7.3 IDI Block - Is It Turbo Block? Is at 4.150" (.040) - Too Much???

bulletpruf

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My 7.3 IDI turbo (with factory Garrett setup) came out of a '94 cab and chassis truck and I have zero history on it. It was turning over but not running.

I got it apart and figured out it was a reman -- the rods have been stamped, but some knucklehead stamped two rods #7 and there's no #6. In addition, there was a handwritten tag on a valve cover indicating 200 hp at 3,000 rpm.

The wrist pins are 33mm, so has turbo pistons and rods.

The turbo oil feed fitting threads .527" OD, so that should be 1/4" NPT, correct for a turbo block (non-turbo has 1/8", right?).

However, the stamped engine number is "7.3D U2U1056997". I thought a turbo block had a C or K in the number.

In addition, the block casting number on the driver's side by the engine mount bosses ends in C1, not C3.

I'm thinking it's not a turbo block. Maybe someone drilled out the oil feed hole and tapped for 1/4" NPT?

Also, the bores are 4.150" so it's been bored .040". Some of the pistons are cracked, so if I use the block, it will need, at a minimum, new slugs.

I haven't checked the bore taper yet, but all of the cylinders seem to have very minor rust, one has a ridge (not sure why the rest don't), and one cylinder has some minor scratches that I can barely catch my fingernail on. It may be good to go with a hone, remaining at .040" but that seems like it would be sketchy, at best.

This won't be a radical build; just looking for close to 500 ft/lbs at the wheels, so maybe a drop-in turbo, Stage 1 injectors, and an upgrade on the pump, but I still think the walls are too thin, and I have no idea whether this engine got SCA's, either.

I realize I can get all the cylinders sleeved on the 7.3, but for what that will cost me, I can source a used 7.3 block with standard bore.

My truck is an '87 F350; the original engine is a 6.9, and I have that as an option. It should be standard bore, but one cylinder will likely need a sleeve (had water sitting in it). I realize that with a 6.9 I have smaller head bolts, but I would definitely upgrade to studs, keep an eye on EGTs, keep boost at a reasonable level, etc.

Thanks in advance for any input!

Scott

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FrozenMerc

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Can you get 0.040" over sized Turbo pistons? I haven't seen anything larger than 0.030" over. Custom pistons may be more expensive than sleeveing the block back down to standard bore.
 

gandalf

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According to the information I have that is not a turbo block. The serial number is too low.

I'll paste in a post from 2005.

icanfixall
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Every idi motor has either 1/8 or 1/4 inch oil ports. These are pipe threads too. Now if your motor really is a turbo block then it will have the 1/4 inch port. Otherwise all the other blocks are 1/8 inch ports. The turbo block serial numbers start at 1,116,331 and go up from there. Anything lower is a non turbo block.

 

bulletpruf

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According to the information I have that is not a turbo block. The serial number is too low.

I'll paste in a post from 2005.

icanfixall
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Every idi motor has either 1/8 or 1/4 inch oil ports. These are pipe threads too. Now if your motor really is a turbo block then it will have the 1/4 inch port. Otherwise all the other blocks are 1/8 inch ports. The turbo block serial numbers start at 1,116,331 and go up from there. Anything lower is a non turbo block.

Thanks, Ken!
 

hacked89

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International spec you dont go more than 0.030 over. Turbo pistons go up to .030 and NA generally available up to 0.040. I had an engine that was rebuilt and machined 0.040 over. Lasted like 10k miles maybe before cracking a cylinder wall. I have a video of it if you are interested.
 

bulletpruf

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International spec you dont go more than 0.030 over. Turbo pistons go up to .030 and NA generally available up to 0.040. I had an engine that was rebuilt and machined 0.040 over. Lasted like 10k miles maybe before cracking a cylinder wall. I have a video of it if you are interested.

Don't need a video, the story is good enough! Given as much time as it takes to remove and install one of these buggers, I'm not inclined to run it.

Thanks!
 

IDIBRONCO

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However, the stamped engine number is "7.3D U2U1056997".
Here's your real proof the this is a N/A block. The Factory Turbo engines had "7.3TU2U" here. I believe that the "C" or "K" were in the VIN, not the engine serial number. Even the Factory Turbo blocks had all 1/8" NPY oil ports except for the one the feeds oil to the turbo. That was the only one was 1/4" NPT.
 

david85

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Hi Scott, I stumbled over your YouYube channel this week and was thinking to invite you over here after our brief exchange in the comment thread. Looks like you found your own way.

Starting to look like that 6.9 block is worth a closer look. Have you taken any measurements yet? You might be able to simply bore the 6.9 block and not worry about sleeves. I did 30 over on mine when.
 

bulletpruf

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Hi Scott, I stumbled over your YouYube channel this week and was thinking to invite you over here after our brief exchange in the comment thread. Looks like you found your own way.

Starting to look like that 6.9 block is worth a closer look. Have you taken any measurements yet? You might be able to simply bore the 6.9 block and not worry about sleeves. I did 30 over on mine when.

Hi David -

Yes, I found my way here last month, and I'm glad I did.

I have not measured the bores on the 6.9 but I will probably do so today. I agree that the 6.9 appears to be a viable alternative; certainly preferable to an .040 7.3. Having said that, I'm supposed to check out a reasonably priced parts truck with a low mileage 7.3 in a few days. That might be too hard to pass up.

Thanks!

Scott
 

bulletpruf

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Can you get 0.040" over sized Turbo pistons? I haven't seen anything larger than 0.030" over. Custom pistons may be more expensive than sleeveing the block back down to standard bore.

Got pistons cleaned up today - every single one is cracked on the crown - and they are name brand, too - Mahle. Pics to follow.
 

bulletpruf

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One piston looks like it ate the end of a glow plug, too.
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Big Bart

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I have seen cracked pistons coming out of turbo’s. (Most or all cracked.). Not sure if extra heat, strain, or both cause it.

Now the dent on the side, hard to say but if your EGT’s get too high, it’s suggested you can start to melt a piston. So is that from a dent or the start of the melting of the piston edge? Hard to say.
 
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bulletpruf

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I know Ford anodized the tops of the pistons in the IDI turbo motor. I wonder if there's an updated/superior coating that would help the pistons live longer.
 

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