Splayed Main DIY
 

I just purchased the 3 pcs Program Eng. 4 bolt splayed mains for a 400. Shops local to me either wont touch a Pontiac to add them or are 7 months out to do the job. I work at a machine shop building plastic injection molds so I have machines that I believe I can rig up to do the job, and a boss that seems excited for me to attempt this task. I have a bridge port manual mill and large cnc's. But my questions are...has anyone done this? and what is a good way to fixture for this operation? I was thinking about making a 'saddle' for the deck to sit on.

There’s at least 3 machinist on this board that should be getting back to you.

I hate to be the guy that advises against this... but I would use the correct equipment for the task. I have used the Van Norman, Sunnen and Rottler CNC F69A style machines. I always finish them a little on the small side and finish with an align hone after the bore. If you had a scrap block lying around then maybe. One mistake and your block is not useable.
There may be some here who have done it, but my 35 plus years as a machinist doesn't have the warm and fuzzy about it. You may be headaches ahead to find a shop. You are not far from Scott Williams, find out who does his machine work.

Splayed Main DIY
 

I should have clarified, I am not going to touch the main bore, i have a shop to do the align bore and hone. I am only needing to mount the caps to the block and then machine the thrust face to match the block.

Oh well forget what I posted.....Yes,I have done a few of the drill and tap process on a manual mill.

The valley ends of a Pontiac block seem to be exactly a 6" radius. See the attached picture of a pair of saddles that I made to mount my block in my Bridgeport for a different purpose.

I have a block that I was thinking about installing splayed caps on. I have a set of the Milodon splayed caps. They come with a drill bushing and say to use that and a hand drill. The Bridgeport seems like a better idea.

The thrust surfaces on the #4 cap seem to be the tough part. I have not found anyone local to me (San Diego) that can do them.

And you probably already know this, but with splayed caps, you cannot run a dipstick in the normal location.

I like your saddle idea

I had a thought to address the thrust face. I was planning on bolting the No.4 cap on, indicate the amount of stock on the cap to the block face, then remove cap and cut measured step off clamped in a vise. Obviously do a semi finish and verify stock removal is on the right track and square.

The machine shop that will be line boring the 3 center caps should be able to cut the thrust faces as well. It's part of the process. My Sunnen line bore attachment for the line hone will cut the thrust faces. It's a little crude, but it will cut them. Billet caps are really tough and can produce a little chatter. Check with your machine shop. Not sure how to cut the thrust faces in a Bridgeport without a rotary table and a fly cutter. That would be pretty tough. Mounting the caps is pretty easy in a Bridgeport. I just use a transfer punch to line up the drill guide. Drill and tap. Pretty simple.

Tom Earhart, who was the Engine Machinist/Dyno guy for Marty Palbykin's 1967
400 cid 2 BBL 2 bolt main block, (no 4 bolt main drilling in the block), added the
PROGRAM Steel Main Caps to that block in the 1995 time frame.

So it has been done with success in the right block application. The issue is finding
someone capable of doing the work properly. The engine as posted, made 1600 hp
for 3 years without failure. Tom had the Bridgeport as well as the other equipment required.
He had a lot of very good Engine Machining equipment.

https://www.snowmobilehalloffame.com...s/tom-earhart/
Tom Earhart began his career building and racing drag and oval track sleds in Michigan as chief engineer for Rupp.


The point is finding the right guy to do the work. Not sure if Tom is still doing work.
If so He and You are both in Michigan. He is on the west side of the state.
Thomas Earhart's current address is listed as 10751 Gun Lake Road, Middleville, MI 49333.

Tom V.

Tom is retired and moved to Florida.

Thank You, Mr Twister.

Tom V.

Had no idea Tom was involved with Pontiac projects,he was very well known for his work with Kohler snowmobile race engines with Rupp and the Kalamazoo Kyotee sno pro sleds,I've been collecting parts to build a Kalamazoo Kyotee replica

Mike at Engine Supply in Santa Ana, (714) 556-0310. Very knowledgeable and knows Pontiacs.

...square out the head n block by tramming in the oil pan rail. while you are on the bridgeport drilling you new holes.(thrugh a guide bushing in the cap) Dont forget to spot face the parting line before you try to tap it!! ;)Then when you bolt on #4 cap make a skim cut across the TOP of the cap this will then be parallel to the parting line giving you a good clamp ability in the vise to cut the thrust surface. Yes take a measurement from block thrust surface to cap...cut some off cap faces....replace and RE-MEASURE making sure your NEW cuts are square with block surfaces and parallel to block thrust surface.. ONCE you achieve face cuts that are parallel to the blocks thrust face....then you can indicate cap and finish it up. Yeah its alot of back n forth but takes longer to type it than to actually do it. Been a Journeyman Tool & Die & Mold maker for 30+ yrs. Also NO OIL while tapping cast iron

Great thread... I too have this on my to do list. I had a cnc 5 axis in mind or a manual horizontal deal...

Nice fixturing there sherminator2 ! What max angle can you get out of it ? This is what machining is all about.. the creative routes!

Does anyone know the common angle of the splayed holes ?


Thanks
Kris.

"Also NO OIL while tapping cast iron"

I've never heard this. What is the reason?

Because the tap can not evacuate the chips up its shank if the tap has lube on it since the chips will stick to it and you will be backing out and cleaning off the chips forever!

Taping cast iron is nothing like doing such in Steel or Aluminum.

I have noticed that tapping the cast iron benefits from the chips falling out by gravity-pull rather than making a paste out of then. PMD Iron taps beautufully.

I will add, when drilling or taping stainless steel, use Elmer's glue as a lube. Just the plain old white glue! Sounds crazy, works beautifully. I don't know why. Friend who owns a sheet metal shop showed me that.

I did not intend to get a large angle. Just enough to square the engine block to the table. I was thinking of nodding the head of the mill to do the splayed bolts.

This does bring up an interesting thing though. The block is inherently unstable on this fixture until it is bolted to the table. Visualize the center of rotation below the table and the center of mass way above it. The block will literally try to roll right off of the table.

BE VERY VERY CAREFUL! Keep the block hanging on an engine hoist until it is well secured to the table.

I just measured the Milodon caps that I have and the bolts are canted 18°.