7.3 cooling mod

[DrCharles]

Yeah, that's why I asked. 2-cylinder John Deeres are another one of my hobbies, and I have read in several places that the 435 (with its Detroit 2-53) really needs higher compression pistons, and injector upgrades, because they are very hard to start in freezing temps or below.

 

[Joseph Davis]

Thanks for the cool information. I order my 6.9 head Gaskets and will pull the plugs and post the info when done. The holes could have been for casting the heads at factory it gives the machine reference point to start milling the heads and block down the line. Thanks for the reference to your post.

 

[IDIBRONCO]

You're welcome. I did it to try to help others understand what's involved. I also tried to break down the explanation to a very basic level since a lot of readers may not have ever been inside an engine before. These same holes are open coolant passages on the 6.9 blocks.

 

[Justin B]

So I remembered reading something about this "mod" during my research. I've got the heads pulled off of a 6.9 and the heads have plugs in them. I'll attach a picture for reference. I figured out earlier that this motor was rebuilt, now I'm also assuming it had a head job and they put those plugs in assuming it was the same setup as a 7.3?? A lot of what ifs with this motor at the moment, and I don't have any history on the shop that did the work. I'm half tempted to leave them alone, half tempted to yank them out.

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[Thewespaul]

Pull them out. It could be someone dropped on some used 7.3 heads. What do the rockers look like?

 

[IDIBRONCO]

I'm sure that they are 7.3 heads. That plugged hole is a different shape on 6.9 heads. It's not round.

 

[snicklas]

If it is a 7.3 head on a 6.9 block, show us a couple pictures of what they did for the bolts/studs.....

7.3 = 1/2 head bolt
6.9 = 7/16 head bolt

There are some solutions out there, just wondered what they did on this one.

 

[Justin B]

So it's definitely a 6.9 head, just tried some 1/2" bolts and they don't fit, measured the hole and it comes in around .475, ARP stud threads measure .437 (7/16).

Head has slightly off center glow plug holes as well.

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[Thewespaul]

That’s insane. You have a real one of a kind head there, I’ve never seen or heard of any 6.9 heads with the 7.3 treatments. What year is this engine?

 

[laserjock]

Maybe a late run 87? 7.3 casting but machined to 6.9 spec?

 

[IDIBRONCO]

Maybe a late run 87? 7.3 casting but machined to 6.9 spec?

That's the only thing that I can figure. If the coolant hole in the block is open, then why plug the matching hole in the head?

 

[BR3]

I've got a "certified" 87'. 6.9 in the basement about to be torn down for a rebuild, so when I get the heads off, this will be the first thing that I will check. I've got the 7.3 style glow plugs system for sure on this block, but the flywheel seems to be a dual mass, and I read somewhere that 87 was supposed to be the only factory year for single mass.

I'll get it torn into and report back what I find

Sent from my Moto Z (2) using Tapatalk

 

[Macrobb]

So, just thought I'd chime in again. A few weeks ago at Hunting 4 Horsepower, I saw Justin of R&D IDI Performance and actually asked him about this cooling mod(considering he's going all sorts of mods to make power etc). He doesn't see it as doing much of anything and doesn't see any issues with cooling in stock 7.3s - the limitation is simply the radiator.
Now, I'm not entirely sure he's 100% correct, but if there's one person I'd take the word of on something IDI related, It'd be him.

 

[IDIBRONCO]

With a stock 7.3, I'd tend to agree. I think it would make a bigger difference when you turbo one and turn up the fuel to get more power out of it. I think it would be more of a benefit with a Factory Turbo engine Vs. one that's N/A since it already has a power adder.

 

[Macrobb]

With a stock 7.3, I'd tend to agree. I think it would make a bigger difference when you turbo one and turn up the fuel to get more power out of it. I think it would be more of a benefit with a Factory Turbo engine Vs. one that's N/A since it already has a power adder.

Sorry, by "stock 7.3" I meant one with this cooling mod. He's got 300-400HP IDIs he's working on(including the ~400HP bronco that he ran there) and didn't do the mod on them.