M38Cdn Refurbishment

[Marc Montgomery]

Peter- love the work you're doing.


there seems to be quite a dialogue online among expert mechanics, (racers, hotrodders, bikers, restorers) and even manufacturers of copper gaskets re annealing... some say heat red and quench, others say heat red and air cool, because quenching rehardens the metal...
I was taught to quench, but am wondering now...???

[David Herbert]

Marc,
If annealing steel, it makes a huge difference how quickly you cool from red hot because of crystal growth within the steel. Copper does not really do this so it makes little difference how quickly it is cooled.
Also the copper items that are used in engines are of such small thickness that they will naturally air cool very quickly so the choice would be to slow the cooling process even more which would be difficult and pointless.

David

[Lynn Eades]

Following on from what David said, Quenching tends to clean the copper, so that's the plus there.

[Peter Phillips]

More positive news . I removed the wheels and put the jeep on sturdy wooden blocks and ran it through all gears and 2/4wd driving functions and it performed nicely. I just finished stripping and de-greasing the tub, tailgate, windshield frame and assorted floor plates in preparation for sand blasting on Friday. And what a surprise when a fellow member informed me that I need to ground my dash in order for the gauges to work, ....they now work .

[rob love]

You are lucky they work. I found that usually on those gages, the fuel in particular, as well as the temp and oil pressure, would burn out without a ground.
The later M-series added a short ground wire from the panels to the dash which helped prevent this. There are times that you have the dash backed out (cable or gage replacement) that turning on the ignition switch can have bad results.

Same goes for testing gages on the bench. You must provide a ground to the case or the negative stud before applying power and sending variable negative thru the wire.

[Peter Phillips]

Originally Posted by rob love

You are lucky they work. I found that usually on those gages, the fuel in particular, as well as the temp and oil pressure, would burn out without a ground.
The later M-series added a short ground wire from the panels to the dash which helped prevent this. There are times that you have the dash backed out (cable or gage replacement) that turning on the ignition switch can have bad results.

Same goes for testing gages on the bench. You must provide a ground to the case or the negative stud before applying power and sending variable negative thru the wire.

Interesting Rob, never knew that bit of info...thanks . I haven't tried the fuel gauge but the ammeter, oil pressure and temp works fine. Interestingly I don't remember seeing a ground symbol coming from anywhere on the dash....unless I missed that?

[rob love]

The gauges take their ground thru the case, or for the later plastic housed gages, thru the clamp and onto the studs on the back of the case.

Many guys test the gages on the bench by putting power to the power terminal and full negative onto the sending unit terminal. The results are usually quick and not good....you need the case grounded. Cheap insurance for any M-series vehicle is to run a ground wire from one of the screws for the panel lamp (use a longer screw than original so you can get a ring terminal, a couple of internal tooth lock washers, and a nut onto it) and run the ground wire to a screw behind the dash, such as the screws holding the circuit breaker in place. You can put a set of Douglas connectors in between to make it easier to remove the complete panel if that day ever comes, or leave it as a solid wire.