MTFCA Forum

Hello all. Trying to gather some parts for a engine build, I’ve come to understand SCAT cranks is not making the Model T crankshaft that I would like to buy, so I am looking at alternatives to counterbalanced cranks.

•This leaves me with the Late Model ‘B’ crank that is counterbalanced, can anyone tell me the modifications they have done to their engines? I have read some people welding cranks, and one fellow in particular cutting a taper in the end of his cranks and having a press fit flange to avoid breakage. All this done for the shortening of 5/8” to keep the geometry of everything else. Would like to hear some input on that.

•Another thing I have been wondering is what kind of rods and pistons are used in conjunction with the model a and model b crankshaft, since the stroke is a 1/4” longer. Can you use a stock low head? Do you need a spacer?

Thank you all in advance.

A option to consider is to shift the block ahead 5/8”!

Les Schubert wrote: ↑

Tue Mar 22, 2022 9:32 pm

A option to consider is to shift the block ahead 5/8”!

Les, I have just been reading some of the things you have said in past threads, your information proves very valuable to me, I would like to avoid shifting the block forward 5/8” I would be interested in hearing more about your tapered flange Crankshafts and how they’ve been working out. Thank you

Over the last 45 years I have;
1. Cut and welded (still going strong). Bolted on counter weights.
2. Shifted the block.
3. Press taper fit shortening.
I hear that the special shot pistons are no longer available.
In the past guys welded A and T rods together to make a version that works. I have never done this.
There were cast aluminum rods made years ago and Scat rod shells can be used with them.
Many options

The strongest proven method is a very fine thread cut of 15/16" on the crankshaft to the desired length. Find a donor crap crankshaft for the flange, thread to the tightest thread possible. Cut a slight bevel on the flange and crank to accept a weld, after it is set where you want it, drill 2 each 1/4" dowel holes exactly in the threads @ 180 degrees from each other in a parallel line with the crankshaft. Install 2 each 1/4" drill rods just short of the end of the flange. Now heat extremely well and equally in an appropriate furnace and weld with the correct rod. Go into the correct cool down cycle by the metallurgy bible. Know your Rockwell hardness scale. Machine to specs. A Model A crankshaft will do the same thing counter weighted and crossed drilled. Been there done that. Use A rods with special wrist pin bushings. Another option I like is a 1928 Chevy crankshaft!

Hank

Les Schubert wrote: ↑

Tue Mar 22, 2022 9:51 pm

Over the last 45 years I have;
1. Cut and welded (still going strong). Bolted on counter weights.
2. Shifted the block.
3. Press taper fit shortening.
I hear that the special shot pistons are no longer available.
In the past guys welded A and T rods together to make a version that works. I have never done this.
There were cast aluminum rods made years ago and Scat rod shells can be used with them.
Many options

Les, do you still do the tapering and pressing process, or even the threading and welding? I’d like to have one of those processes done. What would I do about the stoke issue?

Henry K. Lee wrote: ↑

Tue Mar 22, 2022 9:51 pm

The strongest proven method is a very fine thread cut of 15/16" on the crankshaft to the desired length. Find a donor crap crankshaft for the flange, thread to the tightest thread possible. Cut a slight bevel on the flange and crank to accept a weld, after it is set where you want it, drill 2 each 1/4" dowel holes exactly in the threads @ 180 degrees from each other in a parallel line with the crankshaft. Install 2 each 1/4" drill rods just short of the end of the flange. Now heat extremely well and equally in an appropriate furnace and weld with the correct rod. Go into the correct cool down cycle by the metallurgy bible. Know your Rockwell hardness scale. Machine to specs. A Model A crankshaft will do the same thing counter weighted and crossed drilled. Been there done that. Use A rods with special wrist pin bushings. Another option I like is a 1928 Chevy crankshaft!

Hank

Henry, glad to have you chime in on this, I see you are selling Model A cranks, are they they shortened in the threaded and welded manor you spoke of? As for the rods I’m not excited about welding them.

Stephen
Unfortunately I have stopped taking on projects for other people. If you need someone to do it, then Henry is probably the answer!

Check the Classifieds, Hank has several for sale.

I’ve done the hybrid T/A rod thing, as well as shortened the A rods to use A type pistons. Shortening/grafting the rods by cutting, welding, and fish plating has always seemed kinda sketchy to me... I prefer to mill the webs out of the I beam, then box with 14/16 gage steel sheet. Have done a few sets, and they are a LOT of work! When I saw that SCAT was making new H beam rods, I swore I would never box another rod again! I really hope they continue to produce cranks and rods...

PS, the best thing about a threaded crank, is that when they break you can just screw em back on, and re-weld (don’t ask me how I know). Have welded a couple by double V grooving to achieve full penetration, and neither have broken (both were poorly welded cranks that had broken before)

Kevin Pharis wrote: ↑

Tue Mar 22, 2022 11:08 pm

I’ve done the hybrid T/A rod thing, as well as shortened the A rods to use A type pistons. Shortening/grafting the rods by cutting, welding, and fish plating has always seemed kinda sketchy to me... I prefer to mill the webs out of the I beam, then box with 14/16 gage steel sheet. Have done a few sets, and they are a LOT of work! When I saw that SCAT was making new H beam rods, I swore I would never box another rod again! I really hope they continue to produce cranks and rods...

PS, the best thing about a threaded crank, is that when they break you can just screw em back on, and re-weld (don’t ask me how I know). Have welded a couple by double V grooving to achieve full penetration, and neither have broken (both were poorly welded cranks that had broken before)

Kevin, Thank you for the insight that is very interesting, are the rods that Scat sells the stroker rods? From what I see in Lang’s catalog they say for use with Scat crankshaft I am wondering if they are the appropriate length for use in a model A or B Crank? And can they be Babbited? Used with the aluminum stock replacement piston on the market? Thanks

Stephen I can honestly say I do not know the true method of shortening on these crankshafts as I purchased them from a reliable source already done, that's why I am asking $800.00 each. I know there is a $1,000.00 worth of custom machine work (Magfluxing, cross drilling, plugs, weight and balancing, and grinding surfaces).


Hank

Stephen1915: If you are going to do one of these conversions, you should consider drilling the crank and setting it up for full-pressure oiling with an oil filter; if you are going to use inserts, it is necessary.

Another reason for an improved oiling system is something many don't take into consideration when doing one of these conversions - the main and rod journals are larger in diameter than a T shaft, and because of that, the shaft speed on the OD of the journal increases and it travels in the bearing at a faster speed.

When I was doing these conversions the shaft was magnafluxed before and the rear journal and shaft X-rayed after the welding. It was done by expert certified welders at Mercury Welding using the corrrect rod and pre-heated with a controlled post welding cool down. None of them ever broke. At the time they were in the nuclear power plant welding business and had a shop near a nuclear power plant here in VT.

David, do you know of anyone running a B crank with the standard splash system?

Stephen my Dad’s 1914 is a splash on the rods with pressurized mains (Model A crank shortened). Goes like a bat out of hell. Been running strong for 25 plus years.

Hank

Henry, that is encouraging. Do you think it would be feasible to run an A or B crank without pressurized oiling for the mains? Does your father’s engine have’A’ rods with special pistons or something else. Thanks!

I run pressure to my mains and splash for the rods on a shortened A crank. Many many miles and smiles. I have two running buddies with shortened A cranks that are splash to mains as well as rods with no problems. The three of us run the Egge pistons on stock A rods. Sadly those pistons are no longer available but custom pistons can be had for enough $$.

Stephen another cool option is keeping the crankshaft length original, cut and extend the oil pan (4 dipper) by the necessary amount, and add a nice piece of 1” x 1/8” bar steel for the hogshead extension, redrill holes for the emergency brake and paw quadrant at the frame mounts. If you are making a Speedster, Z the back of the frame for lowering and no mods to the torque tube. Brake rods normally are long enough. More than one way to skin a cat! I used Model A rods (drill larger hole at bottom and make your own scooping dippers) with Egge pistons but are no longer available I think. A Chevy 265 V8 standard bore should match up. Dimple pan for throws and and you need a 5/8” inspection plate extension, cut out the back two rear bolts to accept the counter weight on the crankshaft. We use our Datsun B210 oil pump injecting on the mains, timing gears and at the top of the transmission bands! This method will not allow you to use your internal mag unless you extend it aswell.

Hank

Stephen1915 wrote: ↑

Wed Mar 23, 2022 11:21 am

David, do you know of anyone running a B crank with the standard splash system?

No, but there are a number of people that do it. On the other side of the coin, the oiling system can be completely hidden inside of the engine.

David
I am wondering how you handle the oil filter if you hide everything inside?

Hank
On the “block shift “ I shorten the front of the pan by relocating the front support from the outside to the inside of the nose. Yes the fan gets a bit closer to the radiator, but the hogshead stays in the stock location. I can post pictures.

Les.., I am sloooow and back…, woods and wards!

There was an 80’s Buick V6 that used an oil pickup filter, not sure if it’s as fine as a canister filter tho...

Hank
Pan pictures

Press/shrink fit shortened A crank

Another approach that works!!!!!!

Skinning thou cat!!!!!!

Kevin
I certainly like a inlet screen on a oil pump, I certainly wouldn’t want it fine enough to be considered a oil filter. It would be a great way to destroy the pump and the whole system!

Agreed! That’s why the one I bought years ago is still sitting on the shelf... and a screen is in the motor!