crewcabxlt

the non intercooled piston has a larger piston bowl. wish i could post a photo. better performance design for timing advance to keep spray in bowl. the intercooled piston was made to reduce emmissions i believe. i would like to know more about ve timing advance. what is stock base timing in degrees vs full advance in degrees ? at what rpm does the pump reach full advance? how does case pressure effect timing? does lift pump pressure effect timing. Ive read past posts but didnt see much info stated in degrees of advance. any info appreciated .

mhuppertz

[quote=Alwaysworking;2435595]When you shave down the piston, it retards the timing but gives you a larger sweep. You then have to advance the pump to make up for the retard.

Alwaysworking

why not just add a spacer on the advance side?

Alwaysworking

non intercooled piston
http://i289.photobucket.com/albums/l...s/DSCF3627.jpg

http://i289.photobucket.com/albums/l...s/DSCF3623.jpg

crewcabxlt

I,ve measured the bowl on a 90 non i/c and had the head off a 91 non i/c and a head off a 93 i/c and early 98 i/c p-pump. the bowl on the 90 & 91 were 3/8 " + wider across the the newer motors. in your photo your piston bowl looks small? am i seeing it wrong? thanks for picture.

Alwaysworking

thats a picture of my 91 non intercooled one i had the head off

crewcabxlt

the bowl looks small? strange. i,m pulling the head off a 90 in a few weeks. I,ll take a picture. anyway,back to timing.

mhuppertz

The goal here is to increase the total advance in degrees, not to just advance the pump. This way you can have it retarded at low RPM's for a smooth idle and snappier throttle response, but have a bunch of timing at higher speeds to give it time to burn all that fuel and or meth.

The P-Pumpers don't have this. They have to advance the crap out of it so the idle quality and efficiency suffer.

Alwaysworking

cant you just keep it close to the factory timeing marks but have more swing withthe spacer?
less static timeing but more dynamic?
i could alway put a spacer on both sides but thats a little hard to do in the truck

apwatson50

If you put a spacer on the advance side of the piston, you are going to limit the total amount of advance as the piston won't be able to move as far.

I have done this modification on my w250. The result is that with 2mm shaved off the retarded side of the piston, is I have the pump gear advanced 1 tooth, so now I have close to stock base timing, but gain ~5 deg of total dynamic timing. For example stock you could go from 12 deg base timing to 22 deg total advance. But NOW I can go from 12 deg base timing to 27 deg total advance.

Aaron

apwatson50

Also check these threads out.

https://www.dieseltruckresource.com/...ad.php?t=94833

https://www.dieseltruckresource.com/...dvance+degrees

Alwaysworking

well my truck runs good where the timeing is now, but i i'm trying for more top end only.
which is why i dont see why, just getting more travle out of the advance piston, to the advance side can hurt if i can keep the spring tension enough and not have the spring bind when going to full advance.

looking at more core pump the pistion can travle out of the case about 1/4 inch each way.
so if i keep the retarded side of the advance piston the same, and do not change my static timeing (which is about the standard 1/8 bump) i sould gain advance with a spacer on the advance side, if the spring doesn't bind and i retain the tension to hold it to the retarded side.

Rafter B

What's the mixture out of all this to get the best mileage and a little extra power to pull a load? My 93 gets about 13 mpg.

RollinCoalSmoke

While you pump guys are on the subject of pumps I have a question. I want to start experimenting with my 14mm H/R. They have been of questionable reliabilty because of seizing up supposably due to heat. If you open up the fuel return will this change the pump timing or did I misunderstand apwatson50? Can you open up the fuel return and add a "Little more pressure" and somewhat more volume to overcome the timing issues and use this for a cooling effect on the pump? Any and all info., lessons, and tips would be appreciated. Thanks!!

apwatson50

So you want to build a spacer to space the KSB housing out? If so I think that would work, other than making sure you make it seal as that has to hold case pressure which can get up to 100-200 psi. But yeah that would work.

I can tell you that doing it the way I did, definitely gives you more top end while still having low timing on the low end. Even with bosch 190 injectors that thing will pull hard to 3200+ rpms. I get scared and get out of it at that point. haha

I am no pump expert by any means, but from everything i've heard you DO NOT want to mess with the return from the pump. If you do it will mess with the internal pump pressures which will mess up the dynamic timing among other things.

Aaron