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?
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
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).
Why do you say that?NO YOU CANT.
NO YOU CANT.
Im sure its been done, but why the hell would you want to even try? Just to eliminate the reliability of the 6.9.
The 2 that were tried local to me cracked within 10k miles.
The 7,3 is not "just a bored out 6.9"
They did use different cores to make sure the cylinders would survive , and we all know how that can work out sometimes.
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.
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.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.