8 replies to this topic

[the_soon_to_be]

i have just been given a supposed 1380 block and pistons, bores are 73.5mm correct to 1380

the pistons measure 72mm roughtly, being new to engine building not sur eif this is correct, the piston is stamped STD on top.

gaz

[ginigwunkle]

they will be standard pistons then.......

2.78 inches is std bore.....

you need some 73.5mm pistons,about a hundred for a new set inc rings....

[Sprocket]

Pistons should be measured at the bottom of the skirt, across the pin (not along the pin), then you need to add the piston to bore clearance, usualy the maximum clearance, this will give you the bore size. Alternatively you can measure the top of the bore where no wear should take place.

[CraigyBoy]

they will be standard pistons then.......

2.78 inches is std bore.....

you need some 73.5mm pistons,about a hundred for a new set inc rings....

hundred seems very cheap for a set of new pistons, including rings?

anything i'm missing?

[ginigwunkle]

theres a few sets on here for sale, bought for projects that changed there minds.....

from a dealer there from 160ish a set

[Ethel]

72mm sounds a bit big for standard 1275 pistons. You need to find out what they are to get the correct rings for them really. Clean them up and see if you can spot a part number.

[ginigwunkle]

+40 are 71.628mm

+60 are 72.136mm

[the_soon_to_be]

72mm roughly, didn't have my vernier to hand so thats measured of a tape set on 100mm.

just seem alittle slack without rings on, but with rings reasonably tight

[pogie]

Just been out to the garage. One of my old 1380 Powermax psitons measures 72.65mm across the top of the and 73.11 across the bottom. I used a paid or digital calipers to measure.

HTH