6.9 idi piston options and advice

[Captain Spaulding]

Alright, so I thought I had some leads on a couple of sets of pistons and it just isn't happening. Most of the venders are saying everything is discontinued or they don't have an ETA for new stock. I haven't reached out to Mahle yet to request a set so that's next on the list. I am reevaluating my next steps here.

My first option is to run my stock sized pistons and hone the block. Hopefully I can get my hands on standard sized rings. The problem here is there was some water that got into two of the cylinders and damaged the cylinder walls. Its not extreme, but seems to be enough to where I can't hone it out with stones. Maybe a flex hone could take care of it, I don't know. The cylinders are well with in spec and if it wasn't for the water in the cylinders I would try to reuse the stock pistons. My only concern with this is that it may need to be honed so much to the point that my cylinders are out of spec. Also a couple of the pistons have little dents in them from what looks like pieces of the glow plugs, they don't have cracks or holes though. I would feel comfortable reusing them. I was told this was a low mileage motor when I bought it and it definitely looks like it when I pulled it apart. The pistons have very little wear and minimal carbon build up. Any thought?

My second, way more expensive option is to order standard sized pistons from 89' to 92' with a 7.3 and bore my 6.9 block to match. The problem that comes along with this is the compression goes way up and the rotating assembly can be unbalanced because of the heavier pistons. I talked to Justin over at R&D, which by the way is a great resource I have come to find out, and he let me know that it is possible to do this. He said he would be able to mill them down to bring the compression back to stock numbers. Have any of you done this before?

Thanks for reading my long winded thread and I appreciate your responses.

 

[franklin2]

In this situation I would be hunting up a good machine shop, or maybe several. If you have it all torn down and cleaned up, and bring the pistons too, most guys in most shops will have time to look at it and give you advice. They do this for a living everyday, they should be able to look at it and tell what's possible. An experienced eye is invaluable in this case.

 

[IDIBRONCO]

Try R&D. His site says that all pistons are now special order for the foreseeable future. You will have to contact him. Maybe he can come up with something.

 

[IDIBRONCO]

Try R&D. His site says that all pistons are now special order for the foreseeable future. You will have to contact him. Maybe he can come up with something.

Never mind. I see that you have already contacted him. My mistake.

 

[hacked89]

Alright, so I thought I had some leads on a couple of sets of pistons and it just isn't happening. Most of the venders are saying everything is discontinued or they don't have an ETA for new stock. I haven't reached out to Mahle yet to request a set so that's next on the list. I am reevaluating my next steps here.

My first option is to run my stock sized pistons and hone the block. Hopefully I can get my hands on standard sized rings. The problem here is there was some water that got into two of the cylinders and damaged the cylinder walls. Its not extreme, but seems to be enough to where I can't hone it out with stones. Maybe a flex hone could take care of it, I don't know. The cylinders are well with in spec and if it wasn't for the water in the cylinders I would try to reuse the stock pistons. My only concern with this is that it may need to be honed so much to the point that my cylinders are out of spec. Also a couple of the pistons have little dents in them from what looks like pieces of the glow plugs, they don't have cracks or holes though. I would feel comfortable reusing them. I was told this was a low mileage motor when I bought it and it definitely looks like it when I pulled it apart. The pistons have very little wear and minimal carbon build up. Any thought?

My second, way more expensive option is to order standard sized pistons from 89' to 92' with a 7.3 and bore my 6.9 block to match. The problem that comes along with this is the compression goes way up and the rotating assembly can be unbalanced because of the heavier pistons. I talked to Justin over at R&D, which by the way is a great resource I have come to find out, and he let me know that it is possible to do this. He said he would be able to mill them down to bring the compression back to stock numbers. Have any of you done this before?

Thanks for reading my long winded thread and I appreciate your responses.

I think very few people would disagree that Justin is the leading expert when it comes to machining / building IDI engines in non stock configurations. If he is confident than I would personally trust him. There is a dwindling amount of machine shops that do IDI work and count on less than one hand those that will deviate and try things not to OEM spec.

 

[IDIBRONCO]

Northern Auto Parts lists 6.9 pistons in standard and +.020. I don't know if they're in stock or not. The site let me add them to mu cart and that's as far as I went.

 

[BlindAmbition]

Jegs, Summit, etc, all seem to be sourcing the same pistons from UEM. Might be worth calling them directly to find out which distributor has them/can order them.

UEM's website does not even show the 6.9 IDI as an engine option, I'd give them a call.

UEM Pistons

www.uempistons.com

 

[IDIBRONCO]

That's funny. When I clicked on your link, the page that showed up had a 7096D piston that's listed for a 6.9. Granted, it's +.060 and I wouldn't recommend that any one use it, but I know that there's other options too. Over on the left hand side, the option lists includes 6.9L displacement. Also a 421 CIG displacement which is the same thing.

 

[IDIBRONCO]

I also found a listing for 6.9 pistons on +.030 on the UEM site. I think the entire part number would be 7096D.030. The part that gets me is that the compression ratio is listed as 19.7:1 which is a little on the low side. I know nothing about the Dualoy brand, but it seems legit to me.