Timing advance

[RDBuck]

I'm considering advancing the timing on my intercooled 92 but am concerned about losing low end torgue. To those of you who have advanced timing, how far did you go and do you feel any loss of low end? I have a 5-speed manual and when I plow snow I need the grunt as soon as possible. I also have the 12 wastegate turbo even tho my signature does not show it. [Can't figure out how to change my signature]



My signature also shows a viscous coupler which I have since removed. The coupler did not stand up to my use and lost its' silicone thus becoming totally useless.

 

[formula]

I advanced my timing by rotating the pump 1/8". This has been estimated to give 1. 45mm plunger lift BTDC. Don't know what that comes out to in degrees. I was a bit scared to do the adjustment at first. But thanks to Case500D, it was real easy, only took about 10 min to do the adjustment. (that's after bending some wrenches to reach the top and bottom bolts)



Can't really coment on any low-end performance. Due to my stock torque convertor the "low-end" starts at about 1500rpm. However, I did experience better power and throttle response throughout the entire rpm band. The most noticable improvement being in the upper rpm's 2000-2800. EGT's are down about 100 degrees at cruise and 50 degrees at WOT. Less smoke all around. Max boost stayed about the same.



Sean

 

[JFitzgerald]

RDBuck, I advanced mine a hair over an 1/8". I "think" I felt a slight loss of low end, even so, I'd never go back. The increased pull through mid and upper rpms is great when I'm towing my 12,000 lbs. of toys. Mine's a 5 spd. like yours. The one time it was dynoed, it did 196 HP and 572 TQ "at rated rpm" according to Scheid's. The max numbers were 204/606. So even if there was a slight loss of off-idle torque, I don't think the numbers are too bad for a truck with stock injectors.



It's easy and cheap to do, if you don't like it, you can always put it back easily. With your 12cm housing, you should have pretty quick response anyway.

 

[Midnite]

Mine's at 1. 5mm of plunger lift--I'm not sure what that would translate into degrees of advance though.



You're not going to loose much low end power at all if you go to 1. 4 - 1. 5mm. Besides, your 12cm housing will help, and you can turn in the smoke screw a little to boost fueling a bit at low throttle.



Mike

 

[BushWakr - RIP]

Midnite,



When I had my timing bumped up (about 15*advance) I did notice a slight difference in low end power. Now don't missunderstand me here, I'm NOT talking about "HOLY COW" losses here. It was just a tad difference. Overall I would not hesitate to do exactly the same thing again. Our trucks run extremely nice anywere from 14. 5* - 17. 0* advance.

As I understand it, 17 is the upper end that is usually considered max. I stand to be corrected here, by the more knowledgeable specialist, but I think that is rough upper end.

I found better throttle response, some decrease in EGT's, much better mid-high end response, slightly less smoke, and generally better idle quality.

All in all a good change. Our trucks were set at 1. 25mm, I think around 12-13* degrees advance. ( I sure wish Piers would re-post the conversions for ours). This was primarily due to emissions rules.

The earlier 1st Gens came with 1. 35mm, and were non-intercooled.

So, after all that, you are going to find no reasons for not upping your timing to atleast 15* advance. Performance injectors have higher pop-off pressures, which has the effect of retarding timing since they release later than stock nozzles. This later release needs to be compensated for by timing advancement.

You should actually hear a difference in engine sound, I did.



Bob.

 

[Tim1]

Hey Sean, it only took you 10 min. to change the timing? It took me 1\2 hour to go through my 2 tool boxes with no results on the right wrench to loosen thes bolts. Could you please explain the "bent wrench?" Thanks bud. Tim

 

[formula]

Ah, let me clarify the 10 minutes. That was 10 minutes to adjust the timing after I spent about an hour bending the 2 wrenches. You'll NEVER get to the bottom nut without some sort of bent wrench. I bent one wrench in a C-shape to reach the bottom nut and one with a sort of Z-bend to reach the top nut without removing the fuel line. After making the wrenches, I loosened the 3 nuts on the pump and the one on the support bracket, gave the pump a tap with my hand, grabbed the top and bottom of the pump, rotated it about 1/8" toward the engine, tightened all of the nuts and that was it. I think that snap-on may sell the wrenches, but I had some crappy ones hanging around so I didn't mind taking the torch to 'em. I'll post a picture of the wrenches soon.



Sean

 

[Scot]

I use the box end of a 13mm Crapsman wrench that is cut off to about 3" long for the bottom bolt. No bending necessary.

 

[formula]

Originally posted by Scot

I use the box end of a 13mm Crapsman wrench that is cut off to about 3" long for the bottom bolt. No bending necessary.

Ah, I didn't think about that option. One more reason to be a TDR member .



SP

 

[formula]

here are the pictures of the wrenches I made for the timing adjustment. You may notice that they're 1/2", but they're cheapies with poor tolerances so they fit just fine.



Links to the larger versions of these pictures:

#ad


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#ad

 

[BushWakr - RIP]

... ... hey look, official TDR malformed wrenches... ...



Now those are just plain "twisted" buddy... .



bob.



edit: amazing, he runs out to the shop and takes a pic to post... this place surprises me every day... . way to go... . your name is in the draw for 5 bonus HP... .

 

[formula]

MUUAAAAHAHAHAHAAA!!!!!#ad




Hummm..... you say "twisted"?..... it's not just the wrenches#ad




Sean

 

[Old Smoky]

The wrench made for the job is the Snap-On SP-144. It makes getting to that bottom nut much easier.



Mike

 

[boatpuller]

Amazing likeness!!!

It's amazing, I've got 2 wrenches just like formula's in my tool box, they are very simular, great minds must think alike.



Happy Rammin,

Caleb

 

[BushWakr - RIP]

Ummm you guys with the "twisted wrenches" should maybe submit the pics to Robin (TDR Admin) for posting in the next TDR mag. There are LOTS of guys who want to adjust there own timing and that would help one heck of a lot so they can 'fab up' their own wrenches instead of having to buy them.



Just a thought. Besides, it'll mean more 1st Gen stuff in the mag and we could always use that, right



bob.

 

[JLEONARD]

Sean,

Thanks for posting the wrench pics... ... ..... I'll be a bendin' some soon

As far as the pics for the TDR mag... . how about tracing them on a piece of paper and submitting them too... .

Maybe Robin would print that too... then we'd have a pattern to bend them toOo.

 

[Tim1]

Bend

Sean, thanks so much for the pitcures, I can make those bends, no problem. With the pod injectors, I have plenty of power however, I would like to get the timing right also. Thanks again. Tim

 

[Mark_Kendrick]

Anything that easy I have to try. Thanks for the tips fellas.

 

[Mel Fuelling]

I would like to have the wrench bending pattern, but in the mean

time, you can get straight wrenches on the pump mounting bolts

if you take the two 5/8ths bolts out of your power steering/vacum

pump(and also the support bolts) and slide the whole assembly

about 4" to the rear. If you are nervous, stuff a shop rag into

the hole in the accessory drive cover. This gives you excellent

access to both the timing pin and the pump mounting bolts. The

main advantage to this approach for the novice Cummins mechanic is that you can see what you are doing. After you take

it apart this way the first time, you are ready for bent wrenches

the next time. It is the only way that I have tried to both see and

manipulate or adjust the timing pin.



If your pump and drive housing are fairly clean and you have enough light to see what you are doing, this process takes about

ten minutes coming out and ten minutes going back together.



I've been into this area 3 times and have always reused

the same old vacum/power steering pump to drive housing gasket

after rubbing a thin coat of "ultra black" silicone seal on both sides. Dry and leakfree so far.

 

[formula]

I'm working on making some patterns and measurements for bending the wrenches. I should be able to post them in about a week.



Sean