Smelly exhaust

[El_Mecanico]

I gutted out the cat and now the exhaust stinks. It doesn't smell like its running rich though. Kind of a rubber smell any clues?

[steely]

My nose may not be tuned, but mine has a definitely oil smell I attributed to being normal for an air cooled oil drinker. Cat was off when I got mine. Somebody likened it to older volkswagons. is this what you mean or is it different? When I was a kid, I hung out around an old train yard, almost similar smell.

[cgarr]

Bad Gas?

[El_Mecanico]

My friend told me its smelled while following me. Maybe your right! It doesn't show much smoke though. Maybe I need to overhaul? She had 180 or 190 on all 6cyl for compression. I guess the CAT hides problems.

[deshetlr]

Mine does the same thing since installing my M&K. The general consensus is it is running a bit rich. However I just did an emissions test with no problem.

[Talewinds]

M&K premuffler here too. I just thought it was that yellow insulating fiber inside the premuff burning off, but months later the smell is still there when the car's running and warm.
It's a very odd scent.

[Steve@Rennsport]

Hi,

LOL,...now you know more about what cats do on these cars,....

For us old guys who were around when there was no such things as catalytic converters, thats a normal smell (slightly rich). Enhanced by the obnoxious smell of today's gasolines, you are experiencing the reality of an "open" exhaust. Back in our time, pump gasolines smelled a bit like today's race gas (unleaded) so it wasn't all that unpleasant.

As long as the AFR's are OK, its something you live with when the cat is removed. If its too much to take, using 100 octane unleaded race gas will make things more "fragrant" to a motorhead,....

[deshetlr]

Steve,
Is there a DIY way to check the AFR? While I have been considering a pre-muffler and SW chip I have not removed the cat as of yet, I just bolted on an M&K muffler. I do love the way it runs though.

[Steve@Rennsport]

Originally Posted by deshetlr

Steve,
Is there a DIY way to check the AFR? While I have been considering a pre-muffler and SW chip I have not removed the cat as of yet, I just bolted on an M&K muffler. I do love the way it runs though.

Yessir, there sure is.

Two ways: take it to a Dynojet facility and buy a few dyno runs. They usually have a good wide-band sensor setup that will display WOT AFR's on the graph. The other way is to buy something like the Innovate LM-1 hand-held AFR meter. This enables you to check & monitor this any time you wish. They even make a nifty in-dash unit.

For accurate figures, you will need to install an additional oxysensor bung by the factory one (pre-cat) for the wide-band one.

[tobluforu]

Innovate also makes a device that inserts into the muffler and works pretty damn good, but a bung is the way to go.
You should drive behind my 72 mfi with an M&K dual tip muffler, no back pressure for the most part, and damn does it stink.