Main Bearing Clearance

[aspekt9]

So I have a decision to make. Just torqued the mains down to 50ft-lbs and measured with a bore gauge against a micrometer and used the same micrometer to measure the crank journals. The machine shop align honed the mains which is why material was cut off.

Block Mains were 2.4023 - 2.4026

Crank Journals were 2.2431 for every journal.

Using ACLs catalog of bearings, their bearing thickness for std. size bearings is 0.0783 so I calculated it out and I'm around 0.0027 - 0.0029 for oil clearance. I have the balance shafts out, I'm looking for around 300-350HP EVENTUALLY, for the next month or two I'll be running stock boost. What do you think, run std. size bearings or go oversized?

 

[AWD92TalonTSi]

So I have a decision to make. Just torqued the mains down to 50ft-lbs and measured with a bore gauge against a micrometer and used the same micrometer to measure the crank journals. The machine shop align honed the mains which is why material was cut off.

Block Mains were 2.4023 - 2.4026

Crank Journals were 2.2431 for every journal.

Using ACLs catalog of bearings, their bearing thickness for std. size bearings is 0.0783 so I calculated it out and I'm around 0.0027 - 0.0029 for oil clearance. I have the balance shafts out, I'm looking for around 300-350HP EVENTUALLY, for the next month or two I'll be running stock boost. What do you think, run std. size bearings or go oversized?

What is std oil clearance? I was about .0007-.001" extra clearance on my last rebuild. It has 4k miles on it and is doing fine. I'm running 10w40 oil as a precaution though. ACL sells their race bearings which are .001" thinner allowing for more oil clearance.

I wouldn't go anything over .001" extra.

bryan

 

[aspekt9]

What is std oil clearance? I was about .0007-.001" extra clearance on my last rebuild. It has 4k miles on it and is doing fine. I'm running 10w40 oil as a precaution though. ACL sells their race bearings which are .001" thinner allowing for more oil clearance.

I wouldn't go anything over .001" extra.

bryan

FSM calls for .0008 - .0020 with a .0040 limit. Meaning I'd be .0007 - .0009 over.

 

[donniekak]

I would try some different bearings, to try for maybe .0025". But being under .003" you will be fine. These cars move plenty of oil for large bearing clearance.

 

[AWD92TalonTSi]

FSM calls for .0008 - .0020 with a .0040 limit. Meaning I'd be .0007 - .0009 over.

I'd run em. Get a set of ball mics and try and mix and match for even clearances if you have tools available to you.

Do some searches on here an you'll find plenty of people running +.001 clearances. Thats what I did and it made me feel a bit better about doing it myself.

Bryan

 

[aspekt9]

Well what are my options, they don't make custom bearings, do they? Should I run a thicker weight oil?

 

[Colt4G63 also]

Mine measured a little on the loose side too, but I removed my BShafts too, so I went with it. It's been fine for going on three summers now, and I drive it like I stole it. My oil pressure (with 10W30) is pegged at 100+ on cold starts, and ranges from 20-75psi when warm depending on RPM. No mods to the OFH.

 

[AWD92TalonTSi]

Well what are my options, they don't make custom bearings, do they? Should I run a thicker weight oil?

Options are:
Run as is
Cut the crank and use the next size bearings
Buy a new crank and use std size bearings

It looks like most of us here are recommending option 1 - I think thicker oil should be run with looser clearances but others may disagree. Keep in mind the factory service manual lists the service limit at .004". Meaning if a dealership tech is in your 100,000 mile old engine, checks the clearances and comes up with .003" they're not likely to raise a fuss.

Bryan

 

[aspekt9]

Options are:
Run as is
Cut the crank and use the next size bearings
Buy a new crank and use std size bearings

It looks like most of us here are recommending option 1 - I think thicker oil should be run with looser clearances but others may disagree. Keep in mind the factory service manual lists the service limit at .004". Meaning if a dealership tech is in your 100,000 mile old engine, checks the clearances and comes up with .003" they're not likely to raise a fuss.

Bryan

I'm going to go with option 1. The cranks aren't supposed to be cut, and buying a new crank doesn't help me, the size of the journals are pretty close to measurements they're supposed to be according to the FSM, maybe a tad under. The crank is practically brand new though it only has 50,000 miles on it. But I guess polishing they could have taken off a little too much?

What weight oil should I be running?

Also, my rod clearances are about .0016, is this good or too tight?

Since my rod clearances are within spec and my mains are not, should I get .001" extra clearance on the rods so they're closer to the mains? Because if I don't and I run thicker oil wouldn't I run into issues?

 

[AWD92TalonTSi]

I'm going to go with option 1. The cranks aren't supposed to be cut, and buying a new crank doesn't help me, the size of the journals are pretty close to measurements they're supposed to be according to the FSM, maybe a tad under. The crank is practically brand new though it only has 50,000 miles on it. But I guess polishing they could have taken off a little too much?

What weight oil should I be running?

Also, my rod clearances are about .0016, is this good or too tight?

Since my rod clearances are within spec and my mains are not, should I get .001" extra clearance on the rods so they're closer to the mains? Because if I don't and I run thicker oil wouldn't I run into issues?

I'm running 10w40 in mine. But I'm just basing that on gut feeling. Do some searching and see what you find.

I don't have the FSM on hand but if you're at the bottom or low on rod clearances I'd bring your bearings/rods/crank to a machinist and have it polished to the middle of spec.

I wouldn't worry about running 10w40 on std clearances.

 

[zulimee]

tuner,

i have 1 question.. how to check oil clearance with plastic gauge.. 1-5 main bearing..
Are the main bearing oil clearance between 1 and 5. If among the five oil clearance is not the same. What should be done, whether the need to reduce main bearing cap bolt torque ...