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P400 in the Burb install

The reason timing gets locked on HO DB2s is to take stress off the cam pin. The added load on the pin from a modified pump combined with the variable advance servo piston spring tension from the LLA armature. Can be too much back and forth stress on the cam pin and they tend to break.

By redesigning the advance system and cryo treating the cam pin im hoping I can keep a functioning advance system on a HO pump. But an all out race pump with big plungers like a .370 will still require locked timing because its so much added stress even the input shaft needs upgraded. So the cam pin stands no chance. If the larger discontinued 4 plunger marine pump advance piston and pin where still available then maybe I could make one work with a functional advance. But those parts are obsolete and unavailable 😕
 
Could the pin and the cam groove/hole be made bigger to allow for the extra stress ?
I dont remember but I think it is a keyway.
 
The hole cant be opened up because it has to seal transfer pump pressure internally in the piston for the timing advance to work

There is a larger pin available that was used in the DB4 AG pumps. But it takes some machine work to make it work other than opening up the can ring and advance piston. The "automotive" DB2 cam pin has a groove machined into it for transfer pump pressure to flow into the cam pin which pushes on the advance servo to direct TP pressure to the back of the advance piston to change timing. So no only does the groove need to be added, but the advance piston and cam ring will need to be opened up at an offset as to no mess up the passages the advance servo controls. The hole needs to be very precise so there is no loss of transfer pump pressure as well as the advance passage would be extremely close to the large hole required for the larger pin. Its doable but i have to find a EDM shop wiling to do such a small project.
 
Last edited:
Will L. said:
I can’t get the link to work. Is it still ok?

I have not used the shop in YEARS- but J&S Diesel in Vegas used to be amazing. But the guy that built my pumps died. Talking to them on the phone- they said the know all the tricks and all detail were shared between the two owners before the one died.
I don’t know enough technical details to tell if they are just fishing for business or actually know what to do.

They do have a solid reputation in town for small to large diesels. If one of you guys that really knows the pumps could ‘test’ the hotrod building knowledge, that may be worth while. Then if they are slinging bs, we would know to scratch them off the list permanently.

yes, mega db2 pumps get no timing advancement. So you play with it and learn what rpm your peak torque is and adjust it for there.

But you are running so much fuel to the injectors that the couple degrees to far advanced at idle doesn’t usually matter.
When Scott would build my hotrod pumps, he would tell me a starting point advanced. Peak power always required adjusting a little on the truck. But the builder should be able to say a starting point.
Click to expand...
It's a facebook video so I think you have to have a FB account to see it, it's just a P400 marine engine with 18:1 ceramic coated pistons on a dyno run. It has marine exhaust manifolds and accessories on it, no posting on the HP or Torque that I could find though.
 
Yea I'm not sure what was going, maybe a shitty connection on the exhaust IDK. Really not much info in the post, just a video.
 
I did a little digging into these folks...

Company is in Ohio, seems they have designed and the motor on the dyno has full ceramic ringless non metal pistons.... Well that's a new one for me, never seen a motor of this size that doesn't have piston rings....

Scroll down the home page and there are pics of a set for something else, but google has a few links and I found one for the 6.5 build, didn't look like much special was done...

And using ringless pistons may be why all the smoke in the video...

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I saw that round engine design they did some time back.
They also did a cat 3206 same ceramic piston & sleeves.

wonder if that’s why they pumped the exhaust back in, to see how much smoke on start up.
I saw the regular piston/ rods. Maybe pin placement of the p400 is too much for the all ceramic piston design so they had to use regular 6.5?
 
There is no pin location change, same pin, same rod center length, same pin to piston top length.... but yes the P rods & pistons are made different but maintain the same center to center measurements...
 
Hey has anyone heard of these guys for injection pumps? My buddy says they are pretty big with the Ford pumps.

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Rockabillyrat said:
He locks the advance piston in place so the pump doesn't advance with transfer pump pressure anymore. So what ever you set your timing at it will stay there, much like a p pump. A few guy said they had to advance the pump gear two teeth to get the desired timing.
Click to expand...
Rockabilly, the guys that advanced the pump gear two teeth were these Fords or GM's? I'm wondering if I need to do the same with my Conastoga Moose pump?
 
Gm pumps. You shouldn't have to advance teeth on a pump with a functional timing advance. My guess is your advance piston is stuck.
 
Rockabillyrat said:
Gm pumps. You shouldn't have to advance teeth on a pump with a functional timing advance. My guess is your advance piston is stuck.
Click to expand...
I have the pump off, can I just move the lever on the side of the pump back and forth to see if the piston is stuck?
 
Take the cap off from the opposite side of the LLA armature. And see if you can push the piston towards the armature. Thats the direction it moves when it advances. If it moves then it could be a worn out bore that wasn't reamed properly. It might be bypassing the piston.

Reaming the housing is a poor repair im my opinion. I have a machine shop that fits them with a steel sleeve. That fixes the design flaw of the advance piston bore. 20201015_204345.jpg
 
FYI this pump housing has less than 500 miles on it and the head and rotor have never had the transmission put in gear, maybe 1hr of run time max. It was a new DB2833-4974 pump not rebuilt.
 
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