Correct timing and which vacuum port

[SirRobyn0]

Since its a 305, you should have ESC and some other stuff on the engine. Removing all of the emissions stuff could cause other running issues on a 305, they can be touchy. If you don't have ESC anymore, you could find that you are having major issues with detonation under load. The only way I know to fix this is to pull initial timing until it stops detonating. The problem is that it will make it run like even more of a dog than a 305 normally does.

Completely agree with this.

The problem, and it is hard to get some people to listed and believe this, but when the 305 was redesigned for 1980 it became incapable of running properly without the ESC and emissions system intact. GM pretty much built that motor to run those things, where as the 350 was not, emissions items were added on to the engine so the 350 does well with them removed. The 305 was built to have the emissions devices so stripping that stuff off is far less than ideal.

 

[Snoots]

I feel really dumb but I guess we are never too old to learn.

You're never too young, old or smart to be dumb

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[75gmck25]

All good recommendations, but you will need to experiment with your engine for best power.

With stock iron heads and near-stock cam on my 350 I used to run about 8 degrees initial, used manifold vacuum, and my distributor added about 18-20 degrees mechanical. My vacuum advance added about 18-20 degrees. Manifold vacuum gave me a better idle, and I could set it at about 750 and have it still idle smoothly when the A/C kicked in.

I now have aluminum Blueprint heads and a 213/217 @ .050 cam. I use about 15-16 degrees initial and still get about 18-20 more from mechanical. I switched to a vacuum canister that maxes at 15 degrees. This combo works well because the 64cc aluminum heads have more compression, but also tolerate more timing without pinging. More initial timing really helps improve the low end grunt, which works well when hauling a load.

 

[texasmike]

Just got back from a 40 mile test drive after changing from ported to manifold vacuum (20" at idle) and the truck runs great. It starts fast, finally has a smooth idle, especially with A/C on, steady acceleration, no bog or pinging at WOT and zero black smoke and no knocking when ignition switch turned off. One of the Rochester Q-Jet mixture screws is 3/4 turn open from closed and the other is 1 turn open. With dist. vac line removed and plugged, initial advance is 11-12 degrees at 730 rpm (hard to read that saw tooth gauge). The original ESC distributor has been replaced with a standard HEI Cardone 38-2437 unit. My 25 year (1970-'95) Chevy mechanic friend said the early electronic spark control system was mediocre at best and troublesome so GM did away with it after a few years. I still have the control unit above the glove box along with the wiring harness connector for the distributor. As for the emission system, the air pump was removed and the EGR is capped off. I don't know what more I could ask for, except for a tad better mpg. Thanks everyone.

Very happy camper.

 

[rich weyand]

Everything you ever wanted to know about ignition timing - and more! - is here.
Ignition Timing for First-Generation GM V-8 Engines

 

[Squirrely Brother]

The best advice I received from the community was from @Ricko1966. He squared me away. Every engine is different. Mine likes 19 degrees initial with all in with mechanical and vacuum advance combined to 51 degrees total timing. I’ve had it this way for almost 2 years. It has power, no pinging and runs cool. HEI, Edelbrock 1406 and external mechanical fuel pressure set at 4.5 lbs. Prior to help I had 8 degrees initial with everything else stock. Always smelled like fuel, bogged and would flood leaving me stranded multiple times. An adjustable timing light and a vacuum gauge to plug into the manifold vacuum port off your carburetor will help show what your engine wants. Best of luck.

 

[Shawn Watson]

Wow, this is great information and easy to understand. Thanks for taking the time to write it all down. I have switched over to manifold vac (20") and set the advance at ~11 degrees with dist line plugged. When I re-connected the line, I had to bring the idle screw down to ~730 rpm and can no longer see the timing mark as I only have an old Sears light. The distributor is a new HEI unit by Cardone. Everything appears to be alright at start, idle and revving it. I haven't gone for a test drive, yet. It's a stock 305 with 700R4 transmission and about 57.7k miles. In town mileage is about 10.5 mpg on no ethanol regular gas.

If your new HEI is non-esc, you should be good to go as is. You run into trouble when you start doing things outside of what the computer is programmed for.

 

[fast 99]

Back when the octane decreased many vehicles on the road couldn't handle it. We had to come up with ways to make customers happy. One way was decrease total advance. We changed the advances that limited vacuum advance but allowed the initial setting to remain. The slot on the right where the rod is bent up is what limits the advance. Advances vairy wildly depending on the application. Find one with a short stroke if pinging is a problem.

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