engine fumes...
Thread Starter
Heel & Toe
Joined: Dec 2004
Posts: 17
Likes: 0
engine fumes...
In March of 1991, I bought a stock looking retired '64 coupe race car. It's got a nice running 283 with a Holley 390, 4spd and 3:36's. Shortly after that month, I changed the headers and full exhaust system for a used side exhaust setup and added Vintage Air. Somewhere along that time (it's been many years and many miles later) and to this day, I have had to put up with excessive exhaust fumes in the interior to the point that I have to have the windows down and heat on or ride with the air on. It's better with windows up and vents closed. I've tried manifold gaskets and no difference and it's got a good working PCV system. Is it typical of side exhaust? Is the hood to cowl weatherstrip the problem? Firewall gaskets? Do fumes enter through a bad seam over the rear wheels. It's at it's worse when I let off the gas and coast. I've been chasing this issue for 14 years and I've had enough! I've only got a couple of weeks before the car is put away for the winter but then will have to deal with it again come spring. 
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,871
From: Greenville, Indiana
Originally Posted by Mr. Miller
In March of 1991, I bought a stock looking retired '64 coupe race car. It's got a nice running 283 with a Holley 390, 4spd and 3:36's. Shortly after that month, I changed the headers and full exhaust system for a used side exhaust setup and added Vintage Air. Somewhere along that time (it's been many years and many miles later) and to this day, I have had to put up with excessive exhaust fumes in the interior to the point that I have to have the windows down and heat on or ride with the air on. It's better with windows up and vents closed. I've tried manifold gaskets and no difference and it's got a good working PCV system. Is it typical of side exhaust? Is the hood to cowl weatherstrip the problem? Firewall gaskets? Do fumes enter through a bad seam over the rear wheels. It's at it's worse when I let off the gas and coast. I've been chasing this issue for 14 years and I've had enough! I've only got a couple of weeks before the car is put away for the winter but then will have to deal with it again come spring.
I'd be looking at the underbody as you suspect for cracks or openings for the exhaust coming out of the pipe getting back inside the body. That is, if you have no leaks between the engine and the pipe tips.
No, this is not typical of side exhaust.
Melting Slicks
Joined: Oct 2001
Posts: 2,740
Likes: 4
From: Marblehead MA
Originally Posted by vark_wso
Do you have the weatherstrip on the trailing edge of your hood to seal the ledge in the vicinity of the cowl vents?
I had that problem and this solved it..... 
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,871
From: Greenville, Indiana
Originally Posted by achapman
I had that problem and this solved it..... I wouldn't argue that it fixed your problem. I've run both my C-2's thousands of miles with the hood popped up on the latches so the rubber doesn't do anything. I get no fumes, whether it be oil or exhaust in the cabin. I know that's what the rubber is there for.
It would seem to me that if the problem was the hood rubber, there'd have to be an exhaust leak under the hood.
If the poster is running factory side pipes with no leak under the hood, there shouldn't be a problem.
Race Director
Joined: Jan 2003
Posts: 17,586
Likes: 3,611
From: Central Arkansas
Originally Posted by MikeM
I wouldn't argue that it fixed your problem. I've run both my C-2's thousands of miles with the hood popped up on the latches so the rubber doesn't do anything. I get no fumes, whether it be oil or exhaust in the cabin. I know that's what the rubber is there for.
It would seem to me that if the problem was the hood rubber, there'd have to be an exhaust leak under the hood.
If the poster is running factory side pipes with no leak under the hood, there shouldn't be a problem.
It would seem to me that if the problem was the hood rubber, there'd have to be an exhaust leak under the hood.
If the poster is running factory side pipes with no leak under the hood, there shouldn't be a problem.
Dan
Thread Starter
Heel & Toe
Joined: Dec 2004
Posts: 17
Likes: 0
Thanks for the replies. I think there are no exhaust leaks under the hood. Recently I removed the fan belt to not have any air blowing over and around the engine and then felt all around the manifolds expecting to find a leak but to no avail. I have even blocked up the exhaust outlets and that stalled the engine! My guess is that the fumes are entering in through the rear wheelwells or out back there somewhere. Reason #1...The rear fan assembly was long gone when I bought the car. (2) When the car is driven in the rain (YIKES!!) water leaks in somewhere over the rear wheels!
Anyway, I'll keep looking and hopefully cure this situation. Otherwise, it's just a blast to drive and even after 14 years of ownership (and fumes), I still find it hard to believe I own it.
I treat it like gold and drive it like a rental!
Anyway, I'll keep looking and hopefully cure this situation. Otherwise, it's just a blast to drive and even after 14 years of ownership (and fumes), I still find it hard to believe I own it.
I treat it like gold and drive it like a rental!
Le Mans Master
Joined: Nov 2000
Posts: 7,246
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From: Going too fast over the hill. Iowa
To locate a rear wheel water leak, pull the carpeting back from the sides, and direct a garden hose stream to the top of the inside wall of the wheel well when water drips into the car from the seam. Mark it and blow the seam dry, then use a Caulking gun with clear silicone caulk to seal the hole.
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Team Owner
Joined: Oct 2000
Posts: 38,897
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From: Washington Michigan
There was originally a water drain hose from the rear ventilation fan housing through the rear wheelhouse, to drain water that entered the system through the vents in the C-pillar. If whoever removed the ventilation fan also removed the drain hose, that hole in the wheelhouse is probably the entry point both for water AND for exhaust fumes from the sidepipe on the driver's side. See UPC 1Asm, Sheet D10 in the assembly manual for the detail.
Race Director
Joined: Oct 2005
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From: Camp Verde AZ
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
Coupes have exhaust fans in the back?? Guess you learn something everyday.
Did they still have the fans after the piller vents behind the side windows were removed?
Does this fan work all the time or is it temp controlled?
Thanks,
Doug
Did they still have the fans after the piller vents behind the side windows were removed?
Does this fan work all the time or is it temp controlled?
Thanks,
Doug
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,915
From: Washington Michigan
Originally Posted by AZDoug
Coupes have exhaust fans in the back?? Guess you learn something everyday.
Did they still have the fans after the piller vents behind the side windows were removed?
Does this fan work all the time or is it temp controlled?
Thanks,
Doug
Did they still have the fans after the piller vents behind the side windows were removed?
Does this fan work all the time or is it temp controlled?
Thanks,
Doug
Melting Slicks
Joined: Apr 2003
Posts: 2,818
Likes: 480
From: Florida
Mr Miller,
I smell your pain. I assume EX RACE CAR=FLARES?
I had the same problem due to poor rear wheel flare instalation. It had sand in the carpet behind the seats and it would get wet if raining. Does yours get wet on both sides? Take off the interior quarter panels and you may see some holes. Mine were about 1x4 inch gaps. I glassed mine back up and it cured the problem.
I smell your pain. I assume EX RACE CAR=FLARES?
I had the same problem due to poor rear wheel flare instalation. It had sand in the carpet behind the seats and it would get wet if raining. Does yours get wet on both sides? Take off the interior quarter panels and you may see some holes. Mine were about 1x4 inch gaps. I glassed mine back up and it cured the problem.
Thread Starter
Heel & Toe
Joined: Dec 2004
Posts: 17
Likes: 0
I'm fortunate that there aren't or never were any flares. I guess I'll pull out the carpeting and try spraying water up in the wheelwells to see where it's coming in and try to seal it up. I bought the car in 3/91, installed the side exhaust in 8/91 and then installed VintageAir in '99. The fumes started as soon as the exhaust system was changed. It's got to be leaking in from out back there somewhere. With a window cracked open or down or with a floor vent open (or any combination of the two), there must be a low pressure situation created in the interior that pulls the fumes in through a leak. I'm trying to get my old snow plow truck ready for another winter so the car isn't a priority now but if the weather holds out, maybe I can get back to it and try to cure this 14 year old problem. Stay tuned....
