Yeah, I think what this means for the 6.9 platform is basically exactly what NMB2 did with his engine. Decompress the Hell out of it (.080" off the pistons) and run a big cam if you plan on throwing any power at it. If you want to push things harder, you are going to have to step up to a 7.3 block and either risk the thin cylinder walls, Partially fill the block, or sleeve it.

 

That is exactly it. Ive sank too much into salvaging an engine which 20/20 hindsight should have had -.080" pistons to begin with, and I probably wouldnt have had the issues I did, and realistically, I would have probably stuck with a 7.3 if given the choice now.


As far as upgrading to the 1/2 studs, I think its the same route as the 9/16, just a couple hundred cheaper in parts, so its still a ton of work.

 

I spent a bunch of brain last night thinking which would be the better way to take the 7.3, either sleeve it down to 4.040" and use my rotating assembly from the 6.9 in the 7.3 and basically have a 1/2" studded version of my 6.9. I would be shaving the pistons again to 16:1 compression and recoating them...


Pro's-
Already have the balanced rotating assembly, Total Seals, Etc.
Super thick stout cylinder wall's plus block fill
No worries about cavitation damage


Con's-
Quoted $1300 to have the 7.3 Sleeved
Stuck with N/A wrist pins and Pistons (Though with Turbo Rods)




I also thought about just selling my balanced 6.9 rotating assembly, picking up some new turbo pistons/rings ($700) and bearings, boring the 7.3 .020", balancing it, Main girdle/studs, filling the block 2" from the top, and run the hell out of it.


Pro's-
Selling the rotating assembly will basically pay for the new pistons
Total cost will be mildly cheaper
Turbo Wrist pins


Con's-
Thin cylinder walls (Though supported with block fill)
Standard/Keystone rings, not total seals (Though gapped properly, not IH style)




Im kind of torn between those two directions at the moment. Part of me wants to start fresh with all 7.3 rotating assembly and the little bit extra displacement, the other part of me wants to sleeve it and build the stoutest block possible... I guess the real question is when does it become worth it to have a stout block with lesser parts versus stout parts with a lesser block, and putting it all into context with the P-Pump and compounds...

 

Yeah guess we found the 6.9's limits huh? Maybe the 7.3 has more in store for us eh?

 

Racin, on your second option you mention boring the 7.3...what are your thoughts on boring a 7.3 over? I mean, how much could you take off and be safe, I know its getting pretty thin on a 7.3...I ask because if I build a 7.3, chances are, it will need cylinder work. Just want to know what the master thinks about an overbore 7.3 lol

 

FWIW I vote 7.3 pistons, I don't think your wrist pin adapters are a good idea with the new goals. IIRC you did that when you had a milder engine in mind, now they seem like a serious liability.


Maybe a hybrid of those two ideas so to speak. Do/If you have a good stock set of IDIT pistons? If so save the money on pistons and put it into sleeving the 7.3 to stock bore.

 

I don't know, I don't think there is enough concrete failure info out there to have an opinion. I know that powerstroke guys push stuff pretty hard on .020" overbores, and that they have thin walls like us, but other than that, I don't know...

 

Interesting Idea, I would have to see what kind of shape my pistons are in when I pull them out... Still would have to buy rings though...

 

Pump is almost ready, just needs to be run on the stand... I have to build some cradles for the pump stand, the shop doesnt have the right ones, that's my project for this weekend, as well as hopefully getting the IDIT torn down...

 

Gonna put a hurtin on some egos when its done thats for sure lol.

Cant wait to see this done, sucks about the 6.9 block but I think the 7.3 ought to hold up ok with a little work.

 

In your opinion, would it have been possible to drill the 6.9 heads and then use them as a guide to drill and tap the block?
Since the heads have a machined surface you could drill them true using a good drill press. With the heads bolted in place after being drilled it may allow more precise hole alignment.
As long as the studs fit in place when the heads are in position, it shouldn't cause issues as you can remove the studs to remove the head.
Just a thought, I haven't looked at them too closely yet.

 

the pics of the pump are awesome,

 

Most definitely a gamble boring out a 7.3l. I had one block bored out .020 over and had two pin holes you could visually see!! In hindsight another 7.3l block I bought had the surprise that it was bored out to .040 over and no electrolysis?? Funny how that works. I ended up by a 2000 powerstroke and am loving it so far. I am going to use my 90' as my daily driver after I do some work. Will be selling my turbo and all components, cold air intake, 3" exhaust with 5" tip, single mass flywheel (stage 2 I think), and the 4wd accessories and transfer case. Let me know if any of you are interested. I would like to sell the air intake, turbo, exhaust, flywheel as one big package.

 

hey if you decide to go 7.3l and not sleeve it for a 6.9l piston then I have some 7.3l .020 over pistons with brand new rings on them. The pistons I bought used from a mechanic but looked like they were practically brand new. ( I am assuming the prior owner had an electrolysis issue lol. )

 

I have a set of idit pistons out of my motor I broke a crank on you can have. They had about 30000 miles on them.