[gata79]

This is a king main bearing. The oil hole looks very small. Should I enlarge it?

[25stevem]

No.
But let me ask this (1) are you assembling this motor for the last time (2) is this a factory block?

[mgarblik]

Originally Posted by gata79

This is a king main bearing. The oil hole looks very small. Should I enlarge it?

If you would have posted in the street section, I would answer it this way: The bearing companies, King, FM, Clevite size the oil hole or slot to be smaller than the feed hole to accommodate minor alignment issues. As long as the entire hole in the bearing is exposed to the feed, your fine. As long as the full width of the slot is exposed to the feed hole in a FM bearing, you are fine. Street performance on a Pontiac engine is generally defined as 500 HP and 6000 RPM


You are posting in the race section, so Lots and Lots of additional information is really needed to answer the question correctly. 1. Oil pump and pressure 2. small or large main bearings 3. RPM range 4. HP 5. Oil Clearances 6. Rotating weight 7. Restricted upper end? 8. Many other factors.

[Skip Fix]

I always wondered why they bearing hole is not centered on the block holes especially on performance bearings.

[gata79]

Sorry, should have been more specific. It’s for a 535 IAII aluminum block with fully ported Tiger heads. I have another engine just like it that I did enlarge the hole. I turn that engine engine to 7800 or so. It’s basically the same build but going in my other car. The hole just seems small and I don’t want it to be a restriction. The oil pressure on my other engine is fine and has given me no problems so far. 80 lb oil pump. Clearance around .003. 3 inch mains. Upper end is restricted. Scat crank Oliver rods.

[Steve C.]

A tid bit concerning the IA2 block...

From this:

http://www.allpontiac.com/online_cat...ding_notes.pdf

CHECK ALL OIL PASSAGES AND DEBURR IF NEEDED

GOODEXAMPLE, take note that the location where the oil passages intersect within the front main cap could use some attention. The depth where they intersect is not the same as a factory block, it's closer to the bearing.
Similar situation on the three center mains. We cleaned up that area for improved oil flow.


.

[mgarblik]

Originally Posted by gata79

Sorry, should have been more specific. It’s for a 535 IAII aluminum block with fully ported Tiger heads. I have another engine just like it that I did enlarge the hole. I turn that engine engine to 7800 or so. It’s basically the same build but going in my other car. The hole just seems small and I don’t want it to be a restriction. The oil pressure on my other engine is fine and has given me no problems so far. 80 lb oil pump. Clearance around .003. 3 inch mains. Upper end is restricted. Scat crank Oliver rods.

Thanks for all the updated info. I am building a very similar Aluminum IAII right now. But 482 Cu In. 4.25" square. Will run 80 lb. pump. Project 6500-7200 sustained RPM, (road race). 10w-30 oil, accumulator, flat tappet solid cam, .040" restrictors, .003 main, .0025 rod clearance. No plans to modify bearings. Running King HP. Will clean up and massage passages as needed in the block. I think they looked pretty good as I recall. I do open up the passage at the oil filter pad where all the drillings and the AN fittings go. It's a little rough in there, lots of sharp edges. Good luck with your build.

[Steve C.]

In my post 6 I believe I now mis-spoke about it being closer to the bearing.

" take note that the location where the oil passages intersect within the front main cap could use some attention. The depth where they intersect is not the same as a factory block, it's closer to the bearing. Similar situation on the three center mains. We cleaned up that area for improved oil flow."

It is defiantly different than my factory block on hand.


.

[grandville455]

I have to do this to all my 113M bearings on my IA2

[mgarblik]

Agree on the 113M bearings on an IA II block. I do the same thing. With King and a hole, not slot, that doesn't seem to be needed. But certainly check. The entire bearing hole needs to be open to the block.

[Dragncar]

Originally Posted by grandville455

I have to do this to all my 113M bearings on my IA2

Exactly what you do to a main bearing. Unless you like spun rod bearings.

[Dragncar]

Originally Posted by Skip Fix

I always wondered why they bearing hole is not centered on the block holes especially on performance bearings.

The problem is on a Pontiac the shot of oil comes from the oil hole on the tab side of the bearing. The oil flow has to hit the back of the bearing, move over and go through that little hole.

[Jromaine87]

Originally Posted by gata79

Sorry, should have been more specific. It’s for a 535 IAII aluminum block with fully ported Tiger heads. I have another engine just like it that I did enlarge the hole. I turn that engine engine to 7800 or so. It’s basically the same build but going in my other car. The hole just seems small and I don’t want it to be a restriction. The oil pressure on my other engine is fine and has given me no problems so far. 80 lb oil pump. Clearance around .003. 3 inch mains. Upper end is restricted. Scat crank Oliver rods.

What did you end up doing? I spun a rod bearing at 12 passes.


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