CHEV 216 VS Chev 235

[Jordan Baker]

I've been reading a bunch of these older threads to figure out my engines. I'm going to be using the orange one since it's a very good runner. However I see I have the "1942" two hole water pump. My older cmp truck has the original one hole style. I understand that I should use the pulley off of the one holer? Do I also press off the flang with the 4 mounting bolts and put that on the two hole pump shaft?

[Jordan Baker]

I tried mounting the early pump and it does fit with the two upper bolts. Can I drill out a new hole into the block to allow for water passage and also drill and tap two new mounting holes. I did a quick spray paint over the rear plate to show the difference between the two.

[Bob Carriere]

Talk with Phil W.

Seems we are up to our necks in water pumps these days.

I believe that Phil did a test to see if there was any flow/volume difference between the two vs one hole and found none.....

gone to see what pictures of my engine I can find.

Bob

[Grant Bowker]

Without anything solid to back my instinct, the spray paint does seem to show a lot of holes in close proximity. Swiss cheese isn't a great structural material....
My next instinct is that if the "correct" size pulley can be fitted to the 2 hole pump and everything else fits I would prefer to accept the slight inaccuracy of the 2 hole pump rather than that much adaptation of the cylinder block.
The commercial adapter plates are intended to fit the 2 hole 216/early 235 water pump to the late 235/261 block (pump impeller within the block, not mounted in front of block and head. Do you have a set of the instructions for the 235/261 commercial adapter plate? They inlcude a table of recommended balancer and pulley sizes. A copy of the instructions can be seen on Phils site at http://www.canadianmilitarypattern.c...ifications.htm

[Bob Carriere]

Taken of the back of one hole pump and two hole pumps.......

I don't think they can be interchanged you will need a pump that matches the engine you prefer.

Grant comments???

[Phil Waterman]

Hi Guys

Will have to sort through my shop notes and photos of water pumps couple of points to keep in mind as you play mix and match.

1. Keep the relative size of the pulley in mind between the crank pulley and the water pump pulley. The really small pulley on some of the 2 hole later pumps will dramatically over speed the fan when used with stock large crank pulley. I would be concerned about fan failure. Testing the 235/261 engines on the stand it was obvious that the fan was turning way to fast. The air stream over the engine was actually pulling oil out of the oil breather. So use the crank and water pump pulleys in sets.

2. If you decide to change the pulley some are bolted on and some are swedged directly to the water pump shaft. Those are very hard to remove without breaking or bending something.

3. The water flow tests I did was to confirm that the 235/261 stock water pumps and the modified 2 hole with adapter plate had the same or similar GPW flow rates through the normal operational RPM range, they do.

Will look to see if I've got good photos of which water pumps I used on which engines and what are the differences.

Cheers Phil

[Jordan Baker]

Thanks Phil and all for all your help.

I'm seriously looking into making an adaptor plate for the early one hole pump to mount to the two hole block. It's frustrating as the throttle linkages all line up perfectly when the one hole pump is used.

I played around with some paper this morning using theo one hole backing plate as he basic pattern. I then overlayed the two hole plate and traced out the two holes. The blue is the holes in the block. The green is where the frost plug is located. The yellow is the original one hole pump hole as found on its backing plate. The cutout portion of the paper is what I'm proposing to remove from the block to give the same amount of flow.

Concerns I have and I have a few.

Obviously drilling into a block and removing material is worrisome. The two small blue circles are the original threaded holes. On the inside of the casting they are solid. If I were to screw in some small set screws would that help make it more solid? On my drawing the two lower red circles are where new holes would have to be drilled and threaded to mount the lower water pump bolts. When I've read over the 235/261 adaptor plate instructions they have you drill new holes.

Thoughts?