Piston

[USN_Green_Addict]

I'm looking into rebuilding a lot of my truck. I would like to ask if anyone can confirm that lds and ldt pistons are interchangeable on the truck? I've been searching but unfortunately there are a lot of dead links. Is there an advantage to using lds or ldt pistons?

 

[biscuitwhistler37]

I'm looking into rebuilding a lot of my truck. I would like to ask if anyone can confirm that lds and ldt pistons are interchangeable on the truck? I've been searching but unfortunately there are a lot of dead links. Is there an advantage to using lds or ldt pistons?

To my knowledge they aren't interchangeable, there's a difference in the shape of the piston tops that doesn't allow the LDS pistons in the LDT. Of course I haven't had one apart, so I'm just going on what I've read. Very curious though, as I have also read that late model LDTs are just LDT tagged LDS's, which contradicts that, and having an LDT manufactured in 91, I'm very curious to know for sure as well.

 

[cattlerepairman]

Well, that question has come up before: https://www.steelsoldiers.com/threa...-between-lds-and-ld-piston-and-liners.148700/

What I would say is that if you are rebuilding or refreshing the LDT , there is no issue with using six new LDS pistons and liners. If only replacing ONE piston, I would be more concerned about weight/balance and shape differences.
If you are rebuilding, you can also change the intake valve rockers to LDS ones and enjoy the ability to make a bit more power with the LDT!

 

[HDN]

If you are rebuilding, you can also change the intake valve rockers to LDS ones and enjoy the ability to make a bit more power with the LDT!

Can that be done without a piston swap, or does the piston swap need to be done for maximum benefit?

 

[cattlerepairman]

Shooting from the hip here, but your LDT pistons may not have an oil squirter at all. If they are later production, they will and you are good. If you really want to dive into the (very subtile) differences between LDT and LDS: https://www.steelsoldiers.com/threads/lds-vs-ldt-and-the-real-differences.56041/

In short: rockers (intake especially) and cam (unconfirmed), injection pump springs and injection pump adjustments and engine timing are all that is different. People report that after swapping the intake rockers they turned up the fuel and got "LDS-like" power.

I have a real LDS and that thing would ENJOY being turned up, but I won't do it. Keeping EGT's low....
200hp instead of 130 is way enough.

 

[biscuitwhistler37]

Ok..... I'm back from the rabbit hole. 37 pages later, and now we know for sure, the answer is yes, you can put LDS pistons in an LDT engine. You should put LDS pistons in an LDT engine because they are the same, or at least after a certain point they were the same. Same cam, crank, everything, except rocker arms, but LDS rocker arms will go in an LDT. To summarize all of it, when it's time to do a complete tear down and rebuild, buy everything for an LDS, it will fit, and after you change to an LDS fuel delivery system, you will have effectively LDS swapped your truck, brand new. I'm going to check my IP as soon as I can, if mines been done already that'd explain a lot.

 

[biscuitwhistler37]

https://maintenanceprocedures.tpub.com/TM-9-2815-210-34-2-1/TM-9-2815-210-34-2-10023.htm

TM 9-2815-210-34-2-1

These don't answer all the questions, but now we know the differences in injection timing, if we didn't already.