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1938 B engine upgrades

B

Bill Marcusky

Member
Bought a 38 B with a locked up engine. Gonna rebuild it not swap it because block number matches. Anything I can do while I'm in there to wake it up a little? Thinking about trying a little farm stock pulling next spring. What can I do to her to make her a "healthy" B on a budget?
 
Well if your going to do a rebuild go with the bigger bore sleeves which will help a little bit. Maybe mill the head a bit to up compression
 
A 3 7/16 sleeve and piston engine kit with a head like below with .150 removed that has been ported and polished.
This one has over sized valves (SBC) More can be done but you would be talking big bucks to go farther.

DSC04571-vi.jpg

DSC04572-vi.jpg

DSC04573-vi.jpg
 
Dick is this an aftermarket head available to buy some where? Also what does SBC mean? This is my first allis so forgive me
 
Probably a stock head with a bunch of mill work and porting. SBC stands for small block Chevy. Dick is a master at the smaller B/C engines if memory serves.
AaronSEIA
 
This head is from the hobby stuff I used do. I have done several over the years but only two for others. This is the last one I did and took over a year to work it in with all the things that had to be done. With me doing everything myself I would not have any idea what the cost would be to have it done in a machine shop. Cleaning out the bowls and ports can be done with a die grinder yourself after the valves and valve guides have been removed. This can be done before going into the machine shop. It takes quite a bit of time cleaning out the restrictions in the bowls and ports by hand. I use a mill for that. Polishing is a hand job and also takes a bunch of time with a die grinder using fine stones and flapper wheels. If you have more time you can go in with felt wheels and polishing compound. I didn't on this head. Anyone that wants to spend the time can do the porting and polishing with hand tools.
I used small block Chevy valves on it and several other B C heads.

DSC04228-vi.jpg
 
Dick, how much power would I reasonably expect to gain with port and polish ? Probably not in my budget to go with bigger valves. And do I need to do anything with the carb to support the head work? Also do I need to worry about any head gasket or overheating when decking the head ?
 
Some but not a lot without other upgrades. The larger pistons will push more air thru with less resistance which gives you a little extra. You might need to open up the power jet a little then but I doubt it. You wouldn't want to do anything to the carburetor until you see how it was running. It needs to have good cleaning. With the stock setup, not knowing what jet was in it, you would be making a guess without facts to make that guess. When you play these games you need to cut and try after it is running.
You would get more just milling the head .100 to .150 and a good valve grind for your money and time. A good overhaul with a milled head will make a very strong puller without spending a lot of money. If you start pulling you will soon figure out that there is more to winning than horse power. You get a sinking feeling after spending big bucks when you get beat by someone whose tractor comes out running on three cylinders and blowing smoke.
 
That's what I was hoping to hear. Gonna do the 3 7/16 rebuild kit and port/polish and mill the head. Valve grind with stock valves. Stay with 93 gas with this set up ? Tractor is hand start only so I don't want too much compression. What would compression ratio be milling .100 vs .150?
 
I would run 87 gas rather than 93. When you get done try both and compare. The firing chamber will still have a large space making it below what is considered a high compression engine that would need a higher test gas.
 
The combustion chamber on these motors is large which gives the original compression in the 6 to 1 range.. I calculated it a few years ago with removing .150 inch off the head face and it does not raise the compression to an abnormally high value...... Im thinking it was still 7 or 7.5 to 1 .
 
I agree with Dick about power. If it is anywhere near a farm stock pull or antique pull an Allis will probably have enough power with a good engine. A little more compression and larger bore will certainly help.
 
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