Building a better db2

hacked89

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I want to like that more than once.

Nasty.
I remember when 110cc was a big deal when i joined a couple years ago.
Awesome work on the RnD taking these pumps into territory that wasn't previous thought possible.

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rhkcommander

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Love the progress, hope all is progressing well in the new shop.

Hopefully someday soon I can upgrade fueling, turbo, cam, and stud my 7.3 :cheers:
 

Thewespaul

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It’s coming together, I need to update the fuel shop thread but I’ve just been working like mad trying to get caught up on everything, been a new disaster each week but keeps life interesting I guess LOL
I’m very pleased with how much fuel this pump puts out, believe it or not this is a (Brand new) 7.3 head and rotor with stock .310 plungers. Next week I have another .330 pump on my build sheet that’s a going into a gm IDI, customer wants at least 400hp of fuel so it will be interesting to see how much I can squeeze out of it with basically the same setup as this pump with just larger plungers, this 310 pump being around 350hp on the street setup and 400 full tilt. I don’t have any orders for them at the moment, but I do have some db4 H&Rs in stock that I’d like to see how far I could push, seems Justin’s having issues with his seizing above 180cc so I’d like to see if I could duplicate the issue and help us both isolate the issue with them. Waiting on some big bore head and rotors to come in, and some parts at the EDM shop but got some big numbers coming soon, been successfully testing the .450 in the 300+cc range, but cannot keep the driveshaft inside the pump, too much load for the weak spot in the driveshaft.
 

Thewespaul

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Most of these belong in the “carnage” thread in the lounge, but figured it would be more relevant here, cost of finding the weak links and pushing the limits.

Broken driveshaft takes out a housing, visibly cracking straight through
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How much is too much transfer pressure? Cam pin shears with the high rpms momentum of the cam ring pushing the advance piston up against the cam plug, pulling it out of its threads and pushing itself and the advance piston out of the housing. Ruined a sleeved housing too
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Found the limitation of the factory driveshaft, at least ones from a core. going to try some new-new ones soon But above mid 300cc this one let go, twice in fact.
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Thewespaul

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Some seized custom head and rotors figuring out big bore stuff. The ones with the rotors sticking out I actually pressed apart with the sleeve.
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Just a few broken cam pins, I do all my test work with db2 cam pins to keep costs down on pumps that could spontaneously eat themselves, and to have a cheapish weak link.

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This cam pin wasn’t a cheap fix, cam pin broke but stayed in the cam ring which rotated with the rotor, taking out the housing and seizing the head.
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Thewespaul

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Little different build from last night, I have a gm customer who wanted a 400hp capable db2 with fueling adjustment to fine tune his rods in. I went pretty overkill with this pump, did a custom dual thrust bearing support since these housings don’t have a thrust plate and washer like the ford housings have for the driveshaft retainer. Also set the driveshaft up for a large C clip instead of the crappy wire clip that these came with.
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This is running .330 plungers with my stroker cam setup from my 130 and larger pumps, just to see what it would do I locked the governor out so the minimax couldn’t interfere with fueling, I saw 170-180cc at 2800 and over 200cc at peak. Still need to dial in my cam timing and transfer pressures to see how much more I can squeeze out of it, but everything looks promising so far. You can sort of see it in this picture, but just to the left of the guide stud I milled this housing out for a torque screw to act right on the metering valve arm, hoping to be able to cut it back to stock like fueling with this adjustment.
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dgr

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I never knew the 6.9 and 7.3 had different plunger diameters. It's cool to see how far you are pushing this simple design.
 

Booyah45828

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At what point does the metering valve become the restriction to more cc's? I think I remember reading about justin running into that problem with his stuff, but memory is a little hazy from back then.
 

Thewespaul

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If you’re setting up the governor to get full opening the metering valve will never be a restriction, but that’s difficult to accomplish and still get enough closure to make it idle at stock rpms, especially with 40+ psi inlet pressure running your transfer pressure way up at idle but I’ve developed a pretty good recipe of parts to accomplish that without having to go to an AG style governor that just sucks to drive. Really the fill passage in the head is tiny compared to the cut in the mv, the restriction I’ll be running into next with these pumps is the discharge port size, if you look at the fluid path in its entirety that’s the bottle neck, when stanadyne went from the 6.9 to 7.3 pumps (290-310) they also increased the fill port size, and the discharge size to match the large plungers, so I plan on similarly upgrading my rotors to complement the big bore pumps, once I find the limit on the stock porting.

Interesting find with cam pin upgrades, if the db4 cam pins begin to start breaking or become nla, I found a more bigger option from stanadyne.
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Booyah45828

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I thought justin drilled more fill ports, or maybe he EDM'd them bigger, and then also EDM'd the discharge port larger. And doing that he ran into the MV not being big enough. Or maybe it was misadjusted at that point and wouldn't idle reasonable? :dunno Sucks that I can't remember exactly, and refinding that info from half a dozen different forums all across the internet from several years ago is a pain.

Good thing you found a bigger cam pin, now whatcha gonna do to keep the plugs for the advance piston from being hammered out?

Truthfully, it likely is all a wash, because at this stage most engines can't handle that much fuel anyways.
 

Thewespaul

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On the early 110 pumps he was running additional fill ports for a few pumps but ran into them developing hot start issues because of it, so he quickly quit doing that mod. Advance pistons pushing out the plugs is just from other things breaking or pushing tp too far, if I keep things reasonable theyre good for a lot of abuse, if I run into them coming out often without pushing my tp, Ill mill out the threads from the housing and through bolt both caps together so they arent relying on the alu-minimum threads.
 
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