block to use for engine build A or B

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Duffy1

Well-known member
I am thinking about building an engine for my 31 s/w . The build would include CB crank , inserts on rods and mains , keep original rear main seal system , upgrade valve train/cam ,h c heads,. Which block would be the best to use A or B block as it relates to performance and durability. Responses appreciated . Thanks
 
Lots of opinions on that question. Each has advantages. The primary B advantage is pressure oil to the mains which may be preferable if you are going with inserts and annular grooves in the mains. (Another point of controversy.) The A has thicker casting on the top, some (me included) say it is less suseptible to cracking.
But as with any modification, it depends on the intended use. Modifications should be part of an overall system, each modification complimenting the other. You dont say what "upgrades" you intend for the valve train/cam, how high the compression, carburation, flywheel, etc. With all due respect, it sounds like you are just plugging in ideas you have heard without considering the overall picture. For general touring I don't think it would make much difference which you used. My incination would be to stay with the stock A block in your car unless you are going to get radical. Then everything is on the table and is a whole different discussion.
 
If I had it to do, I would put a B crank counterweighted into an A block. This possible but you have to relieve the areas where the B rods are close to the pan gasket flange/dipper issues.

I'm still not sure about whether I would do bearing inserts and pressure oil since this requires drilling the crank. But a 500 mile oil change frequency could be stretched out to 3K mile frequency more like a modern car - and the engine will probably last longer to boot.

Someday maybe...

Joe K
 
Thanks for the responses Gentlemen ; I am not building a racing engine . Just want a durable touring engine . Will keep stock carburation . Have lightened fly wheel ,v8 clutch ,over drive ,16 in wheels . Sounds like the A block is more robust than the B block .
 
With the heavier,stiffer crank of the B and the 3/8" larger brgs,you will not need to adjust the brgs near as often as the A crank,especialy with the 33 & later CB crank.Both my A,s have 33 B,s & I like them.One of them is still running the original babbitt.I change the oil every 1,000 miles-no filter.
 
my touring engine is an A block, the original engine from my car. It has a counterweighted crank, Stipe cam, B police head, insert bearings and larger intake valves. It also has 40,000 miles on it since being built and runs as smooth as a sewing machine. It has been a good touring engine. At 15K miles, I had the pan off and checked the bearings. They looked so good I put 'em back in. BTW, the oil is full flow filtered. I think the filter makes a huge difference in longevity.
 
Duffy1 said:
Thanks for the responses Gentlemen ; I am not building a racing engine . Just want a durable touring engine . Will keep stock carburation . Have lightened fly wheel ,v8 clutch ,over drive ,16 in wheels . Sounds like the A block is more robust than the B block .
Click to expand...

This true and where I would head with what I described.

The same sort of mod is usually put to Model T engines, EXCEPT they use an A crank in the T block.

And the result is an engine with a little more durability.

Joe K
 
For what you are going to spend, I think it would be cheaper and better to ge a touring block from Antique Engineering out side of Chicago. Everything is done very well. Five people in out club have them now and everyone is happy with them, and you can't beat the price.
 
bill44 ;

Totally agree with you . If I were going to buy an engine I would most likely get one from Antique Engineering . We have some folks in our club running them with no problems. But I need something to keep me busy. I would like to restore a model A but do not have room in my garage for another model A . My wife thinks one model A is enough .So I am thinking about building an engine. Thanks for the response .
 
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