4.750 piston

we are looking for a 4 3/4 m&w piston for m5 block. any help appreciated. Steve

do you just need 1 or a set?

steve il,

If you are looking for the M&W/Gould pistons; you may want to broaden your search criteria a bit. Minneapolis-Moline marketed this same series of pistons as #10P2962. Occasionally you may come across this same piston marked as Zollner. Zollner really made all these pistons. They just never marketed them until everyone else stopped selling them. You can mix Zollner, M&W, and Gould pistons in one engine. Just never mix Moline pistons with the other brands. You will not be happy with the results.

Be warned; all of this classic series of aluminum piston, whatever brand, is prone to stress cracks. Make sure you soda blast used pistons and check them for stress cracks from around the outer edge of the top to the first ring groove. This was not a flaw in design. The cracks are caused by the aluminum of the era and detonation. Rubbing and wire brushing will actually hide the cracks.

New 4.751" bore pistons are in the pipeline. Production samples are being made and then they have to be "tested" for a few grueling weeks. Before the flowers bloom; we will be shipping the new pistons.

Think spring.
Charlie

i only need one piston, sorry to not be clear on that. the engine was put together to pull several years ago in a U. one piston had a hair line crack then. it pulled probably 5 years and then was replaced with G engine. then we put that engine in a UTIL. after several more years of use it wouldnt turn over after being shut off. checking through inspection holes one piston seems to be tight. im guessing problem is that cracked piston. cant complain, its run alot of hours. Thanks for the replys guys. could one of the new pistons be run with the M&Ws.

Give Wendel Everret a try
740-922-3335

steve il,

The new pistons are not a copy of the old classic designs. They will be much lighter because of the modern materials and the mill cut profile.

The old pistons were many times cut as a cylinder. They had to be much looser in the bore, when cool, because the older materials would expand greatly when they heated up. New design pistons are ground much like the shape of an I beam. They actually become round when they reach operating temperature.

Another problem is that the new pistons are made from a different aluminum alloy. They will be at least a third lighter than what you are currently running. Balance is a major factor in engine performance. They will also shed heat at about double the rate of the old round and Invar strut type pistons. With one cool piston and three hot pistons; it would be a bear to fuel balance an engine.

Another problem is weight versus RPM. Every time you halve the weight of the piston and rod combination; you can easily increase RPMs by a third, with no change in stress to the crankcase. This is true as long as the pistons are all balanced the same. With an unbalanced load you will build a harmonic disturbance and it would be like smacking the crank with a hammer every second revolution. To get the best performance, and bearing life, you should put the rods on a scale and make all of them the same weight as the lightest rod.

You can always swap out one piston in an engine. You just have to put them on a scale and make sure all the pistons are in balance. Engine manufacturers all balance the new pistons before they install them in an engine. Today they even balance the rods too. That little detail is one reason today's engines run the way they do. They can make the bearings smaller and blocks thinner because they have learned the lesson that balance gives free power with less stress.

Happy motoring.
Charlie

(quoted from post at 22:48:00 01/31/10) we are looking for a 4 3/4 m&w piston for m5 block. any help appreciated. Steve

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Thanks guys for all your help