mains at .003, which undersized bearings

So long story short i bought a crate engine, and it have low oil pressure. I had it plastigaged and the mains came in at .003 or .0005 over max and .001 from ideal.

Can i got .001 undersized to make up for the gap. the engine has maybe 50 miles on it. Or does it have to be .0005 under because there is two halves?


I dont have the time to send the engine back to the company they will send the bearings for free

sounds like they ground the crank mains too small.
typically, bearings come in .010" undersize graduations. so; standard, .010 under, .020 under .030 under etc.

If it was ground for .010 under bearings and the grinder took off too much for oil clearence, there's nothing that can be done but grind down to the next undersize.

It sounds like they owe you a new ****ing motor to install and then you give them the junk one they gave you first back.

The FSM dicusses the use of .001 undersize inserts in sets to bring the clearance to within specs, which may be available from the dealer or a Mopar online source. I haven't looked at the parts catalog to see if they are listed.

Edit: Just checked. Bearing package, .001 undersize part number 83507080, Thrust bearing package .001 undersize part number 83507086 ('99 parts catalog).

Do you have a FSM?

Sidewinder CC said:

The FSM dicusses the use of .001 undersize inserts in sets to bring the clearance to within specs, which may be available from the dealer or a Mopar online source. I haven't looked at the parts catalog to see if they are listed.

Edit: Just checked. Bearing package, .001 undersize part number 83507080, Thrust bearing package .001 undersize part number 83507086 ('99 parts catalog).

Do you have a FSM?

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They are under .001" from standard size. he's bucked if the crank has been machined... which I assume it has.

well its a remanufactured engine so i am going to assume the crank had been machined. I am really boned in the situation.

I bought the engine from Marshall engines(dont ever do again) and i am getting low oil pressure after highway use only. about 10 psi at idle.

The company says plastigages are inaccurate and that the clearance left at .002 now they are willing to warranty it from manufactured defects but on the phone they are saying that there is no way it left unchecked and that if they do check it and its out its because i wore it down and they will send it back in pieces in a box.


they are sending me an oil pump because they think that it is the issue. but according to my plastigage its .0005 over the max

only 50 miles on the engine

"plastigage inaccurate". wow. there's a cop-out if iv'e ever heard one. Plastigage is the standard in the engine building world, and if not plastigage then how are they measuring clearances?

Look on the back of your bearings. if they are undersize they will be stamped as such with the measurement. Then, buy a new quality set (sealed power/federal mogal)of the same undersize and re-plastigage.

I know well Marshall engines and their blueprint brand. They have thousands of BBB complaints and have had the pleasure of dealing with their warranty dept. Luckily, I bought the SBC through summit racing and with their (and only their strong-arm) help was able to get a new engine.
The engine developed a cold piston knock within 5k miles and tried to worm out of it saying there was metal shavings in the pan that caused it. I had well documented the entire engine build from the uncrating to install into a 77 CJ-7 with pics. If there was contamination, it was in the engine when it left their factory in NE as they put all the sheet metal on.

Good luck. I feel your pain.

I feel your pain. Here's a pic of my first ATK reman 4.0 engine at 282 miles...





I dropped the pan to fix the oil leak that started at mile 8 and found this.

it took 3 ATK engines (4.0 xj) to get one that didn't start overheating before the first 2k miles were on it. Even then, it overheats on a hard uphill pull in the summer.

btdt too many times

toates89:
Have the crank journals measured before you buy bearings. If all the mains are the same measurement out of spec and the journals are undersized, I'd say it's a machining error.(and it's probably undersized)

Typically you can get bearing shells in .001 increments up to about .003 undersize from factory spec. This allows you to re-use a worn, but undamaged crankshaft without machining that is very slightly out of spec. Not sure if you can get undersized bearings in the -.010 -.011 -.012 undersized.(probably can for a SBC, but the 4.0 isn't nearly as popular)

On a similar note, I've heard of(but never tried myself) engine builds where they mix std and .001-under bearing shells(2 different sized shell halves on the same journal) to bring all the bearings to within .0005 of the same size.

tbburg said:

toates89:
Have the crank journals measured before you buy bearings. If all the mains are the same measurement out of spec and the journals are undersized, I'd say it's a machining error.(and it's probably undersized)

Typically you can get bearing shells in .001 increments up to about .003 undersize from factory spec. This allows you to re-use a worn, but undamaged crankshaft without machining that is very slightly out of spec. Not sure if you can get undersized bearings in the -.010 -.011 -.012 undersized.(probably can for a SBC, but the 4.0 isn't nearly as popular)

On a similar note, I've heard of(but never tried myself) engine builds where they mix std and .001-under bearing shells(2 different sized shell halves on the same journal) to bring all the bearings to within .0005 of the same size.

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The FSM does talk about mixing bearing inserts to get the desired cleance, but cautions to never use a pair of inserts that differ more than one bearing size as a pair. For example, DO NOT use a standard size upper insert and a .002" undersize lower insert. Acceptable mix would be a .001 upper and a .002 lower.

This is from the ****er at rockauto who is siding with marshall

"Marshall makes these parts and makes sure to check all specifications before they send these long blocks out. As you can imagine, they would not do very well if they sent parts worth thousands of dollars out with problems. We know they do extensive testing for these long blocks and they are very experienced technicians so we have to rely on their expertise for diagnosing these kind of problems. From what I spoke with Marshall about, their technician Ken spoke with your mechanic and based on the measurements the main rod bearings are not out of specification. Marshall informed me that Ken diagnosed this as an oil pump as being the problem which is why they are sending you an new high volume oil pump to get the long block working correctly. I am also aware you were concerned about what is going to happen if the oil pump does not fix the problem but again, Marshall would not do very well if their technicians decided to send expensive oil pumps to "try" and fix a problem. The technicians at Marshall are the professionals and we have to rely on their expertise for this kind of diagnosis."

My rebuttal was that if the problem was indeed an oil pump why would they be sending me a high volume

toates89 said:

So long story short i bought a crate engine, and it have low oil pressure. I had it plastigaged and the mains came in at .003 or .0005 over max and .001 from ideal.

Can i got .001 undersized to make up for the gap. the engine has maybe 50 miles on it. Or does it have to be .0005 under because there is two halves?


I dont have the time to send the engine back to the company they will send the bearings for free

Click to expand...

It's an old "make-up trick" to install one +0.001" and one 0.000" bearing when it's just a bit off - I've done this, but I have the habit of "breaking" the corners on the U/S shell just slightly (one pass with a fine flat file will usually do.)

The bearing "undersize" means the bore size - so if you're at 0.003" oil clearance and install a +0.001" bearing, that should bring you right to 0.002" anyhow - right in spec.

EDIT - And I didn't edit your post - I just hit the wrong wretched button.

5-90 i understand putting a .001 bearing in would take up the clearance but what i didnt think about is the mains the crank are going to be ground down so i would have to find a .011 or .021 or .031 and i wont find any that size

toates89 said:

5-90 i understand putting a .001 bearing in would take up the clearance but what i didnt think about is the mains the crank are going to be ground down so i would have to find a .011 or .021 or .031 and i wont find any that size

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Oh - I didn't know if it was just ground or welded & ground (and neither do you, without close inspection - potentially destructive. You didn't mention an undersize on the bearings - or I just missed it. My sleep cycle's been screwy for the last few days, I think I've slept about every other day for the last week or so...)

@Digger87 - Plastigage may be the industry standard, but I consider it "so-so." Given a choice, I prefer direct measurement of the crankpin, then direct measurement of the bearing bore (cap screws torqued,) then apply some math.

Plastigage is reasonably accurate if it's properly used, but it's painfully easy to screw up if you're not paying attention (most common error being shifting the cap or allowing the crank to turn, which will "smear" the plastic and cause a "false close" reading...)

@ 5-90 - I'm well aware of the possible failure of plastigage when used improperly however, when all that is pulled is a main cap, with the engine still in the vehicle, plastigage is as good as it gets. yes?

Marshall engines have a poor record with honoring warranty, and act quite high and mighty when trying to speak with them in a professional manor. I don't know how that they could determine that a measurement of .003" oil clearance is acceptable on a fresh rebuild. A high volume oil pump will fix the symptom but is not the right way to repair the OP's engine. It's the cheap way.

yeah, that's the "oh shit we screwed up, how are we gonna make this sucker's engine last till the warranty is up" way of fixing the problem.

On the other hand... did your mechanic do a proper breakin? Did he remember to put oil in before starting it up for the first time? I'd expect to see bearing damage if not, did your mechanic show you pics of the plastigauge + bearings when he did it or just tell you the numbers?

Did you establish your PSI readings with a known good mechanical gauge or are you basing it on the OEM electrical gauge / sender ?

Just curious.

I understand that NO WAY should bearing clearances be on the high side or over max clearance spec form a "reputable" (or any) engine builder.

In all my rebuilding, I got lazy once and bought a short block from a local builder, what a POS and nightmare that turned into.
Since then I have done a couple more and checked everyone's machine work and haven't had anymore problems.

Digger87xj said:

@ 5-90 - I'm well aware of the possible failure of plastigage when used improperly however, when all that is pulled is a main cap, with the engine still in the vehicle, plastigage is as good as it gets. yes?

Marshall engines have a poor record with honoring warranty, and act quite high and mighty when trying to speak with them in a professional manor. I don't know how that they could determine that a measurement of .003" oil clearance is acceptable on a fresh rebuild. A high volume oil pump will fix the symptom but is not the right way to repair the OP's engine. It's the cheap way.

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Yeah - as long as you don't bump anything. The key is deliberate, planned movement.

What's the oil pressure at 2000 rpm?