High Compression performance

updraught

updraught

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85.7 mph! Yikes. :eek:
Not long after I put a 5.5 head on my tourer, I asked a friend to drive it and give me his opinion as I hadn't driven any other Model A before at that stage. When he came back, he couldn't believe what the car did so he put one on his roadster. He went to his favourite test hill where he knew he had to change down to 2nd gear at a certain point. When he went over the top in 3rd gear, he became the best advertisement for the HC heads around here!!
A little extra compression certainly gives more low end grunt.
 
I too am interested in a high compression head. My car runs very well however I do shift down on some of the hills around here. The problem I have with a high compression head is bearing life. If the car has more pull then there is a heaver load on the splash lubricated bearings. What effect does the extra load have on the bearings? Does anybody have 25k + miles on a high compression head with stock lubrication that can answer this Question?Buy the way, 85.7 miles per hour is a little fast for my car.
 
85 MPH with fenders! I bet that motor was screaming to move that much air and her steering must have been fairly light.

Kimlinh, as far as the bearings and splash oil system go I have 10K trouble free miles on mine. I would not worry to much about that but if want you can run a line right from the pump to the center main. Since that is one that seems to go first, especially on a stock crank.

Mike
 
Lots and lots of folks have high compression heads on an otherwise stock Model A engine, with no ill effects on the bearings. The biggest issue and danger is running a HC head with too much spark advance.....that will cause damage to the bearings. I would think if you limit HC to 5.5 or 6.0, prudent use of the spark control will ensure no problems. That assumes, of course, that the bearings are not already worn or sloppy.
 
I always recommend adding a counterweighted crank to the engine, no matter what head is used or any other mods. That was one mistake in the Model A, to not use counterweights. For the slower speeds and roads of the day, the A was OK, but with better roads and more speed, I'd want a higher compression head, counterweighted crank, and a 3.27 ring and pinion. Those 3 mods should make anyone happy on faster drives, which everyone seems to do these days.

With newer cars and freeway speeds, many people are out of control. Don't believe me.........just drive through Chicago, even in the middle of the night. :eek::eek:
 
Higher compression and a bigger carb are the 2 quickest and easiest ways to better performance, and believe it or don't, better gas mileage. The Model A has more bearing area than the 216/235 Chevy, which were also babbitt, no problems.
 
We've had same experience as in posts #3 and 5 with bearing load due to advanced timing with out of the box FS zipper ignition. Some say no ill effects but it may be preferable to have the ability to control the spark manually on hills.
 
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