Modifications for the 6.9/7.3IDI
- Thread starter airflo71
- Start date
Cat_Rebel
Does not compute
Glad to see you finally came over here. 
Glad to see you finally came over here.
Man you post as fast as I get done writing the last letter...Good to see you here as well!!
The whole reason why i ask this is somebody is already casting 6.5 GM blocks with much more strength. Now they can boost higher and make a lot more power. I was thinking if enough interst is here for a 6.9 block somebody can start casting , machining these and we can see some PSD 7.3L output numbers.
First of all my understanding of the 6.9 block is nill. But I would think a redesign(where it counts, more material in the block, sorrounding the cylinder bore, sleeved, main girdle kit. oil cooled pistomn squirters, forged rods, coated pistons. redesigned cylinder head etc...Could be a real killer?
Dirtleg
Full Access Member
I am completely on board with your intentions here. I too like to remake the old stuff better. The issue as I see it getting enough demand to make it worthwhile. I think it would be cheaper and just as effective to have one offs of the girdle, main web beef, etc fabricated at a good race shop if you are really hell bent on acccomplishing this. Dropping the coin to re-engineer and eliminate the shortcomings of the 6.9 and then spending the money to re-cast everything is going to cost a buttload. No way I see to even get anywhere close to each motor not costing ungodly stupid amounts of money.
I would love to see it done, don't get me wrong. I just think if you want a race motor, build 1 only. I would like to know where the performance limit for the IDI style motor is. So far no one has made one with stupid power that hasn't blown up. From all I've read, Dave Sponaegle (sp?) is the only guy who's running a way above average amount of boost reliably. But we still don't know what the power levels are. (I'd really like to know too)
So with that said, what are your ideas concerning the cylinder head combustion chamber design? How do you feel the precups should be modified or should they be eliminated all together? My opinion would be to eliminate the precup and redesign the piston to move the combustion chamber there. But then it wouldn't be an IDI anymore. I really don't have any information or knowledge of the benefits and drawbacks of the precup design but it seems to me it would be the limiting factor in ultimate power output.
Maybe if you had a 2 stage injection to start the combustion in the precup and then a second injector to add additional fuel to an in piston combustion chamber after the ignition event. Timing would be a real PITA I am sure. I don't even know if it could work but that's the thought I came up with. Then, if you were cramming 50 lbs of boost in there you might be able fuel it as you would have to have a second injection pump.
I've been wondering lately if anyone has ever really attempted to significantly beef up the valvetrain on these motors. Roller rockers and improved retainers. Stiffer valve springs and better lubricating valve guides. Hell bigger valves while we're at it. With the amount of dropped, or close to, valves that the 7.3's seem to have this would be a great place to start. There might actually be a small market for a bulletproof valvetrain.
On that note, if you were to re -cast the 6.9 motor make it use 9/16" head studs and 7.3 heads/gaskets. Keep the 6.9 bore.
O.K. those are my ideas at the moment. Anyone else got any.
I would love to see it done, don't get me wrong. I just think if you want a race motor, build 1 only. I would like to know where the performance limit for the IDI style motor is. So far no one has made one with stupid power that hasn't blown up. From all I've read, Dave Sponaegle (sp?) is the only guy who's running a way above average amount of boost reliably. But we still don't know what the power levels are. (I'd really like to know too)
So with that said, what are your ideas concerning the cylinder head combustion chamber design? How do you feel the precups should be modified or should they be eliminated all together? My opinion would be to eliminate the precup and redesign the piston to move the combustion chamber there. But then it wouldn't be an IDI anymore. I really don't have any information or knowledge of the benefits and drawbacks of the precup design but it seems to me it would be the limiting factor in ultimate power output.
Maybe if you had a 2 stage injection to start the combustion in the precup and then a second injector to add additional fuel to an in piston combustion chamber after the ignition event. Timing would be a real PITA I am sure. I don't even know if it could work but that's the thought I came up with. Then, if you were cramming 50 lbs of boost in there you might be able fuel it as you would have to have a second injection pump.
I've been wondering lately if anyone has ever really attempted to significantly beef up the valvetrain on these motors. Roller rockers and improved retainers. Stiffer valve springs and better lubricating valve guides. Hell bigger valves while we're at it. With the amount of dropped, or close to, valves that the 7.3's seem to have this would be a great place to start. There might actually be a small market for a bulletproof valvetrain.
On that note, if you were to re -cast the 6.9 motor make it use 9/16" head studs and 7.3 heads/gaskets. Keep the 6.9 bore.
O.K. those are my ideas at the moment. Anyone else got any.
Some good stuff here, I know that it would cost a lot of money, and a one off design would be the best bet, getting the interest up will be the hardest part of anything that I do. I will probably look at a lot of different gas engine intake manifolds to get the best idea of a manifold runner design. Obviusly atomization of the diesel fuwl will be a huge factor here, getting the 6.9L volumetric efficiency up will do wonders as well. I don't know I will have to start taking apart a motor and go from there. I just thought that hooking up with some guys on here that have way more knowledge than I ,is a good start.
Dirtleg
Full Access Member
Ultimately whether you get anywhere with this idea or not it should make for a good discussion if some of the smart guys get onboard. (I'm not one of them unfortunately) I am down for a good discussion.
Cat_Rebel
Does not compute
I think some lower compression & pistons that can hold up to some EGTs are the first things in order.
Welcome to the site. Interest in performance IDI's seems to be on the increase of late, especially as the truck pulling "hobby" comes of age. What seems to be needed most is a reliable way to reduce compression and make more boost. Beyond that, getting rid of the "I" in Idi seems to be the big issue to me. If someone would cast up some direct injection heads, then I think you could really do something. Once you get to the point where you can blow the bottom end out reliably, then you've actually achieved something!
I need to persue this further, I read an article on a guy that was looking for more aftermarket support for his 6.9L...It inspired me...Then I found some old sales brochure on the Banks Turbo kit for the 6.9L..At one time the 6.9 was the top of the heap diesel engine for light duty pick-ups...There was no real money in aftermarklet parts at the time so the 6.9 got left out in the cold...Now we have a beautiful array of new technology that can be adpated to the 6.9L,,,it just has to be invented......If i could get some more interest in this topic,,,I might start some research before too long...
You got that right! I bought the first Ford Diesel pickup my dealer sold, and I watched the sales flourish. 6.9 powered pickups were as common in that day as the PSD's are now. You couldn't drive very far without seeing another one, and every ambulance, tow truck, brush truck, rollback, landscaping truck, etc. was an IDI. The GM diesel pickups were there, but the ratio was at least 10 to 1. Banks was the first to offer a popular turbo, and we were all excited about it. Alas, for this 20 year old with a $600 a month truck payment, the turbo was just a dream.
flatlander
plays dirty when losing
You know what's sad is that this is an untapped market. With the popularity of diesel pickups and the initial cost of newer models, the guy who could make power with an older model will own the market.
Think of the way you make power on older carbureted engines, you bore bigger holes, change cranks, heads, cams etc. . . We basically have that option but it'll take someone who is willing to invest a great deal into R&D.
It's too bad that Ken dropped the ball the way he did.
Think of the way you make power on older carbureted engines, you bore bigger holes, change cranks, heads, cams etc. . . We basically have that option but it'll take someone who is willing to invest a great deal into R&D.
It's too bad that Ken dropped the ball the way he did.
flatlander
plays dirty when losing
They didn't have 72 month payment plans back then, did they?
