The V8 Owners Forum -

Does the webber 500 carb have the facility for vacum advance?
And when using the edlbrock manifold does the thrmostat housing sit in the same positionas standard?

steve

steve b wrote:Does the webber 500 carb have the facility for vacum advance?
And when using the edlbrock manifold does the thrmostat housing sit in the same positionas standard?

steve

In answer to your first question yes it does. In fact it has two ports, one is timed so that there is only vacuum once the throttle plate is slightly opened. The other is a constant vacuum port.

Having said that the Edelbrock carb provides too much vacuum from the timed port in my opinion. (And in the opinion of others "in the know")

This has the effect of making the pickup jerky if you run a decent amount of static timing.

I've set a few engines up with this carb now and in my humble the best compromise is to not run the vac system but run the following:-

3.5 engine....14 degrees static, 36 all in at 2700-3000 RPM.

4.6 engine.....12 degrees static 32-34 all in at 2700-3000 PRM

(I used to quote 28 degrees all in for the 4.6 engine but mine definitely pulls better with the higher figure). Of course if you are running a mega high CR or a mild, low overlap cam you might need to adjust the figures slightly.


The thermostat on the eddy manifold is at the front just behind the outlet stub. I don't know where it is on a standard manifold.

Pete

sidecar wrote:

steve b wrote:Does the webber 500 carb have the facility for vacum advance?
And when using the edlbrock manifold does the thrmostat housing sit in the same positionas standard?

steve

In answer to your first question yes it does. In fact it has two ports, one is timed so that there is only vacuum once the throttle plate is slightly opened. The other is a constant vacuum port.

Having said that the Edelbrock carb provides too much vacuum from the timed port in my opinion. (And in the opinion of others "in the know")

This has the effect of making the pickup jerky if you run a decent amount of static timing.

I'll definitly agree with that, but it took me some £500 worth of experimenting and fighting (new carb, manifold and dizzy) before I discovered it.

Mine used to fart through the exhaust and have an audible/feelable erratic intermittent misfire at idle and low rpm, until I eventually put the vacuum hose back on ported vacuum. Then it ran smooth as silk.

I also did some mods to the dizzy to enable the correct timing advance. Mine would only go to about 26 degrees, but after I finished it would hit 34. (With vacuum disconnected)