Exhaust gases in Intake manifold with Cams?

vitoal18t · Jul 20, 2005

Here is the question to all you guys with Cams.

Do you ever smell small amounts of unburned Hydrocarbons (HC) under your hood?

When I start the car, sometimes at idle I get a very light hint of HC smell.

I think it is occasional exhaust gas excaping through the intake valve, I mean that is very possible at low RPM with Stage 2 cams. What do you think?

Of course it can be a number of other nasty things, like bad head gasket or cracked exhaust manifold.

I don't think it is burning oil, since oil seems to have a sweeter smell, atleast to me.

pzev04boy · Jul 20, 2005

It's possible. Do you have the cam timing adjusted? or stock cam timing?

mievil · Jul 20, 2005

What does "unburned Hydrocarbon" smell like?

pitchblack23 · Jul 20, 2005

Gasoline, I guess.

YellaPZEV · Jul 20, 2005

yeah...gasoline is a hydrocarbon.

well you do get more overlap at idle and it would allow for some gasses to escape but i think the only way this would happen is if the intake valve starts to open on the way up on the exhaust stroke. even then, i'd think the vacuum in the cylinder would pull it back in.

fastfocus04 · Jul 20, 2005

I do not smell any with mine.But on a further note I will give you dyno results on Friday....

wheeler · Jul 21, 2005

I don't smell anything with mine. If I remember right my exhaust cam is -6 and my intake is +4. Don't know if that helps. I hope yours is nothing serious.

duggyd123 · Jul 21, 2005

hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm thats not good you could have a bad pcv valve which reciculats hydrocarbons back into the intake but i dont know with out looking

Exhaust gases in Intake manifold with Cams?

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