Boring main support

[FC-Pilot]

The newspaper cam in there looks high tech too...lol.

They wanted to keep the cam specs a secret so they covered the cam up. They were afraid that if you saw the lobes you might be able to figure out the specs. LOL

Paul

[1972ho]

May be one of those 55 or 60 mm cam journals ,because he could have taken the cam out.

[cgarb]

I would think the newspaper roll was there to keep dirt out from grinding and polishing.

[plovett]

Wouldn't much smaller holes function just as well for pressure transfer?

paulie

[dwilliams]

I'm noticing the same spacer shells we use to install a 283 main crank into a 350 main size block. What's up with that?

There was a fad for running small journal cranks in large journal blocks for a while.

[dwilliams]

Wouldn't much smaller holes function just as well for pressure transfer?

When the LS motors came out GM claimed the holes drilled above the mains did all kinds of wonderful things. I kept looking at the pictures and thinking that since the whole bottom was still open even with the fat main caps, how could it make any difference?

[1972ho]

Would this be the LS bored main web

[racear2865]

I'm noticing the same spacer shells we use to install a 283 main crank into a 350 main size block. What's up with that?

There was a fad for running small journal cranks in large journal blocks for a while.

Geez, this is not a fad. It is still performed everyday. Look at Nascar with Honda rod journals. $00 main SBC sized down to 350. Its called bearing speed. I do it every week in drag motors and some roundy motors.
reed

[pamotorman]

I'm noticing the same spacer shells we use to install a 283 main crank into a 350 main size block. What's up with that?

There was a fad for running small journal cranks in large journal blocks for a while.

Geez, this is not a fad. It is still performed everyday. Look at Nascar with Honda rod journals. $00 main SBC sized down to 350. Its called bearing speed. I do it every week in drag motors and some roundy motors.
reed

the NASCAR deal also reduces the weight of the rotating assy parts.

[bill jones]

-I'd like to see how you go about drilling those holes thru the main webs of the SBC engine---looks like it takes something more than normal---needs some out of the ordinary equipment.

[pamotorman]

-I'd like to see how you go about drilling those holes thru the main webs of the SBC engine---looks like it takes something more than normal---needs some out of the ordinary equipment.

bet they drill straight thru from the timing gear area and then plug the front holes if necessary using a NTP plug.. I believe GM now casts the holes in the LS blocks

[panic]

WRT "smaller holes function just as well"
In some bulkheads, the cylinders on opposite sides are far apart in terms on piston vector, and balancing the pressure at the bottom of the bore through the bulkhead is more helpful than using the pan volume above the oil level. The escape velo of the charge will be in the ratio of bore area to the vent area.
Obviously, some pairs are worse than others, so an analysis would begin (I would suppose) with a comparo of cylinder volumes in the bore below the pistons and firing order.
My current literary work-in-progress (Chevrolet Gen-2 "stovebolt") is an L6 with #3 & 4 cylinders traveling as a pair (360 degrees apart) as to both direction and position, but the #1 & 2, and #5 & 6 pairs are far apart and will have pumping back & forth between them, so their intersections (adjacent bores in #1-2, 3-4, and 5-6, and bulkheads in #2-3, and 4-5) have been dealt with (and illustrated in my own primitive way) differently.
Since it has the traditional 1-5-3-6-2-4 firing order, what works here should transpose very well to other 5 main bearing engines (slant 6, Ford 170, Pontiac 239, PlyDo 230, Chrysler 265, GMC 270), and to a limited extent 7 main bearing engines (Chevrolet Gen-3 250, RB26, Ford 300, my own 2JZ-GTE, etc. with all bulkheads).

Click here for more details on the booklet itself: http://victorylibrary.com/235BK.htm

[ec1]

According to a GM dyno guy i know when they drilled the holes in the LS1 it was good for 15 HP on the dyno. I guess it's hard for the windage to get around the large main caps. Hence the reason they improved that method in the LS2 on up going with the block scallops around the outside of the main caps and the windows under the bores.

[pamotorman]

According to a GM dyno guy i know when they drilled the holes in the LS1 it was good for 15 HP on the dyno. I guess it's hard for the windage to get around the large main caps. Hence the reason they improved that method in the LS2 on up going with the block scallops around the outside of the main caps and the windows under the bores.

it is the extended block below the crank centerline that adds to the windage problem