The Stovebolt Site Forums The Shop Area Engine Shop diference between 55 and 56 chevy 235

What is the diferance between a 55 and 56 chevy 235?? I have 2 55 blocks, 1 first series and 1 second series. Second series serial number by dist. is F255x. the first series number is F55mb.Sealed power lists a CS 293 mech. cam as a 261 cam, but it says it will fit 56 to 62 235. why won't it fit a 55 block??

1955 and 1956 235 block difference Taken from the 1956 Truck Supplement to the 1955 Manual

The dowel in the upper half of the precision main bearing has been discontinued for 1956. A tang is provided at the butting edges of the new upper bearing. The tang ,which registers with a slot in the cylinder block and locates the upper bearing, also butts against the bearing cap to prevent rotation of the bearing. The adjustment shims formerly used between the bearing cap and cylinder block have also been discontinued. With the new tanged bearing and elimination of shims, dropping of the crankshaft in “Main Bearing Replacement” is unnecessary and “Main Bearing Adjustment” is eliminated for the 1956 engines. Whenever main bearing are checked and excessive clearances found, new bearings should be installed.

All 235 truck engines had mechanical solid lifters and I think aluminum cam gears. The cars with power glides had hydraulic lifters with a fiber cam gear.

Maybe it has to do with the distributor gear there were 2 styles I forgot which year was what but I think the camshaft was either steel or cast iron.

The 1955-2nd (255) will have block/water-pump fitting like the 1956 and later.

The 1955-1st will have a block/water-pump fitting like the 1954.

They are both truck blocks, so they have both have a metal cam gear and mechanical lifters.

All 1955 (and later) cams and distributor-gears were the same material (most, if not all 1954's were the same material as in later years). However, the 1956 camshaft style changed to a higher lift design (the 261 camshaft?) and the higher-compression "848" head was introduced (resulting in greater horsepower).

As described by Tiny_Jaime, the change to non-adjustable main bearings began in 1956.

In case you are interested: the F255MB originally came in a 1955 3800 (1 ton) Task Force truck equipped with a Hydra-Matic transmission; and, the F55X originally came in a 1955 3100 (1/2 ton) Advance-Design truck with a standard transmission.

Ok thanks for the info, but will the 261 cam listed for 56 to 62 fit in a 55 1st or 2nd series block?? Is it because the lifters and push rods changed?? The cs293 is listed as a mechanical cam, this means it is a solid lift cam right? If the difference is lifters and pushrods, will 56 parts fit the 55 blocks?? THANKS for the help!!!

1955 235 & 261 camshaft specifications on page 154 of the PDF.

1957 261 camshaft specifications on page 177 of the PDF.

From these specs, the only cam differences are in the intake & exhaust ramps.

Maybe the Heritage center links can help you with your other parts questions? I have my learning hat on right now, and am just sending you what I was reading up on. What you're asking is a question for the builder pro's... I'm on the sidelines of a similar swap, so I'm just tracking the info. If the individual parts are identical, they won't know what year engine they're going in.

Brad

I have a 261 cam in a 1954 235 block.

Regarding: "will 56 parts fit the 55 blocks"

- which parts?
- which 55 block (1st or 2nd)?

TCLEDERMAN what brand cam and what lifters did you use (part number)? The 1st series is in the machine shop for magnaflux and boil, if no cracks it will get cam bearings and freeze plugs. The 2nd series block is going to be a spare motor. I am going to build the 1st series motor and would like to put the 261 cam in it if it will fit. My question was, Sealed power lists a CS293 as a 261 mechanical cam that will fit (1956 to 1962) will this cam fit in a 1955 1st series or 2nd series block??? Can I use the old style lifters on this cam. There are many of them out there, but the AT874 new style lifters that are for this cam (1956 to 1962) are getting hard to find. Again will this cam fit the 55 blocks and use old style lifters??

Tim, I was under the impression that the 54 235 had a small journal camshaft. That being said, how did you shoe horn that 261 cam (large journal) in there?
Carl

1954 was a change over year, some have small journal and some have large.

The 54 235 I'm rebuilding has the large journal. The only way to know for sure which one you have is to measure the journals.

Actually it is easy to tell which cam you have by the width of the distributor drive gear on the cam. Pictures of both gears.
This will require pulling the distributor to tell.
BTW the steel cam is the small journal.

Good info.
Good info on your site also, I've been perusing it quite a bit.
Dave

Well then, I'm glad that I didn't jump all over Tim. Learn something new all the time in here!
Carl

Carl,

I never mind a question or a correction. Jump all over me or pound on me any time.

I hope like heck that I put the correct 261 cam in my 1954 235. We might start the engine before hibernation.

Dave, what will happen if I have the wrong 261 cam? It is supposedly a Corvette 235-engine replacement cam. I have another one of these cams - I'll post the part number if I can find it.

Dave & Others,

Here is a 261 cam, supposedly for a 1953-55 Corvette 235 and my 1954 distributor is next to it.

There is ring below the gear teeth in this distributor. I have 4 distributors: 2 with that the ring below the teeth, and two with no ring.

Flats are cut in the cam, on either side of the distributor gear.

Are the cam and distributor a safe match with respect to the distributor gear?

I'll take a better photo (better lighting), if that will help.

Thanks,

It looks like the width of the drive gear on the cam is somewhere between the width of a cast and steel cam. That is most likely because it is an aftermarket cam.
The parting line on the cam makes it look like it is a cast cam.
If the distributor has a groove just below the gear than I would say you have a good fit