Author	[Modern View]
LarryM 07-22-2012 10:41:35 199.193.96.189 Report to Moderator	I posted here before and thought I had an idea of what my issue might be but I have been unable to correct it. I have a C-281 engine that I bought that has a step piston that is the same design as the ones Tractor Supply sold back in the 70's. The problem I have is it loses about 4 hp on the dyno after about 1-2 minutes operating at 540 PTO. I currently have 93 octane in it. When I first crank it down it will hold 66 hp at 540 but then it slowly goes down to 62 hp at 540. I think the manifold is frosting up. If I let it run at no load for a few minutes until the manifold warms back up then it will go to 66 hp at 540 until the manifold cools down. I valves are set at .018-.019, it has electronic ignition, and new AC Delco C88L plugs. I had Auotlite 386 plugs in it and changing the plugs had no change. I wonder if it has soemthing to do with the fuel formulation today versus when these tractors were built. I have very little knowledge about fuel formulation but I am thinking that is where my problem lies. I am hoping someone on here has an idea of what is happening. [Reply]   [No Email]
Ed Carlsen 07-23-2012 08:06:26 67.142.130.40 Report to Moderator	Re: Farmall M C-281 issues in reply to LarryM, 07-22-2012 10:41:35   Just some thoughts Are your valve's and seats hardend to run no lead fuel valves could be not getting lube from no lead Your valves may be expanding in your guides and hanging a little Your combination dosen't require 93 octaine Higher the octaine slower the burn wrap your exhaust manifold. If you think your manifold is the problem try heating it under load see if power comes back (butaine torch) be careful not to crack intake hold away and heat slow or a heat gun would be better Think of manifold as a blow gun from a air hose faster you blow the gun the end will frost Hence heat riser on 460 560 intake on those tractors had short intake runner Just thinking out of the box seams you tried everything else Also what venturi are you running? My Super M with an LP head I used a W9 venturi Just a thought [Reply]  [No Email]
LarryM 07-23-2012 19:53:46 76.208.71.55 Report to Moderator	Re: Farmall M C-281 issues in reply to Ed Carlsen, 07-23-2012 08:06:26   I have a C-281 power unit carb. Same as a normal 450 but the choke lever is ont he outside like an M. I have a jet out 719 combine engine that I think is a 301. It has four sets of holes instead of 3. My venturi is a 33. I have a 27, 33 or 35 or 36 on the shelf so I used the 33. [Reply]  [No Email]
high octane 07-23-2012 20:11:11 72.53.194.237 Report to Moderator	Re: Farmall M C-281 issues in reply to LarryM, 07-23-2012 19:53:46   does the carb have an economizer circuit? [Reply]  [No Email]
Mlkgsmer 07-22-2012 18:15:22 174.232.14.15 Report to Moderator	Re: Farmall M C-281 issues in reply to LarryM, 07-22-2012 10:41:35   I see a n inline fuel filter. Did you remove the sedamant bowl when this was added. I had a clear one on mine and found that the bowl was a fuel restriction because the filter barely had fuel in it. I found out in the track and even found full throttle in the shop no load to be a problem. Also a old time puller told me low octane explodes better unless compression justifies it. My manifold runs water off of it and ices, then it really runs good. Maybe its all in my head, never had on dynometer though. [Reply]  [No Email]
perrycountyfarmalls 07-22-2012 13:33:02 107.8.112.91 Report to Moderator	Re: Farmall M C-281 issues in reply to LarryM, 07-22-2012 10:41:35   is the dyno getting to operating temp. before you are tsaking your reading? [Reply]  [No Email]
LarryM 07-22-2012 16:44:23 76.208.71.55 Report to Moderator	Re: Farmall M C-281 issues in reply to perrycountyfarmalls, 07-22-2012 13:33:02   The result is identical whether the dyno oil temp is at 80 or 180 or any temp in between. [Reply]  [No Email]
Ole Johnny 07-22-2012 12:11:55 67.142.164.24 Report to Moderator	Re: Farmall M C-281 issues in reply to LarryM, 07-22-2012 10:41:35   At first indication, if the manifold is frosting up, you should be able to see frost on the outside of it and the base of the carburetor. It would be very rare if the manifold or carb would frost at WOT since there is no restriction to make turbilances. I suspect that the intake air somehow is becoming HOT and you are loosing density and thus volume. Make sure the intake tube and the pick-up point is away from the manifold or the exhaust flow. [Reply]  [No Email]
LarryM 07-22-2012 13:26:32 199.193.96.189 Report to Moderator	Re: Farmall M C-281 issues in reply to Ole Johnny, 07-22-2012 12:11:55   It is not truly frosting up but it is getting very cold and condensate is profusely forming and running off of it. I should have taken a reading with my IR gun. It is 90+ degF outside. I have nothing attached to the carburetor intake so the only thing affecting the incoming air temperature would be the air coming off the radiator. My drop in horsepower is directly proportional to my drop in intake manifold temperature. There is one thing that I failed to mention in the original post. I have my main jet drilled out to .100" and I can make it lose horsepower and smoke black with the main jet adjustment screw so I believe that lack of fuel is not the issue. [Reply]  [No Email]
baldwin racing 07-22-2012 13:21:24 67.249.232.93 Report to Moderator	Re: Farmall M C-281 issues in reply to Ole Johnny, 07-22-2012 12:11:55   is it getting enough fuel? once you put it under load and bowl gets sucked down is it still getting enough fuel? once you take off load fuel fills bowl back up and will put down the power again....? dont know just putting it out there? kelly [Reply]  [No Email]
LarryM 07-22-2012 16:45:49 76.208.71.55 Report to Moderator	Re: Farmall M C-281 issues in reply to baldwin racing, 07-22-2012 13:21:24   I already thought of this and verified that there is more than adequate fuel present. [Reply]  [No Email]