Overheating?

[DanEC]

A little different tack - your temperatures don't sound like anything to worry about based on your description so far. But, it may pay to check your timing and make sure it's where it needs to be and is not retarded. Also, if you have vacuum advance on your distributor (probably not) be sure it's hooked up to a manifold source of vacuum. You don't want ported vacuum advance - that's a 60's era pollution control device.

Insufficient timing advance is a major contributor to engine overheating - especially around town and at low speeds.

[snakesaway]

Originally Posted by DanEC

A little different tack - your temperatures don't sound like anything to worry about based on your description so far. But, it may pay to check your timing and make sure it's where it needs to be and is not retarded. Also, if you have vacuum advance on your distributor (probably not) be sure it's hooked up to a manifold source of vacuum. You don't want ported vacuum advance - that's a 60's era pollution control device.

Insufficient timing advance is a major contributor to engine overheating - especially around town and at low speeds.

I do need to check the timing just need to find the timing gun but that was something that has been suggested. On the vac advance front the dizzy does have vacuum advance and it is feed from the carby which is a holley. I recently replaced the tube for this as it was old and didn't fit tightly.

Thanks

[DanEC]

Originally Posted by snakesaway

I do need to check the timing just need to find the timing gun but that was something that has been suggested. On the vac advance front the dizzy does have vacuum advance and it is feed from the carby which is a holley. I recently replaced the tube for this as it was old and didn't fit tightly.

Thanks

OK - Holleys have different vacuum sources depending on the model. You want to hook it up to a vacuum source that comes from below the throttle blades and not above. Basically just make sure it's pulling a strong vacuum signal when idling by pulling the hose off the carb and making sure there is good suction.

A ported vacuum source is from above the throttle blade and has a low vacuum signal at idle but it will increase at steady throttle as the throttle is opened and airflow increases. OK for the highway but doesn't do much at idle or low speed.

I have an old Corvette and factory was ported vacuum advance - switching it to manifold vacuum outlet off the Holley dropped it's water temperature when running around town by probably 15 - 20 degrees. It was a startling difference. Good luck.

[snakesaway]

Ok thats very interesting see the picture below. You will notice there is a small black pipe coming off the carby on the right hand side this is the vacuum advance pipe does this look right to you.

Thanks Andrew

[DanEC]

Originally Posted by snakesaway

Ok thats very interesting see the picture below. You will notice there is a small black pipe coming off the carby on the right hand side this is the vacuum advance pipe does this look right to you.

Thanks Andrew

That larger black hose coming off of the right side, rear area of the carb is usually for a PVC setup or valve cover brearther - something like that. The full time vacuum source you should hook to your distributor is under the front bowl, coming out at an angle and currently capped.

Not completely sure but I think the upper port on the right front side of the carburetor and fuel bowl is a ported vacuum source. You can check it with the engine at hot idle and see if it reads the same as your manifold vacuum. I doubt that it does and I would not use that for the distributor.

Hope this helps a little

[cycleguy55]

Originally Posted by DanEC

The full time vacuum source you should hook to your distributor is under the front bowl, coming out at an angle and currently capped.

Agreed - in the photo you can see the end of the black cap sticking out a bit from under the primary fuel bowl - that's a manifold vacuum port. Just remove that black cap and connect the vacuum line which is currently connected to the timed / ported vacuum fitting on the side of the metering block. Don't forget to cap the timed / ported vacuum fitting on the carb that the vacuum hose is currently connected to. I believe both ports take 3/16" hose.

You'll find the idle speed will go up and the idle will most likely be a bit smoother after switching from ported / timed vacuum to manifold vacuum.

I used manifold vacuum for my connection and had to adjust the idle speed screws to drop the idle by about 200 RPM after I made the switch. Make sure the engine is fully warmed up and off fast idle before you make any idle speed and/or mixture adjustments.

Originally Posted by DanEC

Not completely sure but I think the upper port on the right front side of the carburetor and fuel bowl is a ported vacuum source.

I checked a Holley diagram and confirmed the upper port on the primary metering block is a timed / ported vacuum source.

[snakesaway]

Dan and Brian thanks guys for you input looks like I have some testing to do on the weekend. Will be interesting to see what I find out.

Thanks again Andrew