RPM

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration
Model T Ford Forum: Forum 2005: RPM
Top of pagePrevious messageNext messageBottom of page Link to this message  By john curry on Friday, March 14, 2008 - 11:10 pm:

ok, what limits the top rpm on the t engine? we have been doing lots of driving and by the charts and mph it appears to me most of the engines are topping out about 1700 rpm.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glen Chaffin on Friday, March 14, 2008 - 11:28 pm:

John, The stock model T camshaft with 0.015 In valve lash and most of the regrinds and new cams reach maxamum torque and horse power at about 1750 RPM. The torque and horse power then starts to drop off from there. The amount of drop off and rate of decline is determined by the cam grind. The new cams available (Stipe and Chaffin) and the Driver regrind drop off slower and have slightly higher torque and horse power at 2000 RPM (and higher) than the stock Ford cam.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Barker on Saturday, March 15, 2008 - 10:42 am:

..... and they can't breath. You have a 2.9 litre engine with a carb venturi that you can't get your finger through. Just can't get enough air. I'm guessing that the venturi is no more than 5/8" which is an area of 0.3 sq in. My 1.725 litre Sunbeam Alpine has two 150CD carbs with venturis of about 1.3" - total area 2.65 sq in. Nine times the inlet area but 60% of the size.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jem Bowkett on Saturday, March 15, 2008 - 12:41 pm:

Ford always ensured you couldn't blow his engines up by restricting the breathing, both on the inlet and exhaust sides. Ultimate speed freaks with both 4 banger and V8 engines have been known to regrind the cam to swap inlet for exhaust ports and so run 4 carbs.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Saturday, March 15, 2008 - 06:27 pm:

Jem
Why regrind the camshaft. Just swap the crown gear to the other side and run it backwards. Ok you would also have to make a new crank ratchet to start it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By john curry on Sunday, March 16, 2008 - 10:11 am:

above, i wouldn't bet that my t engine would rev to or past 1700 rpm, with out a tach. other engines i have worked on would still increase rpm past the max hp point. the t seems to almost get up to its max hp. the posts about the lack of breathing capicity make sence. thanks for the responses. john


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Sunday, March 16, 2008 - 10:30 am:

The 3.63 rearend, 40 rpm/mph, was chosen to maximize the top speed of the car, which is 40 mph at 1600 rpm. Change to 3:1 gears or 4:1 gears without modifying the engine, and you will have a lower top speed.

Modify the engine, and you will want to change the rearend ratio to maximize the top speed.

This chart was posted before by another T-er.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel Denis Chicoine, MD on Sunday, March 16, 2008 - 01:51 pm:

I've got lots of throttle movement left but no change in speed from about 45 mph. With a slight tail wind, top down, and open windshield I have hit 52mph. I've got stock 3.63 Ruckstell gearing, a stock touring body,.280 cam, and a Z head. From anyone's experience, will I be able to take short runs on the interstate (45mph minimum speed) if I change carbs to a Stromberg or Schebler FA?
Noel


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel Keefer on Monday, March 17, 2008 - 12:55 am:

Noel C,
I have shaved an 1/8" or so from my low head. I can easily run at 45 MPH with a little throttle remaining in my '14 Touring with all else stock.
Noel K


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Harrison on Tuesday, March 18, 2008 - 12:12 am:

Noel Chicoine, I would think you should be able to run faster than 45 MPH, or at least run up to 50 MPH without a problem. I have a 27 Coupe with stock gearing, 280 Stipe cam,Z head, high volume intake and a hump back NH carb, stock exhaust, stock coils and timer. The block has been milled a little. It can easily run 45 MPH. I have had it up to 52 MPH on flat ground and it is still winding up. I don't like the RPM, so I have not taken past about 52 MPH. I would make sure you are getting enough fuel, etc. Mine will start to miss a little at about 50 MPH, I believe this is because the stock timer can't stay up with the RPM.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Carl Sorenson on Tuesday, March 18, 2008 - 11:59 am:

I remember talking to one of the racers that run in the Montana 500...Garret Green from Orange Co.Calif.............He had(has)a tach. on his 27 touring......He placed a plastic coffee cup over the gauge head,,,,,He said "it scared me when I saw the RPM I was tunin'"............Maybe he could comment on this thread if he's out there......He is very savey in this area,that touring he drives run like a "pocket watch".............Carl


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Sacchi on Tuesday, March 18, 2008 - 12:48 pm:

Noel,

This may sound silly, but do you drive with the top up mostly? I have noticed that I can add at least 5 MPH to my speed by simply putting the top down. It acts like a big parachute, slowing you down!

Of course if it rains, you need to put the top up, but under those conditions you should be driving slower, anyway ;)

Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel Denis Chicoine, MD on Tuesday, March 18, 2008 - 01:07 pm:

I don't have a high volume intake, and wonder if I'm just not getting enough air to the engine with the stock NH and stock intake. With the top up, I can't hit much over 45. It drives in town up to 35 with passengers easily.
Noel


Top of pagePrevious messageNext messageBottom of page Link to this message  By EDWARD R LEVY on Tuesday, March 18, 2008 - 01:34 pm:

My guess is that in 1908 the notion of counterbalanced crankshafts was either new or non-existant. I might be wrong but the counterbalanced crank would seem to be a major factor in reaching higher rpm's without the engine self destructing. It's my understanding that a new crank which is on the market is counterbalanced and of course accesorie bolt on weights are also available. Many folks feel these bolt on weights are the way to go both in terms of smoother running engines & higher rpms. I assume the debate on this subject remains alive!!!
Edward R. Levy


Posting is currently disabled in this topic. Contact your discussion moderator for more information.
Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration