VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Restoring my '38 Master Deluxe

My fiber timing gear ran dry from the gunk build up behind the timing gear back plate. It has a small oil groove that get full of carbon and then the gear runs dry and fails . I replaced with the newer alum. gear and matching steel gear for the crank. Make sure you have oil flow-drip out of the little brass nozzel , I`d clean it all out since your down this far ........

So far mine is squeaky clean, it should be since the engine was rebuilt back in 1993 and has only seen less than 100 miles since. I am in the middle of replacing all gaskets & seals that have dried out since.

One item that would cause me great concern is the timing gear. It carries a very old part number of 838436. Chevrolet improved the gear and the number was changed to 3836156 back in the mid 1950's. This indicates that the rebuilder never replaced the timing gear. A timing gear failure is one of the most common major engine failures of that engine.

Either that or the rebuilder got a NOS, since the teeth seem to be in perfect condition. Now that you mentioned this, I will be losing sleep & having night sweats.

Will check to see what's available before putting the engine back together. Already put the timing cover on, another gasket wasted....

Thanks, though....

Just the texture of the surface of the gear it looks old and used. Also if it were mine I would remove the front mounting plate to be sure the oil passage on the back of the plate is clean. It runs from the timing gear opening down to the nozzel. Or at least be certain the palte was removed.

When I had the timing cover off of my '38 I took that opportunity to unscrew the brass oil fitting and drill the hole out to a slightly larger size. Since it's a gravity feed the larger hole will let more oil flow onto the gear & not be a danger for over filling. FWIW it was a good thing I did because I found a piece of red RTV partially blocking the oil passage behind it.

Chevrolet doubled the size of the nozzel opening in the later years and made other modifications to get better oil flow to the gears.

The timing gear on my 38 has "Westinghouse" logo... I imagine they had bases covered just in case..

Ollie

Chevrolet had several suppliers. There was also a ton of aftermarket available but they did not have the Chevrolet part number on them.

Many current suppliers stop listing part compatibility years at 1948, and it appears that the timing gears are of the same specs from '37 & up, correct?

Fiber, aluminum, and a "quiet" type choices are available...cost difference between fiber and aluminum is minimal, the quiet type is about 30% higher....I am more inclined to use the fiber to keep the originality and I don't plan to drive the '38 any more than a couple thousand miles a year....

I am more inclined to use the fiber to keep the originality and I don't plan to drive the '38 any more than a couple thousand miles a year....

Other than yourself its not likely that anyone would know or question what type of gear you have in your car.

The 1959 parts book lists the 3836156 for 1937-1959 except heavy duty trucks that used aluminum. The aluminum is stronger but produces more gear noise that is why its use was limited.
The steel crankshaft gear (which should always be replaced when installing a fiber gear) was different from 1937-1939 from the 1940 and up. Reason, the valve timing was changed in 1940 to give the engine more power over 3000 RPM.
That being said I ran the later steel gear in my 1939 with no problem.
The reason for replacing the steel gear is the fiber gear leaves a mesh pattern on the teeth of the steel gear and that will also cause gear noise.
A properly lubricated fiber gear will last forever.

If I leave the steel crankshaft gear in place and just replace the fiber crankshaft gear with another fiber gear, will that pose an issue? I don't want to replace parts unless I absolutely have to....

It could. Examine the wear surface on the steel teeth. It shold be smooth and shiney.

Just read the repair manual again....they are saying that if I want to remove the cam gear, I have to remove the whole camshaft and put it in an arbor press to press it out...it appears that with ingenuity, I should be able to use a puller to get it off,

I am not going to save the gear, so I am not concerned about damaging it.....

The problem with trying to remove the gear with the camshaft still in the engine block is damage to the retainer plate, distributor gear and maybe other parts. The cam gear is very hard to take off as there is not much space between gear and block. Even if it takes more disassembly I think it is worth it.

The common practice with a lot of mechanics years ago was to break off the fiber gear, split the steel center hub with a chisel, and you were 1/2 done. To install the new gear they removed the fuel pummp and had a helper pry forward on the fuel pump lobe while the gear was installed with a hammer.
you do run the risk of dislodging the plug in the block at the back of the cam. Also if the original style retaining plate was used theend play could be off. With a new gear and the new style retiner plate this would not be a problem as the new style plate comes with an inner ring that limits how far the gear can get pressed on. Still not the best practice, especially for a first timer.
What I did on my last gear installation was remove the old gear with a chisel, drill and tap the center of the cam shaft and draw the gear on with a bolt and some spacer washers. Uesd a corase thread 3/8" bolt and it pulled the gear in place with no effort. Also the cam drills very easily.

Used Gene's idea several times but does have a few pitfalls.
Tony

I have done a number of GM 2.5 cam gears very similar to Gene's above method. I tap a 3/8" thread into the end of the cam first. Then use a 1/8" drill bit to make a slot on the cam gear. The slot made by drilling holes next to each other works good to put a chisel into it so you can split the gear. You need to be real careful to not drill to far into cam retainer plate or the block. Make sure you have plenty of rags to keep the bits and pieces from going into the oil pan. I also use my shop vac to clean things as I go. I also use a dead blow hammer.

.When I worked at a garage in the 50's the camshaft was never removed. Gene's gear replacement method was always used.

The drilling and taping I learned from many of my tool customers. In GM dealerships many timing gears were replaced in the IronDuke 2.5 engines and this is what the mechanics did to beat the flat rate time.

The balancer on my 1957 283 also had a tendency to back off. I drilled and tapped the crankshaft for a 7/16" bolt and used a bolt and large heavy washer (like the later small blocks used) to solve the problem. Also works for installing the balancer.

Gene: Your idea is great, I would like to try it first before dismantling the engine covers again.

Unfortunately for me, I already put the oil pan back on, and realized that I have to take it back off in order to get those two bottom timing cover bolts off. I did some more searching on this site and found that several folks modified those bolts for this very reason....

Ordered Sealed Power cam & crank gears, they were not as expensive as I predicted...$46 for both. Now I have to get new oil pan & timing cover gaskets again.

Many thanks for all of you for helping out.


p.s. Why are front motor mounts plentiful, but rear mounts are not? Seems like only chevsofthe40s and fillingstation are the only ones selling these....

Forgot to ask about the timing cover bolt mod...I assume you guys have drilled out the timing cover holes and tapped the block holes to reverse the bolt installation with slightly larger bolts?

The rear mounts fit from 1935=1948 and even NAPA may have them.

I just did this mod on my 40. I have a picture of this mod on my smartphone but not clear to me how to postpic here. You should pull the brass oiling nozzle and drill out from one sixteenth to one eighth inch as per chevy engineering change order in 1948.mine was totally clogged resulting in a blown cam gear.