VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Cam Gear

I finally got "all" of the parts in to rebuild the '38's engine. The cam gear is backordered. I'll have to call Monday to get an idea of when they expect it to be back in stock. Does anyone have a NOS cam gear for a 216 in case it's going to be a while?

Order one from NAPA or a good parts house.They fit up to 1962.

I'll do that. Thanks Gene.

Personally that is one part that I would not go for as an NOS. I wouldn't have faith in the stability of that original fiber material.

Good point. I'll call the vendor Monday to see how long they expect it to be backordered. If too long I'll get one locally.

I've been doing some checking of new gears and there are both fiber and aluminum gears available. There's also one listed as "silent type" sold by Sealed Power. I remember someone posting some time back that the aluminum gears are noisy. Is the new fiber gear the best choice? What's the difference between the fiber gear and the "silent type"? The "silent type" is almost double the price of the fiber gear.

Chevrolet used the aluminum gears in heavy duty trucks starting in 1948. They claimed it was more durable under heavy duty truck use where higher RPM's were more common due to trucks being run in intermeadiate gears morre frequently for pulling power.
As long as the oil passage behind the front mounting plate is free of sludge so the gears get proper lubrication there is no problem with the fiber gears for at least 100,000 miles.
The aluminum gear will make the most noise wen the oil is cold and not dripping down on the timing gears.
On a stock engine with the low tension valve springs I have always used the fiber gear and never had a problem. Important that both gears get replaced.
Even the modern 7 main bearing 6 cylinder engine (1962-1984) used a fiber gear as did the 4 cylinder "IronDuke" GM engine used a fiber gear.

Gene, you mentioned in another post that a 40 fiber gear was different than a 37 ....it changed the valve timing and maybe gained some " performance ". Can you clarify?

From the 1940 Service News......
The valve timing has been changed 6 degrees on the 1940 engine to permit the intake valve to close later, therefore, admitting a greater charge at high speeds to improve ocerall performance and economy. The change in valve timing is accomplished through a change in the crankshaft gear.
The horse power remained the same in 1940, at 85, but was produced at 3400 RPM rather than 3200 RPM.
The fiber gear was changed for the same reason in 1948 .
these changes will result in it being necessary to set the timing (fine tune) by ear as they do change the valve timing - or a later distributor could be used.
All that still will not increase the power by any measurable amount at the speeds you usually drive - between 20 and 55 MPH in high gear.
It incresed the top spped of my 1939 from 75 MPH to 80 MPG - as per the speedometer with the 4.22 rear end. It will now go past 80 with the 3.73 gears but in my old age I have never pessed it to the top..The aluminum pistons may have helped a litle also

Gene, if I'm reading this correctly I need to set with about a 6 deg advance from the ball on the flywheel?

Actually there is a difference in a valve timing advance and ignition advance. The difference is in the piston position. The cam gear advance changes the position of the piston when the valves begin to open and close. Timing advance changes to piston position when the spark plug fires.

Cam timing basically changes the way the engine breathes and the gas (air, gasoline, exhaust) composition in the cylinder. I could try to explain further but it gets a complicated and a bit hard to understand exactly what happens and why. I hope I have not lost too many so far.

Chip, you lost me at "Actually". I just need to know how to time it after the rebuild. Do I time to the ball on the flywheel or do something different?

Set your timing where the engine runs the best. That is what the octane selector does. The factory timing light and ball setting is only the base setting. The octane selector allows you to fine tune it from that point.

So, I,m guessing, keep advancing the spark till it resists starting then back off a degree or two. I like this idea due to the various gas I use, up to 100 AV gas. Should we do this with the engine warm, or cold?

Tiny, time it to the ball and use the octane selector after that. No need to make this a scientific project.


Randy, 100 AV gas. Is that cheaper? Anyway, it doesn't seem that that much octane is not necessary or needed. And if not needed, then you may be both throwing your money away and/or damaging your exhaust valves. Best I recall, the higher octane will burn relatively slower than say... 87 octane.

Maybe Chipper, DrDavid or someone else could weigh in on this. I'm no expert.

Charlie

Okay in reading thru this thread, Tiny was looking for a 38 fiber gear and Chevgene said he could order from a parts house as they fit up until 1962. A little later in the posts I think I read the gear changed in 1948. But if I go to the local NAPA (or some other parts house) and order a gear, how do I use it in a 1939 car if they're different after 1948. What else do I need to change or do different?

Jim

That was the jist of my query too Jim. I think I'm going to follow Charlie's idea and set to the ball then use the octane selector to fine tune.