: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : I am building a UB puller and was wondering about cams. Did you have to get your U cam reground to get .370 lift or is it out of another tractor, ie M670, G? Also, the only difference between a U and G carb is that a G has a bigger jet. So if you have a U carb you can save some money by just buying a G jet to put in it.: : : : : : : : : Thanks for the "G" jet info. MM made two cams for "U"-670 tractors. "U" & "G"s had part #451 cam. It had a lift of .315/.318 int/exh. Later tractors had #44442 with .325/.330. Duration was the same for both. Columbus Col-Weld Corp. reground my #451 to .370/.370 and extended the duration about 5 degrees. This is what they recommend- they have several out in competition and they run well. Their # is 1-800-686-6708, Columbus, OH. Ask for Frank, he is the cam grinder.
: : : : : : : : : Berry Cams, 1948 175 street. Lester Prairie, MN. also regrinds MM cams. They have a mild grind of .360/.365 and about 5 extra degrees. They have a wild one for big motors with .430/.435 and about 15 extra degrees duration. I chose Col-Weld because they charged $120, Berry wanted $250 for theirs.
: : : : : : : : : : : : : : : : Hi,
: : : : : : : : I'd like to get in on this jet stuff if you guys will let me, The Venturi in the carb is different between the U and the G. It is worth at least 8 hp. I got the last one I bought from Abeline Machine. The G venturi is significantly bigger than the U's. : : : : : : : : On the camshafts Hoosier cams puts a HD 800 well motor grind on the four cylinder cam that is a excellent piece.
: : : : : : : : Us MM people should help each other out to dominant tractor pulling. My biggest problem is getting a good enough track to hold the thing to the ground. : : : : : : : OK GUY's : : : : : : : Have a question???? What is the most Stroke that you can put on a 403 cam??? : : : : : : The question should be how much money do you have to spend? Several years ago a 6.5" stroke in a U was considered big. Then guys would notch the cam for room and go to 6.7". Now they are going to a small rod journal and moving the stroke out to supposedly 7.5" The result with big pistons and sleeves is a 740" U. : : : : : : If you are going to do this I'd recommend working on the transaxle too. The GB had a excellent overload block in it that can be adapted into a U. Many will say it is not necessary but it support the ring gear and negates gear missmesh. : : : : : : This, a 740" U is a very impressive tractor to watch. They can spin out on a clay power track in third gear effortlessly. : : : : : : Before I built such a piece I would let the NATPA publish their new rules that are supposedly going to not change for three years. After you get the rules detemine the best build up with what you can work with. ie, U blocks, G blocks or well motor blocks, each would allow a longer connecting rod than the perceding piece.
: : : : : : Smokey Yunick sez, put in the longest connecting rod and win races.
: : : : : My U will spin 18.4-34s in 3rd at 5500lbs on
: : : : : a good clay track and it only has 436 cubes.
: : : : : This brings me to a question, do all those extra : : : : : cubes help if you can only feed them through : : : : : a stock carb and manifold? How much hp are
: : : : : they getting? mine has 140. Mine does have : : : : : G blocks and rods which I think is a big advantage. : : : : Ok,
: : : : We have to get a life here. Consider the difference in the outside diameter of a 18.4 x 34 against a 18.4 x38. The difference in circumference and contact patch against the ground is considerable. Your 436" G motor must run very well but the 740" U will run third gear with 18.4X38 in the 6500 lbs. Granted the volumeteric effeciency is not the to fully utilize the total increase in ci but it will eat you.
: : : : When was your dyno calibrated. Expert tuners have told me the most they could get is 110 hp from a 403.
: : : You didnt say before what size tires and what : : : weight class you were talking about. so I think : : : my life is ok. so how much hp can you get : : : from 740 cubes? Im just curious because Im : : : thinking about building another engine. : : Hello again,
: : I don't know how much power is attainable from this set up. I was suprised when I saw the guy open the thing up I don't think I took it all in.
: : When we got home and watch the video the thing puffed smoke. I figured he needed a fuel pump to keep fuel available in the float bowl.
: : Where are you at? : I want to state some thoughts and questions about big motors: It seems that all motors above 500 ci are about equal. Seems to make little difference if they have a lot of bore, a lot of stroke, or some of both, they appear to produce about the same amount of power. I have seen 500 ci motors out perform 650ci regularly. I believe this happens because 500-550 ci is about all you can feed with a stock induction system. Bigger motors may produce more torque, but at a lower RPM. Rpm drops off until volumetric effiency comes up. The tractor then slows down and its' distance is shortened. Questions: What stock manifolds are best? What about cutting down a big 6 cyl manifold to 4 cyl? Is anyone producing a "replacement" manifold larger than stock? I have seen some big updraft carbs at swap meets. Will these work better than a "G" carb? Someone told me that a JD combine carb was a hot setup. Last question, what pistons are available to rebore 800 blocks oversize? Feel free to respond to any or all. I hope this message board does not run out of space. You could be right about the little motor out preforming the big one.. Naturallly the big one make more torque. That means it can break the tire loose easier. The biggest need when you are making megapower is a clay track to hook it up on. Another reason that the little motor can work better that the big on is since you have a confined space, deck height, to put crankshaft throw, rod length and piston, when the throw gets longer the rod gets shorter. This makes the rod ratio less ideal. Before you decide on your recipe of part get a copy of "Smokey Yunick Power Secrets" book. The stuff in it is directly related to small block Chevy but with common sense it reapplies to these engines too. The G-1000 intake chopped off works as well as any legal intake manifold, The 670 exhaust manifold is as good as available. The 800 has a stock bore of 5.319 . Arias is one aftermarket manufacture that can make a piston to 5.500. You need to decide the crankshaft stroke you want to run, and then decide what it take to bring the piston, connecting rod conbination together. If the new rules set up by the NATPA make the well motor blocks will become the hot setup because with the greater deck height allows a longer connecting rod ie. better rod ratio. The JD combine carb could be a hot setup depending on the throat size it would have to be at least as big as a G carb to convince me to change.
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