|
Title: Piston markings Post by: Pahs59 on July 18, 2021, 06:30:26 AM Hi
I have two sets of pistons with the numbers 7406474 stamped on top but one set also has LO stamped just above the numbers..can I mix these to make a set Title: Re: Piston markings Post by: my8thholden on July 18, 2021, 07:17:06 AM Pah ..If the part numbers stamped on all pistons is original factory GMH numbers then they must be the same , usually any changes , improvements etc made over time usually brought about a change of part number , do they look the same , do they weigh the same , are all ring groves identical ? are they dimensionally identical ? The LO mark ? , not sure , is it also original mark ? If they marry up in all aspects ,then I would use them . There can be small changes made at the factory when testing revealed a need that does not bring about a part number change , example extra oil drain hole/s in the oil ring land , change of piston pin circlip, these improvements where usually covered by a bulletin , 60 odd years later you can only deal with what is in front of you , and seek information ,like you have ..keep well Vern .
Title: Re: Piston markings Post by: Pahs59 on July 18, 2021, 07:57:53 AM Thanks Vern
I’ve checked both pistons with the verniers at the top, at the Gudgon pin and at the bottom and there the same measurements, sat them side by side and heights are the same as well.. the dimple in the middle of the piston with the 7406474 number only but the 7406474 LO piston has the dimple about 1/4 of an inch from the edge of the piston head facing forward.only thing I haven’t checked is the ring grooves like you mentioned to see if there are any extra holes or any small differences..I’m only needing the one piston as when I pulled the motor down every compression ring was broken and on one piston a piece of broken ring worked it’s way up under the other piece of ring and spread the ring groove,straight away I figured the bore would be knackerd but luck was with me there’s not a mark in it Thanks for the info Vern |