big block chevy fueling for your IDIT+!!

[wix51085]

I shall pick up the trail these fine gentlemen have started

I placed a summit order for an IDI pump and a big block pump last night. Plan is to plasma cut a simple jig that I can mount the IDI pump in and take a series of measurements to the cam contact surface on the arm. Then can mount the big block pump with a swapped IDI arm and see if measurements are the same or if adjustments need to be made. Although I plan to measure off various points on the jig since that’ll be easiest/ most consistent, all measurements would be theoretically be referenced off the bolt holes since that’s the mounting point to the jig.

I am hoping it’s a direct swap and think it would be, but the end of the arm breaking off the first pump Bull Diesel made certainly raises some questions.

I’m traveling for work for a couple weeks and got other projects to tackle when I get home, so I don’t foresee giving an update until end of March / early April. Give me a shout though if you don’t hear from me.

 

[IDIBRONCO]

I’m sure he’s busy with something. Hopefully he’s doing well.

If I'm right, he just ended building up a crew cab Bronco and got started on another project. He didn't actually finish the Bronco but he did get it onto a trailer to go to someone else.

 

[jwsfarrier]

Yes, please keep us updated. I think this would be a great option once its dialed in. Appreciate everyone's R & D on this!

 

[hce]

I shall pick up the trail these fine gentlemen have started

I placed a summit order for an IDI pump and a big block pump last night. Plan is to plasma cut a simple jig that I can mount the IDI pump in and take a series of measurements to the cam contact surface on the arm. Then can mount the big block pump with a swapped IDI arm and see if measurements are the same or if adjustments need to be made. Although I plan to measure off various points on the jig since that’ll be easiest/ most consistent, all measurements would be theoretically be referenced off the bolt holes since that’s the mounting point to the jig.

Sounds like a decent plan. Not that far away from mocking up the eccentric on the cam as this point.

 

[wix51085]

I was thinking about that too @hce . I’m not sure it’s necessary unless I run in to issues but still kind of interested to do it. Does anyone have measurements of the lift pump eccentric or a spare cam floating around they could grab some?

I’d also need something like a measurement from the outside of the eccentric to the outside surface of the block. I can probably manage that myself when I get around to taking the pump off though.

 

[hce]

Wix51085, why do I feel I am at O'riellies ordering oil filters for my wife's jeep. Totally agree with it not being necessary but kind of interesting. Also would need to figure out where in the ~5.58 in crank to cam centerline where the pump mount sits.

 

[wix51085]

Alright, so I got the cheap-o Summit Racing brand pump. Fun fact it has the Holley part number stamped on the side so pretty sure it's the same pump for half the price. I don't know if I like the pivot pin being staked in. For one its going to be way more annoying to disassemble without messing it up and second just feels a little sketchier to reassemble and be confident the arm isn't going to fall in to the engine. I like the ones IDIoit and Bull got with the pin in a hole from the side.

I noticed right off the bat the face is thicker on the cheby biggum block pump than the IDI. The mounting surface to the outside of the pivot pin is ~.290" compared to ~.225". Not a lot but its going to pull the arm back off the eccentric and make it ride more on the tip. Maybe just enough to explain why the tip snapped off Bull Diesel's pump. Probably worth milling the face down or making a longer arm.

EDIT: Alright, I just re-reviewed pictures now that I'm back to a computer and I now see it was the opposite end of Bull's arm that broke off. Was kind of hard looking at pictures on my phone. Hmm..

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[hce]

The top pump not an old style idi pump its off a 302.

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[wix51085]

Having some pumps in hand now and being able to check out pics on an actual screen instead of my phone have helped me. After much goofing off with calipers, googling, drawing CAD ********, etc, I think I have come to part of a conclusion.

So first, I think Bull Diesel already figured it out. With one of these big GPH pumps, use the OG stock IDI arm. I'm pretty dang confident the pump housings for the original IDI, chevy big block, chevy small block, and ford small block are all the same exact thing just with different arms on them. It should be a direct swap with no issues and I don't think further R&D isn't really necessary on that solution.

As far as concerns for over extending the diaphragm and figuring out why Bull Diesel's first attempt broke... it's impossible to overextend the diaphragm by slapping an arm on there with a longer fulcrum-to-cam distance like he did. This goes for both his modified arm and OG arm. This arm is just a lever and increasing length of the "effort" (cam) side of the lever is actually going to decrease the travel distance on the "load" (diaphragm) side. If anything, there's a bigger safety margin on the pump with the IDI arm now. (Okay, this is also assuming cam eccentrics between the IDI and chevys are roughly the same. But that's a pretty fair assumption given many factors)

I think the reason Bull Diesel's first attempt broke is because the arm design isn't just a lever but it's also kind of a wedge. Please enjoy my pretty picture.

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Where Bull cut the arm and welded it back together I think he essentially moved the diaphragm pin UP that wedge. So instead of the diaphragm having a starting height of 0", now it's a starting height of like 0.2" (or something. idk. just an educated guess). He said there was always pressure on the arm and the diaphragm wouldn't close, and I think that is why. From what I've gathered poking around this thing, these diaphragms don't move a huge amount during operation. I think a hypothetical extra 0.2" would almost certainly be beyond intended operating limits and put undue pressure on the arm, leading to it eventually breaking. Plus gotta factor in possible weakness from heat during welding (maybe became more brittle or more soft)

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Okay, so, (at least in my own mind) I feel very confident in Bull's second solution for a reliable swap. I also feel confident that A) over extending the diaphragm/ binding/ breaking stuff is impossible with that version and B) I now know why Bull's first version failed and that isn't an issue for the second version.

Thank you for coming to my Ted talk. Please let me know if you see any flaws in my conclusions here and if we need to revisit stuff.


All that being said, I may have also found a swap alternative for people who threw their stock arm in the trash long ago... TBD.. gotta order more stuff and take more measurements

 

[wix51085]

The top pump not an old style idi pump its off a 302.

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Soooooo what are the chances a 302/351 pump might possibly be a direct swap and all of this was unnecessary... ? Cause a carter 302/351 pump kinda looks exactly the same as a carter IDI one. Edit: okay not exactly the same... suspiciously close though.

 

[Clb]

To all the guys trying to get to a solution to the issue.....

It's late, I'm burnt out, but how are those pumps being all the same( hypothetically) and having the huge flow/volume differences?

I'll get back to this later...

 

[miked]

302/351 pump might possibly be a direct swap and all of this was unnecessary

Unless the camera distorted the optics
The distance from the fulcrum point to the diaphragm rod, on the 302 pump in the picture looks shorter than on the idi pump below it.
That would definitely lower the amount pumped per cycle.
Asuming the diaphragm diameter's are the same. And cam eccentric's are the same and distance to the cam is the same.
Lots to look at.

 

[hce]

Unless the camera distorted the optics
The distance from the fulcrum point to the diaphragm rod, on the 302 pump in the picture looks shorter than on the idi pump below it.
That would definitely lower the amount pumped per cycle.
Asuming the diaphragm diameter's are the same. And cam eccentric's are the same and distance to the cam is the same.
Lots to look at.

It is shorter, but take a look at the diagram of the old style idi pump vs new. The arm on the old style is not contacting directly on the bottom but off the side at an angle and the arm could be shorter. It is probably still too short , not enough angle or something of the sort.
I found it interesting how the arm on this fuel pump was built out of laminated sheets with a u channel where the eccentric contacts. It all rived together.

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[hce]

I'm pretty dang confident the pump housings for the original IDI, chevy big block, chevy small block, and ford small block are all the same exact thing just with different arms on them.

The bolt flange is the same and is used everywhere, most US v8 and a lot of diesel lift pumps. My 1958 fordson major diesel built in England uses that flange. The IDI fuel pump housing appears to be the same as the IH v8- 304,345,392. The housing on the IH pump is longer from the face of the flange to diaphragm center then most pumps.

 

[wix51085]

Okay, I will get in to my big ol logic string of how I came to my conclusions and offer some clarification.

I'm primarily saying the top cast part is the same. Not the whole pump. I didn't go in to this, but my theory is there's really only 2 designs for the top casting on the pumps that use this pattern mounting flange. There's the short neck and there's the long neck. That's it.

If we look at Carter's current offerings, the Ford Windsor and IDI use the same exact upper pump casting with the longer neck and the Chevy small block and big block both use the same upper pump casting with the shorter neck. Chrysler actually uses the same housings on their pumps too, but with an extra hole drilled in them for some reason. All the vehicle-specific changes are just to the bottom bits and the arms.

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What we know for a fact is that the IDI pump used to be shorter. As HCE provided above, the 302 Windsor pump also used to be shorter. Some people on the internet say they were redesigned on purpose to keep people from mounting the arm wrong. Seems unlikely but who knows. My claim is that they didn't just used to be shorter, they used to be the same housing as the Chevy's. This is proven by the fact that Bull Diesel's Original short IDI arm fit in the pump for a chevy.

I originally thought these aftermarket high GPM pumps were a redesign that Edelbrock or Holley or someone else came up with from scratch. Nope, these are all copies of Carter re-buildable pumps. Here's an example of a Carter rebuildable pump.

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And if you think about why, it makes complete sense. Saves everyone a lot of money to re-use the same components and designs. Carter can reuse the same upper housings across a whole bunch of pumps and all the after market companies don't need to redesign a perfectly good housing. I also suspect Carter kept the arm measurements the same so they could re-use those between their standard pumps and the rebuildable ones.. the original short IDI pump arm Bull Diesel used fitting perfectly in his after market chevy pump again proves this to me.

So, all the after market manufacturers just copied these Carter housings to a T. Summit/Holley even kept the flat on the side of the housing for drilling the fulcrum pin hole despite not even using that feature on their pumps. (Likely cost cutting measure. Quicker to just stake the pin in and get rid of the drilling operation)

Alright, so where are all these GPM increases coming from if it's just the same pump? I'll use the Summit/Holley pumps as an example:

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Summit was nice enough to put all 6 versions of "their" pump on the same picture. The top row is all 80 GPM pumps for chevy small block, chevy big block, and ford windsor. Bottom row is all 110 GPM pumps for the same motors. They took all these pictures at different angles so they initially look kinda different. But if you pull each of these up, the 80 GPM pumps are all clearly the same top and bottom bits with different arms and the 110 GPM pumps are clearly the same top and bottom bits with different arms. If you start looking across other brands, they almost all look exactly the same as well. The 80 GPM pumps have a long arm on the upper house and the 110 GPM pumps have a short arm on the upper housing.

The GPM increases these guys are boasting really comes down to improvements made in the guts. Some of the manufacturers basically say that much in their descriptions. The shorter neck, IE shorter fulcrum to load distance, is actually going to end up in less diaphragm travel though. This doesn't seem to line up with the short neck being used for the higher GPM pump. However, that shorter fulcrum to load distance also creates a higher mechanical advantage. A possible theory is that they chose this shorter design to leverage the higher mechanical advantage so they could incorporate a heavier diaphragm, which would pump increased volume. The bottom half of the pump is also different between the 80 GPM and 110 GPM versions, which has to be for a reason. I opened up the SUM-250021-1 I got and it has 2 "in" valves and 1 "out" valve. I imagine the lower volume version only has 1 of each. Additionally, the bottom "reservoirs" on the higher GPM after market pumps are bigger, which is going to suck in and push out more fuel with each cycle of of the pump.

Looking at the stock carter version for the Windsor, there's really no reservoir at all. Just two tubes sticking out of the bottom. Each of those tubes can only fit one valve. So there's a couple factors on why they probably produce so much less right there, despite everything up top being the same.

The housings really don't matter (that much). All the GPM after market guys have managed to squeeze out of these pumps is due to the guts. As further proof, the rebuildable Carter pump everyone copied only produces 40 GPM! And the housing on that is clearly the same as what Edelbrock, Holley, etc have managed to get 110+ out of.

In summary:
-There's only two upper housings
-There's two lengths of arms (as far as fulcrum to load-end distance)
-Short IDI arm fit short pump
-Long IDI arm fit long pump (hypothetically. We only have real life proof the short arm fits the short pump right now)