so i know the plenum can clogs cats but on my truck my cat is gutted out so it has no whatever was in it from the factory.... so since i don't have a cat to clog could my muffler get clogged from the leaking plenum?

i ask this because my truck seems to be quieter than it was when i had the flowmaster muffler put in 1.5 years ago....

 

doubtful. The catalyst in the cat has holes just a few millimeters in diameter whereas your mufflers internal passages are more likely several inches in diameter. You'd have to be blowing serious chunks out of your engine in order to clog the muffler in only 1.5 years I would think.

Maybe the loud muffler is causing you to go deaf and so it only seems quieter now.

 

lol maybe like if when my truck is outside idle when i let it warm up in the morning i can hear it in my house running but now its hard to hear it sometimes..... oh well i guess it gives me a reason to do long tube headers and true dual exhasut after winter

 

Mufflers with no cats ahead of them will develop carbon deposits, no question. Back in the day before catalytic converters were invented we used to see soot and sticky carbon falling out of compromised mufflers all the time. It wasn't all that uncommon for such an abused muffler to come apart -- usually it just got loud after blowing out chunks of rusty metal and clods of carbon, but every now and then those chunks would choke off the exhaust and put the engine at risk.

The greater concern if you've got a blown plenum gasket is the carbon that's not getting as far as your exhaust system. It's forming solid masses of baked on crap on your valve stems, piston domes, and combustion chambers. It's stretching your valves and causing valve leaks, and the finest particles of it are blowing past your rings so the engine oil can carry it to bearing surfaces. It's turning your motor oil acid, etching away at things that should be polished smooth.

If its compromised, fix the damned gasket.

 

That must be why those smoking old jalopies from the seventies when I was a kid never seemed to have mufflers on them.

To add add to this ominous warning, the guy who I was paying to put in my hughes plate and new timing chain when I first bought my truck claimed the carbon build up got so bad on my engine (iirc in the back two cylinders on the driver side) due to cracked head and apparently non sealing rings, that it would make more sense to drop in a rebuilt engine than try and fix it at that point. It was expensive.

 

Muffler off, coat hanger wire on!

 

yeah should i run some seafoam in the crack case plus throw the a vacumm house to to help clean up some of that carbon build up?

 

Don't put it in the crank case. Just change your oil regularly. Run some thru the intake though.

 

I'd run Sea Foam through the intake (brake booster hose), for sure. For the crankcase I'd just get in the habit of running a quart of Marvel Mystery Oil in place of a quart of engine oil for a good many oil changes. I'd also make it a point to run Chevron gasoline if there's a station that's not too far out of your way, or add Techron to whatever other fuel you might be getting.

The biggest concern I'd have would be the valve stems. The piston domes can be fairly carboned up without causing problems, and just waiting for all of the cool chemicals to do their thing is not a bad approach. But if you've had a leaking plenum for quite a while, you'll have significant buildup of carbon on the intake valve stems, and that buildup will cause them to overheat, and the carbon will be interfering at the valve guides. This will cause sticking valves and valve stem stretch and may cause catastrophic failure of the valve.

Courtesy of aa1car.com, a nice photo of the thing I'm talking about:



Mmmm... fudgesicle intake valves! Yummy. Though caused by leaky valve stem seals in the above photo, it's exactly that kind of thing that goes on when the plenum is sucking oil into the intake stream. Same problem, different source.

First things first: Fix that blown plenum gasket. It'll do a lot more damage than just fouling a catalytic converter and ruining your fuel efficiency!

 

I personally use Rislone in place of a qt of oil and use MMO in the fuel tank every other fill up. And the Techron once a month depending on the miles I have put on. Great results. Been using the Rislone for close to 30 years. JMO