T500 Cylinder markings

[GT500Andy]

I've got some cylinders possibly 1971-73 era with different casting marks S-1 and S-2. I presume the S-1 are early and S-2 are later models, but don't directly see any difference between them? ( may be the ports are slightly different?) are they interchangeable as sets, can you use the later pistons without the ribs?

Andy

[geck0]

I have question this myself. I dident see a measurable difference except the added fin in the intake port of the > 1972 years

This is what I have
very bottom / 2 fins up / intake port fins
71 stock runner - S-1 / nothing / no
72 stock project - S MADE IN JAPAN / unreadable / no
76 stock parts - S MADE IN JAPAN / S-2 / yes
3 sets of Jugs -
S-1 / nothing / no
S MADE IN JAPAN / S-1 / yes
S MADE INJAPAN / S-2 / yes

I think the pistons were different in the 68 . The 69-77 should work in the S-1 and S-2

[Vintageman]

gecko

I am not sure I understand. Clarify where I am wrong

You have access to 71, 72, 76 cylinders?

You see no port dimension differences between them?

Except the added fin (what us that) is this the separator splitting the flow into either of two intake ports,

I hope I am not hijacking but have some questions too.

GT500Andy how are yours different if at all.

MY motivation is to see if the port are dimension are different between the 69 77 years. Or just subltle changes like intake port fin only.


Thanks



Thanks

[geck0]

Sorry My last post was a bit messy. It posted different than I typed it. Should have imported a spreadsheet.
I have 6 sets of jugs 3 sets are installed onto motors in frames. 3 other sets are off motors

I see no measurable difference between the 3 sets off the motors except for one set which has an intake port divider fin and has a S-@ on a raised boss between the second and third fin from the bottom.

[GT500Andy]

I can't compare, measure the ports excreta. Until next week because the one set of cylinders are being heli coiled at my work. But the only visual difference that I could see was the intake port divider and the pistons were the old type with the ribs.
Found some aftermarket .5 oversize pistons on e-bay for $60 the set, with rings, gudgeon pins and clips going to check the tolerances on Monday.

According to the parts catalogue in Europe:
1968 was the piston with the gate port 12110-15000
69-74 open bottom with ribs 12110-15101
75-77 same but smooth 12110-15103
I understand that from 69-77 you can use the new type smooth piston

Andy

[geck0]

yes on the pistons 69-77 smooth pistons. The GT750 pistons work as well, which I hear are a bit stronger. I would have to see them side by side and weigh them.

[Vintageman]

GT500Andy,

Yes post reply when you can. I am thinking there was no change from say 69 on (maybe other than the divider). We'll see. Anyone else have any jugs to compare ports? Thanks