Reference: Peter B. Water pump / air lock / Engine temp range....

[Bob Carriere]

Fire away Peter......

Is this 216 the original engine....

Is the pump a 216 in the block water pump or did you use a hybrid set up with an adapter plate

Why do you havea throttle set up like a Cab 11 CMP....? never seen that before....



My 261 has a hybrid 216 water pump and was strongly recommended by other engine builders to insure that a short by pass tube be used and NOT to plug the threaded outlets with pipe plugs....... Like you..... I ran a rubber hose for a while but did not like the stress in the rubber tube so I made a solid bypass with regular 1/2 inch house soldered copper pipe.......

Does you engine have a steam line running from the rear temp hole in the engine head to the elbow of the radiator

Do you have a modern mechanical temperarture gauge that you can connect to the engine or relying on the original CMP gauge

What temperature thermostat are you using

I have pictures that I can share.......

Over to you.....

[8threcce]

Bob,

This is the set-up that was with the vehicle

The engine is a 216

Cooling might have been altered in a previous life by the Forestry of Norway

No adapter plate as far as I know and can see

Does you engine have a steam line running from the rear temp hole in the engine head to the elbow of the radiator : No don't see any connection for such a set-up

Do you have a modern mechanical temperature gauge that you can connect to the engine or relying on the original CMP gauge : Just the one in the dash no additional measuring only for oil pressure

What temperature thermostat are you using Unknown to me can I check this?? the Original was used that was already mounted on the engine ..since that is the case I'm wondering to replace it .so that I'm sure

[8threcce]

I believe there was an attachment on the radiator
But was removed

[Bob Carriere]

Your HUP came with the engine that you have but you are not sure if it is original or not.......[I]You may want to do a search on the serial number stamped near the distributor........

I stand to be corrected by any one else but the picture you showed of your water pump also shows a cab 11 throttle linkage that I have never seen on a HUP........ might be clue that the engine was once changed.

On the steam line........ it has been my experience that all CMP have a steam line that runs between the rear of the engine head between 5 and 6 cyl. and connects to the elbow filler neck of the radiator...... my GM Chev book learning is the same they all have them. I understand that under severe road conditions up and down gullys ...... air can be trapped in the high spot at the back of the engine head so a simple remedy was provided. If one is not present on your truck you may need to install one if for no other reason but to get ride of the air lock you are currently experiencing.......
Having said you need one it is possibly more than a home job tobe done. You will need to have a threaded fitting soldered to the radiator tank....or if you look carefully at your filler neck of your rad right at the ebnd is where you may have had a hole. In any event any brake line that will match up to the fittings you will use will be sufficient. On the engine head where the existing temperature bulb is attached you need a brass T fitting...... one opening will be for thesteamline one opening will fit in the block of may need a reducer brass fitting and thte top holeof the Tee will take the original bulb. You may have some searching to do to find a brass fitting that will accept the original square four sided nut of the temp. bulb nut. I did not want to trust the original CMP gauge onmy truck with an expensive fresh rebuilt engine and opted for an after market mechanical temp. guage........ it registers at 165 F and sometimes at 175 when being driven hard. One note on thermostat temperature ratings........ they come from 165 to about 210 for pressurized system....... all they do is promise to open up full at the set temperature....... they will not prevent a dirty engine block or plugged radiator from having the engine run over hot and boil over.... it only shows the temperature at which it is designed to fully open. On freshly rebuilt Chev 6 cyl driven in the street of Canada I would consider a 185 or 190 thermostat to make sure the it keeps the engine hot up to the indicated heat rating due to the 6 months of cold weather.....but for my 261 truck engine I opted for a 165 thermostat as I know how hot these engines tend to run during the Summer....... I have driven my truck hard at sustained 3000 rpm aned never recorded anything over 175..... another trick is to keeping it cool is to
increase the engine oil volume...... I did away with the original CMP by pass oilfilter can and replaced it with two PH-8 screw on oil filters that gives my at least and extra liter of oil to carry the heat away. You may want to consider buying a new modern mechanical temperature guage just to run some test for a few hundred miles and go back tothe original once you are satisfied it does not run hot and reinstal the original dash temp. guage of the CMP

Sorry break time...... wife did her famous Linguini Carbonara Roma for supper..... just out of this world......

Just out of curiosity is your dash the civilian rectangular guage set or thelater military round gauges??? If you have the original rectangualr civilian dash it may indicate an ealry production HUP with whatever isntrument cluster was regualrly available....... not a guarantee has I have seen Autralian 1944 C60 built with civilain guages.....

One civilian truck 6 cyl engine such as the 261..... made in the late 50s GM drilled small holes in the heads between the 2nd and 3rd and 4th and 5th cylinders and called them stream holes.......

Now this one is long enough......look forpart two.

[Bob Carriere]

If you are curious you may want to check the existing thermostat that you have..... and find out what setting it has..... of course you need to drain the block and drain some of the coolant...... while the radiator drains slowly and only half drained is OK..... start boiling yourself a cup of tea..... you know this HUP is a British design..... with your thermo stat removged and rinsed tie tring to it and suspended it in the hot water.....use your wife;s best cooking thermometer.....wait until the temperature of the water is near what the numbers are stamped on your thermostat..... if it says 185 F it should be fully open at that temperature AND returned to shutting when it cools. Some modern thermostat are design to open and stay open.... they call it fail safe position.... get rid of that and use a normal open old style thermostat......around 180 F........

If you do remove your radiator to have a radiator shop solder a threaded fitting for a steamline it might be a good time to have the radiator boiled out by the rad shop BUT do tell them to test for leaks at ONLY 2 or 3 pounds of pressure as these CMP radiators are not run under any pressure... ..meanwhile when the rad is removed try flushing the engine coolant core with some rad cleaner to see if you have any build up of rust sediment in the block........... on the passenger side....left side.... near the bell housing you should have a drain pet cock that allows you to drain even the lowest part of the engine cooling system...... it should flow slowly or you have deposit in the coolant passages...... try with a piece of steel wire to work it free... if not close the valve and wait for the next engine rebuild....

Sorry if Imissed correcting some typo Ihad too mcvuh wine with supper.....

[Bob Carriere]

....from my truck or overall collection.....

Having problems with my software tonite but here are some photos.... firts one shows my early attempt at making a bypass on the water pump....notice that I am using a 216 Water pump with an adapter plate onmy 261 engine......

second photo.......Carburator is a rebuilt YF689....work real good...... after market fuel filter with glass bowl...... because I had to plug the original vacuum connection on the intake manifold with a brass plug I needed to create new vacuum connection site .....so I had a solid steel plate milled as a spacer below the carb...... this allows the connection for the wipers and a vacuum gauge onthe dash.......NOW right behind is the testing connections that I put together that allowed me to connect a temp.gauge and the steam line to the engine....in your case you willneed an adapter to the head.... the T fitting..... a line to the radiator and again an adapter that is suitable for the bulb of your temperature gauge. You can see the green coolant n the temporary plastic tubing........ I would run my truck in the field for 30 minutes with the v\lave closed than stopped and open the valve and watch all the froth/foam green coolant purge itself....... if I drive leaving the valve open it only shows the occasional bubble....I concluded that it needed to be in place. I eventually replaced the whole set up with a permanent steel tube to the rad...... if that fooaming coolant stays inthe head for too long you risk over heating and possibly warping the head with resulting cylinder head gasket leaking.

I will post other photos as I find relevant pictures.....

Please do hesitate if you have any other questions........

For the strong of heart....... I ust run my stock rebuilt 261 engine at 2000 rpm at 32 mph or close to 3000 rpm flat out for brief scary moments around 44 mph. I just finished a 652 miles cruise on abandoned logging roads in less than 3 days....... mostly in 2nd and 3rd gear....4x4 hi range....lost some body screws and bolts to vibration and leaked a shock absorber with airborne jumps and bumps...... truck did good I was busted....never again but now it is scratched off my bucket list.......also lost all brakes..... but being a good CMP and having engraved in my mind the brake adjustemnt process, I spent 20 minutes in a church parking lots readjusting each wheel with a 3/4 in, spanner and the two snail nuts on the backing plate of each wheel..... presto brakes again/////// but it was fun!!!

[8threcce]

At least in all my remaining parts I found a connection