[slowbird]

We used a cutoff wheel to make the grooves.

[ho428]

Originally Posted by slowbird

We used a cutoff wheel to make the grooves.

That's what I was planning. I'd always seen it cut to both sides of center though, the pic of the IA block was the first I'd scene cut to one side only.

[Mike Kasparian,Sr.]

I am aware of this modification but have never tried it but going to look into it for the new block . With puting more oil holes in the main bearing help with getting more oil to rod bearings with this mod ? Any real world info ? In my mind I struggled with it because of the grooved bearings .

[Half-Inch Stud]

Originally Posted by Skip Fix

This mod is also shown in one of the GM published Chevy high performance engine books.

Yea butt, that could be a fix for Chebys. we could hope it's an improvement for our brand.

[Tom Vaught]

Just as a point of conversation HIS, a Pontiac Super Stock racer was having troubles keeping his engine together going down the track some years ago. The guy who built his previous successful engines was not able to keep the things alive.

So the racer went to Tony at BES and the problems went away and the engine I believe had the groove as one of the mods to the oil system.

Tony has been doing this mod for years on Pontiac Engines. just saying.

Tom V.

[mike leech]

Originally Posted by Half-Inch Stud

Open to understand; what is done exactly.

PMD grooved the Main Lowers in the 59- early 60's.

We all know about fully grooved (groove too big!?), and 3/4 groove (seems just right).

I have to ask what is better about block saddle grooves and two bearing shell holes, vs a properly grooved bearing? Ultimatley; why not implement the whole thing into the bearing shell?

Sorry Mark. But you wrong on this. It does work. And helps provide a hydrodynamic oil film continuous across the main cap where some of the oil pressure has subsided due to leakage and heat. Also heaviest bearing load.

Works.

[mike leech]

I should have kept reading. It's good seeing everyone else already explained it well.

[Half-Inch Stud]

Mike, Tom, Thanks, HIS

[mike leech]

Originally Posted by Mike Kasparian,Sr.

I am aware of this modification but have never tried it but going to look into it for the new block . With puting more oil holes in the main bearing help with getting more oil to rod bearings with this mod ? Any real world info ? In my mind I struggled with it because of the grooved bearings .

Scalloping the trailing edge of the oil hole in the crank kinda does the same thing for increased oil feed and prolonged pressure to the rod bearings.

[chiefbigb]

Good information. Thanks for posting this.

[chiefbigb]

Would be nice if in the future this was a option on the aftermarket blocks now available.

[Dragncar]

Sounds like a great idea to me. No downside, only upside.

[GOSFAST]

Not 100% certain what you're trying to accomplish here but if it's trying to extend bearing life AND loads I can give you a real good dyno and track-proven mod for the main shells that will do exactly this!

We've used it on all platforms and all mfr's on higher-end builds, 1000 HP and up. Have been using it for many years now.

It incorporates machining grooves in the UPPER shells that carry the oil to outer edges of the crank where the "hydrodynamic-wedge" is mostly needed.

I'll place a few shots below here, one showing a before and after bearing comparison when the first failure occurred (front main) and the second shot showing the same lower bearing (front main) shell after running under the identical circumstances but from a set with the mod done. This was with the same unit for the comparison, the "crush" on the good shell was still perfect.

On a side note, wishing all here a Merry Christmas and a Happy New Year!

Thanks, Gary in N.Y.

P.S. The mod takes about a 1/2 hour of machining on all 5 inserts, fairly simple, and is worth every penny it costs.

[Half-Inch Stud]

GOFAST Gary,

That looks clever, and much better to retain crush than my wide on-ramp approach done at the Lower shell parting-line on the going down side (3:00). Worth a ponder, and hope its get challenged here.

Perhaps only the 2:00 position (after-noon) UPPER need the groove, whereas the 10:00 (before-noon) UPPER is moot?

To reflect, my "first effort" was to use fully grooved Mains in the mid-late 80's; was a harmless experiment at the time, but really haven't "done the development" to conclusion.

[Tom Vaught]

The Mod has merit. I have seen it done where the trailing edge of the slot had a slight radius to smoothly transition the oil to the non slotted portion of the bearing. The opposite side of the bearing was not slotted. Can you explain your reasons for the symmetrical slots on that side, the end of the load cycle side?

Tom V.

[Half-Inch Stud]

@Tom, So ah Post 34 & 35 ask for an answer to the same question. Clarity being a good thing.

[BruceWilkie]

Has me wondering what a "V" chamfer from 12:00 to 3:00 with convergence of the "V" starting at oil hole and "tails" of "V" ending before the outer edge of the bearing...chamfered so groove is shallowest at ends of "V" would do.

If crank was cross drilled 455 style mod (vs straight shot 389/400 style) perhaps lower shell v'd the same way from 6:00-9:00 would add benefit?

Garys mod seems easier and effective. Just curious if oil wrap could be further improved. Flow more oil to further cool bearing and perhaps at tighter clearance and keep rod bearings happier too?

[Tom Vaught]

Cross-drilling has been found to cause other issues with oiling which is why straight shot oiling is a better scheme.

Personally except for the mod being a bit harder to do (groove the main saddle behind the bearing), the Tony B method seems to be working for a variety of people with Pontiacs.

I was amazed at how quickly the bearing temp went up on the rig as the engine rpm was raised slightly. The oil has to carry away a massive amount of heat in that area.

Tom V.

[mgarblik]

Concerning the groove in the block. Since there seems to be some consensus that this modification works and the OE's do it in some applications, I would offer the following. In our Pontiacs this area is one of the weakest and most crack prone spots in the engine block. Cutting and removing material from an already weak area must be done very carefully with minimal material removal and very careful de-burring/chamfers. This is an ideal area for stress cracks. On an aftermarket block, I would be concerned about opening the oil feed to 5/16" AND adding the groove. If I added the groove, I think I would stay with the 1/4 inch drilling as delivered. There is going to be a complex trade off between how much additional volume is needed, the cooling effect of that volume, and the possible advantage of an elongated oil wedge from the added groove. The viscosity of the oil used and the bearing clearance also figure into the equation. So even though BES and some others have had success with this modification, be sure to get the total package they run to duplicate their results in your engine.

[Dragncar]

Thought I would bring this thread back to the top. Got to make plans on a IA2, and this is one of them.