[Gmecm] Bellhousing Design-Iron Duke

[Jason M.]

Well In my case I had planned to make one until finding the cheap TCI 
adapter, at the time it was only an hour drive to summit racing to pick it 
up.  Lucked out and got a $140 K&N Xstream air filter assembly out of the 
scratch and dent bin for $50.  Someone simply returned it without the 
package or hold down stud.

As for actually making one, There are several ways to go about it.  I have a 
book with a dimensioned drawing of a small block Chevy.  Forget if I found a 
dimensioned drawing of an Oldsmobile block.

Once you have both of those drawings it will be simple geometry to set up 
the coordinates of each hole then put it on a mill.  The mill I have access 
to is not for personnel use but they sort of look the other way if you go in 
when nobody needs it and use your own tooling.

Then in a not so easy way you can put a straight edge at the bottom of your 
part, then use a square to draw out the locations then carefully drill out 
on a drill press or by hand.

There is a third option that requires the least amount of 
measuring/dimensioned drawing.  Use transfer punches.  They are specifically 
made for doings stuff like this.  They are a round cylinder with a small 
cone tip.  Set the transmission on it's front flange, on top of the metal 
for the adapter.  Find a transfer punch that just fits inside the hole, then 
smack it with a hammer.  This would work best if you have a Chevy and a BOP 
transmission setting there.  After the first one's pattern is transferred 
drill out the holes and install dowel pins in the adapter to align the 
second.

Another way you could align it is to maybe put a piece of pipe that just 
fits over the input shaft of the transmission onto the adapter plate, weld 
it down.  As long as it's ridged and lets the bell housing flange rest flush 
you'll know the input shafts are centered.  Then using a straight edge along 
the plate you can measure to a pair of bolt holes, one on each side.  When 
the measurement is the same side to side then you know the bell housing 
pattern is parallel to the straight edge

However the most important part in all this is to make sure you have good 
steel stock with dimensional variance +-0.001  over it's surface.  When 
looking into making my own I found the material would cost between $15-$20. 
Then there is a great deal of time spent measuring.  At the time it was 
averaging between 5-10 degrees F outside, and I didn't have much free time. 
So the price of a Pre made adapter was just fine for me.  Was already 
mentioned by another it was $58, I remember it being cheaper but don't feel 
like digging out the receipt to check.

I also found a company that made a really nice 1/2'' aluminum adapter for 
around $150 as I remember.  Could even get them as a large rectangle to use 
as a "motor" plate.  They actually came with inserts for the crank to center 
the torque converter.  Which makes it more of a straight bolt in, then 
having to rotate the engine several times while snugging down the torque 
converter screws.

I'm possibly going to buy one of the nice aluminum adapters or make one for 
the 500 Cadillac going into a caprice.  Will probably end up buying one 
since this is a common adapter and not looking like I'll have much free time 
this summer.  Have to do the body work and paint the '85 caprice, mock up 
the drivetrain, rebuild the engine, build accessory drive brackets, rebuild 
a SBC to put in my beater car in place of the worn out 350 olds. Back half 
an olds omega for a friend, and I'm sure some other stuff will come up.

Almost forgot, if you don't have a dimensioned drawing, you might get away 
with using a tape measure but it would be so much easier and precise to use 
dial calipers.  Basically just measure everything.  Since this application 
shares the dowel pins you don't need to worry about centering to the input 
shaft while measuring.

BTW, things don't need to be perfect, when I was reading about doing this 
think the guideline I found was to be within 0.010''  For an automatic there 
is some "wiggle room" with the TC splines, and the flexplate got that name 
for a reason, it was designed to flex so production line variance in parts 
didn't have to be so tight.

I've pretty much have gone on long enough, my advice though would just be to 
buy one for $50, unless you can spare the time.  Now if you had some kind of 
odd combination where the adapter cost $300 +(ford FE to GM 700r4) or an 
application nobody makes, like some tractor transaxle to... maybe some early 
1900's straight 8, most American v8's are covered into most tractors.  Think 
you get my point.

Now if you already own a mill... and have drawings, or your mill is tall 
enough to fit a transmission case or engine block in it.  You could machine 
an adapter in an afternoon easy.  Key is it needs to have instrumentation on 
it.

btw, If we are able to send pictures to the list now I could send out 
pictures of the adapter installed on the engine, also with a transmission on 
it.
----- Original Message ----- 
From: "Burntkat at sc.rr.com" <burntkat at sc.rr.com>
To: <gmecm at diy-efi.org>
Sent: Friday, February 17, 2006 7:51 AM
Subject: RE: [Gmecm] Bellhousing Design-Iron Duke


How would you go about making an adapter-- in other words-- how would you
measure the holes from center of the shafts with enough accuracy to ensure
proper alignment of torque converter and flexplate?

Great thread, and I'll need the info for adapting a BOP pattern 5.7 diesel
to my 700R4...