Just wanted to get some thoughts.
Also, always wondered, how much do bearing clearances have to open up to see a change in oil pressure? For example: if I went from a .0025 to a .0032 main bearing clearance, would that be noticeable on oil pressure?
Piston to wall - .005"
Rod bearing clearance - .0021"
Main bearing clearance - .0032"
At first glance, the main bearing clearance seemed pretty large? Just wanted to get some thoughts.
Also, always wondered, how much do bearing clearances have to open up to see a change in oil pressure? For example: if I went from a .0025 to a .0032 main bearing clearance, would that be noticeable on oil pressure?
Got my shortblock from Thompson this week. Clearances for the blueprint are:
Piston to wall - .005"
Rod bearing clearance - .0021"
Main bearing clearance - .0032"
At first glance, the main bearing clearance seemed pretty large? Just wanted to get some thoughts.
Also, always wondered, how much do bearing clearances have to open up to see a change in oil pressure? For example: if I went from a .0025 to a .0032 main bearing clearance, would that be noticeable on oil pressure?
Piston to wall - .005"
Rod bearing clearance - .0021"
Main bearing clearance - .0032"
At first glance, the main bearing clearance seemed pretty large? Just wanted to get some thoughts.
Also, always wondered, how much do bearing clearances have to open up to see a change in oil pressure? For example: if I went from a .0025 to a .0032 main bearing clearance, would that be noticeable on oil pressure?
Launching!
Joined: Mar 2019
Posts: 267
Likes: 171
That's quite a bit of spread between the rod and main bearing clearances. I personally like to stick with .001" per 1" of journal diameter.
The issue with that much spread is you've got rod bearings wanting a 30 grade and mains wanting a 50 grade. You either run a 15w-50 or 20w-50 and risk overheating / spalling the rod bearings or run a 30 grade and risk insufficient oil wedge in the mains. I'd want to get the mains down to around .0024". Unless this engine is pushing 1,000+hp, you'll get better load carrying capacity with clearances closer to .002" anyway.
The issue with that much spread is you've got rod bearings wanting a 30 grade and mains wanting a 50 grade. You either run a 15w-50 or 20w-50 and risk overheating / spalling the rod bearings or run a 30 grade and risk insufficient oil wedge in the mains. I'd want to get the mains down to around .0024". Unless this engine is pushing 1,000+hp, you'll get better load carrying capacity with clearances closer to .002" anyway.
That's quite a bit of spread between the rod and main bearing clearances. I personally like to stick with .001" per 1" of journal diameter.
The issue with that much spread is you've got rod bearings wanting a 30 grade and mains wanting a 50 grade. You either run a 15w-50 or 20w-50 and risk overheating / spalling the rod bearings or run a 30 grade and risk insufficient oil wedge in the mains. I'd want to get the mains down to around .0024". Unless this engine is pushing 1,000+hp, you'll get better load carrying capacity with clearances closer to .002" anyway.
The issue with that much spread is you've got rod bearings wanting a 30 grade and mains wanting a 50 grade. You either run a 15w-50 or 20w-50 and risk overheating / spalling the rod bearings or run a 30 grade and risk insufficient oil wedge in the mains. I'd want to get the mains down to around .0024". Unless this engine is pushing 1,000+hp, you'll get better load carrying capacity with clearances closer to .002" anyway.
That main bearimg clearance does seem excessive but it depends on what application the engine was built for. It wouldn't really hurt anything. You may want to run a Melling 10296 or even a GM VVT pump to keep the pressure at idle at a reasonable level.
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Just to update this thread. I discussed with Kyle today over at Thompson and he was A-OK with the clearances.
Said he had no issue whatsoever with them. I'm running Thompsons recommended Moroso pump, and he also recommended 20W50 for the oil weight.
Motor was build for 150-200 shot of nitrous. 416 LS3.
Said he had no issue whatsoever with them. I'm running Thompsons recommended Moroso pump, and he also recommended 20W50 for the oil weight.
Motor was build for 150-200 shot of nitrous. 416 LS3.
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Verdad Gallardo Also, FWIW, I found an article from Mahle/Clevite stating that they recommend .001 per inch of journal diameter + .0005 for a higher performance application, which does put me right at .003, so really, I am right there I guess.
Launching!
Joined: Mar 2019
Posts: 267
Likes: 171
Just to update this thread. I discussed with Kyle today over at Thompson and he was A-OK with the clearances.
Said he had no issue whatsoever with them. I'm running Thompsons recommended Moroso pump, and he also recommended 20W50 for the oil weight.
Motor was build for 150-200 shot of nitrous. 416 LS3.
Said he had no issue whatsoever with them. I'm running Thompsons recommended Moroso pump, and he also recommended 20W50 for the oil weight.
Motor was build for 150-200 shot of nitrous. 416 LS3.
Last edited by Polyalphaolefin; May 11, 2019 at 04:07 PM.
Okay, so ultimately what's worse case scenario here then? If indeed the main clearance is excessive, what is going to be wrong with this motor?
Thompson, from what I've read, has a sterling reputation around here, so I can't imagine they'd let something leave, that was knowingly going to be a problem.
Thompson, from what I've read, has a sterling reputation around here, so I can't imagine they'd let something leave, that was knowingly going to be a problem.
Launching!
Joined: Mar 2019
Posts: 267
Likes: 171
Okay, so ultimately what's worse case scenario here then? If indeed the main clearance is excessive, what is going to be wrong with this motor?
Thompson, from what I've read, has a sterling reputation around here, so I can't imagine they'd let something leave, that was knowingly going to be a problem.
Thompson, from what I've read, has a sterling reputation around here, so I can't imagine they'd let something leave, that was knowingly going to be a problem.
I'd try to minimize friction and aeration as much as possible. A PAO/POE synthetic with loads of friction modifier would be best. Red Line HP 15w-50, Driven FR50, and Amsoil Signature Series 5w-50 would top that list.
Okay, so ultimately what's worse case scenario here then? If indeed the main clearance is excessive, what is going to be wrong with this motor?
Thompson, from what I've read, has a sterling reputation around here, so I can't imagine they'd let something leave, that was knowingly going to be a problem.
Thompson, from what I've read, has a sterling reputation around here, so I can't imagine they'd let something leave, that was knowingly going to be a problem.
My clearances were right about the same with my TMP motor, I broke it in with the thicker oil but ran 5w30 amsoil after that. Motor is a beast and still strong after 3 years use. I beat on this motor pretty hard and the new owner does the same with zero issues.I did notice oil pressures were a tad low after warm . I wouldnt question your motor for a second. Run it and enjoy it.
Not to beat a dead horse here but I've seen a stock 5.3 where the owner has been running nothing but 20w50 synthetic blend without issue. The engine bearing clearances on the iron block I built was .0025 rods and .0027 for the mains and I run nothing but 5w30 through a Melling high volume pump and don't see below 50psi at hot iidle.
KCS, the pump TMS sent with this motor is the Moroso 22120. It does say it’s a high volume pump.
What would you guess oil pressure would be with the 20w50 VR 1 that Thompson recommends?
And as it was mentioned that the motor would have to live its life on 50w, is there anything inherently wrong with that? Again, I’m trying to give Thompson the benefit of the doubt here, I can’t find any negative press with them, but nor do I have any idea why the motor was set up this way...
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Joined: Jun 2016
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From: Central Cal.
Naw dude, I wasn't laying that on you so much as anyone who would think it IS a good idea. I got what you said, and agree!