The Stovebolt Site Forums The Shop Area Engine Shop 59 Apache with 327 gassy smell from exhaust

I have a 327 in a 59 Apache with a newly rebuilt 327 and a brand new Holley 600 cfm on a contender intake. When the truck is idling the exhaust has a gas smell to it and burns the eyes. I figure it is running rich maybe. But the fella I bought the truck from said he put a "little bigger" cam in it. Before I go messing with the carb adjustments i figured i would ask here on the forum what you folks may suggest that could be causing the issue.

Define "a little bigger". A cam with a lot of overlap between the intake and exhaust valves pulls unburned gas out through the exhaust valve. It doesn't start running efficiently until the speed goes up- - - -sometimes WAAAY up! One engine I ran on the round track wouldn't run smooth below 3,000 RPM, but it pulled strong from 3K to 8K. Below 2500 RPM, it didn't run rough or stumble- - - -it just shut off! That's an extreme example, but engines with somewhat radical cams don't idle well, and they get lousy gas mileage.

The most common mistakes amateur engine builders make is using too much cam and/or too much carburetor for the application. More is definitely NOT better in most cases.
Jerry

I have an almost identical setup in my '40, except carb is an Edelbrock 600. If your cam isn't " radical " as Hotrod mentioned, try leaning out the carb a little at a time. Procedure is on Edelbrocks site - I'm sure Holley also has instructions on line. Tweak it a little / take it for a run / repeat as necessary.

How many times have I looked at trucks/cars for sale and the guy says "it's got a little bigger cam". usually a sales line unless you know the guy. May just have a stock cam. Exhaust always smells like something, right? After all, it's burnt gas. I love it. If it starts, idles and runs good, take britcons advice. Check all vacuum ports/hoses for cracks/leaks too. No gas leaks at carb? No smoke, white or black? Timing off can do this, check timing 6 deg BTDC. Get a good old Rochester Qjet if it persists.

Jerry, that is what I was thinking to, the fella i picked the truck up at in Mobile was building the truck as a show truck. He had been working on it for a little over 3 years until the plant closed he was working at. I'am going to call him tonight and find out exactly what size cam he put into the engine. I may do like i did on my 50 truck with the 400sbc and change out the cam to a stock cam if tweaking the carb doesn't help The 400 in the 50 ran a whole lot smoother after I changed it out and runs very well. And again thank you for all the help and advice you have given me not only on this problem but many others.

Britcon, the engine actually had a brand new edelbrock 600 on it when i picked up the truck. I figured it was a carb issue and exchanged the edelbrock for a Holley 600 and still had the problem

bartamos, I don't mind a little smell of gas in the exhaust but my eyes burning kind of bothers me. The 327 is a brand new build and has all new lines and hoses. The fella did a real nice job on the front end. he installed a front clip out of a 78 camaro and it looks very well done. I believe him when he says that there is a little bigger cam in the engine. The reason being is that he was building the truck for himself as a show truck And you can tell he took a lot of pride in his work. but even he said that the exhaust had a pretty stout smell of gas.

And again thnaks for all the help and advice you guys have given me. I really wanted some input on which way to go at fixing the problem. I really don't want to go to changing out the cam if i don't have to. The cam change isn't really that hard. It took me about 2 days on the 400 sb and that was just taking my time.

You are running too rich.
Lean out your jets until your spark plugs appear powdery brown or tan, and you can then adjust your fuel mixture screws. But first your jets have to be right.