The Stovebolt Site Forums The Shop Area General Truck Talk Fumes / Exhaust in Cab

'55 series 2 with a 350 in it. I've had to take off a few months for working on the truck and am now back under the hood. Last year I installed carpet (molded from CI) with sound deadner/heat shield. However, I still get a exhaust smell in the cab, and while I usually always have the windows down (no ac), I would like to work on keeping the fumes out. I was going to start by making sure I had grommets on where the wires meet the firewall, but am looking for other tips and suggestions. The truck has a full exhaust system out past the tailgate and it seems to be sealed fairly well. I'm guessing the "holes" are the steering column, brake pedal, accelerator.

Any tips and tricks is appreciated.

yes, there's always some minor gaps where outside air can infiltrate, but most likely your smell problem is the outlet position of your exhaust - I'll guess either the pipes don't go all the way back or they exit barely beyond the back of the box in the center third

Bill

Given the fact you say your exhaust exits well back and assuming it's all tight and leak free i'd be thoroughly checking all grommets etc on the firewall,actually the fact you drive with the window open most of the time may well be exacerbating the problem.

The airflow passing through the radiator will be picking up any fumes/smells etc and with the window open it will generate negative pressure in the cab pulling any fumes through even the smallest gaps in the firewall.

I was having similar problems but an afternoon spent looking found a couple of points,one was the heater hoses and a loose wiring grommet.

Having fixed them the cab is fume free and much more pleasant and SAFER to drive.

Have someone hold several rags over the tail pipes and listen for exhaust leaks from the manifold gaskets on the heads all the way back to the tail pipe. With the tail pipes all the way to the back, you shouldn't be getting that much exhaust into the cab if there are no leaks. Do you get the smell while moving down the road?
Carl

To add to what Carl has mentioned,if your exhausts are in fact fully gas tight you should be able to stall the engine by covering the tailpipes.
I used to do it on VW bugs but have never tried it on a V8 though.

There doesn't appear or sound to be any exhaust leaks (this fall I'm putting on new headers and running a new exhaust) but duh, there is a big old gap where the steering column goes in to the cab (guess I was too busy looking for little holes).

I can't tell you if I smell it going down the road becaus the windows are down and I'm too happy about cruising in the pickup. I will take it out tonight and report back on that.


Couple questions:

How do I seald up the hole where the sterring column goes in? I found a rubber peice that appears to go on the inside of the cab around the column but it also looks like the column has to be removed to install it. Any other tips or tricks you all can think of to cover/seal the opening from the engine bay?

Where can I buy grommets of various sizes? Looked at harbor frieght but the only real items I can find are on the usual sites and not cheap.

I have various small holes that appear one of the previous owners had used to mount a variety of things (ac, radio) and so for now I just have a short nut and bolt to fill the hole. You can't see them from the inside of the cab and I'm not worried about what the engine bay looks like, is there any problem leaving those and maybe putting a dab of caulk on them to seal them up?

Again, this isn't a show truck, it's my truck for driving around and I acutally use the bed (gently of course). So I don't need professional fixes, just relying on the sound advice from the bolters here.

LMC,Jim Carter,Classic Truck parts,just to name a few,all sell replacement cab seals and grommets,including the steering column. If your exhaust runs all the way to the back beyond the bumper,I should think that you would have N0 fumes in your truck. Do you have a sliding rear window?? that will draw fumes way more than a side window. Stuff a couple of "Brillo" pads,in the exhaust ends. They're steel wool,and will constrict the exhaust flow,without stalling from back-pressure. Dump a little transmission fluid into the carburetor throat,while having someone control the throttle. This will smoke like a mosquito fogger,but it helps clean valves,too. If you have any leaks in the exhaust,this is the best way I've found to see any,that aren't otherwise obvious. hope this helps.

I have a '55 2nd, and my pipes dump down just in front of the rear axel. My firewall has some holes in it also. I have a Pontiac 400 engine and have a pcv valve which routes all the blowby into the carburetor. I do not get any fumes in my cab, doesn't matter if the windows are up or down. Seems as if you must have a exhaust leak?

Are you sure you are not smelling the variety of hot engine vapors and calling it exhaust? Road tube, valve cover vents, carb bowl venting, etc.
If the engine is tuned well and not burning oil, exhaust gas has very little odor. A hot engine with a little blow by, on the other hand, produces a lot of smells and right in front of the firewall.

Thanks for the tips guys. Jim - you may have hit the nail on the head. I haven't put a lot of miles on the truck since I've gotten it permanently (it was at my father-in-laws house up until August) and I know as he got older he tried to tinker with things and there is evidence of the gaskets starting to leak. The carb is also new (150 miles on it) so that could be it. Going to order a bunch of grommets and put some miles on it, may also try to clean the engine a little.

Something we have done for years is to first have the truck outside and pour some ATF in the carb while running. Smoke will shoot out of every seam, crack, or loose gasket and you don't need good eye sight to see it. If no smoke except out the end of the pipes then it's not exhaust but some other fumes like gas or oil.

Thanks Evan. So just pour a couple ounces of auto tranny fluid straight down the carb and then watch the magic show? How much should I pour in?

GMTK, we used to do the ATF thing to help with carbon build up. Whether or not it worked was debatable. It doesn't take but a dribble and you need to run a a pretty high idle to keep her going. Fire her up, set the idle high and dribble the ATF down the throat of the carb. If you live in town you might want to warn the neighbors cause it's gonna get smokey.

HAHAHAHA. Ok, I will let everyone know it's "supposed" to smoke like that. How long will it smoke for? My wife is going to LOVE this....

As long as you keep pouring then add a minute or so.