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MG MGA - connecting rods

have just torn the eng. down 1960 1600 every thing looked worn out going for a total rebuild . when i got to the pistons and rods some thing did not look right the small end did not have a pinch bolt ! the small end had a bushing and the pin was held in by cir. clips. looks like a B rod. this brings up two questions will the new pistons that i have orderd from moss have cir. cips in them or at least groves for them and will the standard big end bearings fit . cheers mike
mike jones

Hi Mike. If memory serves, MGA 1500, 1600, and 1622 engine pistons did not use circlips to secure the pistons to the wrist pins, but instead use a pinchbolt that clamps the wrist pin firmly to the connecting rod. The pistons then "float" on the wrist pins. It would seem that you do not have original MGA connecting rods or MGA pistons judging from the circlips that you describe. It might be possible that someone fitted "aftermarket" pistons and perhaps aftermarket rods also, but I am wondering if your block was perhaps overbored and was then fitted with later MGB rods and pistons? Have you measured the cylinder bore sizes and compared them to the specs for a 1600 block? If not, I think that is what I would do first. If the bore sizes are bigger than the max specified for an MGA 1600 engine, than it has been overbored for larger pistons. If so, you perhaps could fit cylinder "sleeves" to return the cylinders to their original 1600 spec sizes. Hope this helps! Glenn
Glenn

I don't know what you have but,I would rather have those kind of rods. Are there any part #'s on them? Perhaps you can get the #'s on the back side of the bearing and cross reference them or post these #'s on here and someone can help.The Moss pistons for my 1600 did not have grooves in them, but I'm sure a good engine shop or machine shop could cut them. One major problem I had with my engine is that when I had my rods rebuilt they took off too much material on the bearing side of them and after all said and done I had a rod side clearance of anywhere from .036 to .040. Manual calls for .008 to.012.Ended up getting another set of rods. Newer rods old crank I had .013 to .026. I then bought rebuilt crank and then had anywhere from .010 to .020.I than gave up, returned crank and took old crank and newer rods to John Twist at UML and whoever does his work welded the crank and I ended up with .008 to .010. Motor runs great and has now for 10 yrs. Gary
gary starr

Mike- I forgot, but years ago I used to modify aircooled VW's and one of the great setups was to use purpose made teflon buttons to eliminate those clips so that they would not have a chance to come out. Maybe someone like Summit or aftermarket VW shop would have something you can use or modify. I still have a VW piston and pin and a 1600 MGA piston and pin somewhere, I'll measure it this weekend to see what size they are for you- Gary
gary starr



chrysler outboards used the teflon buttin also. I took one on treade in and found out that it had been overheated by a failed waterpump. The bottons had melted and that let the wrist pin score the cylinder wall.
Sandy Sanders
Sandy Sanders

The factory offered as competition items flat top high compression pistons that had 3/4" diameter full floating wrist pins. They also offered alternative con rods for use with these pistons, see the special tuning manual for the part numbers. These rods for the pushrod engine were essentially the same as later used on the early twin cam engines, later twin cam rods were beefier on the big end and had two large bosses on the wrist pin end. My Sebring engine was assembled using these competition components and they are BMC items not aftermarket, the pistons are marked MOWOG and the rods have casting numbers a digit off of the listed part number. This is something to keep in mind when trying to ID rods, the number cast in the rod is just that, a casting number. The part number listed in the book is for the fully machined casting. These numbers usually differ by one or two digits.

Frank
Frank Graham

thanks for all the info guys the con rods are mowog AEH 645 the piston has a flat top mowog the front is marked plus b61 in very small numbers and letter the block is a 1600 that has not been bored ie standard size. the bearings are .010 under both mains and big ends the mains are marked 2484m the big ends are marked 2797 there is a trade mark that looks like VP any further help would be most welcome. cheers mike
mike jones

This thread was discussed on 11/11/2005

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