D17 intake/exhaust manifold work

i have a 1958 series 1 D17 226 that I'm using for both pulling and farming, i cant do any major work to the motor so I'm trying to find little things i can do. my current thought it essentially to smooth out and polish the exhaust tubes and enlarging/roughing the intake tubes, as if i were porting the heads. I'm not sure if this would give me any noticeable increase in air flow without porting the heads so i wanted to ask here before i spent the time to do it. incase it makes a difference, the manifold is off a series 3 or 4.

Manifold work at this point would be a HP gain in your mind, but if actually tested before/after on a dyno would be a great big nothing. Still need to farm with it you say ?? Your best results for HP increase are these in order: #1. Increase compression from stock 7.25 to 1 up to 8.0 or 8.25 to 1. This is good for 4 to maybe 5 HP and can still be used on the farm.   #2. If you can find some 4 1/8" flat top pistons that calculate out to 8.0 to 1 or more compression ratio, this is another gain over the first suggestion. Probably 6+HP from stock.   #3. A D-19 carburetor made to fit your engine. This is good for 5 HP and the throat opening on the manifold should then be opened up a bit to match the carburetor. This could be taken on and off for pulling/farming, but could stay on for farming if desired.  #4. An off to the side paper air filter to make it easier to get fresh air over your (probably) dirty and partially plugged oil bath air cleaner. This could be made permanent under the hood and throw away the oil bath style.  #5. Remove camshaft and have reground to higher lift that match a model 175 gas tractor engine.   There you go !!  Probably a 15+ HP gain and you can still farm with it. Your flywheel HP could go from 63 to 78 HP.

Edited by DrAllis - 22 hours 42 minutes ago at 10:15am

When you get over 8.5 to 1 compression ratio on a farm tractor, you start needing more octane accordingly.    110 octane is probably good up to 12 to 1 ratio.  I know on my 13 to 1 ratio puller engine I had to use 114 octane. 

I pulled 7500 lbs several times one summer 35 years ago with an old D-17. I had 100 HP and 18.4 x 38 cut rear F-151 Firestone tires. I ripped a tooth off the right bull gear at one pull and decided it was too much weight and traction for that much torque. Replaced the bull gear and went down to 4500-5000-5500 lb classes and never broke anything else again. Series 3 and 4 final drives have stronger bull gears and bull pinions in them.