The Stovebolt Site Forums The Shop Area Engine Shop Need help on a timing issue on my 1941

I just purchased the 41 and decided to do a small tuneup on it. When I started I noted that the octane selector on the distributor was set at "0". To start checking the timing I pulled all of the plugs. Then following the #1 spark plug wire back to the distributor, I marked the #1 spark plug on the distributor cap and the distributor body. I then took off the cap. I then manually cranked the engine around until the pointer was directly over the BB and the rotor was pointing at the mark I made on the distributor for the #1 spark plug wire. I assumed that I was now at TDC on #1. I then took the distributor out and checked the point gap and it was set to .016. I replaced the distributor and ensured that the rotor was again pointing at the mark I made. I then attached my static timing light and turned the distributor until the light went on. So I thought I should be good to go but when I looked at the "octane selector" it was not pointing at the "0" but instead it was now pointing to 10 degrees advanced. So given that it was initially pointing to zero, the spark must have been very retarded. Does this make sense? My assumption was that if I had the engine at TDC on #1 that when I adjusted the distributor to get the light to turn on that the octane selector would be pointing to "0". The reason for all of this was that when I purchased the truck it didn't run very well so I decided to look at doing a small tune up.

Thanks for any help
Mike

Mike - First off, Welcome to Stovebolt! Sounds like your '41 is new to you and your just getting familiar with the ins and outs of your engine and timing. Not a problem, but I do have to ask for more details on the engine. Is it original to the truck, if you know, or is it a replacement as many of our old trucks have these days?

It's best to fully identify what your truck and engine is before we can provide the best helpful information and knowledge. You didn't mention if its a Chevy or GMC and we don't want to assume and send you on a wild goose chase.

Perhaps you could share some pics of your truck and engine, including the engine serial number and casting code/date info so that we knw what you have too. If you need help figuring out where to find those engine identifiers, or figuring out how to post pictures, let us know and we will help out on those things too.

Once again, Welcome!

What does the light being on indicate? Is it just a "points open" indicator?

Yes..it indicates that the points are open

A number of these flywheels had the BB at the proper factory setting for timing, not TDC. Does your flywheel have another set of markings near the BB marked. U!C. ? If so, the vertical mark between the U and the C is TDC.

Dan-
Thanks for the warm welcome. I am new to the truck world. I have pretty much been a sports car guy, both domestic and foreign, my whole life. I have never owned a truck or any vehicle this old. My truck is a 1941 Chevrolet 1/2 ton pickup. I think the designation on it is an "AK". It had been restored in 2000. It looks like the engine was rebuilt at the time of restoration but I am not sure. The only numbers I see on the engine are on the block to the left of the distributor. I assume that this it the engine serial number. It is EBM260033. Where would I find the casting code/date? Is there a way to tell if this is the original engine for the vehicle? Also, I do need help in being able to post pictures and pdf files. Additionally, how do I add information to my signature line. I can add my name but anything more than that it tell me I am out of space..Thanks ahead of time

Mike

Great info Bill! Yes I found that my flywheel had the U | C mark so I used that as TDC and set the points to that. It's tough to see if the pointer is aligned with the line between the U & C. Based on where I set set it it looks like it about 2 degrees advanced (that's what the octane selector indicates when the static timing light turns on).

I take a bottle of white-out or nail polish and color the lines, numbers , and letters on flywheels and balancers. It makes them real easy to see with a timing light.

Mike - According to the GM Heritage Files 1947 Chevrolet Truck Data PDF your "EBM" prefix indicates the engine is a 1947 1/2 ton truck regular production 216 unit built at the Tonawanda Plant. The remaining serial# 260033 indicates your engine was the 259,033 engine off the line from that plant that year (serial#s started at 1001).

An original 216 for your '41 would have "AE" for the prefix. Not to worry as most of our old trucks no longer have their original engines.

To find the block casting code and casting date code locations see the 2nd example picture attached below (copied from fellow Stovebolter tclederman's web page. Let us know what those are and we can confirm further details on the engine.

Mike - Check out this helpful guidance on posting pictures.

I think the simplest portion of that thread to help may be this short video by klhansen that gives a simple set of instructions to get your pictures posted.

On the signature line update, send me a PM and I'll help you get that resolved.

You will want to set octane selector on the zero mark and tighten the bolt down. With today's modern fuels, you won't likely ever need to touch that again.
You need to have ball on the needle with the rotor pointing at the #1 wire post on the distributor cap while the #1 cylinder is at top dead center on the compression stroke.
This should be close enough to start the engine and run well enough to check the timing with a timing light. You will be done when timing light flashes and the ball is on the needle.
To make adjustment to the timing, there is a screw on the backside of the distributor which takes a flat screwdriver. Loosen it, adjust the timing to ball on the needle, then tighten the screw. Your timing will then be set at factory specs.

... and don't forget to block the vacuum advance (if you have one) while setting the timing. I found it easier to make the adjustments by cutting a foot or so out of the metal vacuum line to the distributor and replacing it with a rubber hose.

I don't have Chevy specs, but GMCs that use the same distributor say to:

1. set the "octane selector" to zero
2. get the idle speed below 400 rpm (because the distributor's mechanical advance starts that low)
3. start the engine and set the ball on the needle
4. lock everything down and reconnect the vacuum advance
5. set idle speed back where you want it. Mine is 425 in the winter and 550 in the summer to help the A/C work better


Once everything is back together you can see what happens when you play with the octane selector some. The good thing is you can always move it back to zero without needing to hook up your timing light.

My GMC likes the +5 setting. I've never heard my engine ping, though the truck may be making enough noise that I can't.

Thanks to all for your suggestions. The timing is now correct. The truck start and idles great. The problem I now have was the Carter W1 Carb. Should I start another thread posting the issue with the carb?

congrats Mike.

Yes, start a new thread for the carb.