Chevrolet CMP Engine variants

[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!!!

[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.