briankk
Registered User
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?
Machine shop
- Thread starter briankk
- Start date
You should be able to bore the 6.9 out to 7.3 with no issues from what I've heard. Others on here will know better than me.
If the cylinder wall is so bad you need to sleeve it then I would get a new block. Like mentioned before boring out to a 7.3 would make for the cheapest/easiest to find pistons
johnnolanstrtgld
Registered User
I like Dell's.
Hydro-idi
Full Access Member
I’ve done business with Vic’s harbor machine shop in Sacramento. Good group of guys but my cylinder heads had to be redone shortly after they rebuilt them unfortunately. Don’t know of any real reputable shops in the sac area but sure you can find one.
I had a local machine shop properly rebuild my cylinder heads after Vic’s, along with my entire engine and they did a great job. Very happy with his work but he does take his sweet a$$ time lol, as he does not like to be bothered or rushed. That’s hp engine specialties here in Lodi.
I had a local machine shop properly rebuild my cylinder heads after Vic’s, along with my entire engine and they did a great job. Very happy with his work but he does take his sweet a$$ time lol, as he does not like to be bothered or rushed. That’s hp engine specialties here in Lodi.
briankk
Registered User
Understood, but I'd like to preserve as much cylinder wall as I can, and I already have a 7.3.
Lookin' at this to get Bank's turbo and move 12K lb motorhome, FWIW...
Macrobb
Full Access Member
I think the point was that you could bore a 6.9 *up to* the diameter of 7.3.
You want to just bore it the minimum amount to clean it up, in increments based on the piston sizes available(.010, .020, .030, .060 I think).
Also, while you are doing this build, get headstuds. That's the weak point of your 6.9; otherwise, you could probably push 20+ psi of boost and 300 at the wheels without it blowing up(with enough fuel and a big enough turbo).
If you just go with headstuds, a cranked up stock pump and Banks turbo... I'd expect 200-220 at the wheels(260-280 at the crank, vs 180 stock), which isn't too shabby. Performance parts can go up from there...
You want to just bore it the minimum amount to clean it up, in increments based on the piston sizes available(.010, .020, .030, .060 I think).
Also, while you are doing this build, get headstuds. That's the weak point of your 6.9; otherwise, you could probably push 20+ psi of boost and 300 at the wheels without it blowing up(with enough fuel and a big enough turbo).
If you just go with headstuds, a cranked up stock pump and Banks turbo... I'd expect 200-220 at the wheels(260-280 at the crank, vs 180 stock), which isn't too shabby. Performance parts can go up from there...
I haven't done any work of that extent on these but that was indeed my point. Everything I've read says unless you have a cavitation problem boring to the 7.3 size will be no problem.
There are people out there who feel the need to get the most "cubes" out of a motor and bore as big as possible. Me personally I like the added security of thicker walls and knowing if you managed to wear it out there'd still be meat left for another overbore.
Basically my point is .030 or whatever shouldn't be an issue on a 6.9. Wikipedia says the 7.3 is a 0.110 overbore on a 6.9. Like Wes said, if it's bad enough it needs to be sleeved good used blocks are really not that expensive.
Macrobb
Full Access Member
Yup. And honestly, no need for more cubes when you have boost.
In the diesel world, there *is* a replacement for displacement!
In the diesel world, there *is* a replacement for displacement!
Why do you say that?
Hydro-idi
Full Access Member
Agreed. Why turn a 6.9 block into a cavitation prone engine? There’s not enough hp difference between the two engines either to justify doing that.
I would have your machine shop bore it .030 over and see how the walls clean up. I think .060 is about max for a 6.9 block where you can sill find pistons to accommodate larger bores.
Then slap a set of arp studs in it and it’ll be more reliable than any 7.3 idi out there, making it more than able to handle at least 20 psi boost if wanted.
Now your explanation showed up, dunno if you edited or if forum glitch...
Yes you can bore them out and the main reason you would is for the availability and pricing of aftermarket pistons and rings. Standard bore parts are much easier to find and much cheaper than buying specific overbore sets. Is it ideal to bore it out that much? No. But it is incorrect to say it cannot be done, it is a viable option in rebuilding and done quite a bit in budget rebuilds.
Yes you can bore them out and the main reason you would is for the availability and pricing of aftermarket pistons and rings. Standard bore parts are much easier to find and much cheaper than buying specific overbore sets. Is it ideal to bore it out that much? No. But it is incorrect to say it cannot be done, it is a viable option in rebuilding and done quite a bit in budget rebuilds.
briankk
Registered User
Well, this is just about the point I was intending to make, you beat me to the draw. I like the idea of thick walls an a lot of boost..
Knuckledragger
blowing chunks and grabbing porcelain
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 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.
Macrobb
Full Access Member
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.
I haven't checked if a 7.3 piston has a nice flat area on the inside of the piston where you could hold it for machining, that would make some difference.
Any thoughts on if this is even possible?
I Think the 7.3, as designed, had thick enough walls.
I had a 88 7.3 overbored by .030" to clean up the taper... and it worked!
No pinholes or coolant usage.(well, up until it threw a rod... but the water jacket still holds pressure!)
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.
I haven't checked if a 7.3 piston has a nice flat area on the inside of the piston where you could hold it for machining, that would make some difference.
Any thoughts on if this is even possible?
I'm not convinced the 7.3 walls are too thin. Cavitation, as far as I can tell, comes from the cores being mislocated on some engines, so you have a thin wall... in one spot.
I Think the 7.3, as designed, had thick enough walls.
I had a 88 7.3 overbored by .030" to clean up the taper... and it worked!
No pinholes or coolant usage.(well, up until it threw a rod... but the water jacket still holds pressure!)
