- Corvair of the Month
- Posts: 9709
- Joined: Mon Aug 06, 2012 12:33 pm
- Location: Lake Chatuge Hayesville, NC
This diagram may be of help in confirming your vacuum connections. The vacuum advance MUST be connected to the vertical "spark port" on the right carburetor. The vertical port only applies vacuum to the vacuum advance mechanism as the throttle is opened, to bring the vacuum advance timing into play at low to medium throttle settings. The horizontal vacuum port is directly connected to full intake manifold vacuum, and is intended to activate the choke pull-off diaphragm to partially open the choke butterfly the moment the cold engine starts. Connecting the horizontal port to the distributor vacuum advance would engage full vacuum advance at engine idle, which is too much timing advance at the wrong time.bbodie52 wrote:I wanted to make sure that some important insulators were not accidentally omitted when your car was worked on in the past…
Carburetor rebuild kits often contain a thin gasket to seal the underside of the carburetor where it mounts on the intake manifold. The Corvair carburetors need a plastic insulator to isolate the base of the carburetor from the intake manifold, which prevents the gasoline inside the carburetor from boiling or vaporizing if excessive heat is allowed to transfer from the hot aluminum intake manifold on the cylinder head to the carburetor body. These plastic insulators can be easily damaged when removed. Clark's Corvair Parts bundles gaskets and insulators together. They are listed near the top of page 56 in the catalog http://www.corvair.com/user-cgi/catalog ... ow_page=56.
If the insulators are not present, and only a single gasket is being used under each carburetor, the fuel may be close to boiling when the car is driven. The use of fuel may allow some effective cooling of the fluid in each float bowl as fuel is consumed and replaced with cooler liquid from the tank. But when the engine is shut down the remaining heat from the heads may continue to heat the gasoline in the float bowls of the idle engine, causing the gasoline to percolate and appear as it drips from the venturi cluster in each carburetor.
The attached carburetor service manual is a useful and informative supplement to the shop manual...
- DELCO ROCHESTER - Models H, HV Carburetor Service Guide.pdf
- DELCO ROCHESTER - Models H, HV Carburetor Service Guide
- (1.79 MiB) Downloaded 12 times
Lake Chatuge, North Carolina
1966 Corvair Corsa Convertible
The vacuum balance tube connectors in Brad's illustration are rubber hoses and a very common source for vacuum leaks because they get cooked being connected directly to the heads.
The other issue is today's gasoline. When the lead was removed (a long time ago) octane dropped and so did engine performance and economy. The gasoline refiners finally got the octane back up by changing the refining process. This made the gasoline more volatile (not an issue with fuel injection). On a hot day after a long drive I've heard the gasoline in the bowls literally boiling!!! Of course after a few days the carburetors are dry. This is why many have gone to electric fuel pumps to prime the carbs and avoid vapor lock at the fuel pump.