View single post by Judson Manning
 Posted: 04-09-2006 07:20 pm
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Judson Manning

Joined: 03-14-2005
Location: Atlanta, Georgia USA
Posts: 406
Thanks for the plug Ron, my main interest is seeing your car on track smacking around RX7s and 240Zs.  That is true job satisfaction!

Greg is correct in that the x-drilled conversion can be much more expensive than the ACL bearings.  Not the best option for a street and or budget rebuild.  Regardless of main bearing options, ACLs on the rods are THE only way to go!

The 907 bottom main bearing with it's wide and shallow groove (plus a huge hole in the middle) is the dumbest thing I've ever seen.  Because it is so poorly designed, the 907 mains wear first which cause the rod bearings to starve -  then BOOM!

The ACL  groove design is far superior to the OEM 907 bearings, and makes an excellent choice.  Alternatively, x-drilling and going to 180^ main bearings is a 'worst-case-scenario' option better suited to a competition engine. 

To give you some idea of what we're talking about:  The 907s I've rebuilt using the stock bearings and 20W-50 oil produced 45-60psi when hot.  Ron's engine running 5W-20 oil produced 70-80psi. 

I'm willing to bet the ACL main bearings net a 5-15psi increase over the stock bearings - can anyone share some field measurements?