Changing Pistons

[RocketScott]

In the ongoing goat rope of an engine rebuild...

The pistons for my engine (CPL 1280) are no longer in production, neither Cummins nor aftermarket make them. I can find listings for them all over but nobody actually has them in stock. They were only used in the CPL 1256 and 1280, not a big market

Some alternatives have been suggested. The original pistons had a 15/1 compression ratio. One alternative piston would raise it to 15.5/1 and another would lower it to 14/1

All things being equal what would the trade offs be raising or lowering the compression ratio?

Going up to 15.5/1 doesn't seem like that big of a jump but I don't have enough understanding to know what else might need to change. The builder that made that suggestion said that I wouldn't need to change injector timing or pump settings. Keep everything else the same

[Rawze]

(05-23-2021 )RocketScott Wrote:  In the ongoing goat rope of an engine rebuild...

The pistons for my engine (CPL 1280) are no longer in production, neither Cummins nor aftermarket make them. I can find listings for them all over but nobody actually has them in stock. They were only used in the CPL 1256 and 1280, not a big market

Some alternatives have been suggested. The original pistons had a 15/1 compression ratio. One alternative piston would raise it to 15.5/1 and another would lower it to 14/1

All things being equal what would the trade offs be raising or lowering the compression ratio?

Going up to 15.5/1 doesn't seem like that big of a jump but I don't have enough understanding to know what else might need to change. The builder that made that suggestion said that I wouldn't need to change injector timing or pump settings. Keep everything else the same

maybe an engine ser#, make/model, etc. weould help? .. no one on here knows what engine your talking about otherwise.

[RocketScott]

A Cummins CPL 1280 is a 444xt. The ESN is 11535281

It's also been called an N14 mechanical, NTC-444, NH/NT 855...

[Rawze]

(05-23-2021 )RocketScott Wrote:  A Cummins CPL 1280 is a 444xt. The ESN is 11535281

It's also been called an N14 mechanical, NTC-444, NH/NT 855...

Mr. Hag used to rebuild those old engines.. he was quite good at it... Maybe he, or perhaps someone else experienced will chime in with some advice.

Realistically, the higher compession ratio is the way to go if you can. Just remember that higher compression ratio requires a bit less boost to get the right fuel-air-mix on it back into spec.

Here are the part#s that it calls for...

[RocketScott]

The 3063003 and 3074494 are the four ring pistons. The newer tritech three ring pistons are 3076818 or the plus is 3095069

None are really available. There's a single NOS cylinder kit on ebay right now. The other listings are for resellers that don't actually have the parts. They just see that it's an active part number and think they can get them, either from cummins or interstate mcbee

So I'll order the pistons, day or two later I get an email that they can't get them and cancel the order. I'll even call to confirm they have them. They swear up and down that they "have them in the warehouse". Same result

[RocketScott]

(05-23-2021 )Rawze Wrote:  Realistically, the higher compession ratio is the way to go if you can. Just remember that higher compression ratio requires a bit less boost to get the right fuel-air-mix on it back into spec.

That's exactly the type of advice I was looking for

I suppose that means changing out the turbo unless there's a way to reduce the boost on the one I have

[Nilao]

Being mechanical I doubt there's a way to control the boost unless it's a waste gated turbo. You may have to turn the fuel pump up.