The "Sweet Spot"

Discussion Forum
1

I have had my TT now for 3 years. It has always been a runner, but
with a desire to make it go reasonably fast and some gunnysacked rod
bearings, I am on engine incarnation No.3 now. The as-bought original,
a stand-in (while the original was built/rebuilt), and now the original
is back in the truck. After the rebuild, I had a dickens of a time getting
it started, and resultantly, it was not driven much. The build was nice
and tight, and a weak starter made it a PITA to get running. After some
working out of the bugs, I got some drive time on it and the tightness
broke in enough to make it easy enough to crank start and things were
going pretty good.

Then it began “falling out of tune” and I parked it and used my other
truck until I could get a little time to fuss with it. It seemed the timing
was all over the board and once timed, would instantly be back out of time
when I double checked. Turned out, it was a whole slew of problems,
whose symptoms made for a lot of confusion for this neophyte with an
aging bean. Shorted timer wires, a corroded timer from a leaking freeze
plug, oh yeah, and a blown head gasket between No.3 cylinder and a
coolant galley. That whole “cylinder full of water” really makes chasing
an electrical problem hard to deal with.

So, … install the new wiring harness that has been hanging on the wall
for 2 years, a new timer, mill the head and do all that head gasket replacement
stuff, reset the timing for the 800th time, and by golly, … it fired right up !
Now I am fiddling with fine tuning it, hunting for that “sweet spot” I hear
so many old T guys talk about …

It seems to me that if one makes even the slightest change with a Model T
engine, all other factors are now thrown out of synch, and chasing that “sweet
spot” seems on par with chasing a mirage down a hot stretch of desert highway.

Right now, the truck runs really smooth and quiet. But I have to back the
timer off slightly from the top to get it to fire easily (the sweet spot) when I
hand crank.

I know, … long-winded field trip to a basic question, but how do others cut
to the chase and get their T’s to that “sweet spot” where it just purrs, starts
easily, and basically makes a guy like me a very happy T driver ?

2

I have less experience than you, I have had a TT for less than two years. My experiences have been similar.

I want a vehicle that is safe an reliable. I intend to drive regularly on a long term. So, I don’t play when I have a problem. For example, the fuel system. Problems are usually caused by trash inn the fuel line. Start by cleaning the tank and replace everything to the carburetor. I use a fuel pump and filter (I know, heresy), but my TT’s tank is so low that it will cut off from lack of fuel going up hill if the tank is not over 1/4 full. I don’t like backing up hill, the steering is not good going backwards and it is dangerous. I figure if I change the filter every year I will not have any problems with it and my carburetor is protected. A fuel filter makes sense to me, every lawn mower has one, but I am just a newbee.

Ditto for the cooling system, don’t play, don’t take short cuts, do it right.

Ditto for the ignition system, four coils and a timer work great when properly done, and get your coils set up with an ECCT. Then you know they are RIGHT.

Lighting is important for safety. Turn signals, LED lights, generator with a voltage regulator instead of a cut-out, are all necessary. You have to be seen to be safe.

If you want a car to win shows that is another animal. If you want a car for parades, that is another animal. If you want a car for daily driving, you need to not take any shortcuts, set it up right, and run it.

Anyway, that has been my experience.

See, I can run on too!

As far as sweet spot, if you know where to set it to start by handcrank, you have found your sweet spot for starting.

Your sweet spot for driving might be different. My TT likes to run at 15 mph with the ignition at a certain point, not retarded like when she starts. I can tell by engine sound and vibration when she is happy, and that is the sweet spot.

I am still figuring out my speedster. I know her by experimenting her sweet spot for starting. For running it looks like 45 mph is the smoothest running speed. Maybe with more experience I will be comfortable at faster speeds, finding the sweet spot can take time.

1 Like
3

My 26 rpu runs its best at about 30- 35mph. My 27 roadster is still sounding good and pulls good at 40. Some of the guys on the model A clubs cars that have a lot of wear on the engine won’t run more than 35mph. They like to say T models are slower but they are wrong. They run great. Sweet spot seems harder to find on some Ts for sure :wink:

4

Thanks for the responses. I am thinking I did not ask the question
correctly for the answer I am seeking … ?

Let’s say you change your timer, or just want to tweak it a bit to
get it to run sweetly, what process do you go through to dial it in,
fiddle it about, fine tune it ?

As an example, I remove my commutator rod and with the key
turned to battery, advence the timer cover until it buzzes, then
delicately find that razor’s edge where it rests on the quiet side
of buzzing or not. I then bend my rod to fit the new distance
without causing the timer cover to move. In other words, I fiddle
with it until it slides in without budging the timer cover from its
“cusp” position.

Other things I have done is tack weld the control arm at the column
to remove slop there. I also did some creative weldingon the rod
itself to make it hold both ends without slop.

But what I seem to always be chasing is that easy running, easy
starting, perky “sweet spot” where the engine just acts spunky and
happy to git up and go. I may get it for a while, but it fades, and
pretty soon I am having to go chase the dragon again.

Looking for epic ideas of utter brilliance to make this old dog of
mine purr without a bunch of blind fussing about.

5

So, yesterday was our weekly “shop night” at The Ranch. These days,
it is my weekly excuse to drive the old dog. Work is just too busy to
take a day and go driving. So, I cut off early from work (1700hrs, … I
usually work till around 1900hrs) and head to the shop to swap rigs.

Last time I drove it, I needed to pull the timing lever down a skotsch
to get it to start, … timing rod too long and over-retarding. But upon
trying that again, it gave me a fight, so I took the time to reset the
timing and adjust the rod. It still is not starting super easy, like it has
in the past, but HOLY-MOLY ! … does it go like a striped ape ! There is
a tough hill for me to pull between town and home and it is the “test”
for how this thing is powering up. Used to be I was on the low pedal
half way to the top. As things got fixed and rebuilt, that low pedal
moment has inched to the top and to a point where I do not need it,
although I am getting down to a speed near where I would need to
put my foot down. This time I flew up the hill and actually had to
throttle back to keep from getting up on two wheels in the corners !

Had it out again for a quick run tonight and again, it performed with
power like it has never shown before. On the flat, I broke 40 and minor
hills were barely noticeable. I seem to have found the power curve.
Not sure what I did, or if I can repeat it. Now, to get that easy start
or free starts …

6

When I started messing with T’s a local guy who belongs to a T club contacted me and offered help if I had any questions. He has saved me an enormous amount of time, aggravation, and money by answering my simple questions. He test drove my TT after I got it running. He told me what I needed to do and still answers questions when I call him, which is sometimes once a week. The problem is that when you start out you don’t know what is normal or what obviously (to someone experienced) needs adjusting. You need to find someone in your area like that to give you a little guidance. If you can get someone knowledgeable to drive your TT they could give you a lot of insight.

It is probably worth your time to try this: http://www.dauntlessgeezer.com/DG97.html

7

That’s great advice, and something I am well connected on. I
live near, and regularly converse with the guys at the Antique
Auto Ranch. But I still like to reach out and get a wider spread
of ideas.

Another reason for the post was to spur conversation to help
build up more participation on this site. I am sure there are
plenty of other T owners that might find discussion about chasing
the “sweet spot” useful and interesting.

8

OK, you got me. Remind me not to respond to your future posts as if you are serious.

9

Well, I am serious. If you (or anyone else) has methods for
dialing in a T to run and start at that “sweet spot”, I (and probably
others) would love to hear your thoughts. Afterall, sharing stuff
like this is what makes a good forum, right ?

10

The next tech article will be “How to set timing on your Model T Ford”

11

Sounds great. I hope you will share insights on going beyond
simple timing to include finding that “sweet spot”. Thanks.

12

Trying to get in as much driving time as the waning days of decent
weather dwindle down. Took the old dog to the Tuesday night shop
gathering at the Ranch with the intention of trimming brush and
trees in the wrecking yard, but felt the truck was not running right
and thought I’d do a quick timer adjustment before going out back
with my pruning tools. One thing led to another and I never did anything
but work on the truck for the rest of the night. Doing the usual
positioning of the crank to TDC to set my timing, I rolled the timer
around to get buzz at the coil/s and backed it off. The buzz went
into a cat-n-mouse game of being there, then not being there, to
vanishing altogether. This has been frustrating problem several times
now this season. The coil box is rebuilt and solid/tight, the coils
rebuilt and testing excellent, yet the buzz disappears and then re-
appears in a completely different adjustment. I know what everyone
is saying … must be a carburator problem ! :laughing:

Stormo suggested I build up my coil contacts with a little solder, so
we gave that a whirl. I may never get those coils back out of that
box, they are so tight now. The old dog has started and run reliably
since, but I feel it is dogged, … like I need to find that “sweet spot”
again. Two weeks ago it was pounding up hills effortlessly and really
spunky. Now, it is solid and reliable, but lacks the power it had before.

Not sure how to dial this in.

13

You mention intermittent coils don’t buzz as the problem - if that is the case here is an easy way to find out where those problems are coming from.

Connect a jumper wire to a grounding point on the engine. I use one of the nuts on the manifold clamps. With the key turned to “BAT” position the engine so that no coils are buzzing. Then touch each of the coil box upper contacts (yellow arrows) with the jumper.

If you don’t get a buzz from one or more of the coils then your troubles are within the coil box, or related to the coil itself.

If you do get a buzz from each of the coils then your troubles are either the timer or the wiring from the timer to the coil box.

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14

As mentioned, we felt there might be some wiggle room on the coil
contacts and added a little solder pool, filing them flat to get max contact.
That seems to be working. The truck fires right up and runs well, …
just not with the power it can have. But I may never get those coils back
out of the box !!!

Still, with the timing feeling really right, as it responds on the lever
quadrant, that spunky, powerful “sweet spot” is just not there.

Here is what I am driving at … only been doing this T thing for 3
years. Whatever I do in life, I like to master it and not feel like I am
facing “black holes” of mystery that might leave me stranded. I’d
like to learn whatever process those more wise in T stuff do to dial
in that sweet spot.