Chevy nascar bearings?

bgyglfr · 01-06-2016, 03:31 AM

I have read about using Chevy nascar bearings on Porsche engines by turning. The crank down but the threads I have found have been a little vague on what else is involved.

I have a 66mm crank that is ready for its first turn down. I'm pretty sure I can get away with first undersize but I'm considering going to the nascar bearings. Is it just for rod journals or can you do the mains as well?

Custom rods - Pistons?
Machining the case Etc?
Can you squeeze a little more stroke out of it (67-68mm)?

Thanks in advance.

304065 · 01-06-2016, 05:39 AM

Two Inch NASCAR Bearings

bgyglfr · 01-06-2016, 07:04 AM

Thanks for the link. Exactly what I was looking for. Somehow it never showed up in my searches.

stownsen914 · 01-07-2016, 04:42 AM

I just read through the other thread, and it piqued my curiosity so I did some quick research. The Chevy/Buick bearings are .94" wide while 911 2.0L bearings are .86". There is enough room on the 2L crank to account for this difference while grinding and still have good transitions to the fillet/web portion of the crank?

Scott

tom1394racing · 01-08-2016, 06:44 AM

I think you will find that the Clevite rod bearings are becoming pretty standard replacements for the poor quality Glyco bearings.

Porsche 911 (1965-1973) - Main Engine Components - Page 3

KTL · 01-08-2016, 02:26 PM

Quote:

Originally Posted by bgyglfr

Thanks for the link. Exactly what I was looking for. Somehow it never showed up in my searches.

Dang I was gonna link you to that one in our yahoo group discussion but I figured you already saw it. Sorry for me ASS U ME ING you already knew of it!

stownsen914 · 01-11-2016, 04:00 AM

In the other NASCAR bearings thread, I saw a comment about narrowed 2" bearings for use on a 911 crank. Is it best to machine the bearings to the width of the 911 rod bearings (21.8 mm or ~.86" in the case of a 911 2.0L) and use custom rods with 2" big end and that same width? (And obviously have the crank ground accordingly.)

Scott

bgyglfr · 01-11-2016, 07:43 PM

Kevin,
Thanks for your input on the yahoo group. I decided to grind to 3.2 rod size. If you are buying custom rods anyway I though it best to go with the largest size that I could find acceptable bearings.

I have anothe question. Is it good have it ground to low in the range to allow for more oil or high for closer tolerance? Right now, we are planning to go right in the middle.

Thanks again,

Kirk

KTL · 01-13-2016, 07:05 AM

Yeah the nice thing about committing to grinding your crank is you can set your clearances instead of just throwing a set of STD bearings in a good set of rods & STD crank. Because in that case clearances are what they are. I would get your rod selection finalized and then assemble them with your bearings. Then you can measure the ID of your complete rod assembly and that'll tell you what amount to grind on your rod journals.

If you open up the clearance you can have oil pressure loss. But you do have more flow. I don't know how much clearance results in how much pressure loss.

I simply go by the clearances i've seen some of the pros quote. Mike Bruns often mentioned 0.0030 is a good spec to go with. He assisted Gertvr with his 3.0L build and they got 30 thou clearance on the mains and 28 thou clearance on the rods

Gert’s Engine Rebuild & Upgrade (Chasing 300Hp, yes another one sorry)