Model B engine advantages?

bdave_mcc

bdave_mcc

Senior Member
I have seen some comments on people desiring a Model B engine over the A. My question is, what are the advantages, if any, of having a B block over an A block. I'm saving for an inserted, counterbalanced engine that will run a high comp head, performance cam, etc. I will be looking for a block or engine for rebuild or core, locally, I have seen a couple B engines come up for sale in the last few months. Just wondered if its worth the extra cash for having the B block. I know the STOCK B outperforms the STOCK A, but, My assumption is the A would perform as well as the B if built correctly. Thoughts? thanks in advance.
 
In this day & time, I do not think there is an advantage.

Many of the benefits that 'B' aficionados claim that makes a 'B' superior is no longer the case in my view. Some claim the 'B' crank is stronger however with new counterweighted crankshafts available for the 'A' engine, that obsoletes the Model-B's advantage. It used to be that the 'B' camshaft was better however with new Stipe cams available now, that surpasses the specs that the 'B' cam had to offer. Also, the 'B' head used to offer higher compression than the stock 'A' head but with commercially available hi-compression heads now, that is also out the window.

The downside to a 'B' engine IMHO is they are more susceptible to cracks when compared to the 'A' engine, so my vote is there really is not any difference now. The ONLY advantage I can see is there is a fuel pump boss to mount when someone feels the need for downdraft carburetion.
 
If you truely want to know, cal H&H Flathead in California. They build both from stock to Bonneville record holders. I am sure they would know the answer to your question.
 
B engine cores usually cost several times more than an A core engine and usually end up having cracks in the valve seats.
 
The B has 1.5" ports and the A has 1.375" ports. The A ports can be enlarged to 1.5" but it gets dicey to open the B ports much.
 
FWIW, humble opinion:

Just in one (1) specific area of use, years ago, B's were very much preferred for "marine" engine conversion "mainly" because of the added "fuel pumps" whereby:

1. Heavy "larger" gas tanks could be moved to the lower rear of the hull to increase speed for "planning" hulls traveling at about a 15 degree angle -- for slower, (under 15 mph displacement hulls traveling almost level), it made little difference for speed as to where the larger gas tank was located.

2. For all pleasure & work boats, with B engine "fuel pumps", larger, heavier gas tanks could be placed lower which made for a better center of gravity in waves because tanks did not have to placed "up high" for obtaining gravity flow.

But like Mr. Brent intimates, today one can buy an A engine, install an electric fuel pump, high compression head with a B cam, get a counter-weighted crank with a lightened flywheel, etc., etc. whereby it really would not make much difference.

Just one (1) experience from the past.
 
the B crank has larger bearings and a better oiling system. I've been running them since the 50's with no problems. more susceptible to cracks? maybe but as long as you don't overheat them they are fine. you maybe buy my book on building them for performance.
 
According to a article written by George Riley in 1937, he states if you plan on Port and Relieve do not use a "B" block use a "A" block. George must have recognized the thinner casting of the "B" block ?

As others have said, there are no advantages to using a "B" block these days except to spend more money for a "B" block. Just my opinion.

Ron
 
bdave_mcc said:
I have seen some comments on people desiring a Model B engine over the A. My question is, what are the advantages, if any, of having a B block over an A block. I'm saving for an inserted, counterbalanced engine that will run a high comp head, performance cam, etc. I will be looking for a block or engine for rebuild or core, locally, I have seen a couple B engines come up for sale in the last few months. Just wondered if its worth the extra cash for having the B block. I know the STOCK B outperforms the STOCK A, but, My assumption is the A would perform as well as the B if built correctly. Thoughts? thanks in advance.
Click to expand...

Hey Dave,
You asked of the 'advantages of B BLOCK over an A BLOCK.
Most of what you got, tout what you CAN do with the A block to enhance it.
Well, yeah, you can put dual overhead cam/girdle, etc, etc...to improve an A..if you've got the money:)! IMO, you start out with good A/B blocks, It IS going to cost you more $ to 'improve performance ...in the A block...just to catch up to what Henry did to improve to the B block, i.e.-stronger crank..larger rods/mains; oil system pressure to mains; crank already balanced (factory);bigger valves (factory); better cam (factory); better head..well you get the idea.
Now , if as suggested, you want to 'improve' the A block (or B block), my first action would be to get hold of Jim B book, which is a very good guideline to build it correctly.
Another way to answer your own question, is to make a list to keep track of what it will/would cost to do EACH 'thing' to a good A/B block..see what you think. Let us know what your research reveals,eh:D
 
hardtimes said:
Hey Dave,
You asked of the 'advantages of B BLOCK over an A BLOCK.
Most of what you got, tout what you CAN do with the A block to enhance it.
Well, yeah, you can put dual overhead cam/girdle, etc, etc...to improve an A..if you've got the money:)! IMO, you start out with good A/B blocks, It IS going to cost you more $ to 'improve performance ...in the A block...just to catch up to what Henry did to improve to the B block, i.e.-stronger crank..larger rods/mains; oil system pressure to mains; crank already balanced (factory);bigger valves (factory); better cam (factory); better head..well you get the idea.
Now , if as suggested, you want to 'improve' the A block (or B block), my first action would be to get hold of Jim B book, which is a very good guideline to build it correctly.
Another way to answer your own question, is to make a list to keep track of what it will/would cost to do EACH 'thing' to a good A/B block..see what you think. Let us know what your research reveals,eh:D
Click to expand...


To keep all the information factual, please allow me to address a couple of your statements;

First off, I believe we will find that all of the Model-A cranks were balanced from the factory too just as the Model-B's were.

Both the Model-A engine and the Model-B engine have the same sized valves (1.500"). I will say that while the 'B' ports are indeed larger, it is generally considered risky to enlarge the 'B' seats to 1.750 in a 'B' block simply because that casting area is already thin. This is not the case with an 'A' block.

While the Model-B camshaft was improved slightly over the Model-A camshaft, most Model-B cams likely have wear, AND neither camshaft will perform nearly as well as what the new Stipe camshaft will.

The Model-B head has only a slight amount of compression difference over the 'A', and since the water pump mounts are different requiring a different type of pump (which does not fit without modification), the point is really moot.


Generally speaking, I see good Model-B engine cores selling for above $750.00. From my point of view, by the time someone factors in the avg. cost of a Model-A core and use the difference to purchase both the Stipe Cam and a high compression Snyder head. At that point alone the $$ will be nearly the same and the performance of the Model-A will be superior.
 
Yeah I know what you are talking about hardtimes!...that's why I want to make sure I do it ONCE and do it RIGHT. Another question though...is the B oil system better stock, than an A that has been pressurized? Or does pressurizing the A yield the same results as a stock B?

Also, Jim would you please PM me with information about getting a hold of your book?
 
I do want to get a good book to read up on. But from what I'm gathering any advantage of the B block, with the exception of the fuel pump, can be built into an A. I already planned on getting a counterbalanced crank...new camshaft, and head, anyway.
 
I think the B crank is an advantage...not because of the available counterweighted version but simply because of larger diameter, which surely makes it a bit stiffer.
Small diameter cranks, especially forged ones, are apparently quite elastic and suffer from erratic (changes with speed and various internal dynamics) problems in timing because crank position varies in relation to cam functions.
Cracks?? There do seem to be a lot of running B engines around, especially when you note that B production was a tiny fraction of Model A production.
 
I think that the 1932 B crank that wasn't counter balanced would be a good choice for a hot A engine with a few mods to the mains. It would have better throttle response and quicker acceleration than any of the heavier counter balanced cranks and still be way better than a model A crank. I've been looking at my beaver tail cranks and thinking about trying one with a B flywheel in one of my blocks. It should accelerate quick with a light crank and flywheel.
 
Second Bruce`s statement about the B crankshaft vs A crankshaft . So if you are going to put some money in an engine put it in a B engine with stiffer crankshaft and larger bearings. I have a B engine . Lots of power with NO oil leaks .
 
bdave, If I were in your shoes, I wouldn't go either A or B block. For near enough the same money, I would buy a new Burtz engine. With either A or B, by the time you crack test everything, rebore, grind the crank, pour bearings (or machine the block for inserts), you are up for $$$$. Comparing A and B engines to a Burtz is like apples and oranges. If you want performance with longevity, IMO, there is no alternative. 2 inch mains and big end journals, fully pressurised mains, rods and cam shaft bearings, inserted bearings all through it. The block, rods and crank are BRAND NEW, not nearing 100 years old and all the fatigued components that go with that and externally, it looks the same.
If you want it to GO, higher compression heads, better cams etc are readily available. 100 hp is not that hard to get and it will last.
If you can't tell, I love my Burtz.
 
Considering this thread is 10 years old it still holds true with the exception of Terry Burtz accomplishing seemingly the impossible feat

J
 
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