Jig for milling ford rear main caps
 

Hi does any one have or know some who has made a JIG to mill the rear main caps , I have a 40 block that was missing the main caps , took some off a bad 59 block , but they need to be milled so he can line bore it , I’d be glad to pay what ever is needed for the jig , I’d buy or rent , please help , thanks John

Re: Jig for milling ford rear main caps
 

Since I have the correct Quikway line boring equipment to machine flathead blocks I made my fixture so I could machine main bearing caps. The important part of the fixture is the center line needed for rotation to maintain the radiused step diameters. The amount of material removed from the area of the caps that touch the block for the line bore step must also be removed off the radiused step surface. To do this a rotary table is needed plus the fixture.
Ronniroadster

Re: Jig for milling ford rear main caps
 

Interesting. I have always thought they just mill off the contact at the block and let the boring tool make it round again. Is that too much material to take and maintain accuracy?

Re: Jig for milling ford rear main caps
 

A fella here in the UK made a steel cap and turned the register in a lathe. If the cap could be held in a 4 jaw chuck it could be skimmed in a similar way.

Re: Jig for milling ford rear main caps
 

it takes a bit of work to center, i have used a 4 jaw chuck to hold cap in lathe
If you have 3 sets of caps most likely 2 of the sets fit so close that line boring is not needed

Re: Jig for milling ford rear main caps
 

I made a fixture that work in a lathe with a 4 jaw chuck, Pretty simple/ However Most shops back in the day took a.005" cut across the block, this little amount had little afect on the cam gear. I'll look for mine and post a pic of it.
ramps

Re: Jig for milling ford rear main caps
 

There's a few guys I know who had the block surface of there flatheads decked instead taking the material off the bearing caps. Sadly the shops doing the work removed to much from the block. When that happens you now need to find a shop that's able to machine the cam gear teeth deeper that's a very hard thing to do.
In my area no one decks blocks anymore they only line hone all the shops remove the material from the caps including flatheads. Its a simple fast process and profitable for auto machine shops to do it that way.
Ronnieroadster

Re: Jig for milling ford rear main caps
 

I have 2 ways to do it.
1 - 4 jaw in lathe. Disadvantage is long setup time. Advantage is quick machining time.
2 - Vise in mill. Advantage, minimal setup time. Disadvantage, slow machiine time.

Total time for job about the same either way.

Re: Jig for milling ford rear main caps
 

Still confused here, why would one need to cut the radius for the bearing shell, I thought that was what the line bore was for ?

Re: Jig for milling ford rear main caps
 

I have done them in my mill very slowly by hand to contour radius of register. In future I will be setting up to cut them like Ronnieroadster.

Re: Jig for milling ford rear main caps
 

Cas, the discussion is about cutting back the face of the cap where it meets the block. There is a raised register that is a section of a circle. Once the cap is refitted the hole will be smaller than normal and can then be line bored back to stock size.

Please note I have not done this, just saying what I understand.

Re: Jig for milling ford rear main caps
 

Thanks Mart !

Re: Jig for milling ford rear main caps
 

The line boring will complete the bearing housing radius. The radiused step register is the area that creates a more time consuming material removing process.
Ronnieroadster

Re: Jig for milling ford rear main caps
 

Amount of time needed to remove the material from the bearing cap less than a minute per cap. When using a fixture set on a rotary table that's located on the spindle center line. :D
Ronnieroadster

Re: Jig for milling ford rear main caps
 

Align honing of the main line is NOT the way to go for a race block.

Re: Jig for milling ford rear main caps
 

Why not, Pete? Enquiring minds want to know.

Re: Jig for milling ford rear main caps
 

You do not want to move the mainline up. Honing takes an equal amount off the block and the cap. When you bore, you line up on the block so nothing but the disccoloration is removed from the block.
Same deal when you bore pumpkin saddles.

Re: Jig for milling ford rear main caps
 

Here's the fixture I made and how the main bearing cap is held in place. Overall it was a simple back yard Hot Rod project so I could line bore Ford flathead blocks using our own equipment.

The Quickway line boring system we use is extremally accurate mine dates back to the 40's. To date we have used this equipment on everyone of the Ford flathead blocks we have set many records with. Including the five main bearing girdle assembly we use on our 600 horsepower 292 cubic inch ARDUN race engine.

I'm a self taught machinist for a living I worked 38 years on the railroad testing and repairing signal systems from basic old tech to high tech computer based logic controls. That was my dream job loved being on the railroad. In the afternoons after work when time would allow after family stuff I spent time on my passion Hot Rods and Ford flatheads.
In retirement I spend most days in the shop on numerous Hot Rod related projects and also at times some stock Ford items as well. My wife calls me tired retired. :D
Ronnieroadster

Re: Jig for milling ford rear main caps
 

And I can testify first hand that you are one of the coolest guys I have ever met.
Maybe because we have railroad experience in common....

Re: Jig for milling ford rear main caps
 

Often wondered why you couldn't clamp a cap in a vice and file a few thousants off it. Slap it on the block and line bore it. Would the hole be out of round? would it be in the wrong place? would it work???? Probably need a precision file
Gramps