51 B for Plow Days

Building my first tractor which is a 51 B All Fuel. To the point of rebuilding the engine. Tractor was in good shape and not wore out but I've gone through most everything and now ready for motor. I dont enough to know what I NEED to do to the engine to be able to pull at plow days in GA Red Clay. I've got a JD 44H plow that has been gone through with all new or NOS wear parts. Has 14" NOS moldboards. Plan to use 12.4 tires and rear wheel weights for extra traction. Block has to be bored .045 to clean up. I want the tractor to be reliable and not so extreme where it becomes finicky, hard to start, run or tune. There are many parts and shops out there offering high compression pistons, cam grinds, stroker cranks, etc. but I dont want to grind cases or go powerblock. Cam didn't come out because it looked good but it still can. I have a set of 50 rods to go back in, a completely rebuilt All Fuel carb I could possibly swap for a gas carb of any size with the builder and the AF manifold I've already ceramic coated. I have all the new parts ready for the head but dont mind backing up with different valves, etc of that's what I NEED. I've talked to couple of builders, all with parts and services to sell. Not going to be doing pulls but want it to drag that plow through GA clay with relative ease or am I just wishing? Suggestions on pistons, cam, swapping carb, going to gas manifold, head work and/or a good builder to lead me to the right set up?

I have a '50 B that is .045 over, and it pulls 2/16 in NW Iowa black dirt. I think you will be okay.

I have a 51 B that I bored out 90 thousandths. It didn't want to clean up at 45 but I wanted to go to 90 anyway. With M & W pistons and the 90 thousandths overbore I think I should be at 31 to 32 horse power. If I were you I would go with the high compression M&W gas pistons and a gas carburetor. The main difference between the gas and all fuel carb is the main fuel jet. I also put on a cold manifold but don't know how much difference that makes. But some I suppose. I also have 12.4 tires on cast wheels with 2 AB wheel weights. I might have to get a third one for the land wheel. I want to get it on a dyno this spring sometime to get the actual HP. I switched the wico distributor for a delco because the coil was hotter and it started better. I also have a 44H plow and a lot of red clay. The HP pistons bumped me up to at least to 7 to 1 compression which got me most of my extra horse power. good luck!

I would not be surprised if your tractor made closer to 35 hp ?
I had one with those M&W add power pistons and it did. Your altitude will make it vary though. I'm in Ohio. don't think we are that high up even though I was on a hill. LOL.

Good advice below. I'd definitely use gas pistons (either stock or somewhat higher compression), and consider changing the manifold and/or carb. I'd spend money on the pistons first, manifold second, and carb last. It might just be the load nozzle different on the carb?????

I'd also make sure you have ample ballast- either wheel weights or loaded tires.

And have fun. That is an important part.

The only real significant difference in the all fuel carb's main nozzle versus the gas carb's main nozzle is the acceleration well & the back suction economizer. Once the governor has the throttle opened up enough that it's running on the load circuit, the acceleration well is empty (having long since performed its duty) and the main nozzle is ONLY there to mix air with the liquid fuel.

With the exception of the volume of the shot of fuel given at rapid throttle openings, the DLTX carb's main nozzle does NOT actually meter fuel! It is (once it's running on the load circuit) only a brass tube full of holes in which air & liquid fuel are mixed before being delivered to the center of the air stream passing through the venturi.

I agree with the others. At the very least put the gas pistons or high compression gas pistons at the top of the list. High compression may make him a bit tough to crank with the 6 volt battery. The all fuel manifold MAY give you vapor lock issues but then again maybe not. I'd be looking at what will keep him cool before I'd bother with the carb! The all fuel carb is the last item on the list I'd mess with.

Hope that helps.

Al, below, is correct. Your all fuel carb will provide all the fuel it will ever need and air flow is identicle to gas carb. Compression is free HP so up that w/pistons and maybe have Josh Blackburn make you a set of hi-lift rocker arms. Probably a lot cheaper than a cam. You need more valve lift...not duration. I believe the small overbore and these two mods will pull that plow anywhere and no loss of drivability or reliability. Probably 30-32 HP Use the off road 90 octane non-ethenol fuel available everywhere now-a-days. Will work good with 8:1 comp.

i have a 51 b i use for tractor puling brush hog duty and raking hay here is what ive done all fuel or gas carb both make tractor run same i use a jd cold intake i heat wraped my exast pipe my bore is 90 over alunimum pistons i put new valves seats and guides in the head decked the head 20 thosands to clean it up had cam ground delco dist 3116 auto lite plugs filled front tires with balast i run cast center rears with 13.6 38 some pulls let us run 15.5 38 when they do i run theme it dynos at 33 horse dosent over heat on hot days by the way if you are going to pull her hard and long might want to look int clutch i also gap plugs to 035 i use non alky fuel 92 octane with marvel mystrey oil 30 wight oil with lucas aditive probly the best horse power gain i got was the exast wrap it made #2 cyl clean out better best 20 bucks i spent use 12 v batery and alt on it as it turns over hard with 6 volt she holds her own against the red paint and olivers

Thanks mike, I just wanted to stay conservative. I was told at one time that every jump in M&w'S bore size you jumped five horse, but I've been told that is false also. I don't say much until I see it on the dyno. which can be off too, whoever is reading it! I also have a 520 that I got a couple of years ago. It has john deere 45 over hi-altitude pistons in it. I put it on a dyno and it put out 39 horse and died. I think my spark is a little to far advanced. Because it never lost hardly any RPM. So this spring I'll get my buddy and my timing light and check it. She sure spanks the monkey though when it's running. And it seem to run ok on regular gas. Thanks again for update.

Thanks for all the replays. Always get good help here. Popin John is going to swap the AF carb for a gas for me just for shipping cost. Good people there. I'm gonna give Blackburn a call about head and get his recommendations.