Double Pumping

Carburetors.  Archaic technology (hasn't been sold on a car since 1990) and very temperamental (hard to dial in).  I only say this because I have been having a hell of a time getting them to work for me.  I inherited with my car a Holley 4160 600 CFM which comes with vacuum secondaries.  This means the carb relies on the vacuum created at higher rpms to pull the fuel into the secondary fuel bowl (higher rpms require more fuel to be fed into the engine to meet the demand).  It is actually a pretty nice bit of engineering (for the time), and in theory the fuel is delivered when it is needed.  This was not the case for my 4160.  I am not sure if it was due to the lower vacuum my engine pulls because of the bigger cam, or what, but I could never get the secondaries to open on my carb.  I tried lighter springs and a new diaphragm, but I could never get it to work correctly.  It was costing me horsepower. And then one fateful day, the whole carb decided to die in spectacular fashion.  Gas just started spewing everywhere from every seal.  I had enough.

The old 4160

I looked into fuel injection.  They make some real nice ones now like Holley Terminator EFI, but they are real spendy.  Plus it goes against what I am trying to do for this car.  I want to improve the reliability and performance of the car, but also try to make it still look as stock as possible.  So I decided to go with another carburetor.  Except instead of getting another Holley 4160, I went with a 4150.  The Holley 4150 has mechanical secondaries on a progressive linkage that meters the fuel at higher rpms.  It is not as efficient as the vacuum one, but it is a popular option that makes sure you have the power when you need it.

Holley 4150 650 CFM  Double Pumper

Dual inlet fuel rail with pressure gauge

And so here it is, the end of February 2015 and I am finishing writing up something I did back in September 2014.  Man I am slacking at my blog.  I am just running out of projects for the mustang.  I pretty much have it right where I want it.  This spring, I am going to rebuild the back half of the car.  I plan on rebuilding the rear suspension and brakes and add an Eaton Detroit Truetrac to the rear differential.  Hopefully I can get that done and write it up before 2016.