Delivery valve affect on timing?

Gasoline Sucks

Gasoline Sucks

slow 12v
Joined
Sep 21, 2010
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I was recently doing some reading on delivery valves since i thought these 191s had too much fuel down low for my new 5x16s to be clean on the street. I read somewhere that the 191s retard timing a few degrees while adding fuel. If I could find a timing light I would do a back to back test on my truck to see the difference between 191 and 181 timing but I cannot find anyone with a light local. Since I cant afford to buy a light I figured I would ask if anyone has seen a difference on a light.

thanks
Kevin
 
85 views and not even one wise arse remark :eek: This has to be a Comp D record.

I guess I have to simplify this question.....


Do 191's retard timing when compared to 181 delivery valves??????????????
 
I could be wrong, but I don't see how they would change your timing at all. You would have to physically break your injection pump gear loose to change any timing. I think DV's just change fuel flow amount. Because the plungers in your fuel pump aren't going to change when they ramp up on the pump cam. Hope this helps.
 
blos101 said:
You would have to physically break your injection pump gear loose to change any timing. .
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Negative ghost rider, injector pop pressure alone changes timing. Setting timing with a dial indicator (static) will be different than what a timing light says (dynamic). Since I dont have $600 bucks layin around to buy a light. I want to know what the timing difference between 181 and 191 delivery valves when you are checking timing with a light. Thanks anyway
 
Just tryin to help I guess you know more than I do then. Might as well buy a timing light $600 is cheap when doing everything else with these motors haha.
 
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I always thought they increased injection duration, which is why they are so dang smokey. The shorter amount of time you can inject the fuel the cleaner and more power you will make. But I could be wrong.
 
blos101 said:
Just tryin to help I guess you know more than I do then. Might as well buy a timing light $600 is cheap when doing everything else with these motors haha.
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Yea I dont care enough about it to buy a light, just wondering if someone who times their truck with a light noticed a difference. Im trying to make 700hp for $7000 (including purchase of the truck) LOL


Lostnwalmart- That would make sense. I read somewhere that someone noticed they lost 3* going to 191s that would make them even more smokey. With these 5x16s I cant even drive it.
 
you are right they do change timing but a lot of variables can come into play. you would have to take into consideration the dv's, injectors, and lines. if the dv's deliver fuel quicker then that in turn would open your injectors sooner depending on pop off pressure. if you have larger lines then it would require more volume to build the pressure to open the injectors so that could change timing also depending on the combination. this question has been asked a few times before and never got anywhere with it. i think they have said it could vary 1-2 degrees. i dont think anyone has actually sat down and tested the exact changes in timing.
 
Chevycummins said:
you are right they do change timing but a lot of variables can come into play. you would have to take into consideration the dv's, injectors, and lines. if the dv's deliver fuel quicker then that in turn would open your injectors sooner depending on pop off pressure. if you have larger lines then it would require more volume to build the pressure to open the injectors so that could change timing also depending on the combination. this question has been asked a few times before and never got anywhere with it. i think they have said it could vary 1-2 degrees. i dont think anyone has actually sat down and tested the exact changes in timing.
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Got ya, well im looking for some 024s to try now. If anyone wants 191s pm me

thanks
 
Lostnwalmart said:
I always thought they increased injection duration, which is why they are so dang smokey. The shorter amount of time you can inject the fuel the cleaner and more power you will make. But I could be wrong.
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The shoulder that everyone chops off to make them full cuts is what helps END injection sooner, and also the start of injection. So in a full cut application the duration is extended, how much i dont know. Also what alot of people dont know is there is dead volume in the injection lines that has pressure and depending on how high or low the pressure is also will effect timing.

Lots of variables.
 
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Keep an eye out for an adapter to use a regular gas timing light. There is a piece that you hook to the injection line that lets you use the standard timing light. Last time I checked they could be had for around $200. Still more than I cared to spend but another option. Sometimes you get lucky on ebay.
 
Thanks ill keep my eyes open, I wouldnt mind owning one for that price just to check it. Since mine is set at 17ish, Im worried that between my injectors at higher pop pressure (280) -2* and the 191s -2* delaying timing putting me at ~13ish by the time anythings happening :doh: That would explain all this low end smoke too.
 
Makes sense and thanks but it just seems like this whole thread is an educated guess until someone finds a timing light :o
 
Keep in mind that what you're trying to time, is peak cylinder pressure after top dead center. So even with a timing light, the whole combustion event is a little more complex than just the start of injection. So no matter how scientific you get, it's going to boil down to trial and error, and what work's best for you.
 
Id also like to know more about this. I had my truck timed when it had the stock 181's and now i run the .024s and now the truck pops a little when reved
 
the variables have been mentioned and a suggested amount of variation has been said. depending on what has been changed i wouldnt think you would see more than a degree or two change. going from a 181 to 024 would slighty advance it being the injection cycle is starting sooner.
 
My guess is it would change a degree or two. You have to take into consideration your injectors the fuel is going to and the pump that is pushing the fuel through the DV's. When I changed my holders out I saw a pretty big change when checked with the light but what it changes on my truck wouldn't be the same as your truck. An injector with a lower pop pressure would be different than with a higher pop because your line wouldn't be pressurized as much befor the injection event in the cylinder. A higher pop on average will run a higher timing than a lower pop since it takes more fuel pressure in the line to inject. I would think a DV works the same way. The easier it is to push the fuel through the less timing. The harder to push the fuel through the higher the timing but Even with a timing light I think it would be hard to get an accurate reading because the pulse is picked up after the DV so its hard saying what is happening with timing before the fuel gets to your lines. I may be completely wrong but that is a few thoughts I put together.
 
Drothgeb said:
So no matter how scientific you get, it's going to boil down to trial and error, and what work's best for you.
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Couldn't have said it better.

Yes it affects your dynamic timing. So does line size/material, injector pop pressures, etc. I tested a few dv's with a light and was surprised by the amount it changed, however I didn't have much confidence in the accuracy of the light either...

It really boils down to finding what works best for your truck in your application.
 
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