Rebuilding a 7.3 IDI Turbo

[CalebHa]

I am currently rebuilding my 1993.5 IDI Turbo engine due to water in the oil. I was hoping it was something simple and not the dreaded cavitation. I removed all of the pistons which most look fine for 300k but cylinder 4 (If I'm remembering correctly) has heavy pitting and rust which has led me to believe it may be cavitated.

My first question is if there is an easy way to tell if the cylinder is cavitated? I have included a photo of the cylinder to see what you guys think.

My next question is on the idea of sleeving it? I have heard many people frown at sleeving these motors but I'm curious on what you guys think.

I can also find a few blocks on ebay that claim to be within spec which could be an option as well. Are there any differences between the N/A blocks and the Turbo blocks? I know the turbo pistons are slightly different with the ring/wrist pin design but would there be any issue putting a stock Turbo Piston into a N/A block?

 

[FrozenMerc]

If it is just one or two cylinders, sleeve it. However, I would definitely borescope down into the water jackets and look at the exterior of the other cylinder bores (after the block is hot tanked and cleaned). Chances are if one cylinder has cavitation damage, the others will as well.

This is what cavitation damage looks like on a wet sleeve engine. Obviously, this area is a bit harder to see on parent bore engines like our beloved IDI's, but a good borescope should get you the information you need.

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[CalebHa]

Thank you for your reply, attached is a photo I got of the cylinder wall from the coolant side this is what cavitation looks like on the coolant side?

I'm also curious if anyone has any idea where to find piston rings? I've gone through the catalogs and hasting had made the IDIT rings but it doesn't appear they make them any longer and I can only find one set on ebay that is .30 over. Mahle says their rings set 41548 should fit but I am doubtful because they say the same set will fit the N/A motors as well.

 

[IDIBRONCO]

My first question is if there is an easy way to tell if the cylinder is cavitated? I have included a photo of the cylinder to see what you guys think.

With the water in the oil, and rust pitting in the cylinder, it's probably cavitated. What's the background on the truck/engine? Did you just buy it to find water in the oil or has it been running fine for quite a while and suddenly is getting water in the oil? Is it just water or is there antifreeze in there too?

My next question is on the idea of sleeving it? I have heard many people frown at sleeving these motors but I'm curious on what you guys think.

Sleeve it. You'll be fine.

I know the turbo pistons are slightly different with the ring/wrist pin design but would there be any issue putting a stock Turbo Piston into a N/A block?

As long as you use the Turbo rods, crank, balancer, and flywheel/flexplate, you'll be fine.

 

[FrozenMerc]

Thank you for your reply, attached is a photo I got of the cylinder wall from the coolant side this is what cavitation looks like on the coolant side?

I'm also curious if anyone has any idea where to find piston rings? I've gone through the catalogs and hasting had made the IDIT rings but it doesn't appear they make them any longer and I can only find one set on ebay that is .30 over. Mahle says their rings set 41548 should fit but I am doubtful because they say the same set will fit the N/A motors as well.

You can't tell if any cavitation is occurring (and it only occurs on the coolant side of the cylinder wall, eroding into the cylinder bore) in that picture. The block will most likely have to be thoroughly cleaned in order to see any signs of cavitation.

As far as I know, the rings are the same between N/A and Turbo motors. Rock Auto and O'Really's both list the same part number Turbo and N/A applications. I have had good luck with Mahle / Clevite rings in the past.

 

[IDIBRONCO]

As far as I know, the rings are the same between N/A and Turbo motors.

They're not. I don't know what it means and I haven't bothered to look it up, but the Turbo pistons take Keystone rings.

 

[XOLATEM]

Piston Ring Types - Compression Ring

A compression piston ring is a metallic ring used to seal the chamber in a combustion engine in order to maintain gas compression between the piston and cylinder wall, and assuring the flow of heat from the piston to the cylinder.

www.anglo-agriparts.com

A Comprehensive Guide to the Classification of Piston Rings - Knowledge

A Comprehensive Guide to the Classification of Piston Rings

www.wellfarengineparts.com

I just threw this up there so I could study it as well....

HTH

 

[FrozenMerc]

Keystone just refers to the cross-sectional geometry of the ring. It is essentially a trapezoid, rather than a rectangle. Very common in diesel engines, both NA and Turbo. I would be willing to bet, the NA rings are keystone too. I will double check when I get to the shop tonight as I have a set of 0.020" overs for 7.3 NA, new in the box sitting on the shelf.

"The keystone ring is used in the top groove of a piston. It is a compression ring with a wedge cross section. Its tapered sides create a running surface allowing radial movement of the ring in the grooves during engine operation which cause the axial clearance in the groove to increase and decrease reducing sticking."

This is done to help clear carbon deposits out of the cylinder.

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[u2slow]

The "coffee table" TiDi book points out that keystone rings are an improvement over the NA engines.

I can't say what the aftermarket has cooked up since. Maybe NA pistons are being made for the better rings?

 

[IDIBRONCO]

I may be wrong here, but I was under the impression that the ring grooves are somehow different for keystone rings.

 

[FrozenMerc]

You are correct IDIBronco, the ring grooves must match the ring geometry. Keystone ring grooves are cut with tapered sides to match the ring.

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[CalebHa]

Thanks for everyone's replies. I got busy and didn't have time to check the forum. I have decided I will get the block checked over by a machine shop and sleeve the cylinders that are damaged. I will also have them machine the heads/deck. My only issue is the pistons/rings. The only product number I have found that I know would fit my truck is Hasting 2M4873 but they don't appear to be anywhere for sale. If anyone had any idea where to find rings for a STD 7.3 IDIT that would be amazing. I would hate to do all this work just to put used rings with 300k back in it. Also to [SIZE=4]IDIBRONCO[/SIZE]'s question I bought the truck not running and planned on it being a project, I had gotten it running and it ran good but I travel for work so it sat for a few weeks and when I got back there was no coolant in the radiator and the oil was double the height on the stick. I was hoping it was just something stupid like an oil cooler but it does not appear to be my luck.

 

[IDIBRONCO]

If anyone had any idea where to find rings for a STD 7.3 IDIT that would be amazing.

You could try getting ahold of Classic Diesel Designs and see if they have any suggestions.

 

[CalebHa]

You could try getting ahold of Classic Diesel Designs and see if they have any suggestions.

I took a closer look at my pistons and unfortunately I found that at least 5 are cracked. I found some turbo pistons from Mahle and they have a product number listed for the rings to use with their pistons. The pistons plus rings cost about 1k which sucks, I'm not trying to sink too much money into this project which is mainly just a toy. I have heard that some people will just reuse the pistons if they only have a small hairline crack. I'm curious on what y'all think about that? To me it seems like you'd just be setting yourself up for failure but i've heard the IDI pistons all eventually crack anyways.

 

[Nero]

R&D will do a full engine build for I think $6500 with powerstroke rods and all upgraded goodies. I like to think of that as a baseline for how much to put into an engine...
As for the cracking, its hard to say. Depends on how hot they got. Mine had zero cracking in them at 97k when I redid my heads. But it was also 100% stock for the first 95k of its life.