Hi there,

I think my engine runs really good but there's always a certain smell of burnt gas at the exhausts. is it usual also in nicely tuned engines?

here are some some specs about my engine:
-the carb is an Edelbrock 1406 -unmodified I suppose-600cfm ( this carb is the leanest of the line)
-MSD distributor and new spark plugs with modified negative contact ( filed a bit to improve the spark). I didn't checked the new spark plugs but the older ones were just a bit more than tan
-made 900 miles in 4 months and only 200g oil loss ( the fourth part of a 1/4 gal)
-please check the pic of the back of my car. the black spots are the result of about 600 miles
-gas consumption is really good. better than a stock 190hp 79 owned by a friend
-I think I have a 160 F thermostat because myengine takes lot of time to reach the 190F temp
-The gas smell is there also when engine is hot
-some, few, smoke from the exhausts, same as other vettes I've seen on youtube videos.the smoke is really few when engine is hot. smoke is white at cold engine, clear when hot

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[IMG]local://upfiles/6949/FC5BC1DFB97E408A86E642CDA5CA6AC5.jpg[/IMG]

 

androus, gas smell at exhausts huh?white at cold, clear when hot? who is driving thevehicle when you've noticed this?

 

Forgot what year you have but does it have a catalytic convertor?

 

73shark,
1979 and cats

[IMG]local://upfiles/6949/F18D51BED6E74DD9B94C3C820FA9CEC1.jpg[/IMG]

 

Aldo,
How have you been? Are your exhaust pipe tips black? Sounds like you're running "rich." Short of going into the carb, you can go "in" w/ the two mixture screws in the front. Other-wise, it's jets and/or metering rods and springs.

 

Hi Aldo, I agree with Jim on a little bit of fine tuning on the carb. You can hook up a tachometer and vacuum gage to help adjust the idle mixture screws to the fastest leanest idle speed, it may help some on the rich odor. The white/grey smoke on cold starts is typical with older and/or high mileage chevy engines, normally it's a little oil running down the valve guides after shut-down and it burns in the combustion chamber on re-start. You can install new valve stem seals with good results if the valves and guides are not worn badly.

 

Don't know if this matters or not but those particular cats are designed to have fresh air pumped in from either an air pump or intake pulsations. If they aren't plugged, then you'll probably have some exhaust leaking out of those elbows on the side of the cats.

Have you considered putting a heat shield above the driver's side cat? Because if they are working correctly, they get very hot. [] Also the exhaust will have a sweet smell. I'm guessing that they probably aren't working anymore. That style cat also has a honeycomb matrix inside and sometimes it breaks down and then partially plugs the exhaust.

 

If indeed, like "shark" is saying, the convertersmay beclogged, hook up the vacuum gauge and from idle, crack the throttle wide open real quick, not holding it open, and see if the needle drops down to zero. The fast complete drop indicates the exhaust is clear, if the needle doesn't drop quickly, the exhaust is clogged/not free flowing.

 

Thanks everybody,

I have reduced the a/f mix with the 2 screws in front of the carb and now it's a bit better. very little smoke at cold engine and no smoke at all when hot. The gas smell is always a bit there, probably slightly less than before.

I'll check my Cats conditions soon. Actually i should remove them since there's really no need of them. But that's not so easy to me...
Now I have other troubles... yesterday my mech has replaced various parts at the front suspension : tie rod ends, idler arm , PS control valve. But my car doesn't behave good : when I turn left , the behaviour is very scary! The car seems to continue to steer even if I stop steering...
After the parts replacing , my steering wheel has become harder than before and not straight anymore ( high point of steering ar 2 o'clock). We kept tie rod ends same size as olders, but possibly made a mistake at the pitman arm , loosing the high point of steering
keep you posted

 

Aldo, you need to get an alignment, that should help alot.