Hey I missed the fuel pressure regulator question… how can I test this one?

you posted you have 43 lbs constant at the schrader valve on the fuel rail I dont think the regulator is the issue, were the plug wires ever removed ? the 496 has a 2/3-4/7 swap compared to a normal BBC firing order, that plug doesn't look like its firing to me.

As F2 Speedy stated, your 496 firing order is 1-8-7-2-6-5-4-3
not the good ol' chevy 18436572

+1, that plug is soaked

The interwebs agrees with this. 43lbs is just about spec.

I would also agree with the prospect of a set of swapped wires. The coils on my engine coincide with the cylinders they align with. While the plug wires don't go straight to them (they are routed around the exhaust manifolds), each coil fires the cylinder directly below it. It is entirely possible that you have some wires crossed, which would mean you are missing two cylinders. Unless the wiring harness has been altered, I don't think you can really get the ignition connectors wrong. There may be some possibility the injectors have been swapped via mis-routed connectors, but I'm thinking that would likely require altering that wiring harness, as well, as I don't think they'd reach the wrong injectors.

I also recall speaking with Mosetti about the plug wires, and he indicated that the ignition controller chips on the ECM go bad on occasion, as he has been known to fix them. Just an FYI, in case nothing else resolves the issue.

​​​​​​​Thanks. Brad.

What's the color look like on the other 7 plugs?

I am just thinking probably all the coils are the same as they are connected directly to cylinders from the head down… and not in the old fashion way through the distribution cap probably only the cables from the coil to the spark plug could be wrongly wired but in my case they are not… or I missed something?

The firing order is something I dont get it..can you wire coils incorrectly or we are talking about incorrect wiring from coils to spark plugs? And what do you guys think about the spark plug I have installed could be that spark plugs are not correct?

I will check again if the wires to the right cylinders but as I was doing the balance test that would probably mean that cylinders would have 0% power but in my case all the cylinders were apparently working as there was decrease of power in each cylinder I put the coil off. About the injectors I will check wiring also there. Could be possible that ignition controller work on all cylinders but not in the right way but still works… or it is just working or not working? I am also thinking of not good wires between the coils and spark plugs but again this question pops up… during the balance test all cylinders had some power not sure if 100% but they had it. I will also check the spark plugs again and I will take the pictures of all 8.

I will take a picture of all 8 when I get back to the boat.

Vidic,

"Leaking" plug wires is one of those things that can hide at idle and lower speeds (like 1500RPM), but show itself at mid to high RPM. A new set of plug wires couldn't be a bad thing. Mine are fully sheathed for shielding, but they weren't cheap.

I would agree that, if you had a positive cylinder delete result for all eight cylinders, you likely don't have any plug wires crossed. Same for injectors. They both have to be active, and in sequence, in any given cylinder for you to get fire in that cylinder. But SOMETHING is causing you to run rich. Might the shop you took the injectors to be able to inspect the ECM?

Did we ever come to understand what the "strange noise" was when coming off throttle? You may have a vacuum leak.

Thanks. Brad.