'49 G80 Piston

cf160 · Post by **cf160** » Fri Feb 10, 2012 2:35 pm

i think I have to upload the picture to some website and then post the link to this forum , right?
Why don't you just give me your email address and I will send it to you? Or is this a communal informational site where all members want to see the pictures ? That is ok with me either way . I can do either . Which dimentions do you want? Please explain as there are quite a few I could give : Bore
Std. 3.25" or 82.5 mm (at the skirt 90 degrees to the pin. Pin height Pin centre (longitudinal axis) to
crown top (flat) at valve cut out, 1.81" (46 mm)
Skirt to crown-81.3 mm at longest point, 75 mm at the pin. I don't know what other dimentions you wish.

Dave

cf160 · Post by **cf160** » Fri Feb 10, 2012 6:58 pm

In reply to John (Feb 10 Post) about the wrong piston, These are old extra pistons from my shop but some unused although 64 years old. I have a great many of these pistons from a pile I bought about five years ago from an old speedway in California (Huntington Beach) I cannot even find all of them at the moment. BUT, if the piston will function in my bore all right, I really do not care if
it is historically correct or not. I will fit the pistons carefully to my engines so they will run.
I am presently considering using an old side valve piston in one of the overbored barrels I have because it fits.

john · Post by **john** » Fri Feb 10, 2012 11:05 pm

David

I am jealous that you have that number of pistons on hand to look through. I had small cash from my father, which I have nearly used up, it was a painful experience when I had to buy one of e-bay.

A word of caution on the two types of pistons

There a significant difference between them on pin height (13mm)

Wire wound marked W117/5

Heplex marked 9991

I hope this helps and I whish luck looking through the other pistons. If you don't find a pre '48 then I would be happy to swap my +0.030" for a one of your post '48s

John T

cf160 · Post by **cf160** » Sat Feb 11, 2012 3:33 am

Wow John! Great pictures . I wish I knew how to post some to this forum and I would post one of the two pistons I have like yours ,but which are much closer in pin height . I will try to send them to your email address if you have included it in your profile and you can see for yourself.
I do have a few more such pistons somewhere in
the shop , but they must be under something in some box or other and I cannot see them just now.
I will have another look tonight.
Thankyou for the great postings and wonderful pictures.
I have two '46 engines and one '53 as well as a
few extra half cases and flywheel combos including at least one or 350 engine from the same era which I bought on ebay when looking for Model 18 parts and the sellers couldn't tell the difference or didn't
care.
I will look for the other pistons and I think there might be a few that you may be interested in
I am afraid I am far worse than Sam in mixing up
parts for the wrong engines.
David Potter(cf160)

john · Post by **john** » Sat Feb 11, 2012 2:53 pm

Dave

PM sent with contact details

John T

Don Madden · Post by **Don Madden** » Sat Feb 11, 2012 5:57 pm

The significant measurement to compare the pin height is to the edge of the piston, not the crown. Pistons for the same application can have different crown protrusion and/or profile. The long rod was used in 1945-46 with the high pin location. After then the pin height is the same for all long stroke singles but the crown shape changed in 1960 to match the new head combustion chamber.

Twin pistons have much more variety & interchange problems.

Cheers, Don.

Don Madden · Post by **Don Madden** » Sat Feb 11, 2012 6:09 pm

I have added a sketch to the photos section on P/W Singles that shows the various pistons. I also have drawing of the 72MM twin pistons that confuse many. Cheers, Don.

Samuel · Post by **Samuel** » Sat Feb 11, 2012 6:45 pm

Hi Dave,

I've sent you an email about the ww piston

cheers

cf160 · Post by **cf160** » Sat Feb 11, 2012 9:05 pm

In Reply to Don :
I have looked at your sketches , but they do not appear. Do I have to use a password or something?
Dave Potter

cf160 · Post by **cf160** » Sat Feb 11, 2012 9:55 pm

I have posted a few pictures of these two '47?-'49?pistons in Photos *New and "Vintage Machines"
I have sent these pictures to Samuel and John by email before I discovered the Photo upload page .
David Potter (cf160)