gas smell on startup from engine

[IOMss11]

Hey all, have. A question for my 2011 full bolt on, and cammed camaro ss.

On start up, lll get a straight gasoline smell coming from the vents it seems every time and I've had my car cammed.for about 4 months now. Has.anyone else come across this issue and is it just common after doing a cam install? Also I was told by my tuner that the "ticking" sound coming from the engine is common with the LS3 motor that after you install a bigger cam, the valves are opening more hence creating the louder "tick" sound the ls3 has stock. Any feedback would be greatly appreciated!

[GONIF]

Bet your running catless. And with a cam and tune and no cats you will get a wiff of gas fumes . Try running the HVAC on recirculate .

[IOMss11]

I have the hi-Flo cats, but that's it no mufflers. Sorry forgot to mention that.

[954camaro]

High flow cats will still do this (it helps a little with the smell compared to no cats) and i really don't think if you have mufflers or don have them you should still smell gas.

[2012LS3VERT]

Stock injectors? The first 4 seconds of startup are tuned separately from the MAF and VE tables, that could be set too rich. I've seen a bunch of tunes where startup airflow wasn't tuned.

[GONIF]

I do not smell any gas on mine when I start it up in the morning in my garage with the garage door open ,and my car doors and windows closed . SP 1 7/8 Long tubes and what is jokeingly called HF cats ,with a Nick-D tune. .

[christianchevell]

I have about the biggest cam out there I imagine .639/.623 and no gas smell though I have high flow cats, also I have no ticking at all and used 7.375 pushrods as per my gm gurus advice.....never had ticking and still do not... the only gas I can smell is by the exhaust from running a little rich as per needed by a rad cam on start up, and to avoid ever going lean. many do not know to use the length of pushrod I used as many places just sell the 7.40 and its not a common thing to find out anywhere most notable by searching here or there. Then of course I also run driven racing oil......I had a h.p. tune on a mustang dyno by a electrical engineer who does just g.m. products..... wongs performance engineering.

[IOMss11]

Shit, I guess back to my tuner he said it was normal and it's a GM shop, corvettes and camaros.. I just can't win

[Dmpsix]

Same here I had recently had LT headers and high flow cats installed with a tune, I also run muffler delete and there's a slight smell of gas too.

Is this something to be concerned with and head back to the tuner or should I ignore it?

[2012LS3VERT]

Shouldn't be a major concern. It could probably be tuned out, but isn't a big deal. Those HFCs just aren't as efficient when cold during startup.

[alaskacamaro]

I had a mild fuel odor when I first have my tune and catless LTH and ZL1 retro exhaust put in. It went away after a few weeks..

[Jason_SS]

Originally Posted by IOMss11

Hey all, have. A question for my 2011 full bolt on, and cammed camaro ss.

On start up, lll get a straight gasoline smell coming from the vents it seems every time and I've had my car cammed.for about 4 months now. Has.anyone else come across this issue and is it just common after doing a cam install? Also I was told by my tuner that the "ticking" sound coming from the engine is common with the LS3 motor that after you install a bigger cam, the valves are opening more hence creating the louder "tick" sound the ls3 has stock. Any feedback would be greatly appreciated!

What are the specs on the cam? Depending on how much valve overlap your cam has that can effect the "rich" gas smell. My cam has 8 degrees of overlap and I can smell gas at idle and I even have HF cats.


As I understand it if the car has the o2s in tack still it will not be rich at idle since the o2s are pulling and adding fuel to get the commanded 14.7 AFR. The fuel smell is from the overlap of a larger cam. When both Intake and Exhaust valves are open at the same time the fuel coming into the cylinder will make its way straight into the exhaust and never get burnt in the cylinder thats what gives off the fuel smell. Even larger cams will stink really bad at idle even if the tune commands it to be really lean. Hopefully that makes sense.

[IOMss11]

Originally Posted by Jason_SS

What are the specs on the cam? Depending on how much valve overlap your cam has that can effect the "rich" gas smell. My cam has 8 degrees of overlap and I can smell gas at idle and I even have HF cats.


As I understand it if the car has the o2s in tack still it will not be rich at idle since the o2s are pulling and adding fuel to get the commanded 14.7 AFR. The fuel smell is from the overlap of a larger cam. When both Intake and Exhaust valves are open at the same time the fuel coming into the cylinder will make its way straight into the exhaust and never get burnt in the cylinder thats what gives off the fuel smell. Even larger cams will stink really bad at idle even if the tune commands it to be really lean. Hopefully that makes sense.

Yes makes sense a little, here's is the sheet from comp; is this a small/mid/big cam? How are the specs? Thanks

Grind is 281 LRR HR13

[Jason_SS]

Originally Posted by IOMss11

Yes makes sense a little, here's is the sheet from comp; is this a small/mid/big cam? How are the specs? Thanks

Grind is 281 LRR HR13

It's a relative statement but I would say that your cam is on the larger side for a daily driver LS3 cam 231/247 duration and .617/.624 valve lift cut on a 113 LSA with 13 degrees of overlap.

(Intake Duration+Exhaust Duration)/2 - (LSA * 2)= Valve Overlap

As far as the ticking sound, what pushrod length did you go with on your cam swap? The aftermaret cams typically have a smaller core size then the factory cam so if you don't have the proper preload on the rocker arm/valve spring that can increase valve train noise. I'm running 1.425 BTR chromoly hardened pushrods, BTR .660 polished dual valve springs and a Cam motion cam with no ticking sound. Actually my valve train is only slightly louder than stock.

Also are you running an oil high in ZDDP like Amsoil Z-Rod, Joe Gibbs LS30 Or Valveoline VR-1?