C-281 Camshaft

Is there a difference between a C-248, C-264, C-281 camshafts?

They will all interchange, but the later camshaft will provide better power and performance.

C 248 and C 264 engines until around the time SMTA tractors were ending and 400 starting used pretty much the same camshaft. After that C 264 and part of the C 281 engines used the same camshaft. Rest of the C 281 engines used a cam with left hand threads to hold the drive gear on, others used right hand threads. You never know whats in any of the engines unless its checked. Lots were replaced at rebuild times over the years. When IH came out with a different cam for that series engine it was used as the replacement cam for all engines in that series after previous type run out of the parts system. Some aftermarket suppliers reground used cams and also sold new ones.

I forgot all about the left hand/right hand thread thing. I think that change was made because of the issues resulting from the use of the "live" hydraulic pump.

In production on farmall 450 tractors the change in cam threads was made at tractor serial # 12652 and engine # 9861. Cam nut getting loose and causing keyways to wear was another reason cams were replaced. Threads were changed to help with that problem.

Ever the engineer I am wondering how much power and performance?

Probably 20 ftlbs of torque more at rated rpm when a 450 cam is used. ChadS

If I did my math correctly that would 20ft/lbs at 540 RPMs is equal to three Hp

I was wrong. HP = (RPM x Torque)/5252 That would make a engine running at 1400 RPMs have 5.2 more HP. This seems a little unlikely that by simply changing camshafts that much can be gained on a 264 engine with 4.125" pistons.

Just did one today! Took a 320ci Super M with a known M cam, put in a brand new 450 cam, picked up 11 hp, and 15 psi more cyl pressure. I have yet to to retune the carburator. This was just a quick warm up pull to retorque the head gasket, and reset the valve lash after rebuilding the entire valve train, and a few other parts,,,, LOL!

Account for lobe wear, rocker arm tip wear, even slop in the rocker arm bushings or rocker arm shaft can account for loss of power.

Take an old M cam, thats got 5000+ hours on it, the lobes can have .020 worth of wear, and be uneven from Intakes to exhaust, one cyl to the next, no one lobe will read the same.

Recondition them to factory spec, and the grind that is put on the cam, does not have to be a super puller grind, just stock and all even up to spec, and you will see a good 3-5 hp jump and a regain in cyl pressure in the end.

There is one other way to bring lifr to an old cam, rocker arms with a different ratio.

Just remember, each lobe will be worn differently, but, you will see a gain, or gain back whats lost. If you get more than what you had before,,, It cant hurt!!

Best money spent, a new cam, or a reground cam, recondition the lifters, rebuild the rocker arm assembly and dial in the valve lash perfectly.

If you got an engine thats got less than 5 hours on a fresh build, if you have only retorqued the head one time, and have not rechecked the head nut torque, you need to do this ASAP before any tuning is done. If the head is loose, the cyl pressure will fluctuate and it will run worse as it warms up. The head floats, valve lash setting go tight, loose, etc etc.

Those headgaskets are pretty thick! Takes more than one go around to get em crushed right, they will work loose!

Fresh parts, assembled and dialed in with some patience, which sometimes, I dont even have on some days,,,,,,, will be worth an extra 5 hp, or more, over your best dyno run,, just by whats mentioned above.

Want more? All the new parts will need to be tuned, matched up, dialed in.

Reconditon the governor, not turning the rpm way up, but, rated rpm. Worth and extra 2hp easy
at 540, and this probably is what will unlock a massive torque curve that these engine actually do have. They will grunt with a few parts and some upgrades.

Distributors, Look over to the left of this page, all the parts you need, specs too! From parts to rebuilt assemblies.

Carburators, I was looking on this site, for a rebuilt carb, thats a good deal. Then send it over to me and Ill hop it up, or tell ya how, most Ive heard, they dont need anything but tuned in by adjustemnts,, if they need it at all. Look thru the site and price your model today!

A well built carb, a tuned governor, a good IGN, add the valve train overhaul with a new cam, shoot,,,,,,,,, Will blow nebraska test results out of the water, and help a few, trying to work some bugs out of their pride and joy. I have seen 7-15 hp more. Applications vary, be careful wear saftey glasses!

Larry, once all the math, that matters, in reconditioning parts, having done this atleast,,, once,,, If you can tell me that no stone was unturned on a build, I will have to run the follwing disclaimer, that math formula, you gave,, it aint accurate, just yet,,, there are numbers,, on the other side of the point, after that,, then that math problem is ready to be figured. What is unlikely,,,, there is no more work to do. Its called restoration, not hot rod tv.

Anybody ever see this formula in a I&T shop manual?


5hp gain easy, over anything thrown back together.
ChadS