[Speargun]

Has anyone used them?
Thoughts? Better than factory 2 bolt?

$113 @ Summit/Jegs or $80 direct from Speedmaster.


https://www.summitracing.com/parts/s...3/make/pontiac

[PontiacJim1959]

Have not used them, but interesting. Speedmaster seems to be putting out a good selection of Pontiac parts. Now if they are good or bad, who knows.

My comments would be that I would wat to know what the material is, and what Rockwell they come in at.

I don't care for any of the squared off shoulders and if they used a radius in all those areas, I'd like them a bunch more - but guess with a little work this could be done by the installer.

Not a machinist or machine shop guy, but installing a set - could deflection/distortion be measured within the bore/journal radius when torqued down?

$80.00 is not a bad price.

[Jack Gifford]

Much more important than outer corners, there are no "sharp" inner corners- they are all generously radiused.
Hardness numbers are less important than the quality of the steel- uniformity, etc.

[DiamondJim]

Are they made is USA? What grade is the steel? If they’re made in China I would definitely pass.

[Half-Inch Stud]

They look very good. Does a magnet stick to em?

[gtojeff1967]

on Ebay they said 19 sets sold.
1025 steel what i remember that is just mild steel.

[grandam1979]

They are sold out and not available at Summit and Speed master. Most of the Chevrolet caps are sold out also.

[mgarblik]

Originally Posted by Jack Gifford

Much more important than outer corners, there are no "sharp" inner corners- they are all generously radiused.
Hardness numbers are less important than the quality of the steel- uniformity, etc.

Agree with the above with a few additions. 1. The dowel holes need to be the right size for a snug fit and be in the exact correct locations. That's really important. 2. The thrust main cap needs to be made wide enough and NOT be machined on the sides for the thrust bearing. They are never cut accurately enough and must be machined after installation to be parallel and the exact correct width. They are 30% the price of good caps from the former Program Engineering so it's unlikely they are near as good. Not impossible though.

[steve25]

Interestingly with the true comment made above about the Width of the Thrust Bearing area the picture posted does not show the Number 4 cap now does it?

Makes ya wonder why!

[67Fbird]

any 10 grade steel is low carbon steel nothing great there.STILL BETTER than CAST IRON.....when you get into the 41 series (chromolly) now your talking a different story. with forged stuff being in the 40->41 series of molly with chromium...blend

[steve25]

You fully do not need caps to be made from a 40 series steel when there’s no 10 series and no less 40 series steel block to bolt them to.

Sure it would likely be a good selling point, but for the average motor of under 900 hp it is really unnecessary!

First and foremost as posted above is how accurately they are machined!

[DiamondJim]

Are they made it China? I don’t trust anything made in China!

[67Fbird]

i would EXPECT...they are about .010" undersized to be ALIGN BORED per installation..... however...manufacturers may vary...per the English language.

[grandam1979]

We used a set of the pro gram caps for a 400 stroker they where not even close to being ready to use. Funny part you couldn’t tell them apart from the SM caps in the pictures.

[Half-Inch Stud]

Originally Posted by steve25

You fully do not need caps to be made from a 40 series steel when there’s no 10 series and no less 40 series steel block to bolt them to........!

Ahem, assuming the vetted CNC program was lifted from Program Engrg (or better), it seems to me the Caps need only be a precision Sling, much like a Rod Cap, to remain STIFF to hold the Bearing shell without pinching the Bearing Shell. The Hold being registered to the dowels, and nothing more.

So are these Caps STIFF enough for 3.25" Mains?, 3.0" Mains?

[PontiacJim1959]

Originally Posted by Half-Inch Stud

Ahem, assuming the vetted CNC program was lifted from Program Engrg (or better), it seems to me the Caps need only be a precision Sling, much like a Rod Cap, to remain STIFF to hold the Bearing shell without pinching the Bearing Shell. The Hold being registered to the dowels, and nothing more.

So are these Caps STIFF enough for 3.25" Mains?, 3.0" Mains?

Well, another means to add stiffness is the "old school" way of adding a 1/2" chrome moly strap across the top, tied into the 2 inner bolts with the use of longer studs.

When I was building a 409CI stroker using a forged steel big block crank, the 409 has 2-bolt mains. The shop doing the machine work said he would mill the tops of the main caps flat, use a 1/2" chrome moly "strap" across the milled tops, and use main studs to bolt the parts together.

These main caps look like the perfect candidate with a little machine work for such an addition. I'd bet the main studs would pull out of the block before the main caps broke and you would not get any deflection that could take out a bearing.

Someone needs to buy a set and give us a review.

[Dragncar]

Milodon now makes ductile iron splayed caps for 400 Pontiacs. i would like to know how these are working out for folks. Being good quality iron they are stronger than PMD iron, expansion rates will be the same too. Bet they machine easier than billet. And splayed.
I say, win-win.
https://www.milodon.com/main-caps/main-caps.php

[ponjohn]

Last I checked a lot of the program caps were out of stock.

[steve25]

The key to not spinning main bearings is just like setting up Rod big ends that tend to flex.

That is the main bore needs to be honed so that the dimension from parting line to parting line is just a few thousands bigger then the vertical dimension.

Some bearings you can get have this incorporated into there construction, if not then the main cap can be setup on the block with a few thousands worth of spacers which once the main bore is honed will produce the needed oval size at the parting line.

[Steve C.]

Sort of related and might be of interest....

"First trial fitting for the Pontiac main girdle. I have some little clearance issues to address and holes for the center supports are all suppose to be 7/16”, one side ended up to be 3/8”. Overall I am tickled with how it fits!"

Pictured on page 3 here:

https://psp.pontiacstreetperformance...&t=42&start=30


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