I'm about to start putting my 390 back together and i'm using a ported stock manifold. My question is about all the vacuum hoses and emissions. What has to go back on the motor? I'm not concerned about inspection so the less the better. There is the coolant water neck with the 3 vacuum ports on it, do they have to go back on? Or can I just plug those areas on the intake? I'm using a holley 750 carb and the truck is a 74' in case you need to know. Thanks

 

The temp switch on the thermostat housing is for increased idle speed when the engine gets a little extra warm when you get stuck in traffic. There are 2 vacuum sources to it, one manifold vacuum and the other is carb ported vacuum. The 3rd hose goes to the vacuum advance unit on the distributor. You do not have to use the switch however. Just run the ported vacuum from the carb to the dist. vacuum advance unit. The other thing you really need to keep is the PCV system.

 

ok thanks! Then can I just plug the thermostat housing?

 

One thing is, depending on how stock your setup is, if you're removing the EGR system too, you might wanna re-curve the distributor to get the max effect - the EGR system helps reduce pinging at low-to-mid load ... you might have to back off the timing at those RPMs to keep it from pinging after removing the EGR. Again, if you have a stock setup...

Of course, if you're way off of stock, it's a good idea to recurve anyway...


Bear, nice explanation of the fast idle setup - never realized that's what that was for ...

My '74 F250 didn't have it ... but saw it in later trucks. Pretty cool idea...

 

Well well Krewat, you teach me again, twice in one night (other thread)! I never thought about my engine being set up for a egr and then having pinging issues now that I don't have the egr anymore. I know obvoiusly the new 390 is gonna have a totally different curve and advance than my old egr'd 360 but I never though about that. Makes alot more sense now.

 

Yes, you can.

 

Thanks alot everyone!