MTFCA Forum

Has anyone installed a model A crankshaft with the added counter weights into a T block? Looks like modifying the block for the weights may be required. Comments? Pictures?

I will start by saying, to install the A crank the flange needs to be relocated or the block moved forward on the pan. While the flywheel will bolt up, the A rear main is longer.

Depends on the counterweights you would like to use...?

If you use weld on counterweights that do not increase the “major diameter” of the crank, it wouldn’t make any additional clearancing of the block (above and beyond the “normal” A crank mods)

If you are talking about the shrink and pin on “truck” counterweights, those increase the “major diameter” of the crank and may require additional efforts

Block mods are mostly just boring out the main journals, trimming the main journal lengths, and sometimes grinding down the front cam bearing boss to clear the crank. The pan gets a bit of work too. I’m putting one together now, will get some pics tonite

The money you get involved with using an old A crank comes out to the same price as a new Skat.

Amen Joe Bell! Just go with a Skat crankshaft and never worry about it.

Hank on Tin-A-See

I did it back in the ‘70’s. Bolted them on. Also drilled the crank for pressure oil. At the time I shortened the crank by welding. It lasted about 15 years and then the welding failed (no serious damage, just inconvenient). I then developed a taper fit/shrink on process that has worked well. I have also done one by shifting the block forward. On that engine I started with a badly rusted “C” crank with integral counterweights. I ground it to standard A size and drilled it as well.
I feel the cost comes down to how much you can do yourself and the “entertainment “ you get from doing it!! Obviously the first one I did there were no good alternatives. I sure don’t regret doing them.
The first engine with a Sherman head does over 100 mph

Further to the original question, no block or pan modifications were needed for the counterweights. The usual pan denting for the rod bolts with a stroker crank (which I believe even the Scat stoker requires)

I had a Scat stroked crank installed and I would never do that again. A stock scat crank would be the best but a stroked crank, similar to an A crank, required relieving the engine block and getting the oil return line out of the way not to mention that oil pan spacer. I don’t notice any performance benefit for all that work. I wish I would have gone with the stock stroke scat crank.

In regards to the value of installing a “stroker “ crank;
By itself the extra displacement should amount to 1-3/8 HP. Hardly worth the effort.
However consider that the rod bearings increase from 1-1/4” dia to 1-1/2” dia which is 20% bigger in diameter , which is not insignificant when it comes to bearing load capability
Consider that the model A put out double the HP of the T and you don’t seem to hear of many crank failures with the A.
I’m ignoring the possible HP increases that can be more safely accomplished when you have a stouter bottom end.
Just some thoughts

Thanks for the responses, Les, have you installed A cranks without counter weights as well as ones with? Was the benefit of the weights worth it? Just curious. Kevin, if you have any pictures of the crank in the block to show the clearances from weights to camshaft boss please share. Thanks Brian

I’ve done one without counterweights. Just a modest performance engine targeting long distance touring, not a “hot rod”. Quite satisfied.
In regards to counterweights, I made and bolted on ones that “over hung” the throws. So no issues with camshaft clearance or pan clearance.
As stated, I’ve done it by moving the block ahead and by shortening the crank. Both are satisfactory

Les, was the installation of the counter weights a noticeable difference to the one without? Less vibration? Brian

I had heard Egge no longer makes the pistons since Skat came out with his crank? As far as I knew they where the only ones you could get them from? The counter weights do make a difference on the A crank if you strip the flywheel.

Absolutely counterweights make a difference.
I installed bolt on Dunn weights on my 27 T roadster back in 79. It was a considerable amount of careful fitting and then had the crank dynamically balanced as well as the flywheel with magnets. Many thousands of miles later it still runs great and hand crank starts on mag!!
But understand that I do the majority of my machine work myself including my own line boring. I figured out the “100mm spacing “ rule for myself back in the ‘80’s.
So if you can do the work yourself it is definitely worth the “fun”!!

Here is a pic of the front cam bearing in the motor I’m working on now. Boss was clearanced with a long endmill. Doesn’t take much, maybe an 1/8” or so