VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc '31 plug gap

In previous posts there has been much discussion about setting spark plug gap at .040 for better performance. Has anyone noticed a shorter coil life as a result of this change? It seems that the coil would have to work harder to shoot the spark further. My '41 plugs are set at .040, and I'm about to change my '31 plugs to .040 as well. The '31 runs okay set at .025, but I think it would run better at .040.
Thanks,
Sid

Sid -

After learning about that .040 gap for my 31, I was so pleased with the better running at idle and in general that I have changed all plugs on my equipment to the same dimension. This includes 1 cylinder garden tractors, 2 cylinder garden tractors, my farm tractors, my 48 Chevy and anything else I can get my hands on. Have found, (in my opinion) better performance from them all. These all called for .028 gap before changing.

The coil, if I am correct, should put out about 20,000 volts at idle and than pick up to about 40,000 volts as revs climb. Never had any problem with coils on anything after going to .040.

Just my opinion here and best to ya.

Jim.

Thanks Jim, I reset the plugs today at .040, and it does idle better. I know that I also have to advance the timing; I can tell it is sluggish to accelerate, and my vacuum gauge says it is retarded. The distributor is already advanced to the max in its present position (the grease cup is against the block), which means I need to remove the distributor and replace it, one tooth over from its present position. To do this, do I move the dist. one tooth clockwise? I have done this a few times before on other cars, and it seems that invariably it ends up being a huge task, probably because I moved it the wrong way or??
Sid

If you pull the distributor and then reset it with the timing pointer on 12 degrees, the rotor pointing to number one cylinder in the firing order (which should be on compression), and the spark knob pushed in, after the engine is running you will be able to advance the distributor to 18 degrees with no problem. At that setting there should be about one finger width between the grease cup and the side of the engine block....depending upon the size of your finger of course.

I just recently tuned up my 31, when I removed the plugs to replace them for the first time since 2003 and they were still like new and gapped at .040-.045. I think using unleaded gas is the reason. I also have been running at 18 degrees BTDC.

hoppy

Thanks for the detailed instructions Dog, I appreciate your help. Hopefully, I can get it right this time. Also thanks to Hoppy for his comments. Just this morning another friend said going to .040 is a lot for a coil to handle, but many on this site have said it poses no problem, so I went to .040, and I already see improvement at idle.
Sid

1930-32 Tuneup specs.

http://1931chevrolet.com/specs7index.htm

Thanks Bill, I'd forgotten about the tune-up info on your site. It will be very helpful.
Sid

If you have a good coil it will handle the extra plug gap just fine.

Changed my gap on the 52 to .040 today and drove about 30 miles. It idle much smoother now. The plugs are A.C.46. Tomorrow will tell how it effects the start-up.

Good review... I am planning on doing the same thing on Monday... I just discovered that my Landau was timed at TDC. Just changed it to 18 degrees BTCD. --ouch--

So now I'm going to look at everything!!! Vacuum test, sparkplug gap, Dwell and tire pressure.

Today I removed the distributor, and initially turned it the wrong way, but eventually got it in what I believe is the right position. I can put one finger between the grease cup and the block. The engine starts quicker, idles faster, and accelerates better. However, my vacuum gauge indicated the engine was still retarded (it read 15 and "normal engine" is 20). Moving the distributor further counter-clockwise causes the engine to run poorly at idle. I took it for a drive and was pleased that it seemed to accelerate better. However, top speed is only about 47 mph! (based on the speedometer in the car). There are a lot of 4 cyl. Model A fords that run faster than that!
Tomorrow I plan to put a timing light on it to see where it is. I also will check points and gap, and springs in the distributor. I will also check the speedo with a gps.
Since I built this car about 5 years ago, it has been driven around the block and on and off the trailer. I haven't really been concerned with performance (just looks) until now.
Thanks for the help guys.
Sid

I re-set the points this morning. They were at .020, and I re-set them to .018. That's not much of a change, but it may help. To check the springs in the distributor (instead of removing the breaker plate) I rotated the rotor and shaft clockwise. I could tell that springs were working some, but the shaft didn't spring back. Shouldn't the springs be tighter than that, causing the rotor and shaft to spring back counter clockwise into place??
Would weak springs reduce top speed?
Sid

Weak springs can cause a more rapid advance. That can cause people to retard the timing which will affect the top end.

Using my lawnmower's 12 volt battery and a streak of my wife's red nail polish on the flywheel, I was finally able to see well enough to check the timing, and it is at 18. I stumbled into that one without the benefit of the light yesterday! Will check speedo with GPS later, after the rain stops. I see Gary Wallace lists the dist springs. I'll order some Monday. I gotta do everything I can to increase my top speed; can't let a Model A pass me!
Thanks for the help.
Sid

I'm more encouraged today. On the back roads around my house I got it up to 56 mph per the GPS before I let off. The speedo was showing less than 50. 56 isn't so bad, and I think it would do more on a long straight stretch of highway. How about it other 29-32 owners - what is your top speed?
Sid

Well, I had my '30 Coupe up to 50+ on the speedo prior to an engine rebuild. But it seemed like it was all over the road handling wise. As soon as I stopped, the radiator spewed. After the engine rebuild, we had it up to 90kph (55 mph), according to the GPS, on a downhill run trying to pass a truck. We backed off, as the truck continued to speed up. I can cruise all day with it at about 40 mph.

Happy Motoring,

Dan

I used to drive a '31 Coach as my second car. Often drove it on the Interstate at (or maybe a bit over) the legal speed of 55 mph. Didn't have a GPS to know exactly how fast I was driving but not too many passed me.

Maybe they were afraid that something might fly off in front of them?

I've run my 32 on interstates at 55-60 mph for distances of 20 miles or so. It seems to handle it fine but I prefer to cruise at 35-45 so I can enjoy the ride.

Sid
You may not need to change the springs. Considering that there is movement in the centrifical advance system a good lubrication maybe all that is needed and a lot easier.
Tony

Thanks Tony, I'll try that. Dan's comment about being all over the road was also true for my '31 above 50 mph. When my wife and I were checking the speed with the GPS yesterday, she was reading out the speed, and it was all I could do to keep my foot on the gas and hang on, keeping the little Chevy in the lane. A very flat smooth section of deserted interstate would be a better place for such efforts.
Sid

Sid you my want to make sure the front end alignment is good, they will go down the road better. The 30 we had drove much better once I set the toe-in and and had some positive caster.

Yes. The rotor and cam should spring back under spring tension. It is possible that your distributor cam is sitting on top of the distributor weights instead of between them as it should be. You might want to pull the breaker plate and look at the weight assembly that is under the breaker plate.

When I checked the springs again today, the rotor and cam sprang back into place. I don't know what changed to make that possible. A couple days ago I put a very small dab of grease on the cam. Anyway, it looks like the ignition system is now working properly. The car runs better now than the whole time I've had it. Thanks guys,
Sid