Plastigauge measurements - within spec?

[Nathanj1142]

Hey all,

 

Started the engine build today using king racing std size main bearings. I just wanted to check I’ve understood the tolerances correctly following the TSRM.

 

Plastigauge measurements as follows:

 

1: .038mm

2: .050

3: .050

4: .043

5: .067

6: .050

7: .050

 

On the TSRM it states std size clearance to be between .035mm and .053mm, however maximum can be .08mm

 

Does it matter that some bearing clearances are outside the standard size (But still within max) and others aren’t?

 

Interested to know cheers

[Mike2JZ]

Technically will run but not ideal. You seem to have uneven wear on the crank, may cause reliability issues in future.

[Nathanj1142]

Technically will run but not ideal. You seem to have uneven wear on the crank, may cause reliability issues in future.

 

Interesting. How would this be corrected? Crank machining or oversized/undersized bearings?

 

Cheers

[Nathanj1142]

Interesting. How would this be corrected? Crank machining or oversized/undersized bearings?

 

Cheers

 

In addition to this (which I’ve only just thought about, I did use assembly lube when measuring, was this the right thing to do or could that cause variation in my measurements?

[Mike2JZ]

Crank journals and bearings need to be dry when doing plastigage ideally. Also make sure your crank does not spin or move whilst doing it.

 

If your crank is out of whack then your only options are to:

Send it and pray

Grind crank to next oversize (although many people frown on this)

Get another healthy crank

[Nathanj1142]

Crank journals and bearings need to be dry when doing plastigage ideally. Also make sure your crank does not spin or move whilst doing it.

 

If your crank is out of whack then your only options are to:

Send it and pray

Grind crank to next oversize (although many people frown on this)

Get another healthy crank

 

Another thing is, the plastigauge is quite old so I’m not sure if it goes ‘off’ or whatever. Didn’t look too great lol. Will order some more tonight and I’ll give it all another good clean, get rid of the assembly lube see what it’s coming out at. Machine shop said it was all within tolerance so I’m not sure

[Nathanj1142]

update: ran the test again dry, all measurements at 0.038 with a couple clearances slightly larger between .038 and .043. I believe i had the strips set in the wrong orientation too. All happy now

[markssupra]

update: ran the test again dry, all measurements at 0.038 with a couple clearances slightly larger between .038 and .043. I believe i had the strips set in the wrong orientation too. All happy now

 

Well done, nothing quite like building your own engine if you can do it.

 

When I built mine, I checked the crank and rod journals first to see if they were in tolerance. They were all good, between 10 microns (0.010mm) of each other.

 

Did you get the block rebored? If so, did you remove the oil gallery bearings from the block to clean it out properly?

[Nathanj1142]

Well done, nothing quite like building your own engine if you can do it.

 

When I built mine, I checked the crank and rod journals first to see if they were in tolerance. They were all good, between 10 microns (0.010mm) of each other.

 

Did you get the block rebored? If so, did you remove the oil gallery bearings from the block to clean it out properly?

 

Hey mate! Yeah i thought why not, its a learning curve but i'm just taking my time and anything i'm unsure with i post on here!

 

Block has not been rebored, only skimmed and honed then cleaned with a parts cleaner. I had the main caps measured and the crank all measured to ensure it was within spec, as i dont have micrometers etc, which i was informed it was hence why i was confused with my first set of readings.