The Stovebolt Site Forums The Shop Area Engine Shop 235 “Special” casting -- what's that about??

Looking at a 235 engine for sale locally. Has the word “SPECIAL” cast to the right of the block casting number.

What’s that about? Did they do that for Powerglide blocks or something?

I have only seen that one time before and couldn’t find any explanation.

The interwebs seems strangely silent on the topic.

Could be for industrial or ag purposes???

Is the back of the block cast and drilled for a standard Chevrolet bellhousing?

Mike B

Nathan - It would be cool if you could get some pictures and post them. Would be interested to see the casting number, dates and serial number plus that "SPECIAL" detail. The info might help decode or find more info on this oddity.

Good idea. It’s a 3837004 casting. Which (from Tim’s site) makes it like a 55-57 235 block.

It’s a FB ad and the engine IS attached to an automatic transmission of some sort, I assume a PG. But that alone wouldn’t make it very “special.”

Edit: Here’s the FB ad link if someone wants to take a crack at decoding the serial number.

https://www.facebook.com/share/16o16huYnr

Google AI says the word SPECIAL cast on a 235 block means its a higher performance version of the engine. It doesn't give any evidence for that assertion, however. It just lists the possible performance enhancing traits the engine might have - Blue Flame, lifters, aluminum pistons, etc

Nathan - I'm gonna through out a SWAG and say that "SPECIAL" casting marker has to do with the engine being part of a Hydramatic drivetrain package (RPO 308 or 314) according to the 1957 Chevrolet Truck Data PDF. I don't have anything to back up this statement, but maybe others have some recollection or knowledge.

The automatic pictured is in fact a Hydramatic and the serial number plate on it should match the stamped number on the block (wasn't pictured so can't confirm) as these were selected/fitted/matched at the factory and installed into whatever truck it was ordered for. The Truck Data file indicates the engine serial# shown decodes as:

F = Flint Plant
I0 = October (10th month)
02 = 2nd day of October
HD = 1957 3100-3200-3600-3800-4000 with RPO 308 (4000) and 314 (3000 Series) trucks

The block casting date I 26 6 decodes as:

I = September
26 = 26th day of September
6 = 1956 (this date coincides with the 1957 Model year)

If someone is looking for a numbers matching (potentially) 235 and Hydramatic, this just might be the ticket.

Good call, Dan. I didn’t know they even offered a Hydramatic in 57.

There was a reason for the block/transmission serial number matching. The Hydramatic drive fluid coupling torus (which was not a torque converter, BTW) was extremely sensitive to runout between the crankshaft centerline and the trans input shaft. Engines and transmissions were matched up exactly inline by using offset dowel pins where the bellhousing adapter ring attached to the block. There's even a pretty detailed runout checking procedure in the shop manuals, using a fixture that bolted to the crankshaft hub and a dial indicator.
Jerry

I suspect finding a Hydramatic rebuilder would be a fair challenge in most areas? Parts scarce too?

Parts aren't too hard to find. Rebuilders are.

Automatic transmission parts for all makes and models including Hydramatic and Jetaway

Fatsco Transmission Parts
337 ChangeBridge Road
PO Box 635
Pine Brook, NJ 07058
(973)227-2487 or (800) 524-0485
http://www.fatsco.com/index.htm

Transmission parts for Hydramatic, etc

Northwest Transmission Parts
13500 US Route 62
Winchester, Ohio 45697
937-442-2811
http://99.152.162.116/nwtparts/


Automatic transmission parts 40s –60s, rebuild kits

David Edwards Automatic Transmission Parts
56 Dale Street, Dept. A
Needham Heights, MA 02494-1218
781-449-2065
http://www.autotran.us/

Steve P has a shop in Mendon Mass that overhauls HydraMatics. I'll try to dig up his contact info.

Steve's response to "are you still overhauling dual range HydraMatics?" is: Yes I am. Have him call 508-478-8900 during the day and leave a message if I don;t answer. I will call back as soon as I can

Good to know about that resource. I've got a 61 Cadillac 390 engine and a Controlled Coupling Hydramatic from a "commercial chassis" (hearse) that's earmarked for an Excalibur roadster project. I'm planning to use a Toyota Supra independent rear suspension and final drive behind that setup with adjustable rate coilover shocks.
Jerry