Re: Insert bearings

Posted by Bob Carabbio on November 07, 1997 at 18:59:22

In Reply to: Insert bearings
posted by Bill Pursel on November 07, 1997 at 17:19:11

The real problem with "A" engines is the one that Henry got around to fixing in '33.That is - the crankshaft whips - that is the crankshaft bends into a bow with the two middle cylinders and the center main trying to rotate around a different center than the center main provides. This effect increases as the square of the RPMs.
The pervasive vibration that "A" engines have is related to this.
As Mike Flanagan says, if you want to go 45 max all day long The stock "A" will do it nicely, the only addition I'd suggest would be Full Flow Oil Filtering, unless you don't mind changing the oil OFTEN.
If you want MORE RPMs or just smoother running, then the first steps are to counterbalance the crank to get away from the whip problem, and lighten the flywheel.
Insert bearings are only TOTALLY necessary if you want to increase the compression ratio for more performance.HOWEVER
in the Dallas area there's nobody that can do an acceptable job with babbit anymore - so the engine has to be sent somewhere to get done - AND it turns out that the cost for re-machining the block and rods for inserts is the same as babbiting with some extra cost for the inserts themselves.
The cost for an inserted motor isn't necessarily all that much different than a babbited one (at least using Pete's Machine in Albequerque as a source).about $2500 - 2700 seems ballparkey for a COMPLETE rebuild with inserts.
Other than cost which appears to be more of an issue other places, I haven't heard of a downside to inserts.There's some controversy about full-pressure lubrication though.
Nowadays it's generally felt that it's a lousey idea to drill the crank for rod lubrication since the dippers do just fine, and the crank is substantially weakened by the drilling procedure.Pressure fed mains are generally used in this area, although often it's just done by inserting pieces of 1/4" copper tubing down the feed pipe, connecting them together, and feeding them from the oil outlet pipe that normally dumps into the front of the valve chamber.
The tubing isn't sealed into the feed pipes, just allowed to leak back into the valve chamber which isn't really pressure feed, but better than the old gravity flow.It's pretty close to the model "B" method though and is reportedly successful.
Bob Carabbio

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