Did I?

[Ford F834]

The 6.9 cups should make the engine sound louder and give me some better MPGs. The only reason the 7.3 cups came into existence was for emissions. The smaller displacement 6.9 cup would mean more fuel gets burned in the main chamber.

Just curious, what is your source for this information? I'm not contesting nor supporting it, I have been reading up on the pre-cup thing and have not found any evidence to support the emissions or mpg ideas... just hearsay. I would sure like to see some kind of test or comparison that supports these often parroted true-isms. The early 1983 engines also used a different pre-cup. There are lots of threads out there supporting one cup type over another, and people putting 7.3 cups in 6.9's... 6.9 cups in 7.3's... but it all seems based on speculation....

Back to your original thread topic, you said it was an IDIT, and those pistons are getting hard to find, as are the keystone rings for them. Had you not already spent the money on sleeving, I would have recommended the purchase of an engine/tranny donor truck or lift out. It would have been much cheaper than the route you are going. Best of luck to you. It might not last as long with re-used pistons, but I don't think it will have catastrophic failure as long as the ring grooves check out as mentioned. And do check those oilers. Hopefully you will get your money's worth out of the rebuild.

 

[riotwarrior]

I'm f*****g with you on that one brother 110%. Sorry for swearing but, I sure hope it does turn out good and runs strong. I gotta take this thing from Memphis,TN to Tampa,FL!!

The 6.9 cups should make the engine sound louder and give me some better MPGs. The only reason the 7.3 cups came into existence was for emissions. The smaller displacement 6.9 cup would mean more fuel gets burned in the main chamber.

So I hope it gets me to Florida and back and forth to work and whatever else I need to do

Wow, precups make a difference eh? Where have you obtained this (mis) information. Have you real quantifiable technical data supporting this or just HINTERNETHEARSAY?

If data supporting these claims is there please post it or links to it, otherwise it is supposition and not credible.

The differences in emission related heads IIRC is not in the precup but the injector and the depth that it is located in the precup chamber. Now I'm quite comfortable stating I've only read that on this forum so it could be correct or incorrcect however the injector part is correct G code where a different injector for emission in the turbo engine.

Good luck with the build.

BTW are you re-using the old rod and main bearings too?

 

[icanfixall]

I don't recall when it was done but the injectors were lifted up out of the heads and precups for emissions reasons . This was a 60 thousands lift. On my first set of new heads the precup chambers in the heads were very rough machined. So thinking ahead I decided to fabricate an ball end mill large enough to cut out the bad machining and raise the chambers the 60 thousands. I felt I could do 2 things at once. Clean up the chambers and drop the injectors in the head with the one ball end mill machining. So it worked fine. Had the chambers been nice I would have simply machined the seat in the heads down another 60 thousands and be done with it.

 

[JosieGallows]

Wow, precups make a difference eh? Where have you obtained this (mis) information. Have you real quantifiable technical data supporting this or just HINTERNETHEARSAY?

If data supporting these claims is there please post it or links to it, otherwise it is supposition and not credible.

The differences in emission related heads IIRC is not in the precup but the injector and the depth that it is located in the precup chamber. Now I'm quite comfortable stating I've only read that on this forum so it could be correct or incorrcect however the injector part is correct G code where a different injector for emission in the turbo engine.

Good luck with the build.

BTW are you re-using the old rod and main bearings too?

Getting new rod and main bearings. They come as a kit.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

The 6.9 cup is more angled while the 7.3 cup is more shallow.. Meaning the flame front will smash the piston more directly than at an angle, but that's just theory. The 6.9 cup is also of a smaller displacement. Look closely.

I got 8 6.9 cups new for $3 a piece, and 8 7.3 cups new for $7 a piece. I'll sell the ones I don't use.

EDIT: There is also a pre '85 precup. But I could only find 6 so it would be pointless getting them.

 

[Andertusa]

Josie, Honestly, I think you'll be fine with what you have there, the others are questioning the skirts being scuffed-up, but in truth, that little bit wasn't that bad, it wasn't enough to really remove the factory machining grooves off the side. It looks like whatever was going wrong was caught early, and I'd postulate that the damage was likely not from the piston rocking in the bore, if it was, the sides of the piston would be more worn near the bottoms of the skirt than at the tops, and most likely ALL of the factory tooling grooves would be completely bare where it was rocking. You'd see this interesting pattern where the grooves appeared on the skirts near the wrist-pins and then disappeared on the other sides.

The idea of replacing a single piston is tempting, but remember you are running a dynamic reciprocating mass that is accustomed to running as is, the new piston/wrist-pin/con rod set could be heavier or lighter than the others; and if it is, it'll mess with the balance o the engine, so if you do, get the rod/piston/wrist-pin matched so they are all within very close tolerances to each-other, within less than tenths of grams if you can.

 

[Andertusa]

.... so if you do, get the rod/piston/wrist-pin matched so they are all within very close tolerances to each-other, within less than tenths of grams if you can.

I meant matching that one replacement piston/rod/wrist pin matched with the other piston/rod/wrist pin sets in the engine's other bores. NOT matching the rod/pin/piston to and against each part in that combination of parts, just for clarity.

 

[racer30]

Josie You have nothing to worry about with the skirts...cleaning them using a circular motion will put micro scratches to hold oil for lubrication. This engine will run fine with reused pistons as long as you make sure to clean the ring groves of any old carbon. Make sure to put the top two ring end gaps 180* from one another at the sides of the bore and the oil ring gap towards the valley of the engine. Doing this will reduce compression loss from lined up end gaps and having the oil ring gap (up) will keep the oil in the grove from easily draining out between engine start ups. Building a engine on a budget is possible just make sure the piston oil sprayers are clean and the oil galleries are clean. Check out my Budget 7.3 build http://www.ford-trucks.com/forums/1261431-class and my flickr page https://www.flickr.com/photos/racer30/ It will give you some nice info... Good luck and Don't let anyone get in the way of your Dreams...

 

[riotwarrior]

K just so it's clear, I believe it will work, it's just not as good as a full set of new slugs n rings.

Right now you are so close to a fully re manufactured engine, vs an overhauled engine, is it worth it to short cut? Can you cut grass, clean gutters, bag groceries etc to come up with extra $$$ if so awesome!

At this point with a fully sleeved block and used pistons...it's kinda like using a ****** taking it off to wash it and turn inside out n use again...it would work ..just not ideal!

Ifn it was mine, personally I'd get a new ****** nothing like fresh slugs in fresh holes

At the least you can have your new fresh block machined to fit those pistons individually which is a huge plus!!!!

With the sleeved block there will be no taper in the bores, so those pistons won't rock, it's wear/taper and such that causes mild rocking as the engine turns over, this can and does induce forces that over time can scuff the bores. Rings alone in a tapered bore cannot at engine speed stop rocking from occurring.

Again I see this as a working solution on the cheap, but not ideal.

One thing I will say I've seen way worse pistons work in Gassers....for example a fellow dropped a used piston/rod assembly and broke off a lower portion of the piston skirt, picked it up and kept on assembling...engine ran for years...so it's not the worst for sure..


Giver ***** n watcher close, I'm sure it will be ok.