37. The Holley Carburator

When I bought the car, the engine started after flushing a slug of gas into the carb.
Wow.
This would never work on a 4 cylinder engine...

The Holley is a 4160 - 4 barrel type with vacuum secondaries and manual choke. At home I nocticed that the fuel spilles uncontrolled in the engine and it runs not really well.
I decided to work up the carb completly

The first thing I noticed is, that the Holley is not mounted in level as the engine is. The normal US cars do not have a level engine, so the intake manifold will correct this. For level-engined cars you can use a wedge plate - or you mill down the manifold.

I  demounted the Holley and examined it:
- dirty ( like used every carburator is )
- the vacuum secondaries open only partly - the vacuum lever is blocked
- the body has some molding flashes 
- the throttle shaft is wobbling in the body
- there is no thermal isolation to the inlet manifold

Disassembling
So I started to take photos from my first Holley carb. The only experience I have are on the Weber DCOE or the Keihin FCR from my bike.
After a while it looks like this:

Molding flashes
Here you see the flashes at the body

and the after the use of my file set

( from an old goldsmith )

it looks like this

After the rough works are done all the parts will be cleaned in a ultrasonic bath. I will not use any pickle to get the aluminium shiny - it too agressive and will remove the vintage look.


Secondaries
The secondary throttles will not open completly. The reason is, that the lever of the diaphragm is too long.

In the web I found, that there a 3 different version of vacuum diaphragms around - take care, which one you use is the advise.
I only have this one - so I cut out 8mm of the lever and weld it together again. Not the first price in show - but it should work.

Before

With "full" pulled vacuum

The shortned lever...it works !

New gasket set
I ordered a gasket set from Holley to be shure, that everything I need is there.

Everything I need and even more gaskets are in there. The ones I have not used - dont know, what they are for ...


Throttle shaft
If you have a wobbling shaft on a Weber DCOE, best is to throw away the body cause it is worn out. Here the Holley has a really clever design to prevent, that alu and steel will scrub: PTFE.

The wobbling shafts were easy to fit. In the Holley kit were new PTFE slices, which are wind around the shaft where it has a smaler diameter. This will seal it against leakage air and give the shaft a smooth turning.

--> A good solution for sealing the shaft. Well done Holley.
--> Next task is to find a solution, how to change the main jets without disassembling the carb!!!


TPS
As everything is easy to modify when it is laying on the table before you, I thought about a TPS sensor - you know, a Throttle Position Sensor for each throttle shaft. A TPS is a potentiometer in line with the shaft.

It is needed to recorde and visualise the angle of the throttle together with the engine RPM and the exhaust temperature to get an estimation about the setup of the carburator.

I replaced the srews at the end of the throttle shaft with special ones ( a late job ) which have a 6mm shaft - same as the potis. The two 10kOhm potentiometers are connected to the shaft extension with a tube.


Like new...
Now the carburator is clean and every function like the secondaries or the choke should work.

The intake manifold and the thermal isolation plate are the next jobs to do...