Engine and Transmission Tech

Put a tie wrap on the secondary rod and after some full throttle runs through the gears and burying the throttle from 20mph in 3rd gear going uphill, the tie wrap moved down about 1/8". My secondaries aren't opening, which confirmed my feeling that although the Healey is fast, it's not "wicked fast". Here's the set-up. Holley 570 Street Avenger, Ford 5.0 with GT40P heads, Sunbeam Tiger iron exhaust manifolds, RPM Air Gap manifold, Trick Flow stage 1 cam. It dynoed at 345 hp at the flywheel, but that was with headers and a less restrictive air cleaner than the 289 hipo one I'm running. I thought the lightness of the car might be preventing the secondaries from opening, so I changed to the lightest vacuum diaphragm spring. Still not opening. Otherwise, the car runs great in every gear, just that it feels like it's a great running 2bbl and not a 4 bbl. What do I try next?

After 50 years of running carbs and only one year with EFI I will never run a carb again. The fuel injection is just too good these days. I have a stock system from a 95 Camaro LT1 and even though it is not yet fully tuned, it is so much better than the best carb I ever had. Some of the aftermarket systems even have a self learning feature so you don't have to mess with tuning.

By the time you arrive at a satisfactory carb solution you will be most of the way there for an EFI and the carb will never run as well as the EFI.

Just my opinion.

X2

But try it without the spring and see if it opens. Sounds like maybe either a holed diaphragm or a blocked vacuum passage.

Jim

Hey Rick,

#1 make sure that you actually have full throttle. Sounds dumb but it happens a lot.
#2 with the engine "off". Hold the primaries wide open and manipulate the secondary linkage. You should be able to achieve "wide open"
on the secondaries. This should be a smooth movement without any catches or binding.
#3 While operating the secondaries, listen for the air from the diaphragm. You should only hear air from the R side front throttle bore.
Anywhere else and you have a leak. The port for the diaphragm is very small and prone to blockage. It's located at the minor diameter of the venturi. Don't use air to check it as you can blow out your diaphragm or power valve.
If everything checks out then you can try swapping in lighter springs.
Probably what is in the carb stock will be very close.
It's likely that that's all the air that the engine can use right now.
I think that the most likely restriction at the moment is the tiger exh manifolds.
Swapping them out or getting them ported will make a difference for sure.

Live like you mean it.
Fred