Max 360 Main Oil Clearance

-
mopowers

mopowers

Well-Known Member
Joined
Feb 15, 2006
Messages
8,531
Reaction score
4,741
Location
West Sacramento, CA
Am I reading my FSM correct? I'd like to know the specs on allowable oil clearance for main bearings on an LA 360. Under the crankshaft engine specs section, the '73 says: Diametral Clearance Desired: 0.0005"-0.002" and Diametral Clearance Allowed: 0.0025". I've never heard it referred to like like. So, is that the desired and max main bearing clearance for an LA 360?

Also, it looks like rod bearing clearance specs are the same. Is that true?

Thanks!
 
I run mine at .0025 - .0030 main & rods & HV pump.
If you run them tight you will scuff the bearings or worse spin one
 
Factory spec.

I ran mine at .0015-.0020 for the Aspen R/T

Just don't beat on it when first fired up. Let it warm up.
 
My 360, .003 mains, .0025 rods..........standard pump, high pressure spring, Shell Rotella 15-45 Diesel.......

Loose don't break
 
I've just never heard it referred to as "diametral clearance" before. I wanted to make sure that's what they referred to as bearing oil clearance. Thanks!

The engine in question is a stock 360 rebuild my dad's D100. His machinist polished the crank and said the journals spec'd out just fine with a mic, but since he didn't have the bearings yet, hadn't measured the ID of the main saddles w/ bearings when my dad picked it all up. So now, my dad's putting it together and doesn't have the tools to properly measure the clearance, but was told it'd be fine. He used plastigage and got this (picture below). Looks like a tad larger than .002" to me. Maybe .0025"? Would you run it? The bearings are full groove clevites and he was told by his machinist to buy a standard replacement M72 oil pump. I just don't want him to fire it up and have low oil pressure.

Picture0126171645_1.jpg
 
Diametrical means accross the diameter in this case. The bearing bore is not truly round. It's eggshaped. So the clearance you're measuring is the diameter, from the center of the top shell to the center of the lower shell. If you were to measure accross at the parting lines you'd see the "bulge".
Yes - it's greater than .002". Closer to .003" to me. But not a big deal. If the rods are also that size, and you are dead set on full grooved bearings, I'd runt he HV oil pump and the MP HD oil pump drive with it. Just my opinion there. Some guys don't seem to care but I'd want more oil delivery potential if you're beyond .0025 on all of them.
 
Your plastiguage measurement reading is about what you are saying, it will be fine!
 
Here is the same picture my dad sent with a little manipulation. Looks a lot closer to 2 thou than 3 when you see this one.

Picture0126171645_2.jpg
 
No offense meant and with the understanding that a combination of plastigage and posted visuals is not really the best way to check clearances... Cutting and pasting (and hoping) is wishful thinking.
Properly measure the block with bearings in place and caps properly torqued, and properly measure the crank and in more than one place per journal, and do the math to be sure. Then you'll know if the journal is truly round and the clearance is what you want it.
The alternative is what you've done. Interpret it as you will - it's your money and time.
 
Just an FYI, the general rule is .001 per every one inch of journal diameter.
 
moper said:
No offense meant and with the understanding that a combination of plastigage and posted visuals is not really the best way to check clearances... Cutting and pasting (and hoping) is wishful thinking.
Properly measure the block with bearings in place and caps properly torqued, and properly measure the crank and in more than one place per journal, and do the math to be sure. Then you'll know if the journal is truly round and the clearance is what you want it.
The alternative is what you've done. Interpret it as you will - it's your money and time.
Click to expand...

I completely agree. Unfortunately, my dad's in a different state and his machinist didn't measure the block with bearings in place. He only checked that the crank was round and true. I wish I had been able to tell my dad to take him the bearings when the block was at the shop. I've always used plastigage as a last check of everything before bolting things together, nothing more.
 
You can also buy .001 under bearings to tighten it up a bit, if you choose.
 
I'd be more concerned with cleanliness and surface finish. I'd send this in for a polish and bounce to a .001 oversize bearing if it all checks out. But that's just an opinion.
 
You must log in or register to reply here.
-

Back
Top