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I have come into a Speedster kit car. I now have it running after 25 or 30 years. The issue i have is there is a heavy gas/exhaust smell in the cockpit when i drive it. There are no gas leaks that i can find. It has a 73 Karmann Ghia pan. Engine is a 1914cc VW. I am a shade tree mechanic at best. Restored a Karmann Ghia 35 years ago. 

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If it is a raw gas smell, then check under the gas tank up front for any leaks.  Remove the front passenger side wheel for easy access to check on things.

If it is an exhaust smell, then make sure that the engine heat shields are in place (if you open the engine hood and look down in there, you should not be able to see the ground).  Re-check the exhaust fittings everywhere for leaks (you might see some carbon shadows on the tubes if they’re leaking....maybe).

What type of exhaust system do you have?   Some exit right out the back and some exit off to the side.  Straight out the back seems to minimize smells, but not always.  

Give us a little more detail about the exhaust system and maybe we can help more.  I have the rear seat covered by a tonneau cover and only get the exhaust smell when I stop for a light or stop sign and then almost always.  
So you smell exhaust always while driving or just when you pull up to a light or stop sign?

I kept smelling gas from the MG TD replica I'm working on. Tracked it to the filler cap, which was ill-fitting. Closer inspection revealed it was ovoid. Pulled the tank, drained it, let it sit upside down in the sunshine for a couple of weeks, then blew fresh air through it with my shop vac for several hours. Applied my trusty tailpipe expander, it opened up cracks in the weld. Ordered a filler neck that looked like it would fit from Summit Racing. Cut the old neck at the weld point, it was all cold joint and fell apart. That's what you get when you try to weld a tank filled with water. Fit the new neck to the tank and brazed it in. Tricky because it's  much thicker than the sheet metal. Not my prettiest work, but it's sealed and looks okay with paint applied. Added a vent because the new cap isn't vented. Haven't got it installed because I'm still working on patching and sealing the firewall.IMG_20200728_104930933_HDRIMG_20200728_124918398IMG_20200728_132225104IMG_20200728_174027842_HDRIMG_20200729_070345218IMG_20200729_115847329_HDR      


Images (6)
  • IMG_20200728_104930933_HDR: Bad Weld
  • IMG_20200728_124918398: Cut Weld
  • IMG_20200728_132225104: Neck Fitted
  • IMG_20200728_174027842_HDR: Neck Brazed
  • IMG_20200729_070345218: Vent Brazed
  • IMG_20200729_115847329_HDR: Tank Painted

In the past I would send the tank out to have the neck shortened and the vent moved, that became a costly adventure. I came up with a cheap fix,  cut the neck off leaving about 1/2" at the tank end and same at  the cap end.  Get a exhaust pipe adapter from Auto Zone that will fit INTO the tank neck and the other end will accept the cut off neck into that . Cut it down as needed so that will fit test fit INTO the tank's shortened neck. Drill the shortened neck for a small vent, scuff all areas & clean the bare metal. Bush on JB Weld to the short neck section and the lower portion of the adapter do the vent also at this time.  Tap it with a hammer and wood block into the tank neck and smooth the JB Weld .  Slide the cap end of the cut neck INTO the other end of the adapter again secure with JB Weld. This takes less than an hour to do. 

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