I recently acquired a 450 Holley(from an early 70s 302)that has no fitting for ported vacuum.Anyone know if there's a way to modify it to add one.

Thanks.

 

Paul,

Boonville,MO

The Holley 1850 has a manifold vacuum port for PCV connection. If the carb you have does not have this connection, use a spacer plate and drill it for a fitting to connect whatever you want. You need to make sure you draw the vacuum off both back or front carb holes. Drilling through the plate doesn't matter if you do it on the back or the front.

Whatever rocks your boat!

Regards

Rick - West Australia
Do Y Blocks Downunder run upside down? Gravity Sucks!!

I know I can do it that way Rick,but I'd like to find a way to use ported vacuum from the carb to the distributor.I don't like using manifold vacuum to the distributor.I'll probably just need to trade this carb for one that has a fitting for ported vacuum.



Thanks!

 

Paul,

Boonville,MO

Paul.  Got a list number for the carb?  The list number should be located on the choke housing.  Without seeing the base plate, it’s going to be difficult to determine exactly where the plate can be drilled for an extra port.  While I haven’t had to add a ported or staged vacuum source to a Holley model 1850/1860 4V carb, I have drilled and installed new ports on the Demon 4V carbs in which to rephase the opening of the ported vacuum source.  I suspect the Holley carbs can be done similarly.

Lorena, Texas (South of Waco)

Ted............The list number is 7159 and the tag says it's a D4J-F.Just looking it over,I can't see anyplace that could be drilled for a vacuum port,but I don't have a lot of experience with this particular carb.Maybe you can figure out something.

Thanks!!

 

Paul,

Boonville,MO

That carburetor is for a marine engine.

The tag should have a letter "L" after the D4j, read D4JL-F



Marine engines are usually full throttle or idle so don't normally use a vacuum advance only mechanical advance.



For tapping a vacuum source others more knowledgeable than me may know.

marv