10" pressure plate exact drilling dimensions.

[Robert Dip]

Thanks Brian, so we can accurately enough say that the bolt circle is at 11.375 for the 10" PP and the paired holes are at 32 degrees. When I used the caliper to measure between the holes, yes, some differed by a few thousands also, which can explain the differences. Ford usually used pretty standard fractional dimensions to keep it simple and angles are just that, angles. Thanks for your input & help. One thing remaining....where do we place this info in some sort of archives/ library on the 'Ford barn' ?? We can also do this for the 9" and 11"...I have both of these PP here.

[russcc]

If you are like me, you would like to figure it out yourself, and do it on your Bridgeport. But, in reality, I would take the PP & Flywheel to a good engine shop that does all the time or a CNC shop that can scan the PP hole relationship, and bolt circle, and do it on a CNC mill with the data.

[Chisel]

Originally Posted by Ol' Ron

have an adapter that registers in the crankshaft location in the flywheels. By bolting them together I can accurately transfer the bolt holes from one flywheel to another with my drill press. Have been doing this for quite a few years I then have them balanced, jut for kicks.

Ol' Ron has the best and easiest way

[Mart]

I like the plate drilling jig shown earlier in the post. The only thing I might try to do different, would be to Rotate the holes around somewhat, or maybe try and locate the wide spaced pair next to the narrower spaced pair, just so there aren't two holes so close together. It probably isn't a problem, but I would try and do it as it seems (to me at least) to be the right thing to do.

Mart.

[big job]

did anyone mention "bolt hole calculator" its free on the web thats what I use.

[Mart]

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I don't have a 10" flywheel to hand, but I do have a 9" and a 11".

I measured using studs in the holes and good quality calipers and got the following:

11" pcd = 12.375 Angular displacement is 32 degrees.
9" pcd = 10.351 Angular displacement is 30 degrees. Edit: Should be 32 degrees.

The 9" pcd does not match a set fractional size so although I believe the figure, I'd want someone to back it up before drilling metal. I was a little surprised that the angular displacements are different, but using trig, I was surprised that the numbers came out bang on a specific angle.

I do have a 10" pressure plate I will go and see if I can get corresponding numbers for that.

I will edit this post with 10" numbers by the same method. I will also recheck the 9" numbers.

Ok I have remeasured the 9".
I now get 10.361 for the 9". Lets park that for now.

For the 10", measured from a pressure plate, I get:
pcd = 10.384 Angular displacement = 32 degrees.

Now that's measured on a sheet metal pressing.

If I were a betting man I would say each one does match a standard fractional dimension. I'd go with

9", 10.375 with 32 degees offset.
10" 11.375 with 32 degrees offset
11" 12.375 with 32 degrees offset.

I'd trust that ford used standard dimensions more than my ability to measure to within a few thou over such a dimension without a metrology lab at my disposal.

Mart.

[Robert Dip]

Thanks Mart.....I believe your final statement will become the 'Bible.

"If I were a betting man I would say each one does match a standard fractional dimension. I'd go with

9", 10.375 with 32 degees offset.
10" 11.375 with 32 degrees offset
11" 12.375 with 32 degrees offset.

I'd trust that ford used standard dimensions........"etc.

Any comments on creating a 'Ford Barn Info Library' ??

[Dec211975]

I believe you are right Mart, post # 9 with the fixture have a hole spacing difference of .500" on the diameter and the spacing on the outboard holes are in the range of what Robert got with his measurements and I got using autocad. I don't have any flywheels to check but if I did I would center it on the Bridgeport and check the bolt hole locations.

Regards,

Brian

[PeteVS]

Got my pressure plate mounted on a brand "X" flywheel today. I took the flywheel and pressure plate to a local machine shop a week or so ago. I never thought I'd find one nearby but he was very willing to do the job. When I went to pick it up, he told me that he thought that the pressure plate must have been off because he couldn't get all of the screws started. I told him I'd take care of it and brought it home. I made up 6 little guide pins (shown in photo) by cutting the heads off of 5/16-18 bolts that had an unthreaded portion. Turned out that 2 of the pairs of holes would fit on the machined holes in any of the positions. I eyeballed where the other pair of holes were off and slowly opened them up with a rat tail file until they all would go on the guide pins.

Now, I just have to find someone to balance the assembly.

Flywheel holes were drilled and tapped 5/16-18 x 3/4." They were "counterbored" with a 5/16 drill 1/8 deep. I made sure that all bolts were able to tighten onto a washer thinner than the pressure plate stamping.
Pressure plate bolts are ARP, 5/16 for Fords. I got them from Speed Way.

[GB SISSON]

I recently had a flywheel for an 11" clutch re-drilled to take a 10" clutch. I took it to a machine shop on the mainland that is owned by an old truck friend. His machinist said he could do it and he did. But when I picked it up it was 235.00 to drill the six holes. Machinist told me he had two hours into locating the holes before he drilled. I brought him a 10" pressure plate for a guide. It bolted up fine and was properly countersunk and took the 20 ft lbs of torque no problem. I just wonder if he had had this info if it would have sped up the process. I am all for an info library. Also, he did drill the holes in between the holes for the 11" clutch. Thank you all for this thread.

[PeteVS]

Originally Posted by GB SISSON

I just wonder if he had had this info if it would have sped up the process. I am all for an info library.

I had given my guy the 11.375 diameter and 32º angle information along with a complete set of X and Y coordinates. He verified my X and Y data on his own CAD system and charged me $85. I gave him more, just being so happy to have found someone willing to do it.

[AnthonyG]

Serious vibration issues if off a bit. I had one on a rebuilt engine I bought. Completely installed and running. Not too bad to 1000 rpm then vibration got pretty bad. Removed bought recondition PP factory drilled to match PP only. Smooth as silk after.

[42merc]

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[Ken Crans]

Just got done doing exact job, Here is the way i did on CNC mill with a CMM Machine checking location of holes before machining. Mounted clutch pressure plate and had .003 run out. Checked with I D and O D.Here are the numbers..