Info needed: Chevrolet 235 c.i. conversion for CMP

[Hanno Spoelstra]

This is a photo of a 1954 235 cu.in. engine.

What would it need to convert it to fit in a Chevrolet CMP?

Obviously it needs to be converted to RH drive: bell-housing and pedal linkage.

What else? Only repositioning of the water pump as per Phil’s instructions? Ref. https://www.canadianmilitarypattern....ifications.htm

[Jordan Baker]

Make sure if has a front engine mount and not the side mounts. I do not remember what year the engines started using the side mounts.

You may also have to change the exhaust to match the engines exhaust manifold.

Otherwise I believe that is it.

[Phil Waterman]

Hi Hanno

As Jordan points out the front foot engine mount is needed. The front plate will swap from 216 to 235. Be sure to check on the cam gear lubrication nozzle, I have found them plugged or broken.

Now to the bell housing l had very good luck changing over clutch throw out pivot from left to right. Cut out for through side for the arm and then drill and tap for the pivot ball stud. As long as you have a CMP bell housing for measurement to copy not a big problem. In my experience the CMP bell housing should bolt up to 235 engine directly. You will need to check dowel per the manual. Also check that the transmission hole is truly centered on the crank.

On one of my conversions from 216 to 235 or 261 engines the centering dowel in the housing didn't match the dowel hole in the block. Strangely all of the mounting bolts did line up, I left the dowel out, torque all the bolts and nothing has move in 20 some years of driving.

I'll look for photos of the bell housing conversion.

Cheers Phil

[Grant Bowker]

I think it is covered on Phil's web info but care is needed to fit the throttle linkage across the front of the engine when using the water pump adapter plate. The commercial water pump adapter plate is made to fit 1942 or later water pumps that have 2 holes in their backing plate. The earlier plates (as used on all CMP as far as I know) had only 1 hole in their backing plate. I think I've posted on this but if you have difficulty finding let me know. The 235 is likely to have a distributor that uses a higher profile cap than the 216/CMP and it isn't quite as simple as just swapping the caps - better cap, rotor and distributor body ass a unit. Also, some people have concerns about early/late distributor gear to camshaft material compatibility.

[Hanno Spoelstra]

Thanks gents,

Looks like this one has the front engine mount, correct?
Sorry for asking, I don’t have my references at hand.

[Jordan Baker]

Hanno, it does have the front mount so that is good.

The side mounted oil filter will need to be removed as well.

[Harry Moon]

three of my trucks are 1954 235's. water pump is perfectly situated but the pulleys and balancer should be swapped, not sure by your pictures if the water pump has a longer shaft but I haven't come across one that was different before.you do need to use the exhaust and intake from a 235 not the 216 and as always I recomend swapping the exhaust manifold for a set of Fenton cast iron duel exhaust. you can work out relocating the filter to the head bolts or delete it altogether.

[Grant Bowker]

The question on the front mount is (like so many things) a little more complex than it may seem at first glance. Yes, Hanno's engine has the plate with the lower edge flange for mounting the CMP style rubber mount. I can't see if it is punched with the two square holes for the carriage bolts that hold the rubber mount in place. As long as the flange is there, it would be possible to drill and file holes for the bolts and have a functionally identical mount to the CMP mount.
For the style cylinder head shown, the CMP oil filter mount isn't a direct bolt-on. It is possible to make head bolts with an extended hex and threads pointing up to engage the filter mount - weld two bolts head to head (and since my welding was messy but strong, clean up the surplus).
Concerning timing gear lubrication nozzles, there are several styles and I'm quite sure (should confirm...) that there were two different size holes made in the nozzles to allow different oil flows.
For more information on the water pump relocation (using either a CMP pump or one that looks close to the same) to raise the axis of the water pump and fan to be better centered on the radiator, take a look on the Stovebolt forum - it comes up regularly:
https://duckduckgo.com/?sites=stoveb...er+pump&ia=web is their website search for "water pump"
https://www.stovebolt.com/ubbthreads...elocation.html
https://www.stovebolt.com/ubbthreads...ater-pump.html

[Bob Carriere]

You need to make sure the various pulleys you use are all the same width for the belt to run properly. Sometimes you need to find a wide pulley groove on a 216 Harmonic balancer to match the wide pulley of the pump and generator.

Is this for a cab 11/12......... if so as Grant pointed out the 54 dizzy is too big and the whole dizzy assembly needs to be changed.....Pertronix now makes a magnetic device to eleminate the points and condenser witihareal hot spark. On a cab 13 the larger 235 dizzy should fit...... using the 216 harmonic balancer and a 216 water pump pulley will insure the pump does not turn to fast and induce cavitation.

One more thing the water pump will usually have on the rh side an outlet./intake location that should be fitted with a by-pass pipe.....rubber is easy but the 180 degree ebnd will eventually crack.....better to install a 1/2 inch flexible copper pipe soldered to threaded brass fittings.

My experience has been to buy an adapter plate that once fitted allows to use a rebuilt 216 water pump with the two holes at the back.....it does require to drill into the engine block water jacket and tape but relatively easy if the engine is on a stand.

If you need pictures for my set up let me know....

Cheers

[Bob Carriere]

..... would be nice to retro fit a 216 valve cover and a new thick corkgasket.....

Kits containing the necessary longbolts and acorn nuts a readily available....

From my memory....some 1954 and only 54 trucks valve cover had slits cut on the top for air intake for the PCV or draft tube.... and will allow dust/dirt to enter the engine. They can be brazed shut from the inside but then you will need to install a small 216 oil bath air intake filter on the valve cover as per a CMP 216 valve cover..... or the engine crank case will develop a vacuum.

[Bob Carriere]

I enlarged the photo and the holes are visible....all you need is a rubber mount

[Dave Newcomb]

4 different cyl heads available;
3836848 79.1 cc's 58-62 years
5913 86.2
6850 86.2
3703570 92.5 cc's combustion chamber
From Inliners International Club [Chev engine experts in USA]
Dave in Oregon

[Hanno Spoelstra]

Thanks again for the load of info. It’s clear many conversions of this sort have been done. Relocating filters and swapping pump and pulleys etc. sound all very doable. I have a donor 216 with RHD bell housing which could be swapped over.

As this engine is already fully rebuilt it would be worth doing these conversion jobs. I’ll try to get some more photos and have a look at the engine in person.

[Bob Carriere]

That explains why the XXXX848 heads have higher compression and the best to have.......

...and shaving the heads on the Chev engines is almost impossible and better to true up and shave the block surface.....

Thanks Dave


Bob C

[Hanno Spoelstra]

Went to have a look at the engine and I liked what I saw so I bought it.

It was advertised as a 1954 235 c.i. truck engine with solid lifters. The block casting number deciphers it as a 1958-1962 235 block. It has the 1956-1962 3836848 high compression head.

Now to pick it up and convert it to CMP standard.

[Hanno Spoelstra]

I picked up the fully rebuilt engine last week, now looking at it and online sources to get to know the differences between the 216 and the 235 cu.in. engines, mostly to determine what needs to be converted to fit it in my C15 4x2. The previous owner rebuilt this 235 c.i. with a SM420 4-speed transmission/ gearbox with crawler 1st gear and synchro on 2nd, 3rd and 4th gear. He was planning to fit this in his 1932 Packard 900 Coupe Roadster. He had sent away the Packard engine to be rebuilt with cast white metal bearings etc. As this was taking a very long time, he decided to rebuild a Chevrolet engine as he has the skills and spares to work on these. Of course, as things go, by the time he had the Chevrolet engine done, the rebuilt 320 c.i. 8-cylinder Packard engine showed up in his workshop after four years at the rebuilder.

I reckon the overall length of the SM420 gearbox is pretty much the same as the wartime non-synchro one in the C15. If it is longer, that's no problem as I can shorten the drive shaft (I have a spare somewhere).

Still need to figure out if the rear engine mounts are compatible to the setup in the C15. Front engine mount is the center one. Not sure if I need/ want to convert the water pump. RHD gas pedal linkage to be swapped over from spare.

Plus I need to figure out if I fit the RHD bell housing off a CMP - would it swap over using this gearbox? Else I have to convert the current one to a right hand clutch fork as per Phil's instructions.

[Harry Moon]

that bellhousing doesn't have the proper mounts so converting it to right hand won't fix that.

[Bruce Parker (RIP)]

My understanding is that the block length and height are the same between a 216 and 235. The front mount is the same and both use the same bell housing. And since the bell housing also has the rear engine mounts it solves that problem. I agree with Harry that you need the correct RH drive bell housing which means you can also use an original transmission if you chose to. The only thing that may cause problems is if the water pump is too far forward and interferes with the rad.

It's a shame we live on the opposite sides of the ocean as I have a spare bell housing and transmission.

[Bob Carriere]

Bruce is right on target....

Far easier to find a CMP bell housing....... 0.05 cents each in Ontario and the SM420 will bolt on directly....... it would silly to pass the convenience of the synchros on the SM420.....and it's a straight bolt on.

You will in all probability need to find and adapter plate to instal a 216 water pump which will not only shorten the lenght of the engine but will also better align the fan blade to the center of the radiator......and to the changeover ofo the water pump BEFORE you install the engine in the CMP as you will require to drill and tap into the engine block......sounds scary but not so complicated.

We built a small drill guide using a flat plate and a piece of tubing welded to the plate.....bolt the plate on the block using the other existing water pump holes and drill and tap the hole by drilling from inside the tube as a guide.... it will insure near 90 degrees.... I used a heavily greased rag stuffed inside the engine block to catch the metal shavings from behind..........mark your drill bit so you ONLY drill deep enough to reach through the water jacket BUT not into the cylinder casting. Use pipe thread sealer on the bolt threads .....
When you install the pump with the backing plate you may have to use some washers as shims if you find that the new pump does not fit perfectly flush even with the block leaving a tinny gap that may cause some distortion when the pump bolts are torque properly........ not all blocks are exactly the same but on some we had to use washers made thinner with a grinding wheel......

I have a picture somewhere and will try to dig it up......

If you buy an adapter plate make sure you do a good tracing of its shape in case a friend in EU had a need for one......very easy to copy in 3/16 flat plate......

Cheers

[Bob Carriere]

....and while working on the water pump do not forget to install a bypass tube where the heater hose would connect to the pump.....best done with brass fittings and a flexible copper pipe prebent on the workbench ready to fit in place.....

Now for the pictures....... look at the new higher location of the new pump which is better centered on the rad....

Happy plumbing!!!

[Bob Carriere]

These are off the web but shows well the adapter plate in question and once instaled using the (old I hope) pump housing as a guide.

I also discovered that the true "CMP" elbow fitting that bolts onto the head is cast with a small flat area......which gives a tinny bit of additional clearance for the crazy throttle linkage of the cab 11/12 I eventually had to fabricate my linkage as a custom fit to get good free motion...... You do what you gotta do!!!

Cheers

PS 6 blade fan came from a C15a water truck

[Bob Carriere]

one is a web picture the other composite came from Phil. W. site....

[Bob Carriere]

Original 216 water pump is equipped with inlet / outlet to connect a water heater inside the passenger cab...... it is highly recommended to install a bypass to facilitate coolant flow....... read it somewhere did not want to risk over heating the engine..... so used a rubber hose temporarily while doing short running tests than replaced with solid copper pipe.

[Bob Carriere]

216 vs 235...... the adapter plate lifts the center height of the fan blade about 4 inches.

[Paul Singleton]

Here’s a link to the plate.

https://davisspeedequipment.com/prod...adapter-plate/

[Hanno Spoelstra]

Good info, thanks! It is a lot to take in, will digest and come back on this topic later.

[maple_leaf_eh]

Another fascinating series of lessons learned the hard way. Thanks guys!

[Hanno Spoelstra]

This will yield some useful parts like gas pedal linkage, bell housing and then some

[Hanno Spoelstra]

These are photos of a GM 270 ci engine fitted in a C60S Wrecker. As one can see the radiator has been moved forward. This should work for a 235 ci engine as well.

[Harry Moon]

The 270 is definitely longer and on the GMC CMP's the radiator dismounted farther forward. That is not necessary on the 235 if you adapt the early water pump to it.