3208 In-line Pump Conversion for the IDI

[Thewespaul]

Happy Fourth of July!

Alrighty folks finally getting caught back up on things and had a moment to make this thread as i had mentioned in the other build thread.

Backstory/history in this post, next post will have pics/specs/progress. So skip ahead if you don’t want to read the history of this project, you’re not really missing anything

Starting from the beginning, I have been working on this conversion for some years now, and have spent a good amount of time ruling out certain pump options and trying to find the best fit for our engines, mostly dealing with availability of parts/cost, packaging size, and firing order. This conversion is not about making 1000+ horsepower IDIs, because frankly I don’t think these engines will ever do it, but more as an upgrade from the problematic db2 platform. Don’t get me wrong, a rotary style pump is great on an 80 hp tractor because it’s simple and small in size, but it’s a real limiting factor in the performance and reliability of these engines.

My motivation for this conversion is to get a pump that:

1- Doesn’t require a rebuild every 150k miles, but instead out lives the life of the engine

2- Is compatible with bio fuel, wvo, and wmo

3- Is easily modified to support 500+ hp

4- Provides a flat fuel curve to support the rpms these engines can run

After whittling down my list of pumps to try I found that the old 3208 cats I grew up with had the same firing order as our engines, and their injection pumps were in a V configuration with two seperate banks of plungers which made for a much nicer package.

Doing more research it seemed these pumps were pretty middle of the ground in performance and came with 8mm plungers, and 8.5mm on the turbo models. Lowest horsepower rating for this pump is 225 hp, and highest being 475 in a marine application, so this pump should be able to go from a mid 200hp setting to double that with a turn of some screws and no internal modifications.

Recently I picked up a 3208 pump for very cheap, and got right into making measurements and seeing what gotta be custom and what can be made to work:

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[jwsfarrier]

Sounds cool! Can't wait to see what you come up with. Thanks for doing the R and D on this. Happy 4th

 

[MtnHaul]

Awesome project. Best of luck to ya'!

This reminds me a while back I did see an old Ford that somebody had stuffed an N/A 3208 into--that was one cramped looking engine compartment.

 

[F350camper]

scary cool man, subscribed!

Yes, that is two bags of popcorn!

 

[TurboSurge]

Watching

 

[Thewespaul]

Thanks guys, be warned this will be a slow project as I’m paying out of pocket for parts and machining, and this kinda stuff gets expensive fast, but here’s what I’ve done so far just making some quick checks:

As I mentioned in the other thread, this style pump has a tapered shaft, and the db2 is just a straight shaft with a keyed fit, so going to need to adapt the idi timing gear or have a custom gear made. Luckily the the 3208 pump has the same rotational ratio as the db2, so the same tooth and diameter gear can be used, assuming I can make it work.

Started mic’ing things out and looks like the idi gear will work on the 3208, but with the tapered shaft the bore will protrude into the three mounting bolt holes in the stock gear.

Pictured here is roughly about how much:

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I’m no machinest or engineer, but speaking to my own pops who is a retired machinist, he thought it wouldn’t matter, but I’ll speak with my pump guy and my machinest to see what they think. If it’s an issue then the holes could potentially be filled with weld then machined out, not ideal but trying to keep costs down here.

Next task was to look at the gear cover and see if that could be made to work, the snout of the db2 is A bit under 2” and the 3208 is 4.75”, looking at how much would need to be bored out of the gear cover there’s enough surface area, but it would place the pump too high and it wouldn’t line up with the gear. So looks like a gear cover will need to be custom which isn’t a big deal, it’s a simple design to replicate and I could add some features to make timing changes a breeeze, so sort of a win win.

Here’s the pump bolted to the idi timing gear:

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Next work in order is to take this pump and run it on the test stand to see how much fuel we can squeeze out of it. I’ll see about making a video when we do, these things sound pretty wild loading them up on the stand.

That’s all for today!

 

[bbjordan]

 

[jwalterus]

Let me know if you need any Cat information......

 

[catbird7]

I don't know a dern thing about them however here's some pics!

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[TurboSurge]

What about a deeper valley pan? If the pump is too tall than a deeper valley should help lower it down to where the idi gear will line up? Just a thought. The valley pans are really thin but they can be tigged. I welded my CDR hole up in mine.

 

[typ4]

I would try to use a cam gear??
IIRC the cat has advance mechanism built into the gear.

 

[Simmonscoating]

Hope you can pull it off... big props if you do.

 

[ShadetreeV]

I'm amazed at the similarities between the pumps. Having the firing order and even the same gear diameter and tooth count match up is quite the coincidence.
The pump drive gear looks cast iron? Modifying for the tapered shaft could cause potential areas for stress fractures, especially if welding is required. then, warpage and runout of the gear may hold some issues. Is it possible to modify the drive shaft of the pump to accept the idi gear?

 

[Thewespaul]

Let me know if you need any Cat information......

Will do!

I don't know a dern thing about them however here's some pics!

You must be registered for see images attach

You must be registered for see images attach

They are great engines, they were known as "throw away" blocks because they had no sleeves, a lot of times guys would just buy new blocks from CAT and throw their 500k mile rotating assembly into the new home. Just stories but ive heard of a few rotating assemblies that made it through multiple blocks with same rings bearings etc... dunno if theres any truth to it, but these are one of the best sounding diesels imo

What about a deeper valley pan? If the pump is too tall than a deeper valley should help lower it down to where the idi gear will line up? Just a thought. The valley pans are really thin but they can be tigged. I welded my CDR hole up in mine.

Thats a thought, but the clearance issue is with the block not the valley pan, and with a custom cover I could make timing changes a breeze instead of trying to do it through the lemon cover.

I would try to use a cam gear??

IIRC the cat has advance mechanism built into the gear.

Ill pull an idi cam gear out of my parts pile and take a look at that, thanks Russ!

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I dont believe theres anything special about the 3208 gear, timing those is just the same as any inline pump, pin the pump pull the nut rotate the engine to tdc then rotate the engine over to the degree you want advanced.

Hope you can pull it off... big props if you do.

Thanks man!

I'm amazed at the similarities between the pumps. Having the firing order and even the same gear diameter and tooth count match up is quite the coincidence.
The pump drive gear looks cast iron? Modifying for the tapered shaft could cause potential areas for stress fractures, especially if welding is required. then, warpage and runout of the gear may hold some issues. Is it possible to modify the drive shaft of the pump to accept the idi gear?

I think it was meant to be! It is indeed cast, I dont think modifying it will be much of an issue, I may end up milling the center out and welding a custom center hub in, Id like to have an adjustable gear so you can just pin it at whatever timing you want, so all the adjustment is made in the actual gear to hub timing instead of the timing gear to cam timing, but Im getting ahead of myself there, one step at a time...

 

[typ4]

This is a timing advance gear for a 3208. not sure what all
they are used on, some marine apps and turbo.

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Kind of small lol