Chevrolet CMP Engine variants

[BSM]

The few engines we have been working on in recent times were all single hole, narrow cross section (front to rear top) models per attachment 1. The 3 engine we have acquired in more recent times are all 2 hole water pump models with a wider front to rear cross section per image 2. This then causes a problem with the throttle linkage from the former model as there is insufficient room to mount same. Can anybody shed some light on the variations please. Have we got hold of a few car engines?? One of the latter came in the C60S tipper chassis. Regards.... Rod

[Phil Waterman]

Hi Rod

Which Pattern are you working on? I've worked around the later design 2 port water pump on both and can take some photos of how it was done. Really not difficult, just some fabrication.

I've got the water pump and throttle link age apart right now on my Pat 12 so can take detail photos.

Cheers Phil

[BSM]

Phil thanks much for the quick response and yes please I would appreciate the images and any advice. Not being expert in the field of Chev. 6's this one caught us out temporarily. We have taken the test run engine (2 hole pump) from the tipper after a few repairs and it is now sitting in the No 6, Arty Tractor. It was not until we got to that stage that we realised that we had a linkage problem with the 2 hole water pump variant. From what you are saying am I correct in assuming that both 1 and 2 hole (water pump) 216 engines were used in Chev CMPs. Thanks again..... Regards.... Rod
PS: the third image is the 2 hole block in one of the other spare motors.

[Phil Waterman]

Hi Rod

First my understanding is that the 2 port version of the 216 engine is actually post war. But as the engines are otherwise identical you will find them as replacement engines in CMPs.

My solution to the throttle link is simple it that I fabricated a new cross shaft bracket that moves the shaft forward about 1 1/2".

This picture is of the stock bracket



This is of the fabricated bracket




You also make new lever arms but it is all done from simple materials. You also have to check the arm angle on the shaft to be sure to get full throttle swing. Also check your side engine bell crank that connects the link age up to the carb. Be sure that it is free and allows the peddle linkage to over swing with out trying to push the carb past full throttle. (Carb will break if this happens.)

Little difficult to post all the measurements on MLU if it would help I can post all the photos on my web site I took 40 some photos of the two throttle linkages.

There is also a slightly different approach if you are installing a 261 or 235 because the thermostat housing is different shaped and I'll post pictures of that version as well.

Now to the coincidences of you asking this question while happen to have the bracket out of the truck. I'm in the process of swapping out bent cab frame on my Pattern 12 for a straight one (thanks to Santa Bob for the straight cab frame) also trying to solve an engine over heating problem so the whole nose is off the truck. Also plan to swap out the 216 for a freshly rebuild 235.

But the coincidence is even bigger because earlier this week when I start the project I came in from the shop to find a private message from Alex van de Wetering asking a question about how to tell the difference from Pat 11 and Pat 12 Cab Frame.

The wonderful world of CMPs and MLU

Hope the information helps.

Cheers

[cletrac (RIP)]

Phil, I don't think there's any difference between the 11 and 12 cab frame but there is a difference between the 4x2 and 4x4 versions.

[Phil Waterman]

Hi Rod

Probably no difference between Pat 11 & 12, but there are differences between Pat 12 and 13.

Here are a couple I've noted:

• Length of cross shaft
• Drivers side lever arm is different length.

But these differences are pretty self evident when fabricating. Trying to this with the nose sheet metal in place is very difficult but with the radiator remove and nose removed on Pattern 13 removed or the center sheet metal panels on the Pat 12 off it isn't bad.


Cheers Phil

[BSM]

G'day once again Phil and many thanks for the wordy response including the pics. As you say....a Chev is a Chev is a Chev etc. All very interesting and now one has to weigh up just how much of a purist one needs to be on such a project. As there is a need to get some benefit back from the time and dollars put in, the post War engine seems to fit the short term bill! I was hoping to have the tractor towing the Bofors in a major Anzac Day parade last April but the ongoing mechanical problems with the motor prevented that from happening. Also there is only so much time you can put into volunteer pursuits etc. apart from one's personal interest in the subject.
Yes I would also appreciate a couple of pics from your site if you get the time to put them up or alternatively you could PM me a few higher res images.
Strangely enough I found the makeshift arrangement which is a modified original linkage and I will include a pic with a temporary install. Not bad for a quick fix but certainly not as mechanically sound as the two variants that you have produced but a simple stop gap until a more professional result can be fabricated. Something else I just picked up on and that is the absence of the 1/4inch post for the 2 linkage springs under the manifold. This is being made at the moment using the one attached to the discarded engine as a pattern. Also including an early restoration pic of the Tractor when it was powered by the post war car engine at a display for our local branch of the Dept. of Veteran Affairs etc. which will give you a better idea of the project. It has been taken back to chassis and rebuilt. Nearing completion at this time. Thanks and regards.... Rod

[Phil Waterman]

Hi All

To try and help Rod and other people around the problem of the original front linkage not fitting the later style 216 (two hole) water pump either on a later 216 replacement engine or on 235-261 engine swap. I have loaded a whole bunch of pictures and some notes to my web page along with some notes that I hope to expand on. http://canadianmilitarypattern.com/T...age%20Page.htm

I took the route of fabricating completely new front cross over front crossover linkage and bracket instead of modifying the original. This preserves the original part and probably took about the same amount of time. Both of these linkage have been on the trucks and working for a number of years. Please note that the page is broken into Patter 12 and Pattern 13 versions.

Sorry for not posting it all on MLU but until I get it edited down it just too much stuff and too large of photos to fit on MLU.

Hope you find the pictures of some use. I'm going to go back and number the photos so once that is done please ask questions and I will try to provide more detailed information.

Cheers Phil

[Jordan Baker]

Tonight I pressed off the early one hole water pump flange and then put it on my two hole water pump shaft. This way I can fit the original larger wartime pulley on the two hole water pump fitting the engine I'm going to be using. However I find that doing this has made no room at all for fitting the throttle linkage. I've read that if I use the smaller pulley I will overspeed the water pump causing cavitation and or possible fan failure.

Any suggestions?

Or can I just put the smaller pulley that came with the two hole pump back on and use the 6 blade fan? But if I do that do I need to also change out the pulley on the generator?

[Bob Carriere]

It is important to note that the part that bolts in to the head, and accepts the Thermostat is special on CMP....... their is a very visible flat surface in the elbow directly above the fan pulley...... after war civvy parts DO NOT have the special indentation and you loose over 1/4 inch of much needed clearance.

I adapted a 1959 Chev 261 using the proverbial "adapter plate" and did have to modify the linkage that fits below the next and above the pulley. I will scrounge my pictures to find some illustration..... and similar to Phil I am referring to a cab 11...... and I have traded many cab parts between cab 11 and 12 and they all fit.

Stay tuned photos will follow.

Cheers

[Grant Bowker]

Is there enough space between the pump housing, thermostat housing and pulley for the throttle rod? If so, would it be possible to create a different shaped support frame for the throttle rod that would support it within the (tight) available space. When I made an adapter plate to allow the one hole water pump on a 261, I don't remember having to make a special throttle linkage. Maybe I should have taken more/better pictures to help my memory. I will try to find any pictures I might have although you are trying to solve a different combination than I was.

[Jordan Baker]

Thanks guys.

I'd ultimately like to use the one hole 216 water pump as it gives all the room that is needed. However as I posted in the other tread I'd need to do some serious surgery to the engine block and make up an adaptor plate.

Bob, I believe I've got the correct elbow with the flat spot.

I'm just confused by all the swaping around of pumps and pulleys.

[Bob Carriere]

If you use the harmonic balancer of the 216 ( it while fit the 235) and keep the 216 water pump pulley than you have the same speed.....however, I used an alternator ( sorry I sinned) so I had to change the pulley on the alternator to match the 5/8 belts requirements of the rest.

Note some 216 had large 7/8 pulleys.

what ever you do do not remove metal from the block..... I would be concerned with creating a weak area even if the later 261 had a huge hole to allow the pump to sit inside the block.

Let me follow with some basic photos.

First just to clear up the cab 13 versus cab 11/12

The first picture shows a cab 13 set up..... the rod is shorter and is connected to another straight rod that goes to the gas pedal.


PS...... just noticed that the second and third picture show evidence that the throttle shaft was grinded above the pulley to gain clearance...... shinny area.

*****(The second set of grey engine set up shows a cab 11/12 longer arm set up.) **** WRONG it show same cab 13 set up.
There is a flat stock piece of steel that fits behind the rod.......

I will follow up with my modified set up to gain clearance.

[Jordan Baker]

Bob, in your last picture is the throttle rod ground down to provide clearance?

[Bob Carriere]

First the original set up on my cab which was equipped with a GMC 228 engine BUT I have verified with other cab 11/12 and the set up was near original.

[Bob Carriere]

Has no modification and he made it fit ...... not sure how????

[Bob Carriere]

Too many pictures gets confusing......

I think we better wait for Phil's pictures which will be far more accurate.

sorry!!!

[Jordan Baker]

My understanding is that Grant used a 261 and a home made adaptor plate to fit an early one hole 216 water pump. Using the one hole pump there if enough room to fit the throttle rod unmodified.

My engine is a late 216 that used s two hole water pump, this means I have to either modify the throttle linkage to fit or find a way to fit the early one hole pump to a two hole pump engine. I'm not sure this is possible.

[Bob Carriere]

Would it not be easier to find a rebuilt 2 hole pump????


I think I am going to bed to think about it....

Ps one holer are $200 on ebay but a rebuilt two hole is $90


Water-Pump-CHEVROLET-1942-1946-1947-1948-1949-1950-1951-1952-CORVETTE-1953-1954.............. search for this item.

[Jordan Baker]

Ive got a good two hole pump that came with my orange engine. I'll try it with its original pulley back on. I thought I had to remove the pulley flange from the one hole pump and install it on the two hole one. However doing this seems to have taken up all the room for the throttle linkage.

[Grant Bowker]

Originally Posted by Bob Carriere

Has no modification and he made it fit ...... not sure how????

At this point I don't recall if it was careful parts selection or pure dumb luck but I think it was a close fit although I do remember it not having a lot of spare space. There are a variety of thermostat housing castings, each a bit different from the others WRT wall thickness, clearance angle at lower front and overall bulk. There are also slight manufacturing differences in the throttle linkage across the front of the engine that can help/hurt. And... there are several different casting numbers of each of the 1 and 2 hole pumps that vary slightly in shape (plus aftermarket pumps) to add or reduce clearance. I remain very nervous about the idea of modifying the 2 hole 216 block to accept a 1 hole pump. it just looks like more holes, closer together than I am comfortable with - but it might be alright in spite of my nervousness.