G cylinders

[1948 mm]

How large can a stock gtb jug be bored and what piston can you use?
 

[Charlie Bilerx]

Sir,
4.8125", or 4+13/16", is getting pretty close to an absolute max for general boring on a G jug. I personally do not go that big. I have seen a few cylinders start to pin hole fail at that diameter. MM offered 4+13/16" pistons, for a short time. They stepped back to 4.751" true finished bore diameter and never looked back. At that diameter, problems all went away.

There are a lot of sixty, ninety, and one eighth inch overbore pistons out there that will fill the bill, and replace the original pistons. Many are using Dodge pistons and using a thick walled bushing to go from 1.0625" to the 1.25" pin diameter needed to use G rods.

To select a piston for your needs; you need a piston with a 2.843" compression height to equal the old original MM pistons.

Happy wrenching.
Charlie at Moline Parts
 

[1948mm]

I have a G already and it had 4.75" pistons installed. Just wondering what thoes pistons might have come out of. I am building an lp u and I plan on installing stock G jugs and pistons, but I might consider boring it out before I put it together.


Thanks again
 

[gtx1967jewison]

Charlie, I need 2 rods for a G but was told there's 2 different ones. What is the difference &/or how do I tell them apart? Thanks!