Farmall C-281 engine horsepower issues

LarryM · Aug 15, 2012

I have a C-281 in a Super M that I have tuned up pretty good. The high idle is at 1600 and the 540 PTO horsepower is 66. The issue I face is that it holds 66 hp for about 30-50 seconds and then it slowly loses 4 horsepower at 540 over the course of the next 50-90 seconds. If I let it sit and run at high idle for a few minutes it will run at 66 hp for 30-50 seconds. I have all the holes in the sediment bowl assembly bored out and I have a 5/16" hose and fuel filter going down to the carb. If I pull the plug on the carb fuel runs out fast and keeps on running fast when the bowl gets empty. The ignition & valve clearance have been checked and rechecked. I only have two ideas left. 1. The 450 three rib manifold is getting to cold and the fuel is not atomizing. 2. I need to try an elctric fuel pump. Anyone see this before?

Dougct · Aug 15, 2012

If your missing the 4 hp at the pto,could it be the rear oil getting picked up after those few seconds?

Super-H-Mike · Aug 15, 2012

Wouldnt a cooler intake manifold help HP because of greater density of air/fuel charge? My guess would be fuel related, could try raising the float level a bit and see if anything changes. I would think you may want to do away with the in-line filter all together, but at least remove it and retest without it. I imagine you are running a paper air filter not the stock oil bath ? Otherwise it could be restricting through the oil bath, again I would run without it to see if anything changes.

Dblair · Aug 15, 2012

try another dyno . I think the oil temperature is rising in the m@w and making a difference. are you sure it's hydraulic oil.

Super-H-Mike · Aug 15, 2012

Or try a similar HP tractor on the same dyno to see if it reacts the same..

High Octane · Aug 17, 2012

mechanical advance, could be a 40 degree when u need a 23. if you have a M&W governor, it will open the carb up open at first, then close the butterfly just a tad when it settles in under load. those r famous for that. mechanical advance springs, could be too soft in tension, n kickin in the advance at high rpm, n weights r staying open till it idles down. can mess with ur timing under a load at different rpm n cause a hp loss. a 2 weight farmall governor will out perform a M&W governor on the dyno everytime, cause the 2 weight does not settle back when tuned in correctly. you wont see a rpm drop under load with the 4 weight on the dyno, just a power drop when it sets itself. you could have a worn throttle tip on the carb linkage, if its loose fitting, itll fluctuate the carb shaft position under full load. Ive seen these descriptions on the dyno, and thats what i found that cures it. stiffen up the advance, use a 2 weight governor, n make sure linkage is in good condition.

Farmall C-281 engine horsepower issues

LarryM

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Dougct

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Super-H-Mike

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Dblair

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Super-H-Mike

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High Octane

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