Bearing clearances too tight?

[freedomtanker]

just clearanced my main bearings with plastigauge and im getting 0.0015. Book spec is .002 min so that puts me too tight. Building a high power engine, should i go with the .001 oil bearings? Acl race.

I thibk i was looking at this crosseyed because i just looked again and its between .0008 and .002..... what a dumbass

 

[lasthope05]

If it we're me I would definitely get the +.001 bearings. A good rule of thumb for bearing clearances is .001 per inch of journal diameter . That and .0025" is where I like the mains at.

 

[freedomtanker]

I asked the tech guy at extreme psi and he said not to run the undersize bearing. The tolerene is towards the looser side of the spectrum and i plan to run nothing but good oil. I think i should be good with what i have.

 

[lasthope05]

You are building a high performance motor. You are not suppose to use factory bearing clearances setup for a stock 200hp engine spec'd to run 30wt with no oiling mods done. But by all means run what the "tech" tells you.

 

[freedomtanker]

now you got me worried. I think I'm gonna order a set of +.001 bearings and run a little loose. no use getting this thing together and having the main bearings seize because I didn't want to spend the extra 50 bucks.

 

[SasaniFab]

now you got me worried. I think I'm gonna order a set of +.001 bearings and run a little loose. no use getting this thing together and having the main bearings seize because I didn't want to spend the extra 50 bucks.

You have a quality micrometer? Plastigauge isnt the best way to measure clearances.

Dial bore gauge

 

[donniekak]

You have a quality micrometer? Plastigauge isnt the best way to measure clearances.

Dial bore gauge

For someone not used to using a mic and bore gauge, plastigauge will give a better reading, and won't scratch the crank.

 

[SasaniFab]

For someone not used to using a mic and bore gauge, plastigauge will give a better reading, and won't scratch the crank.

Imo, learning how to use a micrometer at the minimum should be a prerequisite before building an engine. Jafro has some great videos on youtube start to finish. I find using plastigauge to me more labor intensive. I cant stand having to pick it all off. Drives me nuts

 

[freedomtanker]

I used plastigauge to determine the clearance. Called my machinist and he said the clearance will be fine for a summer daily and weekend warrior.

 

[SasaniFab]

What are your final clearances numbers on the mains and rods?

 

[freedomtanker]

Have not done rods yet, mains were .0015 accross the board.

 

[SasaniFab]

Watch your oil pressure.

 

[freedomtanker]

To high? Im taking the crank out to the shop to have him polish it. Hopefully that takes some off to open it up before i waste another 75 bucks on bearings.

 

[donniekak]

If polishing takes off any real amount of material the crank journal will be tapered.