Model B Head on a 1931 Tudor

[Chevmn56]

Hey guys i have a few questions again hopefully not as stupid now, i have learned a bunch in the last week with my Les Andrews book!!!!! While doing a tuneup new plugs and wires, setting the point gap etc etc.....i noticed that the head had a big "C" on it (see pic). I did some research on the head and found it is a Model B head and could give them a slight increase in compression, is this true???? what are the pros and cons of the head?

I assume that all the plugs and anything maintenance wise should be the same as the model A head ???? ie: plugs, belts etc. I already found the water pump is a bit different.

On plugs i am finding a huge variance on what the gap is supposed to be. Les's book says .035, the box that the plugs come in say .025 i also find .030 mentioned a lot, is the gap for the "C" head the same as the A's???. Being that i have no clue the state of the internals of the motor any suggestions???? i gaped them at a tight .035 already , but i am willing to redo it!!
Thanks in Advance

 

[SSsssteamer]

On the spark plug gap I have searched through "Dykes Automobiles" and found that 0.025" plug gap is recommended for magnetos because a wider gap in a mag would possibly cause the high tension voltage to arc internally to ground within the magneto. Modern ignitions easily handles the 0.035" gap. For our model A Fords I have selected 0.030" as a dependable gap to use. Higher compression engines need either a hotter spark or a smaller gap because a spark finds it harder to jump in a the denser compression air. Lower compression engines can use a larger spark plug gap because their air isn't as dense at TDC which makes a spark is easier to jump in its spark plug.

 

[Marshall V. Daut]

"what are the pros and cons of the head?"

Well, since you have asked...

The increase in CR is from 4.2 to about 4.6, hardly worth the effort, expense and messy hassle of changing heads, studs & nuts, head gasket and water pump. Years ago in the 1970's Model A community, the "hot" set-up was supposedly to put Model B engines in Model A's, especially among the So-Cal crowd, the movers and shakers of the hobby at the time. If an entire engine swap wasn't feasible, just the B cylinder head (with the "C" embossing) was recommended for the Model A block. This was before so many reproduction flatheads with varying CR's and combustion chamber designs became available in the late 1980's and since. Unless one was fortunate enough then to find a Ford Police head, about the only flathead upgrade was to either locate a well-used and abused "racing" head (Ansen, Weiand, Riley, et. el.) or install a Model B head. The performance increase with a Model B head in my opinion (and based on extensive cross-country driving experience and experimentation) was negligible unless all the other Model B engine goodies accompanied the upgrade = camshaft, intake manifold and carb. The larger Model B crankshaft journals and in most cases counter-balanced crankshafts were a plus, but didn't really add horsepower/torque. Besides a lukewarm performance increase via-a-vis the expense and hassle of making the change, the main problem with the Model B head was the special three-bolt water pump. There were two versions: I believe the '32-33 pump had a longer shaft than the '34. Either way, a special, hard-to-find and expensive pump rebuild kit was required. I never had any luck with Model B water pumps, even after rebuilding them. The most catastrophic water pump failures I ever experienced happened with Model B pumps.
Today, your options for better performance than afforded by a Model B head are almost limitless, both in flathead form and OHV systems, all brand-new, ready to bolt on. Lots of racing forums, magazines and active organizations have turned up long dormant racing cylinder heads from the day. The number of repo heads with at least 5.9 CR is almost staggering, with seemingly a new one coming on the market every few months. Almost any of these heads will far out-perform the Model B head.
Don't be discouraged, though. You at least have a fairly low supply cylinder head that a collector would want for era nostalgia or to complete a Model B short block. Enjoy your Model B cylinder head, but be aware that on the performance enhancement scale above the stock Model A cylinder head, the Model B is only one rung up the ladder from stock.
Do you also have a Model B block underneath that Model B cylinder head? If so and if it is complete, you have a 10 horsepower increase to 50HP from the Model A's 40Hp. The lack of an oil return pipe on the passenger's side of the engine and the presence of a fuel pump port beneath the valve chamber identify the block as a Model B. Of course, you probably already know this - but some readers may not.
Marshall

 

[Chevmn56]

"what are the pros and cons of the head?"

Well, since you have asked...

The increase in CR is from 4.2 to about 4.6, hardly worth the effort, expense and messy hassle of changing heads, studs & nuts, head gasket and water pump. Years ago in the 1970's Model A community, the "hot" set-up was supposedly to put Model B engines in Model A's, especially among the So-Cal crowd, the movers and shakers of the hobby at the time. If an entire engine swap wasn't feasible, just the B cylinder head (with the "C" embossing) was recommended for the Model A block. This was before so many reproduction flatheads with varying CR's and combustion chamber designs became available in the late 1980's and since. Unless one was fortunate enough then to find a Ford Police head, about the only flathead upgrade was to either locate a well-used and abused "racing" head (Ansen, Weiand, Riley, et. el.) or install a Model B head. The performance increase with a Model B head in my opinion (and based on extensive cross-country driving experience and experimentation) was negligible unless all the other Model B engine goodies accompanied the upgrade = camshaft, intake manifold and carb. The larger Model B crankshaft journals and in most cases counter-balanced crankshafts were a plus, but didn't really add horsepower/torque. Besides a lukewarm performance increase via-a-vis the expense and hassle of making the change, the main problem with the Model B head was the special three-bolt water pump. There were two versions: I believe the '32-33 pump had a longer shaft than the '34. Either way, a special, hard-to-find and expensive pump rebuild kit was required. I never had any luck with Model B water pumps, even after rebuilding them. The most catastrophic water pump failures I ever experienced happened with Model B pumps.
Today, your options for better performance than afforded by a Model B head are almost limitless, both in flathead form and OHV systems, all brand-new, ready to bolt on. Lots of racing forums, magazines and active organizations have turned up long dormant racing cylinder heads from the day. The number of repo heads with at least 5.9 CR is almost staggering, with seemingly a new one coming on the market every few months. Almost any of these heads will far out-perform the Model B head.
Don't be discouraged, though. You at least have a fairly low supply cylinder head that a collector would want for era nostalgia or to complete a Model B short block. Enjoy your Model B cylinder head, but be aware that on the performance enhancement scale above the stock Model A cylinder head, the Model B is only one rung up the ladder from stock.
Do you also have a Model B block underneath that Model B cylinder head? If so and if it is complete, you have a 10 horsepower increase to 50HP from the Model A's 40Hp. The lack of an oil return pipe on the passenger's side of the engine and the presence of a fuel pump port beneath the valve chamber identify the block as a Model B. Of course, you probably already know this - but some readers may not.
Marshall

Thanks for the info Marshall that was good to know, and i did not know that about the model B block.....no i ran the numbers on my block its a 29.

Thanks again

 

[Ian in Mississauga]

Google "piriano's model A engine tests", you might be pleasantly surprised.