7.3 IDI Turbo Build for '87 Crew Cab Dually 4x4

bulletpruf

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Ok, so the back story - I bought an '87 crew cab 4x2 ZF-5 DRW dually a year or so ago.

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The 6.9 was seized; had water sitting in the cylinders and would have needed sleeves.

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Bought a 7.3 IDI-T non-running for $1000. Disassembled it to find the block was .040. Junked the block and kept everything else.

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Bought a running low mile (30k IIRC) '88 F350 4x4 plow truck. Falling apart from rust, but had a good running NA 7.3 that I yanked. Sold the carcass for $500.

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Converted the project truck to 4x4 using Sky's Offroad kit and a king pin Dana 60.

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Starting on 7.3 build. Figure I'll use turbo rods, standard bore turbo pistons (need a set of these), aftermarket camshaft, head studs, aftermarket valve springs, upgraded IP and injectors, as well as a new or rebuilt/upgraded turbo. Not going crazy, and don't plan to run an intercooler.

I'll be doing videos of everything on my YouTube channel but I plan to post details here, too. https://www.youtube.com/@THEBULLETPROOFGARAGE/videos
 

bulletpruf

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Well, I started off the day with good news -- the heads I pulled off the '88 NA motor were nice and straight (couldn't get a .002" feeler gauge under the straightedge) and pre-cups were nice, too -- only minor cracks; nothing extending outside the combustion chamber.

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bulletpruf

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After a good start, things went sideways. I have a crack in the valve seat and between two valves in one chamber on one head. This head is junk right?

FYI - the first pic is magnaflux; second and third are dye penetrant.

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bulletpruf

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From there, I went to the 7.3 IDI heads from a 1994 turbo engine to see if they were good.


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No cracks in the heads, but all pre-cups have multiple cracks, some past the fire ring. Still haven't found a source for new pre-cups so this could be problematic.


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The '94 heads are not warped, but the driver's side head is right at .002". Figure since it's less than .003" I'm good, but I haven't found the specific spec for an IDI.
 

IDIBRONCO

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You could possibly knock the precups out of one of your N/A heads and put them in your Turbo heads. If you do that, just be sure to make marks on the edges of the precups like in your last picture. That will make sure that they don't come out.
 

bulletpruf

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You could possibly knock the precups out of one of your N/A heads and put them in your Turbo heads. If you do that, just be sure to make marks on the edges of the precups like in your last picture. That will make sure that they don't come out.

I had considered that; just worried that the cracks in the NA precups will get worse when knocking them out or re-installing them.

Thanks
 

hacked89

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You can try googling 31811288.
Also calling suppliers like dales super store or Jen sales and asking if they are able to get pre cups. They were discontinued awhile ago but the fact that heads are still for sale make you think they are out there.
 

bulletpruf

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You can try googling 31811288.
Also calling suppliers like dales super store or Jen sales and asking if they are able to get pre cups. They were discontinued awhile ago but the fact that heads are still for sale make you think they are out there.

Will do! Thanks!
 

bulletpruf

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Checked the valves today to see if the stems were still within spec. Measured at top of valve (area where it doesn't enter valve guide) and then measured 1/3 down, and then 2/3 down the stem (areas where it travels in the valve guide). All valves were within spec, I believe, with no more than .001" variance on each valve.

All the 1988 NA 7.3 valves were .371: with one exception that was .372" for two measurements. Pretty sure this engine was never rebuilt.

All the 1994 7.3 turbo valves were .386". This engine had been rebuilt, so the rebuilder must have found the valve guides to be a bit loose, so they ordered .015 oversize valves and honed out the guides a bit.

I haven't checked the guides yet, but my guess is that the guides on the '94 heads are a bit tight because some of the '94 valves are showing wear on the stem and several of them were difficult to remove from the heads.

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bulletpruf

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Measured guides this weekend with small hole/split ball gauge and a mic.

The '88 NA heads are pretty damn good - all in the .0022" range, give or take. The factory spec was .0021" or so and max allowed is .0055" so I'm nowhere near that. Too bad one of the heads is cracked in between the valves; even if it passes a pressure test, I'd be nervous about using these.

The '94 turbo heads are another story. Most of the exhaust valves had some galling, and after checking clearances, I could see why -- some were as tight as .0005"! If I'm going to use these - and it looks like I am - the guides will need to be honed out (.002" on the intake and .003" on the exhaust?) and it will need 8 new pre-cups and probably all new valves, too.

I can pop out the pre-cups and install some new ones, but I'm going to leave the valve honing to a pro. I'd like to get a Sunnen valve guide honing setup but it's not in the budget at this point.

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94turbocrewcab-lb

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Boy I wish I did this before I swapped my motors. It’d really take the guessing “you sure this motor is good?” Out of my head. But then again..it was all to hard either.

Good luck!
 

bulletpruf

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Boy I wish I did this before I swapped my motors. It’d really take the guessing “you sure this motor is good?” Out of my head. But then again..it was all to hard either.

Good luck!

Yeah, I like to be thorough when I can be. Not in a huge hurry on this build.
 

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