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°.

He ever take you for a ride in his 1000 hp chevy Pontoon Boat??

Tom V.

The dowels in the block are .308 DIA and the New billet caps came reamed already to .312. The new caps should just drop on with slop, they do not. It seems like the spacing between dowels on PMD is not the same as the billet. Has anyone encountered this? It sounds like I need to re-establish location with a mill cutter and maybe open up to 3/8" dowel and not just re-ream the block holes.

I've never heard of using Elmers for a tapping lubricant in SS! I'm guessing you see much more tap life with it?

The biggest difference I have seen is when drilling SS with high speed steel or cobalt bits. The glue doesn't let the bit overheat and the SS doesn't turn blue like it often does. Use the glue and moderate to slightly high constant pressure and it drills right through. Again, I don't know the science behind why it works, but it does.

Stock Pontiac dowels are about 0.3096" diameter. With the Milodon splayed caps that I have, a 0.3096 dowel will drop into the holes, but a 0.3125 is not even close to fitting.

And BTW, I have bought dowels from http://www.precisionautomotivespecialists.com/. That is the only place I have found proper 0.3096" dowels. I also like the extra length of his.

Yes the 400 block I had converted the shop id not really check fit. One of the billet caps drops on the other 2 are tight as the spacing must be a hair off.

Current Progress, I think the fixture is coming along nice. Now I need to pick up locations of dowels in the block and in the cap to figure out what amount to move holes to get back in line with each other. I am going to try to make 8mm dowels work.

I made the plates able to hold the block square and at 18°.

Looking good! Alot of work for a 1 off project but moving rather well. Is that couple of injection molds i see laying around?

Nice work!

Thank you, yeah its a bit of work but I am sure any engine machine shops near me would have totally hacked this thing up. Good eye those are some molds back there. Its crazy how many guys I work with making these custom molds and none of them have any idea what they are looking at when they see an engine block. One guy asked me “what are you doing for the exhaust there?” I said “what exhaust?”, as he pointed at the 3 freeze plug holes lol

A lot of different knowledge levels out there. Congrats on a very nicely engineered fixture to drill your block.

Are you using bushings in the outer main caps holes to help locate the center lines of the drills when doing the initial small bit drillings
in the block?

Tom V.

I did make a drill guide ‘sleeve’ to fit inside the splayed hole and have the ID be the tap drill for 7/16-14. I was going to use that for if I had to use my bridgeport with the head tipped. Now that im doing it in the cnc. Im not sure if I am going to use it or not because I am planning on installing the caps on dowels with block set on the 18* fixture side. Then tramming center zero in cap and spot facing, center drill, tap drill then tap.

Thanks.

Tom V.

I have the new dowels installed and they fit very nice now. I have layed out the thrust 'step' dimensions. I will do a rough cut and re-install and make sure measurements are lining up before finish cut.

For drilling the 18° holes, how deep until the water jacket becomes close?

http://forums.maxperformanceinc.com/...22#post2332622

All the info you need is here.

Thanks to Pontiac Jack and others.

"You don't really want .001" interference fit in the block. A "light press fit" is called for, which means very close to a "zero" fit. Usually the first 1/4" or so of a reamer is slightly undersize (some fraction of .001") and gives the fit you want.
You also don't want a 34mm long dowel- more like 5/8"-3/4", with more than half of it into the block. You could shorten them with a cut-off wheel, then grind a little chamfer on the cut end." Pontiac Jack





Tom V.

Out of curiosity, do you race guys use dip sticks? Or do you just assume no significant oil is lost between oil changes or tear downs? The reason this matters here, is that I have not figured out a dip stick solution that works with splayed caps. The stock dip stick would route through the splayed bolt. Something through the side of the pan could work.

I don't use a dipstick on my race motor and it does not leak oil at all. I change the oil frequently enough it's not an issue.

The only way as far as I know is to install one on the side of the pan. Canton makes a weld in version for their pans. You could adapt it to any pan if you wanted to bad enough.
I has Steffs weld in a bung for this on my aluminum pan I bought from them.
Not sure if I will even use it as there are plenty of knowledgeable racers getting by without any dipstick at all.


https://butlerperformance.com/i-2445...tegory:1285261

What I did on mine is to weld 6AN fitting then use a braided line then cut it to length for the dipstick to read correctly. This way its flexible enough then when ur done, just cap it with a 6AN plug. Incase ur running a vacuum pump.

A little grinding on the corner of the main cap and I used a stock dipstick with my deepened Canton.

Finally got it done! Everything came out awesome. Caps fit perfect, thrust is cut within .001 and the tapping went smooth with no vented water jackets.

You did an excellent job on your splayed 4 bolt cap conversion. The only thing I like better is to put a stud on the outer bolt as I feel that the stud is better on clamping load. Excellent work!!!

Superb work!

I just want to say, DIY ? That machine shop looks nicer than 95% of the shops that do splayed billet caps for a living.
Very nice, good luck with it.

Good for you! You didn't need any real help, just a nudge from the forum to get it done...
Nothing like taking on a task like that and succeeding... it will feel great knowing the muscle under your hood was done by you!
Job well done!

Good job.. thanks for sharing your adventure

Well she is back in my hands and its time to start checking clearances. I am wondering what torque sequence is proper for the Splayed caps? Do I finish torque studs then do the splayed bolts? or incrementally both of them? The engine machinist specified 100ft/lbs on studs and 65ft/lbs and splayed.

Correct, torque the main studs in steps to final torque, and then torque the splays in steps; typically mains in 3 steps and splays in 2. The main studs secure the crank and set bearing crush and the splays tie the block together. Grade 8 bolts for the splays; not nitpicking and should be fine but just curious.

I took mine down to 20 and then to full tq spec in one long pull.