I bought a 55 that seems to have come off the Air Force base in Victorville CA. Painted crudely Desert Camo Tan.

It has a Dually with 6 lug wheels typical of an F350 and higher even though it was sold to me with a Data Plate as an F250. It does not have a bed, and appears to have been a flatbed.

It's had enough futzing that there's no way to be sure it's the original Data Plate. It has a 55 grill, and the front doghouse appears original to the truck. It however has a 56 hood with rivits both sides of the rear crown, so no way to identify the series my truck was thru the hood emblems.

I thought it had a 239 Y, but I'm begining to wonder if it has a 256 cause it appears to have an original intact 4 Bbl. manifold, which was original to the 256 and larger 55 engines. I suppose someone may have replaced the manifold but it looks like it's never been disturbed. If someone hadn't scavenged the Carb off before I got it, I would be able to clarify whether the manifold was original.

I have a 54 / 55 Shop Manual and the original Dealer Truck Handbook that identifies optional equipment, and a 239 wasn't Spec'd with a 4 bbl. A 256 was Avail. Spec'd in an F600, but my front fender wheelwell openings are not the Big Truck large wheelwell openings.

Now this is all just speculation and hypothesis from the sketchy information I have Avail. It was untitled. I do however know that it is not uncommon for Gov. Contracts to specify changes to equipment for fleet vehicles outside original equipment Spec's.

1) Can anyone help me with casting numbers and locations that will help me clarify this puzzle, Is the block a 239 or 256, is the manifold original to the block?

2) Apparently 55 279's and higher were exactly the same and fully interchangable. The Shop Manual does not indicate the difference between the 239 EBV / EBW, and the 256 EBZ. Were the latter also the same blocks, water passages to heads?

3) The whole question is important to me because I have had a Pr. of heads rebuilt and am trying to clarify which gasket set I need. Are 239 and 256 Y-Head Gaskets interchangable?

I've located a Pr. of original steel 256 Head Gaskets if they will interchange. Thx. for any help this post rustles up. David
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Hi David. Sorry for the delay in responding, but it took me a while to dig my parts book out from the mess. After digging out my parts book, I realized that you'll find everything you need (I think) at John Mummert's Y-Block Site Head Identification and Block Identification . Hope you can use the info.

 

John Mummert's web site mostly deals with car engines, but I think the answer to your question is, yes, the blocks are different - different bore. BTW, you can stroke your 256 to a 272. You can probably also bore it and end up with a 292.

Back by the distributor or underneath the generator is where you'll find casting marks for the DIF blocks.

The casting number on the manifold might be ECZ 9425-A.

 

A lot but not all the ID data is on Mummerts.

However there never was a 4bbl 256 put in a truck from the factory. That and only the F600 had the 256 option and they used EBY blocks.

The stock 239 for a 54-5 F100 thru 350 is the EBV and came only with a 2bbl.

Since the truck seems to be a Johnny Cash special (One Piece at a Time) the engine could be anything. At least get the VIN off of either the glovebox door or off the frame and find out what that is at least.

 

As usual, Carl has the goods on this kind of information. Thanks again Carl.

So if the manifold looks like it hasn't been removed from the engine, you might have a car V8 in there. The engine's casting number should be above the oil filter if it's a Cleveland block. First check it the manifold number. If it's ECZ 9425-B, chances are you have a 312 or a '57 292. If it's -A, chances are you have a 292.