[GregM329]

Originally Posted by Dragncar

One of the most important, and free things to do in a engine like this is make sure your main bearings have the oil slot, or hole drilled in the right place and do the P Dude trick with the thrust bearing. That is free modification anyone can do with a vise, drill and files.

I'm assembling a 400 block soon, and I was not aware of the above quoted crank and thrust bearing specs. Can you tell me where I can out more on these techniques? Thanks!

Greg

[pastry_chef]

Originally Posted by GregM329

Can you tell me where I can out more on these techniques? Thanks!

Greg

From Pontiac Dude's old site:
---------------------------------------

Thrust Bearing Modification For Longer Life

Below are pictures showing how to increase the life of your thrust bearing for Pontiacs.
With higher stall converters and increased line pressure of transmission shift kits, you have more forward thrust loaded on this bearing. This modification, however, is recommended for all High performance engines.

I take the thrust bearing and lay it on a belt sander at a 30 degree angle and grind till the bevel edge reaches the corner of the main shell. Then take a flat file and clean up the flashing with a slight bevel to the edge.

--------------
*** Main Bearing Pontiac mod info: ***

I elongate the oil feed holes to match the angled feed main hole in the block. Usually I only elongate about the size of the original hole in #2 and #4 only. This seems to be the Load & critical areas in Pontiac performance and trouble. The rear main bearing I don't touch as I feel the wider area of the bearing is sufficient to hold oil, plus being the first fed from the pump. I also elongate the front feed hole half the size of the original hole for hydraulic cam engines to allow sufficient supply to the lifter fed through #1 main on the other side without sacrificing oil to the main and #2 rod.

[tininjun68]

More good info, thanks to all! Trap speed is hard to beat. I did well getting chased or doing the chasing when I was the quicker dialed car in Pro ET. Thanks for the good links, I've been checking them out. I do know Adam Strang's cars. His '68 GTO is currently for sale and it's a beaut! Wish his Firebird was for sale

So after a couple days worth of talking, it's likely I won't make the deal for this '68 Firebird I mentioned. I'll still be interested if another similar car comes along.

[Dragncar]

Originally Posted by pastry_chef

From Pontiac Dude's old site:
---------------------------------------

Thrust Bearing Modification For Longer Life

Below are pictures showing how to increase the life of your thrust bearing for Pontiacs.
With higher stall converters and increased line pressure of transmission shift kits, you have more forward thrust loaded on this bearing. This modification, however, is recommended for all High performance engines.

I take the thrust bearing and lay it on a belt sander at a 30 degree angle and grind till the bevel edge reaches the corner of the main shell. Then take a flat file and clean up the flashing with a slight bevel to the edge.

--------------
*** Main Bearing Pontiac mod info: ***

I elongate the oil feed holes to match the angled feed main hole in the block. Usually I only elongate about the size of the original hole in #2 and #4 only. This seems to be the Load & critical areas in Pontiac performance and trouble. The rear main bearing I don't touch as I feel the wider area of the bearing is sufficient to hold oil, plus being the first fed from the pump. I also elongate the front feed hole half the size of the original hole for hydraulic cam engines to allow sufficient supply to the lifter fed through #1 main on the other side without sacrificing oil to the main and #2 rod.

I dont elongate/drill only #2 and #4, I do all of them. I even make the rear main a little bigger. The problem is the main shot of oil comes from the hole in the block on the "tab" side. But the hole in many bearings like Clevite is just a round hole in the center.
So, the oil has to hit the back of the bearing, move over to the misplaced hole in the bearing and on its way. Bad deal since that shop of oil has to get to the main bearing surface AND all the way up to the rod bearings. Rod bearings wont live long at RPMs with just the round hole. Just not very much time for everything to line up and get pressure all the way to the rod. The "detour" the oil has to take is the issue.
So I modify all of them. Must work since my engine was done in 1990 and has had only 2 sets in that time. Rods, 3 times.

[ponyakr]

Here's another Pontiac powered mid 10's '68. Shady lookin ad. Car may not exist.

https://cars.trovit.com/listing/68-p...00.1z11i115Cu-

Here's the CL ad.

https://pueblo.craigslist.org/cto/d/...399620593.html