Bearing identification help needed!

Reply Subscribe

Thread Tools

Search this Thread

Jun 5, 2008 | 02:43 PM

ksubigbuck

Thread Starter

Junior User

Joined: May 2007

Posts: 66

Likes: 1

Bearing identification help needed!

Can anyone here help me identify the main and rod bearings I pulled out of my '90 351w based on the part numbers stamped on the bearings?

Main #'s: D7AE-6A338-AA

Rod #'s: C90E-6211-A-B

I assume these bearings are original because they have the Ford logo stamped into them. The reason I am asking is because the old bearings I pulled out had about .002" of clearance measured with plastiguage. The new standard size bearings I put in have about .003" of clearance in the middle of the crank surface (though the surface appears to have some taper to it). I am wondering if the crank has been machined by the previous owner.

I guess what I need to know is whether or not the old bearings were standard size, and if there is a way to tell if the crank has been machined or not. I know plastiguage isn't very accurate compared to a mic, but I can't understand why the new bearings would be looser than the old ones. Do the bearings need to be broken in before measured? I dunno, maybe my torque wrench isn't accurate and I'm not torqueing the bolts enough....

Thanks for the help,
Hunter

Jun 5, 2008 | 05:11 PM

ksubigbuck

Thread Starter

Junior User

Joined: May 2007

Posts: 66

Likes: 1

Anybody? I'm open to any suggestions.

Jun 5, 2008 | 07:03 PM

85e150

Super Moderator

Joined: Apr 2004

Posts: 34,517

Likes: 2,826

Well, a D7 is a 1977 and a C9 is a 1969.

I'm not sure how the system works, if the part came on line in 1977 does it keep that number throughout it's life?

Numberdummy may be by and will know.

Mains are 3.000 on this engine, rods 2.3110.

A standard undersize would be .010, so the mic is the answer here as to undersize.

Doing a quick internet search (as I am no engine builder) it seems like main clearance of .002-.003 is normal. I would think the clearance should hold no matter where you measure so that raises a question in my non-engine builder mind. Stay tuned, it might take some time for more answers.

Jun 5, 2008 | 07:29 PM

ksubigbuck

Thread Starter

Junior User

Joined: May 2007

Posts: 66

Likes: 1

Thanks 85, I really appreciate it. I thought that .0015 to .0028 was spec. I also thought that I'd do a bit better than .003 with new bearings, even though I'm not having the crank machined. I just started getting low oil pressure, and the motor wasn't knocking or tapping at all.

Thanks again,
Hunter

Jun 5, 2008 | 09:02 PM

kotzy

Elder User

Joined: Apr 2004

Posts: 970

Likes: 3

Perhaps your not aware that bearing are to be had that are .001 and .002 undersize. If you get a look at a Ford shop manual it tells of using one standard shell along with a .001 to arrive at a selective fit. Sometimes you can find a .001 under mark on the insert. This is no doubt why you have greater clearance with the inserts you bought than what was in the engine. kotzy

Jun 6, 2008 | 12:57 AM

Beanscoot

Cargo Master

Joined: May 2007

Posts: 2,071

Likes: 36

From: British Columbia

Plastigage is actually a very accurate method of measuring clearance. Calculating clearance by measuring all the component parts could result in "stacking" of tolerance errors, plus it would be difficult to measure all the component parts.

The C90E number indicates that the bearing shell was originally designed for a 1969 Fairlane. This makes sense since the 351W was introduced in 1969 model year. The number would have been retained till there was a change, and for this particular part there might never have been a revision throughout the engine's production.

The D7AE number indicates that there was some change in the bearing shell for the 1977 model year, and the A indicates that it was decided to assign the part to a full size car.

You might try measuring the thickness of the new vs. old bearing shells. Use a round spacer on the inside of the bearing shell to get proper contact.

Jun 6, 2008 | 07:33 AM

kotzy

Elder User

Joined: Apr 2004

Posts: 970

Likes: 3

I saw in your other post that you are led to believe that the cooper showing on an insert means it is bad. This too is covered in Fords Shop manuals, and nothing could be further from the truth. The lead babbit which is present on the new inserts is a flash coating to allow for easier compatability with shaft irregularities. The lead babbit has very little strenght, however the copper bronze has great strenght as a bearing material, so don't be fooled by copper showing it is no good. Clearence is what is important. kotzy