The Ford Barn

David in San Antonio · 03-07-2025, 12:34 PM

Jeff/Illinois - A bit of DuckDuckGo rummaging suggests that a balance shaft has been used with great success in 3-cylinder four stroke engines. Interesting (to me, anyway) is that Lanchester (contemporary of Henry Ford) designed engines for their cars with balance shafts to quell vibrations. Flash forward to Porsche bumping the displacement of the four cylinder engine in the 944 in two steps to 3 liters (approx 201 cubic inches, just like our Model A engine) and was frustrated by their inability to tame the rocking couples of a big four. Ultimately they capitulated and licensed the system that Mitsubishi had patented for their 3 liter four cylinder engine utilizing dual counter-rotating balance shafts , one high in the block, the other low, which powered the Starion, (a rebadged version was also sold by Dodge? Plymouth? Some Chrysler label), as a competitor to the Datsun (Nissan) Z car, which used a straight six (inherent first and second moment balance) and the Mazda RX-7 which was the smoothest of all with its Wankel rotary. It didn’t vibrate much but had its own issues.
For what it’s worth, my relatively new “touring spec” A engine (counterbalanced crank, Burtz 6.5:1 head, and Burtz cam, but rebuilt A block, not Burtz block) is harsher, noisier, and shakes hard. The ammeter needle is a blur at idle. It is indeed much stronger, accelerates up long hills in third that used to require second gear, and accelerates from 30-55 mph with alacrity, a proces that had been glacially slow. It is not as sweet as before, though. Presuming the motor mounts are in good shape, it may be that we’re crowding the inherent design limitations of a long-stroke, large displacement four cylinder engine with no harmonic balancer by increasing the compression ratio 50% higher than original spec, compounded by a higher performance cam, both made possible by gasoline with double+ the octane rating available in 1928-31.
On the other hand, some Burtz engine users have not reported increased vibration.
Another Model A Mystery.

03-07-2025, 12:34 PM	#11
David in San Antonio Senior Member Join Date: Sep 2022 Location: San Antonio Texas Posts: 545	Re: Burtz vibrations Jeff/Illinois - A bit of DuckDuckGo rummaging suggests that a balance shaft has been used with great success in 3-cylinder four stroke engines. Interesting (to me, anyway) is that Lanchester (contemporary of Henry Ford) designed engines for their cars with balance shafts to quell vibrations. Flash forward to Porsche bumping the displacement of the four cylinder engine in the 944 in two steps to 3 liters (approx 201 cubic inches, just like our Model A engine) and was frustrated by their inability to tame the rocking couples of a big four. Ultimately they capitulated and licensed the system that Mitsubishi had patented for their 3 liter four cylinder engine utilizing dual counter-rotating balance shafts , one high in the block, the other low, which powered the Starion, (a rebadged version was also sold by Dodge? Plymouth? Some Chrysler label), as a competitor to the Datsun (Nissan) Z car, which used a straight six (inherent first and second moment balance) and the Mazda RX-7 which was the smoothest of all with its Wankel rotary. It didn’t vibrate much but had its own issues. For what it’s worth, my relatively new “touring spec” A engine (counterbalanced crank, Burtz 6.5:1 head, and Burtz cam, but rebuilt A block, not Burtz block) is harsher, noisier, and shakes hard. The ammeter needle is a blur at idle. It is indeed much stronger, accelerates up long hills in third that used to require second gear, and accelerates from 30-55 mph with alacrity, a proces that had been glacially slow. It is not as sweet as before, though. Presuming the motor mounts are in good shape, it may be that we’re crowding the inherent design limitations of a long-stroke, large displacement four cylinder engine with no harmonic balancer by increasing the compression ratio 50% higher than original spec, compounded by a higher performance cam, both made possible by gasoline with double+ the octane rating available in 1928-31. On the other hand, some Burtz engine users have not reported increased vibration. Another Model A Mystery. __________________ David in San Antonio Late ‘30 Deluxe "Wretched Roadster" Alamo A’s Club