So... Decided I'm rebuilding the 6.9 in my 86 SuperCab.

So far here's where I'm at.

Gen1 Banks non-wastegate turbo with 3" exhaust.
Mahle .040 ceramic coated (R&D) .010 decompress pistons.
Stock heads rebuilt with 7.3 turbo valves on the exhaust. (Stellite)
Comp 910 springs?
ARP head studs
Balanced rotating assembly
Stock rebuild otherwise.
Stage 1 cam
90cc pump (R&D)
Stage 1 injectors.

Truck is also being converted to a T19 and has 3.55's and 33's. 4x4. Not looking to set any records, just a good tow rig that's reliable. 2xx at the wheels would be nice, but close is good too... 5xx or so on TQ.

A 110 pump might be better, but my wallet will dictate that. There's about a $500 difference...

Thoughts?

Also, since I'll be using the 6.9 NA rods, does ARP make bolts for them and is that needed?

TIA

 

With the limit being the headstuds on the 6.9, you'll probably only want to go for like 10-ish PSI of boost.
This will fit the Banks turbo fine; it isn't going to want to do more than that really.
This also will reduce your fuel need - 90CC should be fine for that. A 110 is overkill until you can get at least 15 PSI of boost at a reasonable temperature(intercooling probably needed).
If you are looking at that, you can probably skip the ceramic coating(I've run my 7.3 at 950-1100 degrees for a few hours and the pistons looked just fine - they have plenty of oil from the bottom).
Comp 910 or Trick Flow valve springs... probably not needed unless you get a bigger turbo. I didn't need them until I managed to get 20 PSI out of a TE06H and the drive pressure was a /lot/ more than that.

I would say that the #1 thing I'd be making sure of is valve clearance. Especially with a rebuild and extra-tall cam, if the machine shop doesn't make the tolerances on valve recession to spec, you'll hit the pistons and destroy your guides in short order.

That's just my 2c worth.

 

A 6.9 can handle more than 10psi with studs though. 20psi is safe on a studded 6.9. Especially with it decompressed. I agree on everything else though.

 

The pistons are coated and the guy I'm buying them from abandoned a 6.9 project in favor of a PSD. I'm basically getting them for the price of uncoated pistons... So since the coating is essentially free.... I'm running coated pistons... Future insurance. Later if I get frisky I'll pull it apart, swap in some PSD rods, moar boost and moar fuel for moar fun...

Yeah, the banks will probably run out of steam around 8-10 I'd expect. If that. Might be 6-7psi, but I'm just going on hearsay from others. 90cc sounds like a good fit for now.

I'm curious about the limits of boost though. I would think I could go higher than 10 with studs. I know they're smaller, but 10 isn't a ton when you've got 7.3's running 30,40 and even 50psi. I'd be curious to see what Mark Strock's running. I know he went a bit overboard building his 6.9...

Because of budget I'm getting the heads and block done separately and I'm going to mate them. I figure that gives me a chance to degree the cam and I can even pull a couple valve springs and check clearances. I can bring the heads back and have them cut deeper if need be.

I wish I knew who in the SE PA area I could trust to put it all together right, but I don't... Mark went to Washington so that tells me something...

Side story, I was busy and people always tell me I need to let others do things for me. So I called a company out to "tune up" my oil heater in my house. Weather got cold and after the 3rd no start when I called to bitch I was told that the .5gph nozzles were prone to clogging and that they'd send someone over to swap it for a bigger nozzle. I went down and pulled the gun out and by eye I knew the igniters were WAY out. Spec is 5/16" above and they were 1/2". They were supposed to be 1/16" forward, they were 1/16" back. Too high, too far back and by eye at arms length in 1 second I knew that. I reset them correctly and it's been running fine since. I know more than the tech and this isn't what I do for a living...

So yeah... I have major trust issues...

 

I'm looking a bit conservative here. I thought I recall Justin blowing a headgasket on a 6.9 at like 20-25 PSI or something like that. The 7/16 studs are by far the weak point as far as I can tell.
I'm being conservative in my recommendation, because if you blow a gasket instantly at 25, you probably don't want to run more than 12-15 for long periods of time... at least that's my thought process here.

I'm thinking that to improve this up to the 7.3 level, we need thicker studs. No way around it really.

Justin actually did drill and re-tap a 6.9 once, but ran into issues keeping the drill straight going down the holes.

I'm thinking that when I try rebuilding a 6.9 for power, I'll have to figure out a way around this - a simple drill guide block and a piloted drillbit should make it a snap.
... But this is just conjecture at this point; I've never done it.

 

It comes down to cylinder pressure. That comes down to how much oxygen and fuel you ignite. Cold air is more dense and carries more oxygen than hot air. So boost pressure only tells you a little bit. Intercooling cools the charge out of the turbo. A turbo that can move more CFM efficiently results in a cooler charge coming out. So someone can run 20psi and be fine and the next guy runs 20psi and blows up. The second one may have been getting more oxygen and with more fuel pressures were higher. HP was higher too...

This is why you can have 12 psi and make more power than someone at 18 psi...

Anyway, I peg the upper limit of a studded 6.9 at around 300/650 at the wheels. Maybe just a touch past that, but Justin lifted a head at 700-ish rear wheel torque.

I'd be happy with low 200's and 450-500 tq at the wheels. Basically a 50-60% increase over stock.

 

That is correct. Justin was around 350hp/700tq when he blew them. As Macrob mentioned, you can drill for bigger studs. Also could upgrade to ARP2000 studs or even ARP 625s. The 625s will be custom though which will run over $1k. They are top of the line and have tensile strength though.

 

I'm not an expert, but I thought you couldn't because of water jackets in the heads? Or maybe block? If it was just the head you could run a 7.3 head.

 

Justin did it. He just had trouble keeping the drill going straight when doing it by hand.
I'm thinking it's doable if you modify the drill to self-center more, by grinding down the first 1/2" or so of it into basically a pilot. This will keep it following the original hole instead of cutting a new one(wandering)

I'm thinking that even if you broke into the water jacket at the bottom in one spot or another, you could just put a bunch of RTV in there and call it good. Just as long as you have a minimum of 3/4" or so of thread engagement, you should be fine -- remember, the threads in the block are weaker than the ARP studs - Even in a 7.3, the threads will pull out before the ARP studs break.

 

Ok... Adding to the knowledge bank, Craig Clifton lifted a head on a 6.9 at 25 psi with studs...

That's probably around where Justin was +/-

So 20 looks like the upper safe limit on a studded 6.9. At least with stock sized studs.

 

And found another, Austin Arps, who lifted a head around the same PSI(25). 7/16 studs and .040 shaved pistons...

Add Austin Presley to the list. Digital boost gauge - it let go at 24.6psi...

Maybe we can add this to the stickies somewhere. How much boost will a 6.9 with 7/16 studs take?
Austin Arps
Austin Presley
Craig Clifton
Justin Anderson

Have all confirmed lifting a head around 25psi.

 

Strock is running close to 30 on his with no problems though. However, he has the decompression gaskets. Either way, going through the effort of turbo / PSD rods in a 6.9 is pointless. Drilling the block out for bigger studs is nearly as pointless, good chance of ruining the block is about all you get.

I cant remember if there are any compressor wheel options for the banks, but i wouldnt be afraid of running a 90 with a banks on a 6.9 with studs. Justin and one of the austins had little bitty turbos on there, the s256, which is a little quick and restrictive imo, especially given the headgasket issues of a 6.9, and justin was runnin the s360 with the itty bitty exhaust housing, same i think for the other austin.

Between the pistons and the cam, i think you will be fine.

 

Spoke to Justin and he agreed and said it would be a good running combination.

I'm not looking for a million hp, just something that runs good and is reliable. If you have enough money just any amount of HP/TQ is possible. I don't have enough money...

 

If you can get a wheel for the banks, 250 /550 should be doable with a hot 90 pump and an intercooler

 

Using a mag drill may work good for drilling out head studs and keeping it straight. Most rental places up here rent them out.

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