2 mm lift on pump timing???

[btoscano]

Hey all,



I bought a timing guage indicator so I could try the "book" method of timing.



I am not sure I followed the procedure correctly, so here is what I did:



1. Set engine to TDC. With injectors removed, insert rod into #1 and turn engine until rod it as its highest. Sanity check - verify timing pin inserts. Mark crank.



2. Rotate engine back until dial indicator hits a flat spot.



3. Preload guage 1 mm.



4. Turn to TDC.



5. Take reading - 2 mm !!



I take it my timing was VERY ADVANCED!!!!!!



If I set the pump (not original to the truck) so the marks line up - 1. 25 mm !!



It doesn't take much movement to get the pump to the 1. 4 or 1. 7 range... by the recommended 1/8" bump I'm already at 2 mm. Do I have some kind of hot rod pump or maybe I'm doing something wrong???



What should I try to set the timing too???



I have not experimented with the timing on this pump very much since the diesel shop turned up the fuel screw and adjusted the RPM and idle screws...



Thanks,

 

[BushWakr - RIP]

No your ok Brian. The pumps on the 93 have a spec of 1. 25mm.

This came about over the last couple years of the 1st gen trucks when they wanted to control emissions... this lowered the timing, installed an intercooler and, ran leaner injectors.



If I were you I'd set the timing at 1. 6 - 1. 7mm

This is agressive enough to handle larger injectors and give you good throttle response etc.

If you go higher then you're starting to raise cylinder pressures more and you'll find a bit less bottom end among other things.....



There are lots of us guys who've experimented with various timing values... . some have gone well up into the 20* advance settings. This makes the truck sound like an old Mercedes did... . kinda metallic rattling sound and the exhaust starts to really smell 'caustic'.

1. 6mm - 1. 7mm will put you pretty close to the " sweet spot" for the average modified 1st gen I would say.....



Any other opinions guys ??????... .



pb...

 

[btoscano]

Great... I will set it at 1. 7 mm.



I can't believe it was so advanced.



Hopefully my fuel economy will increase too.



-brian

 

[dpuckett]

A lighter foot will help that- you wont get 22mpg in your rig at 80 going down a mountain grade. Takes money to go fast.



I moved my timing back from 2. 04 (1/8" advance) to about 1. 7 in my 91. Didnt improve my fuel mileage, but really woke up the bottom end. Lowered EGTs too.



Daniel

 

[btoscano]

Daniel,



Are you saying the 1/8" advance everyone talks about is usually 2 mm and not 1. 7 mm ?? I am getting really confused now.



I have to tear into this thing a bit more. Originally the pump was 1/8" if you recall and that's where we put the reman unit. I had turbo lag. If I turned the pump down towards the factory mark I got smoke and poor fuel economy and no turbo lag. Then, I pulled the pump to R/R the tappet gasket and had a shop turn the screws "by the book" to the high side of fueling and set the timing 1/8" again. The power curve was much more linear but I got blue caustic smoke.



Now, if I use the timing pin and a rougher approximation of TDC watching a rod travel in #1 injector hole, I get 1. 65 mm at/slightly below the factory index mark!!?? That doesn't seem to be right - because based on experience, the timing would be retarded? OR, the timing gear moved one tooth when I had the pump out - BUT I'm told there isn't enough room for that to happen. I'm not really sure I want to pull the timing cover to check the gear marks. A mini digital video camera might help sneak in there and look. Would the truck even run correctly one tooth off?



I'm going to try to find true TDC using one of the "factory approved methods" and see what I find.

 

[btoscano]

Found true TDC

Hey all... I used the FSM method of finding true TDC by valve dropping. I discovered that the timing pin was spot on. So, I think my IP gear moved a tooth when I R/R'd the pump to do the tappet gaset. 1. 65 mm is currently a 1/16" BELOW the original factory index mark. 2. 4 mm is where the pump WAS set... . that seems REAL high!!! Think I blew anything??? Amazingly the truck still performed OK (at least empty) except for the blue caustic smoke. Can't wait to see what its like when I put all back together.

 

[btoscano]

Hey all,



I just want to wake this thread up and revisit and old question,



"What does the 1/8 inch advance that people talk about translate into mm?"



Because Daniel referred to 1/8 giving him 2. 04?



I am asking because my timing gear tooth is probably one tooth off so I can't find out myself with pulling the cover and turning the gear - don't want to do that!



Thanks,

 

[dpuckett]

I said the 1/8" led to around 2. 04 on MY TRUCK; your resulats may vary, due to a myriad of factors- pump wear, dial gauge setting and accuracy, etc, etc.



If the 93 FSM is the same as the 90 FSM, you could be off by as much as half a degree, due to gear lash. Not sure about the valve drop method, but the turning the gear forward then backward leaves one open for inaccuracy.



If your timing gear is a tooth off, it will still come to the same timing, as you have the same plunger lift vs engine crank position, the pump will just be really high or low on teh gear housing. Since your pump is close to factory timing at or near the factory marks, I'd say your gear is right on.



Daniel

 

[btoscano]

I know its different on everybody's engines but was just wondering if I could determine an "average" for the 1/8" movement?



I don't follow what you're sayin about inaccuracy?



Brian

 

[btoscano]

I set my truck to 1. 65 mm and the only mods are a pump with the fuel screw turned up. I get no smoke, no turbo lag, but only 16. 5 MPG going down the freeway at 75 MPH. Even hauling a bunch of wood in the bed (so the truck runs level instead of nose down) I got 16. 5 MPG.