1973 Cj5 V8 304. Where Do You Have Your Vacuum Advance Ran To On The 2100 Caarb?

Where do you guy have the vacuum advance from the Distributor ran to on the carb?? I cannot remember where mine was ran. I see 2 ports on my 2100. One on the front and one of the pass side . I remember one of mine being plugged off since the cto switch valves were gone off mine. Anyone? And thank you in advance!!

 

I'm pretty sure this diagram is accurate...ish. It's for a CJ7, but the emissions should be similar, I think lol. Factory would have been ported vacuum. If this diagram doesn't work, you can take your vacuum gauge and test each port. You should see no vacuum at idle, then when you crack the throttle you should start to see vacuum. You could also run it to a non ported vacuum. I run mine off of full manifold vacuum (Mallory HEI distritubor) with a little extra base timing.

 

Whoops forgot the picture

 

My 74, 304 no longer has the CTO . I think I have the dist advance hose attached directly to the intake on the left forward side if the intake manifold. both of the ported vacuum ports under the carb are plugged. This may not be the best way to do it but mine has been this way for a long while and appears to work fine. either of the ported vacuum access points under the carb might be better. Maybe someone else with better understanding can provide better info.

 

Manifold vacuum is what you want. It will advance the timing under low engine loads and reduces it under high loads. When you are cruising down the road at 45-50 with low engine loads (high manifold vac) timing is advanced, increasing efficiency and reducing fuel consumption. On the other hand if you floor it getting onto the highway (low manifold vac) it will retard the timing to prevent preignition.

Ported manifold will advance and retard the ignition based on flow through the carb which is basically engine speed.

Jeep used this CTO system to switch from manifold to ported when the engine warms up, to reduce emissions.

 

It is the nipple on the side next to the choke.

Manifold vacuum only effects at idle/off idle.

Under any load after the throttle plates clear the port the ported and manifold vacuum are the same.