7.5 degree timing advance

[haydonr]

Hi All,
I'm not a mechanic by any means but having been told that the 7.5 degree timing advance makes a big difference to Model T performance, thought I'd have a go at replacing the standard Ford timing gear with a nylon 7.5 degree advanced gear on our '24 RPU. Now that I've got the original timing gear off and compare them side by side, it occurs to me that 7.5 degrees is simply 1 tooth on the timing gear.
This begs the question, could the original timing gear have been reused by simply making a new timing mark 1 tooth around from the original? Or am I missing something?

I'll probably use the nylon gear since I've already bought it, but if I have issues with gear lash etc once I get to fitting it, would just like to know whether reusing the original (1 tooth out from where it was) would achieve the same thing?

[Norman Kling]

The aluminum timing gears will last longer than the fiber or nylon. They might make a bit more noise but wear longest. You can purchase cam shafts with a higher lift or advance so be sure, if you advance your timing gear, the camshaft is standard or you could have problems. Problem is that if the exhaust valves open while it is still under power stroke, you could get burnt valves and a hot exhaust manifold.
Norm

[Kerry]

The 7.5 advance timing gear is only a half a tooth, going one tooth is too much and will not run correctly.

[haydonr]

My maths says 360 degrees divided by 48 teeth equals 7.5 degrees per tooth... am I missing something?

Pretty sure the existing cam is a standard Ford one taken from my father's collection of parts when this motor was built around 1990 or so.

[Dan McEachern]

Cam / crank ratio is 2:1. Yes your math is correct, but cam timing is reported and discussed in crank degrees, not cam degrees, so 1 cam degree is equal to 2 crank degrees. If the crank moves 1 degree, the cam moves half that amount.

[haydonr]

Ahaaa Thank You Dan. I knew there must've been a reason that people would pay for a new gear rather than just shift their existing gear by 1 tooth.

[John.Zibell]

I'd recommend staying away from the plastic timing gear. I'd recommend the bronze gear https://www.modeltford.com/item/3047BB.aspx Call Langs to see if the 7.5 degree is available from them. I'm running one and it works good. If you have a generator, be sure the spacing is correct to the timing gear. I had to use an extra gasket to space the generator further away for correct engagement.

[JTT3]

Has the type material been changed in the nylon timing gears being produced now? I ask because I recall reading a few post about the old nylon gears having major issues in engines running a generator but not so much if a non generator motor. I’m interested in the responses selfishly because in the past I purchased a few of the 7.5 nylon gears but never used them after reading some of the comments made several years ago. Updates on experiences are appreciated. Best John

[Moxie26]

John and All : .. we've had a nylon advanced timing cam gear in our ' 26 runabout since the engine was rebuilt 20 or so years ago.. no problems whatsoever

[ModelTWoods]

Another thing to consider when using a nylon gear is that most, of not all, nylon gears must use a thinner camshaft timing gear nut to avoid the nut shorting the timer from the timer roller touching it. I think both Lang's and Snyder's include this nut with their nylon gears.

[speedytinc]

I have seen a nylon gear that the mount holes were all wallered out after one Montana 500 race.
I do not recommend their use.

I dont cheap out on parts. I ran a nos iron 3 spoke gear. It broke.
I have run aluminum gears with varing success.
Found some grew over .010". Have to set them up loose. Some wear very fast. Depends on the alloy & anodizing.
Nylon & fiber are not in my list of usable parts.
I guess what I am saying, is I have seen all the above fail one way or the other.
My go to is Dan,s bronze gears. I have not had a precision problem, failure or wear issues.

Better to use the best than rework/redo down the road.

[Steve Jelf]

Fiber timing gears top the list of things I avoid, but nylon gears are a close contender.

[Moxie26]

Steve, with all respect, how many nylon Cam gears have you worn out or had problems with?

[Jerry VanOoteghem]

My go to is Dan,s bronze gears. I have not had a precision problem, failure or wear issues.

Better to use the best than rework/redo down the road.

I go with bronze as well. I tried a nylon gear several years ago, (not manufactured by any of the current sources and not with built-in advance). From a cold start it was noisy. As the engine heated up, it became incredibly noisy and was running in tight mesh, (a gearing no no). I removed it and went to bronze. The sad part is, I bought four of those gears. By the time I learned they weren't any good, the supplier went out of business, so I couldn't even return them. Hey, wanna buy a nylon gear...

I suspect that the current vendors of nylon gears are doing a much better job of it. I'm not really trying to bash nylon gears. But, for now, I'm sticking with bronze.

[Moxie26]

The early supplier of those nylon gears was a big problem all unto itself. The manufactured gears after that were made better and held up like mine with no problems.

[Bill Robinson]

Back in NOV 2015 I got stuck on the side of the road. Here's why (see photo). Upon repair I installed the bronze gear and have had no problems.

[Mark Nunn]

Another thing to consider when using a nylon gear is that most, of not all, nylon gears must use a thinner camshaft timing gear nut to avoid the nut shorting the timer from the timer roller touching it. I think both Lang's and Snyder's include this nut with their nylon gears.

I have a reground cam with a thrust washer kit. That kit requires a cam nut with its fillet removed. When I installed a nylon gear, I had to modify the washer kit and machine the cam nut length.

[Tmooreheadf]

We’ve been running nylon gears on numerous engines with no issue. Both advanced timed and standard. We have run generators and alternators, without issue. I guess a bronze or aluminum gear could last longer. Our current 24 touring car has better than 10k on the last rebuild. The nylon gear looks nearly new. But then again, we run distributors. Don’t know how much drag driving those two gears effects a timing gear if at all. But that’s another topic!

[JTT3]

I’m thinking that since I bought those nylon timing gears years ago (probably 10 years or more) they may be questionable to run so I’ll go with Dan’s bronze ones. Unfortunately of the 5 I have of those, they are all standard not 7.5 gears. I drive quite a bit & at my health/age I’m not looking for any major issues if I’m a hundred miles down the road. Thanks for the feedback & information. Best John

[haydonr]

Appreciate all of the advice.
I wasn't aware that bronze gears with the 7.5 advance were available. When I went looking for an advanced gear to buy, I only came across the nylon ones and to be honest, when shopping from a different country and different time zone, the vendor with the best website and live stock levels normally gets the sale by default. I'm certainly not against supporting other sources for good product, but have found it more difficult to find payment methods that work to individuals in some cases from New Zealand.

Uncertain what to do about this Nylon gear now... appreciate everyone's shared experiences, some good, some not so good... hmmmm

[Dan McEachern]

You can contact me via PM or e-mail thru the forum if you have a problem finding an advanced bronze gear. Dan

[Dan Hatch]

Great thing about Dan’s gears, you can get one gear that will have both 7.5 advance and stock.
Great guy to work with.

[John.Zibell]

John and All : .. we've had a nylon advanced timing cam gear in our ' 26 runabout since the engine was rebuilt 20 or so years ago.. no problems whatsoever

I and a friend of mine had recently made nylon gears have tooth failures as in breaking off. They must have been made better 20 years ago.