I'm working on rebuilding my 84 6.9. I haven't started on my motor yet and I already know I'm stripping it and building it from the block up with a R&D stage 3 turbo, stage 1 injectors, stage 1 camshaft, 7.3 powerstroke converted piston rods, and a new injector pump. But anyway I was wondering if the 7.3 heads would mount onto the 6.9 block. I was also wondering what all parts I would need. I'm getting the rebuild kit and then valves, head studs, and roller lifters but what other parts will I need so I don't destroy my block?

thanks for any help

 

you would have to cut steel tube to make up the size difference from the 7/16 to 1/2 bolt size ..

that aside it will work just the same .. drop a tube over the bolt shaft that fits snug .. that will also fit snug inside the head holes .. and then cut each insert to fit and it should be fine ..

though i would just use the matching heads unless u just have extra 7.3 heads and the 6.9 heads were damaged .. the 7.3 doesn't have any better flow .. it's just bigger bolt holes ..

 

You should be able to use the sleeved washers used to put 351w heads on a 302.

 

Why put psd rods in a 6.9? The headgaskets will blow before you hurt the rods, even with studs, unless you machine for 1/2" or larger.

 

I'm already going to be replacing everything and I might as well put psd rods in it just to say it has them.

 

I know I won't be able to push much psi out of a turbo on a 6.9 but I want to make it as strong as I can especially since it's an 84 block

 

If you are going to go to that extreme, figure out how to upsize the bolts to 1/2 or 9/16. Then, you can run as much boost as you want!

Otherwise, there's no point. It's literally not worth it at all if you can't push enough boost to use it effectively.

I mean... you don't hear about 6.9s breaking rods, do you(aside from running out of oil of course) For a NA or mild turbo setup, they are pretty darned strong. It's only once you get into the 40+ PSI and 400+ HP range that better connecting rods matter.

 

ohh .. one other thing .. use the 6.9 style short valve guide seals ..

do not use the long ones from the 7.3 design ..

the short seals allow a little oil to splash on and leak down the valve stem .. allowing proper lubrication ..

the 7.3 heads had 'upgraded' seals that covered the entire stem and left it to run dry in the valve guides .. then the guides wallow out and the seal cracks and it consumes oil and smokes ..

that is why 6.9 tends to use less oil and the valve guides stay in good condition because of the short style seal ..

they only elongated it to conform to government emissions regulations .. it's only okay for a little while in a brand new fresh motor .. but mid and long term running dry it causes oil consumption and smoke ..

 

Yeah, I can see that. All of the 7.3 heads I've seen have had valve guide wear.

Also, recently I ran a 7.3 for about 5-10 K miles with /no/ exhaust valve guide seals. I thought it might help. I noticed /no/ difference in oil loss(negligible), or smoke.

Next build I'm just plain going to leave them all off; I'd prefer the extra lubrication even if it needs a little more oil... especially when you are talking about significant extra exhaust heat from a turbo.

 

Interesting about valve guide seals. Early CB750 engines had no exhaust valve guide seal, though they had a longer guide made of harder material. When I did my head and ported it I changed to new style brass guides before cutting the seats, and used positive seals (attach to lip on guide and have a lip and spring in the seal). It used to smoke a little at high RPM or under decel, not anymore. The newer guide and seal style came about in the early/mid 70s when the EPA wanted to make an example out of Honda and went after them harder than others.

With a diesel I doubt you'd notice much extra smoke when working it as EGT is high, but I could see it being more smokey at idle and light load.

 

yea .. because the crankcase of a diesel isn't drawing vacuum it won't 'pull' oil down out through the valves ..

what oil makes it down the guide is by splashing not from pulling a vacuum ..

used to be that diesels didn't use any valve seals ..

then they started using just an o-ring ..

then came the short style seals ..

then finally they moved to the oil starving long seals ..

each of these progressions were to meet emmisions regulations as they became more limiting ..

oil consumption - in any event - will be minimal because of the absence of vacuum ..

the exception being the long seal - as the starvation of oil from the valve guide eventually wears it down making for excessive oil consumption because oil then splashes more easily past that larger opening ..

if mine ever need replacement i will use viton o-rings or the stock short style seal ..

 

This.. nothing at all wrong with the stock rods, theyre beefy, just not enough beef for 1000 lb/ft. Rods wont help the weaknesses of an 84 block anyhow.

Damn... i forgot about the valve seals. Never even thought about it, i assume woods probably used the 7.3 ones in the kit when they assembled the heads. Lets hope it will be fine with the hardened guides.

 

One of these days.... I really want to try this! 1000ft lbs from a built 6.9.
I've still got a couple of 6.9 blocks floating around I'm not sure what I want to do with. One 83-84 block which rotates, an 83 block which is siezed and has a big crack on the side from the block heater, and an 87 engine that also seems to be in runable condition.


Simple solution: Decide you need better valve springs.
When you are in there(which you can do with the engine in the truck, it's not actually that hard - just rotate the engine to TDC of the cylinder you are doing the springs on), deal with the guides at the same time.
I did this at one point; it was a good full-day task, but not more than that.

Of course, if you just wanted to get the valve seals /out/, that's even easier - Pull the valve covers and yank the valve seals out in pieces with a pair of needle-nose pliers.

 

They may not have put them in, i didnt notice them through the springs, dont guess i paid it that much attention. I already have comp 910s

 

if you run it like you stole it, it will splash just fine, the worst thing for the IDI is never revving it.