Machine shop

[IDIBRONCO]

Got a question for someone who might know... How big of a deal would it be to turn down pistons?
Just thinking out loud here - what if you bored a 6.9 .030" over, then took a set of cheap used 7.3 pistons(stock size) and just turned them down to the right 6.9 spec.
You'd have to re-cut the the ring grooves... but that might not be as big a deal as it seems.

Wow. That's an interesting question. I haven't even been able to find one that would mill the tops

Oversize pistons for the 6.9 are not hard to find, nor are they particularly expensive compared to standard bore 7.3 pistons.

I will also take issue with Russ about overboring the 6.9 to 7.3 just as a matter of practice. I have been in the casting industry for almost 40 years. If Ford had made new cores (and patterns to make those cores), why would they screw up and make the water jacket cylinders the same size as the 6.9? The only possible answer is that they did not make new patterns, just used the 6.9 ones, overbored them and maybe improved core location. There is not a real good explanation to go with the theory of new patterns for the 7.3, considering the carnage that cavitation has wrought. Teh cast wall thickness was just too thin.

I don't know whether or not they were the same casting, but other than that, I just don't see why anyone would want to bore a 6.9 to a 7.3. It would still have the 7/16 head bolts so you still couldn't use the same amount of boost as you can with a genuine 7.3 and still keep the reliability.

 

[Hydro-idi]

I think the thinnest area between bore & water jacket on a standard bore 7.3 idi block is something like 140 thousandths. Gary @icanfixall would be a good guy to ask on this one. Don’t know about you, but that seems pretty thin to me. Would make sense as why cavitation happens so often with them, and practically unheard of with a 6.9.
Probably could be done, turning 7.3 pistons into 6.9 ones. But for the trouble it would take to make it right, I would just find some 6.9 slugs and call it good.

 

[cj3006]

Anybody have a recommendation for a shop near Sacramento, CA, to bore my 6.9? Should a 6.9 be bored, bored and sleeved, or thrown away?

Find a Caterpillar dealer and ask them or a International dealer and ask them !!
If you have it sleeved there needs to be a lip on the bottom to keep the sleeves from falling into the crankshaft !!
There's too many idiots that bore straight down thinking that they know what's best and ends in destroying the engine !!

 

[79jasper]

Find a Caterpillar dealer and ask them or a International dealer and ask them !!
If you have it sleeved there needs to be a lip on the bottom to keep the sleeves from falling into the crankshaft !!
There's too many idiots that bore straight down thinking that they know what's best and ends in destroying the engine !!

Have you seen that happen on a dry sleeved engine?

Sent from my SM-G892A using Tapatalk

 

[typ4]

I have, but my opinion may not be accountable since ive only sleeved about 20 of these engines.

 

[79jasper]

Lol just curious if it would be different than a wet sleeved engine.
I guess the wet sleeve are held down with the head, so not exactly comparable.

Sent from my SM-G892A using Tapatalk

 

[briankk]

Find a Caterpillar dealer and ask them or a International dealer and ask them !!
If you have it sleeved there needs to be a lip on the bottom to keep the sleeves from falling into the crankshaft !!
There's too many idiots that bore straight down thinking that they know what's best and ends in destroying the engine !!

If I were told it needed sleeves, I'd toss the block and hunt another, on the grounds that boring the guts out of a casting weakens it un-acceptably..

 

[laserjock]

While I have no actual data to disprove that theory, promar sleeves every 7.3 idi as part of their rebuild process. I would think if it were a real problem they would have more warranty issues.

 

[Runningaford]

I've talked with the owner of Motorworks here in Spokane. He only does the 6.9 blocks bored to a 7.1. I asked about sleeving, and he said he used to do the 7.3 with sleeves, but that he found the sleeves needed to be JB welded; he stated that without doing that, you'd leak coolant/oil.

Just passing it on.

 

[Hydro-idi]

While I have no actual data to disprove that theory, promar sleeves every 7.3 idi as part of their rebuild process. I would think if it were a real problem they would have more warranty issues.

Promar does not sleeve every 7.3 idi. When i called last year, the guy I talked to said sometimes they sleeve all 8, other times they sleeve a couple cylinders depending on the block. Very wishy washy.
That’s when I hung up lol.

 

[laserjock]

Hmm. Well the web site says they do. Based on my experience, it would not surprise me if they don’t. I’m not the huge fan I was when I first got my engine after having to pull and send it back.