0.001" undersize main bearings for Scat crank

[Retlaw01XJ]

Looks like my new Scat crank is out of spec on the main journals, requiring some 0.001" bearings from the dealer.... $165 a set!!
First set of bearings were Clevites. Plastigauge showed clearance just under 0.003". Remeasuring with an inside mic and micrometer confirmed clearances between 0.0026" and 0.003".
I could get by with that clearance if I added a high volume oil pump, but I don't want to go that route. So I sprung for the bearings.

With the 0.001" undersize bearings, I'm a hair under 0.002" on all the mains.... right where it should be. Didn't get the extra 0.001" over the Clevites.
Rod journals were fine at approx 0.018" clearance. Rod side clearance is 0.015" and main journal run out was nice with the worst being two end journals under 0.0005"

Thought I'd post this in case anyone else has a similar issue....

[gonridnu]

Did you check the housing bore in your block? You may need an align hone as there will not be enough bearing crush if the housing bores are big and if they are big they are probably crooked too.

My book shows the following dimensions....

Main Housing Bore 2.6910" - 2.6920"
Main Shaft 2.4996" - 2.5001"

[rammit11]

I ended up with same thing. The only place I found the .001 undersize was from the dealer, If i remember right was around $100-$200 range for the set. I don't have the part number on hand , but I believe my engine builder does . I can call him and see for sure and if so I will post back on here.

[SilverXJ]

Do you have a measurement for the journals on the crank? I would have called Scat and had a word with them.

[Retlaw01XJ]

Did you check the housing bore in your block? You may need an align hone as there will not be enough bearing crush if the housing bores are big and if they are big they are probably crooked too.

My book shows the following dimensions....

Main Housing Bore 2.6910" - 2.6920"
Main Shaft 2.4996" - 2.5001"

The main journals measured 2.4990- 2.4992, which is under spec. That explained the excessive clearance, so I didn't check the block bores. Would've been a good idea tho. Are the block bores often off on these engines?
Rod journals measured right on, so it appears I at least used the mic properly! Clevite does offer 0.001" undersize bearings for the rods.... but not mains.

The 0.001" undersize bearings are pn 83507080-AB for the 6 journals..... $15.81 each......$100.56 with tax
Thrust bearing is pn 83607086-AB..... that one is a whopping $63!
I asked 2 guys there for a discount off of the list price with no success. Tough to find online as well, so I paid the price.

Yeah, I have to give Scat a call and ask what's up with this thing.

[gonridnu]

The housing bores can be off on pretty much any engine that has a lot of miles on it, or even just a few hard ones. Hot-cold cycling and pounding from hard use can distort the roundness, size, and location. They should be measured for size, roundness, and with a straight edge running the length of the engine to determine if they have moved.

In addition, they can be off (in size not straightness) from the factory which may explain why they have .001's available. They can even be different sizes as evidenced by the Chevrolet "rainbow engines". Those little jewels had different size bearings at different locations cause someone screwed up and machined thousands of parts wrong. Rather than scrapping them the factory measured and then color coded the parts and put different size bearings in them.

Align honing is essentially the same process as re-sizing rods. A very small amount is cut off the main caps and then a long hone mandrel is run through to re-size them paying particular attention to both size and taper.

Sounds like you found your problem but before you sent the crank back to Scat you would be wise to take it to a machine shop and have it double checked.

[Retlaw01XJ]

Thanks for the reply.
"Rainbow engines'..... that's the first time I've heard that description! The 2001 Jeep manual also has various charts showing color coding for the various under/oversize parts and how to match them up. Apparently quality control was lacking then too.

For the fix, I went with the factory 0.001" bearings. I don't want to deal with the time required to ship the SCAT crank back and forth across the country. Short block is together with the exception of the thrust bearing, which I'm still waiting for. Should've been here today... but no. Next shipment arrives Tuesday. Guess I'll do some painting today instead of assembly.

[4.0 Rambler]

Just curious. Where did you purchase the crank? I am in the market and would like to avoid this issue.

Thanks.

[4.0 Rambler]

Just curious. Where did you purchase the crank? I am in the market and would like to avoid this issue.

Thanks.

[Retlaw01XJ]

I bought it from Summit Racing. They don't charge a shipping fee, just a $12 handling charge.
It was shipped directly from Scat, so Summit never had it in their hands.
I still have to call Scat and ask why it was undersized.

[SilverXJ]

If the crank tunnel checks out fine then it is a fault with scat, not something a supplier does. I would really hope its an all around fault with Scat, not just a every other or so crank that goes out their door. If its every other that says a lot about their quality control.

[4.0 Rambler]

I bought it from Summit Racing. They don't charge a shipping fee, just a $12 handling charge.
It was shipped directly from Scat, so Summit never had it in their hands.
I still have to call Scat and ask why it was undersized.

Thanks for the information. I ended up buying a Scat from Titan through E bay. It should be here shortly.

I' ll make sure to double check the journals.

[Retlaw01XJ]

......Thrust bearing is pn 83607086-AB..... that one is a whopping $63!.......

Typo.... number should be 83507086-AB.