QuestionHi Jim. I have a 1973 Spitfire USA 1500 that a friend and I bought about 11 years ago, restored, and autocrossed a bit. I subsequently bought him out of it when he moved out of state. We quickly dumped the ZS carb during the restoration and fitted used dual SU HS4s (the tags reveal they originally came off a Dolomite 1300), among several other mods to try to extract as much HP from the engine as possible for autoXing, e.g. (wrapped) headers, free-flo exhaust, etc. The engine, we also discovered, was not the original 1500 but a 1300 taken out of what I believe was a '71 Mark IV based on its engine No. FK3XXXHE. Trouble is, ever since I've owned this car, it seems that unless I richen the carbs up pretty well, the engine just doesn't run all that strongly. I/my clothes smell a bit gassy after I drive the Spit - do you think there may be something wrong with the carbs themselves, or is perhaps due to the fact that I have no charcoal canister in place for the carbs/valve cover breather/gas tank evaporative emissions, or maybe both? There currently is no hose connected to the valve cover breather, and the carb vents are just open to atmosphere. I believe at one time in the past we actually put caps on the carb vents (which required different carb richness tuning). Question restated: how do I keep the power without the stink?! Thanks!
AnswerSteve,
Even with the single Stromberg and all the emissions plumbing in place you still will wind up with a bit of the "old car" stink.
One of the problems with the Spitfire is that rather than a normal solid trans tunnel it has the removeable transmission cover... which frequently isn't sealed well to the bodywork. So engine fumes will get into the cockpit along the trans tunnel, through the old/dry rotted grommets in the fire wall, through the heater box vent in the engine compartment, and simply through the airstream flowing into the cockpit due to the lack of a roof.
The Mk IV 1296s were not real powerhouses, down on compression and strangled with the emissions gear, plus the internal drag of the larger bearing crankshaft. If you're running a very rich mixture, how do the spark plugs look? Are you sure you have the timing set correctly?
You do need to get the valve cover breather tied back into the intake manifold as you're getting the oily blowby from the engine itself. Figuring a way to plumb the float bowl vents into the the factory carbon canister setup will also help.
One my autocross car the valve cover breather and the dipstick are tied into plumbing that dumps it a catch bottle up at the radiator. It doesn't do much to slow the smell but it does keep from making the engine compartment one large oil slick.
Cheers,
Jim
