FLATHEAD Tech Question

In preparation of putting my C59A (Canadian 59A) together, I discovered a cracked REAR MAIN CAP.(crank shaft)

I was able to find another; but the concern is now, that to "play safe", the mains should be ALIGNED BORED - or in my case I have access to a MAIN BEARING ALIGNMENT HONE.

To illustrate the problem / question I have, I'm attaching a picture that was in HOT ROD magazine's FLATHEAD Special issue. This picture was of BARON'S method of keeping the cap - rear in this case - from "shifting."


Ford used curved "SLOTS" in the block, and a matching "RIB" on the underside of the bearing cap to LOCATE the cap to the block.

Later model engines are FLAT - no rib - on the underside of the main bearing caps; which allowed for a SMALL amount to be GROUND OFF and produce an "EGG SHAPED" journal opening. Which was then made round by align boring.

So ... the burning QUESTION. HOW do you ALIGN BORE a FLATHEAD??

 

You take the block with main caps to a machine shop and they do it for you.

 

Keep in mind that a flathead uses a gear-to-gear cam drive, so the machine shop needs to take the LEAST amount possible from the block . . . so that the crank-to-cam drive gears don't have a meshing problem. If things are close, then I'd prefer to use an align hone . . . just depends how far things are off. Some machine shops are lazy and don't want to setup the align-bore to take more from the cap than the block - as it is a bit trickier and it is easier to have a chatter condition. Hopefully the shop knows flatty's . . .

Hope this helps!

Dale

 

I know somone that is set up to cut V8 caps. not many shops will do it.
It involves mounting the the cap in a fixture that go's in a rotary table and gets cut on a mill.

PM me if you need more info.

 

Use a four jaw chuck in a lathe and cut the cap. Darrell

 

Dale, I realize taking a "pass" off the bottom of the block can/could upset crank-to-cam gear clearance.
The other thing I'm worried about; is that a cut off the BOTTOM of the block would - slightly - move the center line of the crank CLOSER to the DECK after being align bored. (or honed)
I already have established piston crown-to-head and valve-to-head clearances off the existing crank position.
I never have had to align bore a flathead before.
Sadly, non of the shops around here have anyone left on staff that knows "flatty's."

So ... on to ...

As I was creating this post, those ideas - ways - kind of passed through my mind.

Then the next question would be "HOW MUCH" would you take OFF the BOTTOMS of the caps?
And would a similar cut - removal - need to be made on the "locking" tab??

But, I wondered if anyone had ANOTHER way.

Thanks guys; I think these methods will have to be the way to go.
Dave

 

The guy I know that machines the caps has done V8's for many many years. He has told me that many times he has found caps that work as is. He never takes a cut off the bottom of the block and there are under size gears available. The tabs dont need to be cut.
You shoud call him if your going to do this.
Dennis 916 791 7452
Greg

 

Thanks for the info Greg.
Dave

 

i suggest that before you get too excited that you install the cap and visually check the parting lines for misalignment and then carefully measure with a bore gage for concentricity . you may find its fine as is.....

 

Way ahead of you.

On the rear main cap ...
Slight misalignment at the parting line(s). Thumb nail "snags" at the parting line.
And; NO it can't be installed backwards.
And hole is Slightly out of round. (almost .003 out of spec. from top to bottom of hole)

And ALL caps are held in place with NEW ARP studs.
Front and center caps check out OK.

 

As some have said -- the block is not machined, the caps are. The caps could be cut on a rotary table with a mill - if you had a special fixture (which would be expensive or a waste to build unless you were going to use it all the time). Using a 4-jaw chuck is how I've heard of most shops doing it - and if you look at the cap, you can typically see that was how it was done in the first place.

Where are you located? It is always best to find a shop that does flatheads, but other than the machining the caps issue - it should be standard work. No matter what you do, there will be some material cut or honed from the block side -- just make sure they minimize the amount. Should not be a big deal.

Dale

 

Bored&Stroked - Dale

Sent PM.
Dave

 

Ol Ron on Fordbarn also does not usually align bore--he measures, and says he usually finds one that will work. Finding and trying multiple ones from people's cracked block heap would be a lot easier and cheaper still...
If none match, goal would be one too deep so no machining on block.
Try searchin main bearings/main caps on Fordbarn and look for Ron's words on this. He has probably built a lot more flatheads than 99% of the people involved with them...

 

Dave, if you need me to rooting through my junk for main caps let me know.

 

Bruce, "C59A's - rear main bearing caps - have become "rare as hen's teeth" up in this part of the world. Most "C59A's" are now days keeping boats from drifting away!

The one I DID find IS too deep; so my friendly auto machine shop has agreed to take a pass; indexing off the bottom of the BLOCK saddle so not to upset the crank center line.

Thanks for directing me to 'Ole Ron - again, - check his info regularly.
Dave

 

tin, sent PM.