Clearance questions for mains
Clearance questions for mains (UPDATE) I have searched but can't find a concrete answer. He is what I got:
Speed pro 152M main bearings
Callies Crank with stands main size just polished
I measured with plastigauge each main and have come up with the following measurements:
#1-.0018
#2-.0020
#3-.0018
#4-.0018
#5-.0020
I have read that some think it to tight and some think just right. If I go with an oversize of
.001 that will put two of my bearing clearances at .0030. For a street motor from what I have read is too much?
My rods were sized to crank with a perfect .0025 clearance on all of them.
I plan on running Mobil 0-W40 full synthetic after break in. What are some thoughts about these bearing clearances. Thanks
Just got finished measuring the mains with the dial bore. Measurements came in at
.0020-.0021 across the board. From the info gathered this seems to be in the ball park. Thanks again for the the replys.
Speed pro 152M main bearings
Callies Crank with stands main size just polished
I measured with plastigauge each main and have come up with the following measurements:
#1-.0018
#2-.0020
#3-.0018
#4-.0018
#5-.0020
I have read that some think it to tight and some think just right. If I go with an oversize of
.001 that will put two of my bearing clearances at .0030. For a street motor from what I have read is too much?
My rods were sized to crank with a perfect .0025 clearance on all of them.
I plan on running Mobil 0-W40 full synthetic after break in. What are some thoughts about these bearing clearances. Thanks
Just got finished measuring the mains with the dial bore. Measurements came in at
.0020-.0021 across the board. From the info gathered this seems to be in the ball park. Thanks again for the the replys.
Last edited by lhaitzss; Mar 21, 2009 at 11:45 PM.
I believe the manual says .0015-.0019. I'm in Detroit today and the manual is 300 miles away. Where is your manual, BTW? Big blocks like .003" and high reving small blocks. These motors are very tight.
I have searched but can't find a concrete answer. He is what I got:
Speed pro 152M main bearings
Callies Crank with stands main size just polished
I measured with plastigauge each main and have come up with the following measurements:
#1-.0018
#2-.0020
#3-.0018
#4-.0018
#5-.0020
I have read that some think it to tight and some think just right. If I go with an oversize of
.001 that will put two of my bearing clearances at .0030. For a street motor from what I have read is too much?
My rods were sized to crank with a perfect .0025 clearance on all of them.
I plan on running Mobil 0-W40 full synthetic after break in. What are some thoughts about these bearing clearances. Thanks
Speed pro 152M main bearings
Callies Crank with stands main size just polished
I measured with plastigauge each main and have come up with the following measurements:
#1-.0018
#2-.0020
#3-.0018
#4-.0018
#5-.0020
I have read that some think it to tight and some think just right. If I go with an oversize of
.001 that will put two of my bearing clearances at .0030. For a street motor from what I have read is too much?
My rods were sized to crank with a perfect .0025 clearance on all of them.
I plan on running Mobil 0-W40 full synthetic after break in. What are some thoughts about these bearing clearances. Thanks
Last edited by J&J Speed Shop; Mar 5, 2009 at 11:27 AM.
A general rule of thumb is about .001" for every inch of shaft diameter, so .0025" on the mains would be fine, +/- .0003". You could use a combination of STD and X bearings to get you there, but I wouldn't trust plastiguage on a lawnmower engine.
If it were mine, I'd leave the STD's in there and have the crank ground to get your clearance. That way you know the journals are straight and round, the clearances would be perfect (assuming the crank grinder is good and measurements are accurate), and you don't have to mess with two sets of bearings. With Clevites, I've seen a tendency for Compstar cranks to be on the tight side, even with x bearings.
If it were mine, I'd leave the STD's in there and have the crank ground to get your clearance. That way you know the journals are straight and round, the clearances would be perfect (assuming the crank grinder is good and measurements are accurate), and you don't have to mess with two sets of bearings. With Clevites, I've seen a tendency for Compstar cranks to be on the tight side, even with x bearings.
Those clearances are fine especially on an aluminum block. And J&J is dead on - plastigage is an estimate ONLY, use a micrometer on everything - just be careful not to scratch the bearings or journals.
Do yourself a favor and if you want the money you are putting into the engine to BURN away then DON"T USE PLASTIGUAGE!! But if you measure with a bore guage on our race motors we run .0018-.0022 clearance so that should be fine. By the way our motors spin 9000 for several hours at a time.
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Just ordered dial bore gauge set from snap-on. I tried t-gauges but they suck *** trying to get an accurate reading in a round hole. Should have by next week. i will report back with correct readings. Thanks for all the replys.
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Oooo, how much did that run ya, if you don't mind me asking?
I used plastigauge on mine and came up with .0028 which i thought was a little loose. Had a friend come over and mic everything and he came up with .0022. Ill never use that crap on my own stuff ever again. Real numbers are real clearences, dont trust how much you can compress plastic to get an accurate reading.
