Anybody know where to get .020 over pistons for turbo idi? I've had no luck finding a set.

 

There were some on ebay and rockauto last i looked. Had to look high and low for std bore. Word is mahle stopped reproducing the turbo slugs, so theyre going to get tough to find.

 

Interesting. I was considering picking up a factory turbo engine to build, mainly for the stronger rods. Might be an engine to avoid if nobody makes pistons anymore.

 

The only size difference between turbo and non-turbo pistons is the wrist pin diameter, right?
You could take a set of NA pistons and use extra thick bushings in the connecting rod, or have the NA pistons bored to fit the bigger pin.

Not saying it would be economical, but it would be possible, even if the 'correct' pistons aren't available.

Also... this same pin problem is what you have if you want to use Powerstroke rods in an IDI, so the bushings are available somewhere.

R&D obviously can get them, seeing as they are selling Powerstroke rods bushed down for NA IDI use, for about $75 more than IDIT-converted Powerstroke rods.

 

I have a N/A block and rods, also I have turbo rods. I measured 2 cylinders yesterday and I may not even need to bore. Depends on the other 6. The reason I was planning on going with the turbo pistons is the rings seal better being the keystone design. I do plan on using the gapless 2nd ring though so maybe I don't need them. Turbo pistons are also hard anodized on the top which would be nice as I am currently running a turbo.

 

R&D can ceramic coat a set of pistons, which is probably better than anodizing anyway.

That being said... I'm not so sure how much it really matters. When I had my '88 apart, after having been rebuilt like 10-15K ago, the piston surfaces looked just fine*.
That was a motor running pretty decent boost(and making ~250 at the wheels, probably 320 at the crank), and I definitely towed heavy with it multiple times. I watched the EGTs though, keeping them under 1200 at all times.

I *have* seen IDI pistons with a little bit of "abrasion" at the edge of the piston in one spot, but I've never seen it go more than about .015" deep. I feel it's more cosmetic than anything.

(*Note: Fine meaning in terms of the piston surface. Not the valve-shaped depressions beaten into the piston from the valves not having enough clearance....)

 

Valves and pistons fighting eh? Probably no winners there.
My spare motor with decent looking cylinder walls with minimal wear has all 8 pistons cracked. the previous owner put a banks turbo on it and end of story for those pistons. It does give me a hopefully good block to work with. If I go with the N/A pistons I will definitely have them ceramic coated. Maybe even if I go with turbo pistons too.

 

OK here's my thinking;
Block; std bore (if savable by simply honing), .020 (if it needs bored).
Pistons; either turbo or N/A lowered comp. by 1 pointish, ceramic coated, total seal 2nd comp rings.
Cam; either R&D stage 1 or similar.
Heads: Inconel exhaust valves.
Inj. pump: something new and better than my stock turned up 1 flat.
Aspiration: stick with may Banks turbo and exhaust. 2.5" wye pipe and 3" down pipe with 4" out back.

 

I may be off with my thinking, but it seems ceramic coated pistons would not transfer as much heat to the bottom side of the piston thus less charring of oil that is splashed up against the bottom side of piston. Total seal 2nd compression ring would stop most blow by past the rings also saving oil by not letting as much soot through. Drawback may be less oiling to top compression ring.
I think the blow by on these engines is ridiculous and would like to prevent it if possible. I have a Cummins in my other Ford and different motor , but almost no blow by.

 

This is what happens when your local motor rebuilding shop doesn't do the job right with regards to valve recession(clearance).
One head was in spec, and there was no marks. The other was out of spec by a good .010" and all of the pistons had marks.

Clearance. Matters.

I'll bet you that you've got it backwards - He probably cracked the pistons from overfueling(high EGTs) *before* he got the turbo. The turbo tends to *lower* EGTs, even with more fuel - because there's more air/a leaner mixture.

BTW: - Straight from the Banks literature:
http://bankspower.com/magazines/show...dewinder-Turbo
So... More power *and* lower EGTs.

(which is also what I've seen with my own trucks).

 

You're probably right about the cracked pistons. I don't know much of the history of that truck. Also upon further inspection of cylinders, some have pretty significant scratches on them. If the block even checks out good it will definitely need bored. Hopefully it is usable for me otherwise I'll be looking for another. Luckily the motor I'm currently running is a good motor. I'm just planning on building a new and improved motor to swap out later, probably this winter when I'm not using it.

 

What are the balance differences between a 7.3 IDI and 7.3 IDIT? Flywheel is different for sure. How about the crank and balancer?

I'd imagine the rods and pistons are appreciably different weight requiring the flywheel imbalance and likely the crank to be balanced differently. At which point, if rebuilding it using the R&D modified Powerstroke rods and regular 7.3 pistons, would it be a nightmare to balance and cheaper to just use a regular 7.3 to build?

 

There is alot of difference. They drilled the hell out of my balancer and fly (na) to balance out the psd rods and idit pistons. They lightened the pistons and rods too.

 

But, the IDIT crank is already meant for heavier stuff... so it should require less extra weight added, vs a NA crank, right?

 

The cranks are the same 6.9/7.3/7.3T. The difference is the external balance on the flywheel and harmonic balancer. If i would have ordered an IDIT clutch kit, probably wouldve saved a little work, and same for balancer, but didnt want to have to track them down.