Someone tell me why someone should run more than .040 gap on anything ? I’m all ears.

Have my street car gapped at 025. No difference how it runs from 025 to 055. Put down almost 1100rwhp. Less gap for the win.

Guys,

Pretty sure I managed to save the tapped hole in the exhaust riser base. Not much scarier than turning a tap, with an adjustable wrench, in close quarters, where I have to swing the wrench over obstacles while I turn it. Gotta love form taps, though. I didn't over tighten the bolt, but I don't think it's under a lot of stress. It's just an anchor point for the shifter bellcrank assembly, and there are two more anchor points. I'll keep an eye on it for a while.

Apparently, these now-fangled coil packs cannot be tested with a multimeter. Something about internal switching and such. Oh, well. We'll just do it the old-fashioned way.
​​​​​​​
Coil packs are swapped. Waiting for new plug wires from Mosetti and I'll swap the new plugs in while I'm at it, then it's time to get the boat on the water and see if the wet plugs follow the "bad" coils.

Shout out to Smitty, for enduring all my questions over text. Especially on a Sunday. :ernaehrung004:

Thanks. Brad.
(937)545-8991

Guys,


https://cimg2.ibsrv.net/gimg/www.off...7eeebe324.jpeg
https://cimg4.ibsrv.net/gimg/www.off...d85e18697.jpeg

What is this widget? And should there be something connected to that nipple pointing to the left?

Thanks. Brad.
(937)545-8991

Good question. The aluminum thing under bolt is for sourcing intake vacuum. The sensor on left attached to it by vac line is the map sensor. The round item to left of that is a one way valve. But question i share with you is why isn’t this hooked up to something ? Should it be hooked to fmu or is there a vac line to it already ? Or, shoukd vac line end at map sensor ? I’d talk to ati/procharger on this. Looks like their deal as the oe engine’s map sensor is typically where that aluminum piece is.


https://cimg4.ibsrv.net/gimg/www.off...fdce2c6c34.gif

Guys,

Are these two coil packs interchangeable?



The first one seems more readily available and is listed as a "newer" model. In the event I find I need to replace mine I want to have a plan in place.

Thanks. Brad.
(937)545-8991

Appears to be same.
You can also go to acdelco.com. Go yo parts look up and interchange #.


https://cimg5.ibsrv.net/gimg/www.off...124f742dff.png

SB,

And cheaper than Amazon, too. 😎

Thanks. Brad.
(937)545-8991

RockAuto charges shipping, so need to fully compare total amts. And shipping time, if it matters.

I may be wrong. But IMO I doubt you'll get any counterfeit parts from Rockauto VS the probability from various Amazon sellers.
I do see in the links they say ACDelco store.
So hard to say.
My gut always uses Rockauto.

If you get AcDelco thru a third party on Amazon you run that risk. If you get AcDelco thru Amazon (sold by, stocked by, and shipped by Amazon) themselves, you will be fine. You have to read carefully where it’s coming from or selling by. AcDelco did a deal with Amazon over a decade ago. I buy 100’s of acdelco parts per year thru Amazon. I have no local acdelco dealer.

SB,

Yup. But, at over $8 difference, EACH (I am planning to install all new if I have to change any), I doubt RockAuto is going to charge $65+ for shipping. At least I HOPE not. We'll see.

Thanks. Brad.
(937)545-8991

I work on lots of chevies. I only change coils that are needed. Some last ‘forever.’

Broken record….skip….skip….skip
#1 coil killer is big plug gaps . Same with most all other ignition parts….modules/caps/rotors/wires/coils….if so equipped.

Guys,

Next "what if".....

In the event it's not the coil pack(s), I have to look at the injectors. I've already spoken with Smitty, and have cleaning them worked out. But I'm thinking about what has been said about the CoolFuel module. I've looked it up, and I know what it looks like, but I can't seem to find it. Whereabouts is it located on these 496s?

Thanks. Brad.
(937)545-8991

Guys,

Just swapped plugs. These were run one afternoon, including one extended WOT run of about ten minutes, which was still well under reasonably expectable max RPM. Still no throttle dump; just idled onto the trailer, as previously explained. Also have not test run with coil packs swapped yet. Probably do that Wednesday, but wanted new plugs and wires for the test.


https://cimg3.ibsrv.net/gimg/www.off...f1b9d9e90.jpeg
https://cimg4.ibsrv.net/gimg/www.off...024ae30cb.jpeg
https://cimg5.ibsrv.net/gimg/www.off...a4855b087.jpeg
https://cimg6.ibsrv.net/gimg/www.off...0d37cc894.jpeg

Compare these to the last set of plugs (pictures above).

The plugs that were wet and fouled previously (cylinders 4 & 7) are now spotless, as if never having seen combustion. 🤔

I know what I’m thinking, but I don’t really know what I’m doing. I want the experts’ opinions.

Thanks. Bead
(937)545-8991

You engine shouldn't have the probmatic gen 3 cool fuel setup with the paint issues. Just the filter, 2 pumps and fuel cooler. There could still be issues with the injectors though.

Looks like you missed all of SB's advice on plug gap? 😉

4 and 7 don't smell like gas? Looks like they never had spark?

What's up with plug 5 electrode?

It's hard to see your pictures up close. Are there any signs of small black or silver spots on the porcelain of any of the plugs?

This is a 5% off code for Rock Auto if you (or anyone) needs its. It's good till Sept 20, 2022.
00DCE38C03F1C8

Underpsi,

Good to know on the CoolFuel module.

Injectors will be next on the docket if the coil packs don’t solve the issue. It was one or the other first. Coil packs won the coin toss.

These plugs went in prior to this conversation. They are all factory gapped, and appear to all be ~.060”. The plugs that just went in are gapped at .040”. I’m listening. 😊

No gas smell to speak of. The boat has been sitting for a week and a bit since it was ran last. Not sure if that would allow the gas to evaporate or not. I agree on the appearance of no spark.

Not sure what’s up with #5. Looks to be some hazing. Nothing scrapes off when I hit it with my burr knife.


https://cimg4.ibsrv.net/gimg/www.off...bcae34de0.jpeg

No specks or any kind that I can see. The porcelains all look pretty clean. Even through my magnifying visors. The bases of the threads all look pretty heavy in soot. Probably from the extended run at WOT, but still short of expectable RPM (I’d guess).

Thanks for the discount code. I’ll definitely capitalize on that if I need to place an order.

Thanks. Brad.
(937)545-8991

That plug looks like something hit it? Aluminum?

Take a picture of the side of the ground strap on the plugs, like this. Trying to see the heat line, if there is even one.
https://cimg4.ibsrv.net/gimg/www.off...d61f979354.jpg

Just be sure to enter it in the correct place - it's a little confusing on RockAuto. That code goes in the box marked "how did you hear about us", not a coupon code or discount code box.

Lisle (or other’s) spark testers are under $20 and found literally everywhere, including your local parts store:


https://cimg5.ibsrv.net/gimg/www.off...ec264eb0a.jpeg

DrFeelgood,

Noted.

Thanks. Brad.
(937)545-8991

SB,

I've considered it. Can't you use a timing light to do the same thing? Just curious.

Thanks. Brad.
(947)545-8991

A timing light will flash when any spark is detected , a tester let's you see a spark to help determine the quality. Some more expensive ones are adjustable requiring the ignition to jump larger gaps to troubleshoot weak ignitions.

Sarcasm. Okay, your considering buying coils too. :wink :)

Plug wire off?:stooges:

Underpsi,

#5

https://cimg0.ibsrv.net/gimg/www.off...d6979b5b7.jpeg

#3 (for reference)

https://cimg2.ibsrv.net/gimg/www.off...e07a638ca.jpeg

Thanks. Brad.
(937)545-8991

Offshorejojo,

I would never be so bold as to say it wasn’t possible, but I’m pretty sure I had them on solid.

Plus, I think it would be a pretty strong coincidence that the two potentially problematic cylinders should be the same two that I failed to connect with wires correctly on.

Thanks. Brad.
(937)545-8991

SB,

Yeah, yeah.... I picked one up. :ernaehrung004:


https://cimg2.ibsrv.net/gimg/www.off...24b1ead167.jpg


Thanks. Brad.
(937)545-8991

are you getting miss fire codes on the scanner ?

F2,

We were not last year, when I had it scanned, but their scanner was also not able to initiate either an ignition or injector delete sequence, either, so I’m not sure it was a valid scan.

Thanks. Brad.
(937)545-8991

Guys,

All back together. New plugs, gapped to .040". New wires from Mosetti. #4 and #7 coil packs swapped with #6 and #5 respectively.

Now we just gotta get it into the water and take it for a ride.

Thanks. Brad.
(937)545-8991

was #4 and #7 producing spark when ran on the hose ? Before ? After ?

I don't understand why you would swap some suspect coils to another cylinder to try them out. Just put your inline spark tester on them and see if they work.

Snap,

We're looking for lost spark under load, and I'm not too keen on running the boat with the sundeck up.

This test should prove if the loss of power is due to lost ignition.

Thanks. Brad.
(937)545-8991

SB,

Other than when we put the boat on the scanner, yielding questionable results, we have not run the boat on a hose. We don't know if those cylinders are getting spark or not. I intend to run the boat on a hose before we take it to the lake and will likely check for spark on all eight while I'm at it.

Thanks. Brad.
(937)545-8991

So by changing the coil packs around you think you're going to tell if there firing by how ? looking at the plugs, I think you're chasing your tail by not having a good scanner hooked up, coils at idle might act fine but under load could be a different outcome, good luck I know you are looking forward to getting this fixed..........what did Pro charger say about the vacuum line ?

F2,

Yes. Advice comes to swap the coils and see if the apparent behavior follows the presumed bad ones. If not, then we are looking at the injectors.

Thats why we are taking it to the lake: To run it hard and put a load on the engine. I think the transition from fouled and wet plugs in those two cylinders to squeaky clean in the same cylinders tells a story. That story, along with the raw gas my friend smelled trailing us leads me to believe our lost HP is due to lost spark, and I am chasing that hunch.

I took it to a marine repair shop to have it scanned, and their lack of capacity to initiate an ignition or injector delete diminishes my faith in their scanner. I asked if anybody would be willing to bring their scanner to the lake, and I didn’t get any takers, so I’m doing it empirically. So far, I’m only out the cost of a set of plugs and a probably much needed new set of wires. And, not that I want to make a career of it, I actually kind of like the problem solving sort of thing, even if I have to fold myself in half to do it. 😎

I have not reached out to ProCharger yet, but I am intending to in the morning.

Thanks. Brad.
(937)545-8891

x 2. Thought this was questioned days ago ?
Very important to find out.

SB,

It was. I own a small machine shop and wear all hats. I’ll get to it. Don’t judge…… 😎

I did get the boat hooked up to some water and ran it in the driveway this evening. All right cylinders are firing at an idle. I did not throttle it up at all, as I was only running it long enough to step back, check for the strobe and then shut it off, trying to keep it cool. Y’all know where those spark plugs are, right….?

BUT……

Since we’re discussing our problems…. My wife had noticed a number of times that the left side exhaust is emitting some light steam at an idle after it’s warmed up. This evening, as I was working my way through the cylinders, starting on the right side, then to the left side, I noticed that the left side exhaust riser was considerably warmer than the right (the exhaust risers are a natural leaning-on spot when you’re leaning in to do whatever). After confirming all eight cylinders were firing, I started it back up and let it warm up. As that was happening, I stepped over the sundeck and hung my head over the back and noticed there was considerably less water coming out of the left exhaust tail than the right. Not NONE. Just less than the other side.

Since this engine is a closed cooling system, I’m not too worried about the engine, as I keep an eye on my gages pretty religiously, and the coolant reservoir is still at a good operating level. but I do have to ask: How is the water routed from the seawater pump? I know it goes through the heat exchanger, and some of it goes through the ProCharger intercooler. But how else is it routed. Is it separated at the seawater pump, right side / left side? Could I have a half-gone seawater impeller? A blockage? 🤨

And back to the initial issue…. This couldn’t be contributing to the loss in HP and top end could it? I know the ECM tracks just about everything, but the engine temp has stayed a nice consistent 160-165 since the day we bought it.

Thanks. Brad.
(937)545-8991

All the 502/454mpis have less water that comes out one side of the exhaust at idle and my tails have a 10-20* temp difference at idle.
Not sure if the 496's are the same.