Burning oil after re-jetting 454

I started to have an issue burning oil on my 454, I noticed blue smoke at idle after stepping up two jet sizes to 74 primary 89 secondary. The smoke smells gassy and not like the typical burning oil smell.

The jets in there before were 72/87, and the plug electrodes were white with no color after a few hours of use. The 74/89 started to give the plugs a golden brown color after an hour, but now all the plug electrodes are black. I also replaced the pcv valve to see if that would help.

One weird thing is that it doesn’t always smoke it seems to be intermittent. Could stepping up the main jets to much cause fuel to wash oil off the cylinder walls and burn at idle or maybe a high float?

TRBenj wrote: Main jets aren’t in play at idle. Something else is buggered, perhaps when you disassembled/reassembled. Why were you rejetting?

The plug electrodes were still white/new looking after several hours of
run time so I figured it was to lean, It’s running better now to, but smoking at idle.
Using aimsoil 10w40 marine oil

Go back to the 6.5. Also, the gasket for the PV is very easy to install incorrectly. That leaking will make it rich all around but most notably at idle. Check that and circle back. A spray paint cap works great under the lower bowl screw to drain most of the fuel out.

Not sure why you are saying “oil smoke” if it’s dark smoke that smells like fuel. That’s just overly rich.

Splotches of aluminum on the plugs = too lean. Clean plugs = happy plugs. I would go back to the old jetting when you have your carb apart again. Agree with zach on the PV too (I’d be going higher, not lower- but 6.5 is fine).

What size and model carb is this anyways? Seems like a pretty large difference front to back. Hopefully it’s a holley 800cfm 4150 as those appear to match your original numbers... the 800 and 850 have pretty large spreads. For ref, some stock jetting numbers:
QF M750 = 75/83
QF M800 = 78/86
QF M850 = 82/94
Holley marine 4150 750 = 73/81
Holley marine 4150 800 = 72/87
Holley marine 4150 850 = 88/96

Any oil burning would be unrelated to carb tuning but rich black smoke might look similar. How are you determining oil burn and have you been monitoring it closely since you bought it?

TRBenj wrote: Any oil burning would be unrelated to carb tuning but rich black smoke might look similar. How are you determining oil burn and have you been monitoring it closely since you bought it?

I do have the Holley 4150 800 marine.

It wasn’t burning oil when I got it or smoking blue, I kept an eye on oil level and I’ve put maybe 10 hours on it. I added about 4oz after 1.5 hours of run time to get it back to the same level on the dipstick.

Here’s a start video from today after I did the pcv valve you can see it smoking

https://drive.google.com/file/d/1IIX8Ltme1X1yHO-kK8zVbuAj6Sh7svSv/view?usp=drivesdk

All I see is a platform that needs oiling real bad

GottaSki wrote: Well I can't see the picture , maybe something is amiss there But a white insulator is not reason to adjust 3 circuits at once, nor at all. Take a plug out of s fuel injected engine, it will have a white insulator One looks elsewhere on the plug to determine jetting, an has to be done methodically Plugs self clean when at the right temp If you jet to make the plug look a Briggs or Tecumseh, it's the wrong way and loose performance and efficiency I really don't think you will have to go down that road with that carb, if your only symptom was a white insulator

Yeah that picture was just showing the plug with the white insulator, I’ll put it all back to stock and see what happens.

Another guess on the smoke, I switched to aimsoil from conventional, maybe it started leaking past the valve seals?

It’s not related to anything else and it’s not oil smoke. It smells like fuel and you messed with fuel = it’s rich and it’s likely because the PV gasket is off centered on the PV and leaking raw fuel into the intake. Examine what you did before everyone gets you going in other directions. I agree the jet change wasn’t necessary on a stock engine but, as Tim said, that’s not the source of your Smokey idle.

Crmaverick wrote: It’s running better now to, but smoking at idle.

Does this mean better with the richer jets in it?

It must be time for a quick or maybe not so quick recap of how the boat's running these days and what changes were made to things

If you're looking at the power valve gasket, look at the O rings on both ends of the accelerator pump transfer tube right above the power valve. They'll cause the same richness issues that are most noticeable at low engine speed

Hm.. what's the timeline on the oil burn and the tstat?

increasing the operating temp just opened the bores a scunch.

If that are coincidental, consider putting the old tstat in and give it a romp

GottaSki wrote: Hm.. what's the timeline on the oil burn and the tstat? increasing the operating temp just opened the bores a scunch. If that are coincidental, consider putting the old tstat in and give it a romp

The oil burning started with the old 140 t-stat.

I don’t know if Amsoil is ester based but if it is, and it’s a slightly lower viscosity in particular, this could be a factor in oil consumption. Ester based synthetics like the original M1 formula were known to swell some of the seals and the valve stem seals could be allowing some oil to leak into the combustion chamber and give you the small consumption you’re seeing. Maybe switch back to 15W40 conventional as an experiment while you are replacing the carb gasket.

That’s the ford/universal stat, which isn’t technically recommended for the older Pcm 454 housing. I’m not even sure the 170deg version of that special stat is widely available.

I can say that I’ve run a “normal” 140 stat like the Pcm ford in the older Chevy housing and it has worked alright. It may have run a little cool though, IIRC. Personally, I’d experiment with a few different stats before paying for the $100+ specialty one of the higher temp than ideal. I went in a different direction with a newer stat housing instead.

is that a left rotation prop?