Oh I thought you mentioned that he put in a fuel pin that could not survive for very long. I knew he didn't do anything else but thought he did that... That is why I thought the Db4 was all jacked up.

 

He was told from the start that the DB2 advancing assembly would not last very long being pounded on by a DB4 head and rotor..... he chose to ignore it, and when I broke mine, pretend it was air intrusion.....

 

Got ya. I thought it was something just couldn't remember what it was for sure. Lol

 

so what is the difference between the db4 and large bore db2 beating on the advance cylinder?

 

Did it kaboom?

 

Not yet, been busier than hell at work, long hours, and coming home and not wanting to do a damn thing.

I gave the EDM shop mine and Justin's cam rings and adv. plungers, so they are getting done at the same time. Justin found the replacement DB4 pin, ordered them up, and delivered them to me today. Here is a pic of the new pin next to the old DB2 pin:



Im going to setup my tool post grinding setup on my lathe, and cut the groove in the new pin to match the DB2 one.

As far as the DB4 vs. the DB2 beating on the pin, the main thing is the fuel being pushed through the pump. If the plunger size is big enough to where the same amount of fuel is being pushed with a DB2 as a DB4, then the forces on the cam ring are going to be the same, the only difference is that the DB4 will have more rolling resistance against the cam ring, thats the trade off for having more surface area against the cam lobes and less of a chance of busting a roller.

I found some material at work that will work for my plungers, so Im going to start on those here pretty soon. I still have to make a new input shaft, and im going to add my own touches to it. Other than that, this pump will be ready to go back together. I was talking with my buddy today about getting this thing on my current setup as is, and Dyno it on the same dyno I did before, that way we can have a direct comparison of what a Big plunger DB2 will do over a Turbo-Cal... I think before I dyno it though, I want to get my spare 7.3 re-rung and ready to go in just in case this thing blows its top. I plan on running 30psi on the stock compression...

 

Well If anybody has a better test for a stock bottom end than that, I would be surprised. "Let Her Buck" and see how far the parts fly.

 

It'll be cool to see what your pump does when it is done. You will have the most powerful Db2 Idi I'm sure. I also look forward to your test of the bottom end. I think the bottom end might surprise some people. Especially since it is a turbo engine, it should be pretty stout. My plan is to eventually rebuild my engine using turbo parts and shot peen the rods, cryo treat everything, balance it, and do whatever else I need to do to add strength to it while still being at stock compression. I will run all that at about 30psi. With stock compression, there is more force pushing on the piston per pound of boost. But the tradeoff is that the dynamic compression will be roughly the same a 30psi and Justin's engine is at 40psi. That also doesn't take into account cylinder pressure either. But before I do that, I do also plan to run about 30psi into my stock rebuild. It'll be interesting to see how long it lasts... Do you plan to just run 30psi for the dyno or for an extended period of time?

 

what is the point of the groove? is there a locking pin or something?

what does your shop specialize in?

 

The groove is to bleed fuel and air pressure out of the advancing setup.

DB4's don't have this luxury as they are more primitive ag pumps, they have a mechanical valve you have to crack open to bleed air out of when you hear the advance rattling around. This is partially why the DB4 pin is so big, because it gets beat on a lot harder.

 

Interesting to know.

 

i take it your still burred racin? sucks, but you have to fuel the project somehow.

 

Here is some pics, got NMB2's and My stuff back from the EDM shop today.

Busted out the TPG and ground the slot into the pins...

Obviously there is a big size difference here, but clearly removes this aspect as the weak link in the pump.



Also started on my plungers, I got so far as to make a test plunger, and I was able to nail .39985" on the nuts after I treated the O-1 (I measured .4000" on the finished bore, and my turbo cal pump had .00015 clearance on the plungers)... Unfortunately using T-guages is only as good as the operator, and I was slightly off when I measured, Id say a couple of tenths... The plunger is just slightly too big. But now that I know I can hold some tight tolerances with my little lathe, I should be able to knock out a couple of plungers for this thing... Ill get to it here very soon.

 

thanks for saving me a trip up there this afternoon, don't forget to bring that stuff to work with you! See you in the AM

 

Awesome man so what all do you have left after you make the plungers? Just put it back together?