Today I pulled off my radiator and timing gear cover to install a nylon advanced timing gear that I have had in my tool box for a couple of years. I read here advancing the cam timing makes the inlet valves close slightly earlier thus increasing the compression. I checked the compression before and after installing the nylon gear but, the compression remained 62 PSI both times. There was no change. Now I'm starting to question whether the gear is advanced or standard. How can I tell? Also, is there supposed to be a thin washer between the nut and the nylon gear?
Advanced or standard, the nylon gears are trouble. They will leave you "toofless".
Yes, Bill I'm a little concerned about that. The gear has .001 backlash when I measure it with my dial indicator and I'll set up the generator pinion so it has the same amount. Is anybody offering metal advanced timing gears? If so maybe I'll just buy one of them.
Dan McEachern. He has 7.5 degree advanced bronze gears. Top notch! He also has steel gears.
Contact info: http://www.mtfca.com/discus/messages/179374/193439.html?1298940762
Here is a good thread about nylon timing gears.
If you use a nylon gear with a old worn-out gear on your generator you get what is pictured above.
The timing of the cam should make no difference in the compression done at low speed such as with the hand crank or starter. The difference should be at higher RPM's when the air flow dynamics take over.
Phillip, I have all new gears in great shape. I think I'm going to be buying a metal from Dan anyway.
"Now I'm starting to question whether the gear is advanced or standard. How can I tell?"
Here's a picture of a cam gear that is drilled for both stock and advanced timing:
I've run fibre and nylon gears for many years and many thousands of miles with no grief. I've always just installed them as complete sets and have always verified the lash
.001" of clearance sounds a bit on the tight side though to me. I would be happier with .002-.004
Over the years, I have installed 6 of these nylon gears. At no time did either the manufacturer nor the vendor supply instructions for proper installation. There were no warnings regarding mixing new gears with old gears.
Just now, a quick review of the 2 largest vendors and there are still no warnings about mixing gears in their online catalogs.
Just wondering- how are we supposed to know if we aren't told?
I guess it is hard to know if no one tells you. Growing up with cars, I was told and retold years ago that, just as with ring and pinion gears you should replace both timing gears. I've never run Ts with starters so if I did, I'd replace all three gears, especially if the large gear is not metal.