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MG TD TF 1500 - 51 MG TD Carb Spring

Greetings all,

Stumbled upon some posts about the carb piston spring, different colors, etc. My MG has piston springs but I have no idea what "color" they are, but one of the posts mentioned that the original brass pistons were heavier than the later weighted or aluminum pistons and thus weren't supposed to use the springs. Any thoughts on that?

Steve
SD Denham

The brass pistons dont use a spring.Mine were done by Jim Taylor and had springs in them but he took them out.
TRM Maine

Second above, brass= no springs.
George Butz III

Thanks guys, taking them out and will see if it has a noticeable difference.
SD Denham

I may have a problem; my TD came with the carburetors freshly rebuilt, around 1970. One has an aluminum piston the other is brass. Will it be impossible to synchronize the carbs?
rich40701

On another MG board there was a long running thread where owners compared the composition and weight of the pistons and whether they used a spring; extremely useful since it indicated the spring effect needed to work differing sizes of carburettors effectively.
Ian Bowers

Rich40701,

I don't know how hard it will be to synchronize the carbs, but there is a solution. Remove and weigh the brass piston. Then add enough weight to the aluminum piston to equal the weight of the brass one. This is easy to do with a ring of steel or lead around the top of the piston. Lead fishing sinkers are easy to weigh then melt into the top of the piston.
Obviously, you won't use a spring with the newly weighted piston.
Lew Palmer

I thought all 1-1/4 H2 carbs had brass pistons? Is it possible you may have a 1-1/2 H4 carb in the mix?

Bill Chasser
TD-4834
W A Chasser

Bill, when I first got my car in 98 I sent the carbs to Jim and he called me and some PDO had put 1 aluminum piston in and left the one brass. he then added a spring to the aluminum one. Jim said they were original brass on the 51 and that was replaced by Jim, Carbs still on the car and working like a charm. Jim was a master of the SU's.
TRM Maine

Bill, they are both 1-1/4.
Lew, sounds like a good idea.
Rich
rich40701

Some of the other british cars that used 1 1/4 carb had aluminum pistons. I have seen them mixed before.

Rich. Think I have both aluminum and brass in my spares. Drop a note if interested.
Bruce Cunha

Thanks for the offer Bruce. I think the problem is the carbs are from different time periods, even though they both have PDC 3478 on the bodies there are differences. The brass piston carb has tickler pin and brass dash pot lid and aluminum version has no tickler and plastic knob; older/newer models. I want to supercharge if I can come up with the money so that will solve my carb problem:).
Rich
rich40701

This thread was discussed between 21/04/2018 and 27/04/2018

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