DD fuel pin

[JLEONARD]

Ok Bushwakr, since you asked I thought it better to start a new thread on this subject.

Jim sent the pin to me last week. Our met lab found it to be a high carbon alloy steel. So it appears to made from good stuff, DD just missed the heat treat.

We will get some pretty high hardness (Rc 60 ish) and will use our vacuum furnace to be as gentle as possible distortion wise. Distortion is a by product of heat treating, and I'll have to see what happens to the pin before I make a "calling all soft DD pins" request.

(then hope I haven't used up my last favor in our heat treat dept





It is much easier to do a "custom" grind/polish on the pin after it is hardened. The problem is that the pin is ground concentrically, and there is very little diameter left at the top of the cone... it's almost scary.



And for the record, I could not resist installing Jim's pin the night I received it and taking a 3 mile (or so) test run. (so now there's a place to do the custom grind)



Turned my truck into a huge dog. Unbelievable. Boost dropped from an easy 25+ to barely 18 ... . and that was after waiting for soooooo long with my foot thru the firewall.

EGTs were non-existant, as was the smoke that I get with the stock pin when I nail it at low rpm.

My stock pin is a 75 as I recall, and I think these were the pre-intercooled fuel pin.

Jay Leonard

 

[jdurham]

Question for those of you have used the pin and have mods like my truck:



Will the pin work on my truck better than on Jay's since mine has more mods?



Thanks...



Jim

 

[jbolt]

JD- do you know which # eccentric pin you have? Where is it currently set?



Jay

 

[jdurham]

No Jay, I don't. All I know is it is the same one it left the factory with in 1990. I'll try to take a look as soon as I can (going out of town for the next few days)



Thanks,

Jim

 

[barkerdl]

Guys, I had DD put the pump kit in my truck and it really came alive. I gained 47 hp and 98 ft-lbs of torque per their dyno. The real difference is felt in the seat of the pants when accelerating with my 5th wheel. It was installed two years ago and I have had zero problems.

 

[BushWakr - RIP]

Hey, Jay.....



If the material is of good quality do you have any idea why the cone would start to show noticable wear in so short a time???

Surely the guide pin pressure on the cone can't be THAT high to cause wear so soon. .



Another observation I have made regarding the cones in my truck.

When I did some cone work I used Amsoil Race grade grease and applied a very slight film to the cone.

Each time I took out the cone to do some tweaking I began to realize there was no "witness marks" being made on the cone surface.

I eventually ran out of that grease while doing chassis lubes and ended up using a generally accepted "good quality" grease.

Within oh... . 2-3 weeks I already had marks showing on the cone from the guide pin traveling up and down the cone.

For what it's worth anyway guys.....



Bob.

 

[JLEONARD]

If the material is of good quality do you have any idea why the cone would start to show noticable wear in so short a time???

Because it is not heat treated, and obviously the pin that rides against it is hard.



My factory pin has no witness marks on it. It has an off- white colored grease on it... . feels like maybe white lithium.

 

[JLEONARD]

Jim you're pin is heat treated!!



However I would like to hang on to it for a few more days so I can try it in my truck and make sure that: number 1 it fits (did not get distorted) and number 2 that it doesn't show a wear mark after a trial run. I don't think it will, it's hardened to Rc 56/58 which should be more than adequate for it's function.



I won't have the time to test it until early next week... . I'll make another posting with the results , then get the pin back to you.





Jay Leonard

 

[jdurham]

GREAT! Thanks Jay. Looking forward to trying it out



Jim

 

[JLEONARD]

Jim,

Installed the pin and took my truck out for a 10 mile trial run. The heat treat worked.

I did not polish the pin. It is dark from heat treat, but there is no scale so it is still smooth.

There is a shine/polish mark from the trial that is right next to the score from the original soft trial run. You should make sure you install the pin rotated away from the shine mark.

Then maybe you should take a look at the pin after you run it for a couple of weeks to make sure it is not getting grooved.



I still think however, based on this one trial in my truck, that you and others may be better off buying a number 75 pin from Bosch and trying it in your truck.

This DD pin really knocks my truck back... to way less power than stock with the 18 housing.



The pin will be on it's merry way south by tomorrow.

Jay

 

[jbolt]

ECJ-



The main benifit I got from the DD pin is less smoke at idle with the PODs I have. The DD pin low boost setting minimizes the fueling. While it does not have the same max fueling as the stock (70H) pin (about 10% less max guide pin travel) I found it adequate for everyday driving.



The problem with any factory pin is the fact they only do an offset turning to make the cone vs an offset axis turn. This eliminates the possibility of a min to max setting and there will always be a compramise no matter what. An off axis turning or non concentric cone would be ideal but difficult to do economicly.





Now if Old Smokey would hurry up and get his pin out... ... ... .

 

[jdurham]

Jay,



Thanks! I hope I have better luck since mine has mods, or I may have to try the Bosch, or Old Smoky when he gets done.



Thanks again!



Jim

 

[barkerdl]

Gentlemen,



I'm following this thread with some curiosity. The DD pin made quite an improvement in my truck - just by seat of the pants feel - not even paying any attention to before and after Dyno runs. Am I missing something here?



Dennis

 

[jdurham]

Dennis,



What mods do you have on your truck?



Jim

 

[formula]

If your stock control cone was set on a shallow profile and you switched to the DD cone, you would see an improvement in power. However, if you turn the stock control cone to the deepest profile, trim down the washer, adjust star wheel and smoke screw, there is just NO WAY that the DD control cone can provide more fuel.



Sean

 

[JLEONARD]

That's right Sean... I made some rudimentary measurements and it looks like my pin on max profile my pin allows about . 020/. 030" more movement of the guide pin (the pin that rides against the cone).

Jay