Re: Engine rebuild advice wanted

Posted by Bob Carabbio on July 04, 1997 at 14:16:04

In Reply to: Engine rebuild advice wanted
posted by Steve Watrous on June 30, 1997 at 08:55:10

I think the clue to modifications is as follows:
Where did Ford go from 1928-
1932 - Larger mains - low pressure oil feed to the mains - 4.8:1 compression ratio(up from 4.2)- bigger carbureter venturi.
1933-counterbalanced crank - lightened flywheel
In the Volkswagen world, the engine of choice is the 1600cc Dual port with "Dog House" oil cooler. This is the last iteration of the venerable flat four with vertical fan, and is the most powerful, smoothest, and least likely to "Eat" valves that VW built before stopping the development.
The '34 "B" engine is the last of the out and out "A" type motors that Ford did (there were later 4 cylinder units, but they where of a different breed), and embodies everything that he learned up to that point."B" engines are unfortunately susceptable to deck cracking in the cylinder bore to valve seat areas.
The problem with the stock "A" crank is that it "whips" from end to end due to the unbalanced weight of the two center rods/pistons.This takes out the center main bearing.The whipping gets worse as engine speed increases. NO amount of balancing can compensate for the flexure of the crank.Counterweighting does a lot for crankshaft whip, and reduced engine vibration transmitted to the car. Ford removed the weight from the flywheel that was added to the crankshaft - dropping the '33 flywheel to 39 pounds from the original 62.5#.
Parenthetically, a four cylinder engine CAN'T be balanced perfectly by counterweighting since there's a fairly strong imbalance due to the accel, and decel of the pistons that comes in as a vertically oriented vibration at 2X engine rotation frequency.The "Silent Shafts" that all the modern four cylinder cars are using which are two counter-rotating eccentric shafts at twice crank speed are there to cancel that vibration.
Ron Kelly of Dallas has some insight on "A" performance in his publication at http://members.aol.com/gmaclaren/dyno.htm

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