The photo shows our "Cam Project Tudor" running on a chassis dyno in Oklahoma City. Over the years we have collected data from several dyno runs when we have investigated the effect of cams and heads on performance. Most of the data is in a spreadsheet which can be downloaded. The spreadsheet contains the full power and torque curves, while the basic data is summarized in the table below. Since this data is from a chassis dyno, the values correspond to those at the rear wheels and excludes drive train friction losses. We believe drive train friction losses are approximately 20 percent. For comparison, the Ford 1918 engine dyno data is included, but the values are reduced by 20 percent to account for friction losses.
We used three dynos in our tests: a commercial Dynojet in Tulsa, a commercial Mustang Dyno in Oklahoma City, and our "Cheapo Dyno" which can be downloaded. The tabulated values are from the commercial dynos. The Dynojet and Cheapo dyno were in fair agreed (see cam pages on Dyno Results), but the Mustang Dyno did not agree. The Mustang dyno data (the Sept. 2002 data) was "corrected" to make it consistent with the other two.
These dynos were designed for engines making considerably more power. One horsepower is 5 percent for a Model T, but less than 0.5 percent for a modern engine. We suspect that differences of less than 1 horsepower or 4 ft-lb are probably not significant. Be especially cautious when comparing numbers from the two different dynos (Sept. 2002 versus the others). Just remember your mileage may vary
We believe this data gives a general picture of the effect of cams and high compression heads. For a stock T engine a reground cam can cost you 10 to 15 percent of torque with little or no benefit in peak horsepower. A new Stipe cam is very close in performance to a new stock cam (no wear). A high compression head can give a 25 to 30 percent increase in torque and 40 to 45 percent increase in peak horsepower. Limited testing with a distributor versus vibrator coils gave a small increase in power and torque. We have done no testing of carburetors. To get a better idea of what this data means in terms of performance, check out the Power, Torque and Model T Peformance page.
We have also been present for the "Dyno Day" at the Speedster Reunions held in Lincoln, NE in 2009 and 2011. This data was taken with a Mustang Dyno. We have much less confidence in this data, because there was so much scatter in the data. For example, the torque for a flathead Model T varied wildly from 0 to 100 ft-lb. Also, one engine was run both years with improvements made for 2011, but the dyno showed a loss of power. We could only make sense of the data by fitting a smooth curve to it. Some scatter is normal and smoothing is often required, but for this dyno the problem was substantial. We report the data since it is the only data we have seen for OHV engines.
OHV heads obviously make more power, but they do not appear to make appreciably more torque. The main benefit appears to be that the torque is maintained to higher engine speeds due to higher compression and better breathing. This is something to consider when you set up the gearing for your Model T, especially if it never gets beyond 2000 RPM (50 mph with standard gears or 60 mph with 3:1 gears).