Too much clearance in mains? (I need machinist's opinions)

[vintagemuscle]

Heres my problem.
I am currently assembling my engine and have ran into a problem.
I am using standard oem mitsu bearings with a polished unturned crank.
My main clearances are between .0025-.003 when the suggested clearances are .0008-.0016.
My main journals on my crank read between 2.2435''-2.2440'' when the allowable specs are 2.2435''-2.2832''. This means that my crank is just barely in spec but it is causing bearing clearance to be quite large.
My question is can I run .003 without a problem?
Also, I am using Manley rods and they suggest a .002 minimum to .003 maximum bearing clearance and all of my rod journals are at exactly .003.
I thought I saw somewhere that the maximum main clearance was .004.
Thanks for the help in advance.

Jim

 

[Cesar]

From the mitsu factory repair manual.

Crankshaft main bearing oil clearance. .0008- .0020 LIMIT .004

connecting rod bearing oil clearance .0008-.0020 LIMIT .004

I have been told that an engine that sees a lot of abuse, can use looser clearances, but I don't necessarily believe everything I hear.


Did you search??

Throw all that stuff in there, use plenty of lube, prime the oil pump and make sure you have an aftermarket oil press guage. The factory one is a liar.

 

[vintagemuscle]

Thanks for the info.
I had a talk with my machinist and his book says maximum oil clearance is .0035 so I should be okay.

 

[treebonker]

The standard value for the 6bolt main journal O.D is 2.2433''-2.2839''. So your crank is in perfect condition. Chase the threads, wipe clean the surface and recheck with a torque wrench known to be in good calibration. Better option would be to use a dial bore gauge to check the clearance and finding the root cause(bearing,main bore) if it isn't human error.

"Limit" shouldn't be confused with "within spec". The limit is there to tell you when to make up for the wear from normal usage. While race applications can vary widely, for a street-strip motor stick with the manufacturers specification and not some machinist handbook.

 

[BISHILVR]

Mitsubishi makes bearings that will take up the slack better than off the shelf parts store bearings.

 

[coltboostin]

Heres my problem.
I am currently assembling my engine and have ran into a problem.
I am using standard oem mitsu bearings with a polished unturned crank.
My main clearances are between .0025-.003 when the suggested clearances are .0008-.0016.
My main journals on my crank read between 2.2435''-2.2440'' when the allowable specs are 2.2435''-2.2832''. This means that my crank is just barely in spec but it is causing bearing clearance to be quite large.
My question is can I run .003 without a problem?
Also, I am using Manley rods and they suggest a .002 minimum to .003 maximum bearing clearance and all of my rod journals are at exactly .003.
I thought I saw somewhere that the maximum main clearance was .004.
Thanks for the help in advance.

Jim

I run .003 on the mains on all my motors.

For big power, high RPM, I like them to be a bit loose to run some thick oil.

 

[vintagemuscle]

I run .003 on the mains on all my motors.

For big power, high RPM, I like them to be a bit loose to run some thick oil.

I'm glad to hear that Coltboostin. Maybe I should have asked you or Ken first before I started this thread.

 

[coltboostin]

I'm glad to hear that Coltboostin. Maybe I should have asked you or Ken first before I started this thread.

Jim!

Did not realize it was you. You putting the motor together at your house?

BTW-You even get your bike sold?