MTFCA Forum

What is the maximum RPM is a Model T Ford coil and timer ignition is designed?

Those wishing for for performance change from the factory timer to an aftermarket ignition.

What is the RPM limit for the Model T timer?

At 40 MPH the motor is at 1600 rpm.

Probably outside of the operating parameters for the timer I suppose but the coils should have no problem. I used an ECCT to set up my coils. I should ramp up the RPMs simulation and see.

I don’t know the maximum, but my “16” touring with a ‘26 engine will run up to just over 50 on the straight and level, with cast iron pistons, stock low head, ford timer, brass top coils, and stock ring and pinion. I don’t think that I’ve ever hit 55 without heading downhill or catching a tailwind…

Keep crankin’
Eric

PS, this engine was (re)built before 1965 by a guy that my dad bought the car from (Dad doesn’t remember his name), so this engine doesn’t have any of the typical performance bits that are common today.

I went all in on my rebuild of my 15 runabout engine. Prus head, Scat crank, new forged rods, aluminum pistons and a Chaffin’s 280 cam. It really wants to go. I don’t particularly like to drive very fast but want to know I can if I need to catch up. All I wanted was a car that would drive at 30 or 35 mile an hour comfortably. If I could just get rid of that stupid miss at 40 mph. I’m banking on the timer but it’s probably getting Time to check valve adjustment to.

A stock T engine in good order with aluminum pistons will run very comfortabley at 30 to 35 MPH. A balanced stock engine can do 40 or more under most conditions will a little power to spare. A hot cam can actually reduce performance and driveability at lower speeds. Over 40 MPH, aero drag really starts to kick in, and a headwind can be a nuisance. Due to drag, it takes a lot more power to get a little more speed once you get over 35 to 40 mph. Driving into a headwind on a level road will demonstrate this very convincingly. In my opinion, aluminum pistons, raising compression, and balancing yield good returns in performance without sacrificing driveability. If you can afford a Scat crank, so much the better. I would think a Scat crank in an otherwise stock engine with a good auxilliary oiler would allow 2000 RPM with pretty good reliability. Beyond that, you probably need full pressure lubrication and very careful balancing. The T's cooling ability is pretty limited, too.

the timer turns at 1/2 the speed of the crankshaft. In good condition, it can run 55 MPH just fine as is evidenced by the MT500 folks.

PS: Did you install new valve springs? You may need stronger than stock springs to run fast with the performance cam. Also, higher compression places more demand on the ignition system, so it needs to be in good order. Plug gap may become critical. You need to be able to get full spark advance at higher speeds, too. The entire ignition system needs to be in top condition, and the spark control linkage needs to be working correctly.

Someone mentioned a new timer needs work, I agree, some roller timers I purchased did!
We all go to great lengths to set the timing cover concentric with the Camshaft and the outer cover of the timer (unpainted)
and sitting nicely in the timing cover recess. This doesn’t mean the 4 segments inside are concentric with the outer.
I have had to give the internals a very light cut with the Lathe to get them true to the outer case.

It wasn’t an Engine miss that brought this to my attention but the unusual wear noticed when servicing it after 6 months
of use. I also noticed a portion of the Roller wasn’t in contact with the segments and had to move the roller assembly forward
to gain full contact.
Alan in Western Australia

There are some that talk of a very well tuned STOCK T running 55-60 . . .

babychadwick wrote: ↑

Sat Aug 21, 2021 9:21 pm

There are some that talk of a very well tuned STOCK T running 55-60 . . .

Not just talk, most every year since 1961, for four days in Montana, a group of drivers prove that this is more than just possible…

https://mt500.info/index.php/category/results/

Reading the rules, one might find that all of these cars are more stock than plenty of cars that we consider to be “original”.

Eric

Very well said Eric and I was talking with my uncle about it not too long ago. Maybe when I have time and a shop you will see me up there. Well by that time it may be my son and not me . . .

Thank you guys for all the input. I just really want a car that would pull hills well and drive very nicely at 25 to 35 mph. I think I hit it right on the head. I have another post going that has some of the guys really wound up. I’m not trying to drive at Montana 500 speeds by no means just trying to get the old girl broke in. I’ve probably got about 100 miles on the engine and even though I am trying to baby it’s somewhat I like to goose it a little bit and help sheet the rings in. I’ve always heard it was hard on a new engine to run it easy and at a constant RPM and that you should vary the RPMs and load up the rings a little bit. I’m sure as heck don’t wanna hurt it. This is been a great project for me. I’ve done all the work myself including pouring my own babbitt. I’ve been a machinist for a long time and this was one heck of a good learning experience.

You are doing great, don't let people get you down.

Having read the build details in another thread, I think you're going to have an outstanding engine that in the end, will do everything you want it to do.

Sometimes I’m still a little young (foolish) at heart. And even as we get older we do foolish things from time to time. There isn’t a member on this forum that has never ‘goosed’ it a little is some car. Ha ha.
Thanks again so much for the advice.

Back in the 1970s and early 1980s, when we could buy real gasoline, MOST stock model Ts (even sedans!) could do at least 45 mph. Many runabout and touring car owners often ran close to fifty miles per hour. As long as your timer is good, smooth and properly concentric and centered with the camshaft, and the coils are good and properly adjusted, no stockish model T is going to outrun the timer and coil ignition.
I once heard of a Rajo OHV engine that was run up to 2400 rpm with timer and coils. I don't recall who it was.

You may want to check things over very closely? But unless there is something seriously off in either the timer or coils? I don't think the ignition is your 40 mph miss.
The one thing you may want to look at very closely? Is the timer roller. If it is well worn, or the spring is weak? Or not properly in line with the timer itself (I had one once that the roller was from an after-market Milwaukee timer that had a front-to-back position a quarter inch off from Ford and Tiger timers!)? It could cause troubles.

greenacres36 wrote: ↑

Sat Aug 21, 2021 10:12 pm

Thank you guys for all the input. I just really want a car that would pull hills well and drive very nicely at 25 to 35 mph. I think I hit it right on the head. I have another post going that has some of the guys really wound up. I’m not trying to drive at Montana 500 speeds by no means just trying to get the old girl broke in. I’ve probably got about 100 miles on the engine and even though I am trying to baby it’s somewhat I like to goose it a little bit and help sheet the rings in. I’ve always heard it was hard on a new engine to run it easy and at a constant RPM and that you should vary the RPMs and load up the rings a little bit. I’m sure as heck don’t wanna hurt it. This is been a great project for me. I’ve done all the work myself including pouring my own babbitt. I’ve been a machinist for a long time and this was one heck of a good learning experience.

You are going about "breaking in" the engine the right way. Years ago when I was spinning wrenches for a living, an old guy in our shop told me that the best way to break in an engine is to warm it up to normal operating temperature then accelerate until you are in high gear (not overdrive); then accelerate briskly to highway speed (in a T I would say 40 mph) then repeat the process. Do this ten times in a row and you now have a broken in engine. I have never rebuilt a T engine and do not intend to, but I have put together numerous modern engines and I have always used that method. I have never had a comeback on an engine to which I have done any major work .
BTW: Airplane piston engine manufacturers do not want sustained operation at low power settings when the engine is new. Louise Sacchi made her living delivering new Beechcraft to Europe from Wichita. She would not head out across the pond until the engine had 50 hours at high power settings on it.
Don't baby a new or rebuilt engine, but don't flog it either.

I think the reason for speeding up the engine is to get the oil to splash up into the rings and wrist pins, however slowing down soon after speeding up keeps the tight engine from overheating which would score the cylinders and possibly cause a seize up. The warm up in advance is so that the strain on the engine will be made at the normal operating temperature and the oil is well circulated before putting on strain.
Norm

Actually my miss turned 49 yesterday. I kinda forgot somewhat. To add a little humor here.

Good one Brian!
Love the humour!
Alan in Western Australia