Strong Gas Smell with Triple Webers

[Tony D]

Some sick individual once made an EGR manifold out of Swagelock connectors and T316 Stainless as well...Lesson Learned: Use bigger tubing than you think if you're pumping EGR! (Also that 'brown' stainless steel tubing is damn hot to the touch!)

 

There is no end to what deviant things we can make if we set our minds to it.

 

With the advent of cheap EFI and those tasty EGR Coolers on all the big diesels it may be time for a revisit of this debauchery!

[240zip]

Seems this was covered perhaps 5 years ago ...

 

http://forums.hybridz.org/index.php/topic/29444-tripples-and-fuel-smell-help/page__p__756988__hl__%2Bheat+%2Bshield+%2Btriple__fromsearch__1#entry756988

 

Not exactly the same as mine are Webers. It didn't come up in the search due to the spelling issue. What bothers me is that it seems he never solved the issue but rather went on to a v8 swap. I've seen this a few times. People get Webers (or some similar set of triples) and then dump them for v8's or a L28ET. I completely understand this need - hence the reason I'm building a separate 240Z with an L28ET.

[Tony D]

That was on Mikuinis and their available cooling bodies really help alleviate the situation. Weber doesn't have this, so they stay hot, and off gas.

 

The real issue is vapor recovery (EVAPorative emissions control) for the carbs. All carburettors suffer this, try driving a 1978 Impala Station Wagon with the HD Suspension (4.11 gears out back) with a 350 CID Engine with a Quadrajet...hold your foot to the floor in D and don't let up until just after the secondaries kick in (about 65mph) --- the difference in gasoline smell in the cabin with and without the air cleaner and snorkel on is amazing!

 

Same goes for a hot shutdown. The quadrajet, thermoquad, holley---anything sitting on top of a hot intake manifold will off-gas like crazy after shutdown. Thing is the individual float bowl volume contributes to how much EVAP you will get. Thermoquads are the worst in terms of 'volume' but best in that they have a phenolic construction making heat transfer less an issue. But the others, with die cast bowls... Triple Webers/Mikuinis/Delortos/SK/OER's have far more volume in them than most domestic single four barrel manifolds so naturally they have a big EVAP possibility.

 

The 74 SU's had VERY LITTLE captive volume in the float bowl compared to the 73's and therefore were less prone to the smells. The earlier carbs with the metal overboard dumps smelled even with an air cleaner---but the US Models vented the carbs to the air cleaner, and with a thermostatic element that all would have a closed damper on the front of it, now wouldn't it? All barriers to the nose detecting off-gassing.

 

You will find the EFI car simply won't smell compared to the Weber'd car. Same as if you were running TWM ITB's, they wouldn't stink either...no off gassing after shutdown, only the tau layer on the inlet manifold to dry up and that's almost instantaneous after shutdown!

 

The source is hot gas in the float bowls. The answer is either eliminate the hot gas, or recover the EVAPorative emissions to prevent the smells. Either will work.

 

Personally, I'd go EFI... Gut those babies, make them vintage looking throttle bodies, and run an injector rail on your triple manifold. Bye Bye gas smell after shutdown. Hello 30mpg at highway light cruise! Double payback when going ITB EFI over Webers!

[240zip]

Well this is a follow-up to the whole gas smell issue. It was two eval hoses that were disconnected and stuffed above the mounted gas tank. Not to mentioned rotted hose gaskets. I replaced the gaskets, hoses, and no gas smell. Huge difference both in the car and when left in the garage. It was fortunate the gas sender was defective or else we would have never dropped the tank and found the problem.