Vacuum line diagram for a 305?

[Jarvis-69 GMC 1500CK]

Realize this is not a "factory option motor" for the 69 GMC (according to vin came with a 307, should not affect much though.

Have a feeling my vacuum lines are not hooked up, have quite a few plugged with bolts and my 4 barrel Rochester carb is acting like a 2 at full throttle.


Also blows a bit blue at start, have a feeling that is due to vacuum lines not being hooked up properly and throwing my timing off.


Another question, but for much in the future, is there MPG to gain switching to a EFI system? (HotRod magazine seems to really promote them) Not really looking for a terrible amount of power(just a daily driver), just MPG.

[geezer#99]

Give us some pics of your motor!

[Jarvis-69 GMC 1500CK]

These are the two I happen to have, let me know if you need any more and I'll take them for you.

Oil on the cover due to the oil cap coming off! Currently have a oil cap from a 50's murc my uncle re purposed.

My main point f concern is the silver piece sticking out of the hose in the front of the moter, It seems to have a bunch of empty spaces for lines.

[geezer#99]

That's a newer motor.
That thing on the thermo housing is a thermal vacuum switch. Used to supply vacuum to things like your vac advance, your heat riser or your lockup switch on your tranny.
It doesn't hurt anything like it is.
I see you have your vac advance pot hooked up to a manifold vac port on your carb. THat's good.

I do see small gauge wires on your hei distributor. You'll need to check their size and source. You need 12 gauge wire from a full time 12v source. Either the ignition switch or an unfused barb on the fuse box. If your wire to the bat connection on the cap is yellow or has braided covering, you'll need to replace it. The braided cover line is a resistance wire used for points only.

[Jarvis-69 GMC 1500CK]

Originally Posted by geezer#99

That's a newer motor.
That thing on the thermo housing is a thermal vacuum switch. Used to supply vacuum to things like your vac advance, your heat riser or your lockup switch on your tranny.
It doesn't hurt anything like it is.
I see you have your vac advance pot hooked up to a manifold vac port on your carb. THat's good.

I do see small gauge wires on your hei distributor. You'll need to check their size and source. You need 12 gauge wire from a full time 12v source. Either the ignition switch or an unfused barb on the fuse box. If your wire to the bat connection on the cap is yellow or has braided covering, you'll need to replace it. The braided cover line is a resistance wire used for points only.

long shot, but can you figure out what age range? I need an oil filter and apparently it changes between late and early 305's.

Also what could stop my secondaries from opening up properly?

[geezer#99]

Look here to decipher what your motor is.
http://www.mortec.com/
For suffix codes on the front pad look here.
http://www.nastyz28.com/decode.php

On your secondaries. The air door won't pop open much if you stroke the throttle while parked and looking at it, if that's what you mean.

I see the weather has been crappy out there. Have you had snow yet?