Hi-
Trying to sort out brand new build and hoping to get some advice on possible causes for what seems to be excessive reversion. I am unable to keep an O2 sensor alive (gets wet at anything below 1100 RPM) and in the process of spending time dockside working on tuning/adjustments, I have found that excessive moisture in the oil can accumulate.
The basic question is whether poor idle/tuning can be the main contributor or is the cam selection or something else about the set-up susceptible to reversion. The idle is not very smooth with what feels like a fair bit of misfiring. I have replaced the plugs to eliminate fouled plugs as a potential source but Idle is still quite rough. I am trying to tune the idle to below 900 RPM for drive life (IMCO SC) but so far have not been able to achieve something I would consider "smooth" and consistently firing on all 8 cylinders.
It is a Holley HP EFI MPI set-up running DIS (crank trigger), cam sensor for fully sequential and CNP. The engine is a 555 Dart Big M with Dart aluminum heads with CMI Sport Tube Headers. She made 710HP and 680Tq without really having the time to fully dial things in so it seems to run pretty strong. This is also my first time with fully programmable EFI so I am a bit of a Newb. The engine was dyno tuned but with dry headers and admittedly the dyno work was more for run-in and to dial in at higher power ranges. (very little work done to optimize idle).
I am hoping that if I can get the idle smoothed and better dialed in, I will be able to reduce reversion and have a better chance at using the O2 sensor and the closed loop learn functions of the software under actual use conditions. The O2 bung is located very close to the front of the tail pipe so about 5-6 inches behind the header collection point and approximately 12 inches ahead of the water entry point at the back of the tail pipe. I am also using Gibson clamp-on mufflers if that matters. I have thought about removing them for tuning purposes as something else to try.
It seems to me that I should be able to get the idle smoothed much better but with my limited experience, so-far, not so good. Oh yeah, Cam spec.s are as follows:
Gross Lift .650/.650, Duration @.05 247/253, LSA 112, Duration @ .006, 383/308, Timing Events (OP/CL) @.05 Intake 15.5/51.5, Exh 62.5/10.5.

I know there is a LOT to getting these things right but I am looking for any experience from more experienced tuners that might help me determine if there is something inherent with my set-up I need to focus on. I am getting to be fairly proficient in navigating the Holley software and have fiddled with the idle settings but so far have not been able to get to a stable and smooth idle below 950-1000RPM.
Sorry for the long story but season is getting short up here in Maine! Any help or advice would be greatly appreciated.
Thanks!
Paul

Sounds like one of your settings is wrong and or something is not in sinc.
I have HOLLEY EFI on my 598 and it idles in gear at 700 RPM hot.
And my cam is a LOT bigger than yours.
You have something wrong.
Does your cam have a different firing order than stock?
Any chance you have injector or coils wired wrong?

Tinkerer, Thanks for the quick response. Never thought to ask the builder about the cam firing order being different than stock. Is there a way to tell from the spec.s?
I have the EFI system set up for stock firing order - 18436572. I am using the Holley Coil driver packs for CNP which I did have to wire individually myself. I double and triple checked that before putting the motor in the boat but am not opposed to re-checking. I sort of figured things had to be correct for it to run as strong on the Dyno? Is it possible to get those results with something like firing/fueling order wrong?
I agree though, something seems to be wrong. I have been concerned that the spark may not be all that stable at lower RPM? I am using all Holley components (except for individual coils) including their DIS crank sensor and injector harness so that should be fine.
With the wiring pretty much all enclosed at this point, is there an easy/reliable way to check that the coil firing sequence matches the programmed firing order?
The engine starts right up and runs well over 1500RPM but I am at the point of suspecting just about anything at this point.
I am happy to hear you are having success. Are you running closed loop with the O2 sensor active?
Thanks

Yes I am running the O2 sensor.
My cam builder did the 4/7 firing order swap but I didn't see it on the cam card until I looked for the answer to my problem. Ran badly.
Changed the firing order and found a computer setting was wrong. Idles perfect now

Is your o2 senor mounted near the 12 o clock position on your tail pipe? Are you trying to run closed loop at idle?

Less timing at idle will help with reversion. I run my Holley o2 sensors full
time and use the innovative o2 heat sink to help with water contamination

O2 sensor is at the 9:00 position. And I run closed loop full time.
You can check the firing order by pulling all of the plugs and turning the engine over with a wrench and feeling for compression at each plug hole following the firing order. IF the cam has a different firing order you wont have compression at two plugs following the stock order.
Any chance the rocker arms are too tight causing valves to not close properly?
I had one of the initial computer settings off and lost spark in cylinder #5.
If I pulled the coil wire you could see it spark 7 times not 8. dead spot.
Go back over all of your settings.
Talk to someone that does this for a living.

My O2 sensor is mounted in the collector on my Lightning headers.

Why the heat sink for water? I looked it up and seemed more for heat, how does it help?

Where are you guys mixing the water at the tips or running dry?

Any issues with 12 o'clock? That's where mine is and the biggest problem that I've had so far is it's hard to hide the ugly wires.