6.9 idi turbo build plan and questions!

Crewcab8469

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hey guys!

first post so i wanted to introduce myself.

im a long long time lurker and used to have an account on here from years ago where i posted my first 6.9 truck build (suspension related) but i cant get back into it so here we are starting fresh. little bit of background for me, im a certified diesel heavy equipment mechanic running a field truck in arizona. been working on equipment for a little over 6 years. im going to focus on engines specifically since this is the topic. ive done many overhauls and repairs from large diesels (cat cummins liebherr izusu ect.) in equipment to performance gas engines (usually SBC or LS, some older ford small blocks and big blocks) one of which is in my tube rock buggy (im also a fabricator as a hobby). i have a deep love for the idi engines and always will.

Now for the build details and questions!

im starting with a running 6.9l i pulled out of my parts truck. it appears to be a reman engine bored .040 over with low run time as i have stripped it down and there is literally no crud anywhere in the motor. it doesnt appear whoever did the reman did a great job based off some observations ive made from the tear down so its getting a full rebuild, but more on that later. i am attempting a goal of 350-400 crank horsepower and 650-750 flbs. the engine is getting felpro head gaskets, pistons shaved and ceramic coated, arp head studs slightly over torqued (delivered tomorrow!), powerstroke rods with arp bolts, still figuing out the IP because everyone is behind or out of stock so probably a maxed modded stock pump to get it going with the mods TheWespaul has posted, fabricated turbo hot side similar to justin & R&D makes (unless he makes more stock before i fab), turbo TBD still doing my research, injectors im going to mod shim and match stock ones myself until i can find stage 1's, and possibly a main girdle, and lastly either a type4 cam or an r&d cam. target compression will be 19:1 or so. not worried about possible hard starting but don't want an ether baby so ill stop there. the whole goal is to get it to survive with boost and have the supporting structure to handle the power with room for improvement when i can get my hands on a db4 pump.

now for the questions!

i have a set of powerstroke rods and between my machinist neighbor and i were going to do all the machine work to adapt them to the idi crank like justin has. my biggest question is what grade of material should be used for the wrist pin bushings? i was thinking aluminum bronze but i have never got into the metallurgy on wrist pin bushings before so i dont know what grade or if there is a better material for our idi's.

second question
does anyone know what arp studs will work for a main girdle thats 1/2" thick? ( i know R&D makes one but hes very busy and out of stock, plus i like fabricating)

third question
does anyone know what arp studs will fit for the intake? ill be machining the intake flat, plating, and tig welding a v band on.

fourth question

how much have you guys shaved off your pistons and what worked best for you? ive scoured this forum and read anything from 10 thou to 110 thou but never got a solid answer. id like to run some stuff through the comp calc a few times before i fire up the mill.

fifth question

is an s366 a good size turbo that will allow me to grow from a modded stock pump to a mod db4 pump in the future? if not what are some good options? smaller turbo?

shout out to thewespaul and justin with r&d along with a few others im missing. your info is irreplaceable in this community and i appreciate you guys sharing.
 

IDIBRONCO

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For what it's worth, here's my .02.
With your background, I doubt that you'll have much in the way of issues working on your IDI engine.
While, ultimately, it's your truck, money, and decision, I really don't see any need for intake studs. People have run some pretty crazy boost numbers in their engines without intake studs.
Likewise for the main girdle. These engine have a very over built bottom end and it holds up to a lot of power just like it is.
While there's nothing wrong with running the PSD rods, be aware that you'll also need to use Factory Turbo pistons because of the larger wrist pins in the PSD rods. Wes said that he wasn't seeing any issues with N/A rods (which you have in your 6.9) until about 350 wheel HP. Since you're talking about 350-400 crank HP, you should be fine with N/A rods at those power levels. As for the pistons, it's kind of hard to find the Turbo pistons and rings right now and I don't believe that they're available in +.040.
On to your fuel parts. At your stated power goals, a DB4 pump would be a complete waste of money. It will put out WAAAY more fuel than your engine will use/need at that power level. You can probably do that with a 130cc pump, if not a 110cc. You may net even need stage 1 injectors, but they sure won't hurt anything to have.
As for the piston shaving, you and your neighbor will have to determine how much to shave off in order to be close to your 19:1 ratio that you want. It probably won't be close to .110. Most people seem to shave .010-.020 off of their pistons from what I've seen.
 

david85

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Has anyone ever machined pistons to accept the larger wrist pins? The other thought is to use custom bushings with the forged rods to use regular size wrist pins. I don't know how feasible this is, but throwing it out there.

EDIT: To answer one of the questions, I took 20 thou off the pistons in my engine. This was for turbocharging, but also because I was using remanufactured heads that I suspected had been shaved by 5 though and wanted to eliminate any chance of interference.
 

IDIBRONCO

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I'm not sure if you could modify the pistons that way. By removing that much material from the wrist pin area, you might end up making them weaker to the point where they won't hold up at all. As for that, you'd have to ask someone who's smarter than I am on that kind of thing. The same goes for the custom bushings. You'd have to decide whether or not the thicker, softer material will be able to stand up to the stress. By weaker and softer I meant when compared to the wrist pin material.
 

Crewcab8469

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Thanks for the replies guys

My goal was to kind of overbuild the bottom end on this thing hence the PSD Rods and the girdle. The girdle is probably way way overkill from what you have stated and I can always add that later. Also would like to have the structure to increase the power quite a bit in the future if I wanted. You guys know how it is, once you get a taste you want more . For now I’ll do stock injectors and shim/match them and play with the pressures a bit. I have 16 good core injectors from my other idi truck and another parts truck I tore down years ago plus the 8 reman ones on this engine. I know thewespaul was able to get something like 107cc out of a stock pump with some modifications so I’ll start there for fuel. I have 2 good pumps to mess with.

Now for the rods, I see your point on the thicker bushing possible causing an issue with a soft material. Based off the measurements I’ve read and taken the idi wrist pin is 1.110 diameter and the turbo rods are 1.299 so we have a .189 difference in diameter which would add .0945 thickness to the bushing on top of how thick it currently is (haven’t measured just yet) I did read in an old post R&D made a while back that someone successfully made the custom bushings to bush down to he 1.110 non turbo wrist pin diameter and they held up but what they used for material I have no idea.

And as far as David’s question about machining the piston Wrist pin larger I’m sure it’s possible as you’re only cutting half of the diameter difference off the wall of the bore but without seeing the difference in the turbo piston in that area I wouldn’t try it. Might weaken the piston in that area, or the turbo pistons might just be the same piston with a hole bored to 33mm instead of 28. Maybe someone has a set of old turbo pistons laying around we can get some measurements off of?
 

IDIBRONCO

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For now I’ll do stock injectors and shim/match them and play with the pressures a bit.
You may be surprised at what they will do.
I know thewespaul was able to get something like 107cc out of a stock pump with some modifications
I don't know if that was a Turbo pump, but I'll bet that it was a 7.3 pump. I believe that a stock 6.9 pump puts out less total fuel.
I did read in an old post R&D made a while back that someone successfully made the custom bushings to bush down to he 1.110 non turbo wrist pin diameter and they held up
It's good to know that I was wrong here.
or the turbo pistons might just be the same piston with a hole bored to 33mm instead of 28.
It's been over 20 years since I've seen a Turbo piston. I do know that they're not exactly the same besides the wrist pin bore. Two differences are that they use a different type of ring. They use a Keystone style ring (I have no idea what that means). They also came out stock with an anodized coating across the top of the piston except for a 1/4" (or so) wide ring around the very outside of the top of the piston. While you can buy aftermarket N/A pistons that are anodized, none of the stock N/A pistons had that coating.
 

Nero

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Keystone is just trapezoid shaped piston ring, if you look at it from the split. The design helps prevent the ring from sticking in the piston.
 

Far Right

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No wonder the 6.5 chev guys are quiet on this forum. Ford putting out 350-400 hp the p400 is the only chev I’ve heard of coming close too that, mine is 200hp the opti is like 220 without bulk mods, if it all gets too much mate send me that big Ford donk n I’ll find something too for it in,
 

IDIBRONCO

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While there is one or two on here, this is the wrong sub forum for the 6.2/6.5 in general. I'll bet that there's some pretty big numbers over there. The difference in that the bottom ends of our engines hold up to WAY more power than a GM IDI will. You can repair them if you catch them early enough. Maybe you can strengthen them up some, but I would think that would cost quite a bit.
 

captain720

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While there is one or two on here, this is the wrong sub forum for the 6.2/6.5 in general. I'll bet that there's some pretty big numbers over there. The difference in that the bottom ends of our engines hold up to WAY more power than a GM IDI will. You can repair them if you catch them early enough. Maybe you can strengthen them up some, but I would think that would cost quite a bit.
It costs about 10-15k US to touch lightly modded IDIT numbers with the 6.5. I’ve watched relatives do it, mind you all of that just to nuke your 4L80E. I would rather tow with my NA IDI because I know it’s not going to overheat and split in half.
 

IDIBRONCO

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It costs about 10-15k US to touch lightly modded IDIT numbers with the 6.5.
I can't argue because it depends on what you mean by "lightly modded". I can say that, on the 1994+ 6.5 with the computer controlled IP, you could get pretty decent performance by installing a power chip and a bigger exhaust. Back in the pre-tuner days of course. How those would have compared to a modded IDIT, I have no idea. That "decent" rating was strictly by using the butt dyno.
Ford's look better too.....
I do agree, but it is opinion. I do know that Fords sure felt like they had the better interiors.
 

Jesus Freak

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I do agree, but it is opinion. I do know that Fords sure felt like they had the better interiors.
This is a scientific fact. If a lot of the crap and psudoscience that gets put in text books, taught in schools, and reported on the "news" can be called facts then I can hold to the fact that 80-86 ford trucks are the best looking trucks ever.
 

Black dawg

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Had enough of both brands of idi engines to know that they respond very similarly to similar mods. Less cubic inches yes, but less hp/ci with the same amount of time/money/effort, NO.

The gm idi isnt nearly as strong of platform for bigger mods, and typically pulls a little harder in the higher rpm (like a smaller engine) and less in the lower rpm than the ford IDI.

Stock for stock, 6.5td and 7.3 factory turbo pull pretty similar. With maxxed pumps and boost adjusted to match, I feel the 7.3 pulls harder and is somewhat less prone to overheating, and I wouldnt feel like I was asking too much to run it (7.3) like that for years (towing). If I were towing with a 6.5, I would be keeping fuel and boost pretty mild......it was NEVER intended to be any kind of remotely heavy duty diesel engine. Orignally was just a mpg machine (and did that phenomenally), turbo was added later to compete in the growing TD market, and to do the same work a big block would with much less fuel consumption.
 

typ4

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Without reading the whole post, intake studs , waste of time.
Do not bore the pistons for bigger pins, I have never seen an na piston break unless a valve dropped. I have seen many turbo pistons break right above the pin hole, why? Because the big hole weakened a very tough part.
NA rods will hold 35-40 lbs boost . At 50 they bend. Proven By Justin.
Turbo pistons for a 6.9 are not a thing.
Bush the rods if you are going to use them. If machinist buddy is good you can sleeve and offset bore the pin end to lower compression height.
I do not subscribe to the over torqueing of the head studs, many argue but Fine thread studs clamp harder already sooo,,,.
 

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