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ok bought a vacuum gage today. THe best vacuum I could get by adjusting distributor was 5 inches. Increased idle and got to 15 inches. Not sure if I am doing something wrong or if that is right. My octane selector has retard as counter clockwise and advance clockwise. The distriburor is fully retarded. I am working on a 216 chevy. Had a surge and backfire issue. Now gone. Have slight temp issue. Gets to 200 after 6 miles. flushing radiator now. No thermostat. will put in after i finish cleaning cooling system. Any and all advice appreciated.

What engine & year?

Where are you connecting the gauge?

Where do you have the vacuum gauge attached at? At what rpm were you at when you were adjusting the timing? What is your idle rpm after you turned it up?

Ed, we are headed in the same direction (a ported vs non-ported connection-location)?

First off, where is the gauge hooked up at? It must be below the throttle blades, if its above them, you will get a bad reading. Just look at the position of the port you are using, is it above or below the throttle shaft?

Retarded timing will cause it to get hot, start advancing the timing till the engine perks up, reduce the rpm at the carb if need be and keep playing with the timing. You will need to go back and forth from carb to timing. Once you are happy with the timing, adjust the idle mixture screw in till the engine starts to run bad and slow down. Back it out somewhere between 1 to 2 turns. You may have to go back to the timing and rpm after adjusting the carb as each setting effects the other.

The vacuum gauge is nice, but it must be hooked to direct vacuum. Timing lights help too.

If you advance the timing to far, the starter will struggle and you will get detonation when pulling a hill or under a decent load. Again, there is that fine line you need to stay around or under.

A computer controlled engine will keep the fuel mixture as lean as it can with out damage to the engine and the timing right at or below the detonation point. That is the ideal emissions and fuel economy settings, a computer can change them hundreds of times a minute. With a carburetor and set and forget timing, you need to find a happy medium and hope for the best.

Joe

I am working on a 1941 chevy 216. it all started with overheating issue. I am connecting vacuum gage to line that comes from intake and goes to vacuum advance. disconnected tube from vacuum advance and connected vacuum gage. dont know the rpm. dont have a tach. doing by ear and vacuum. at idle when fully warm 15 inches is all i get. when i rev engine it goes above 20 inches.

ok to follow with this I am cleaning the block and radiator with vinegar. thinking i may have restriction in water ports. When I shut off engine radiator gurgles. Is this from exhaust leaking in to cooling system or do I have major air pocket?

Again any and all help appreciated.

Your vacuum connection is not good location for a vacuum reading (for timing) at idle (the reason is posted by others, above).

Set the idle speed (to a low rpm, steady idle, if you do not have a tachometer).
Connect the vacuum gauge to the port that provides vacuum to the wipers.
Then adjust the distributor/timing to obtain maximum vacuum;
then, adjust the carburetor to obtain maximum vacuum.

Then, reset the idle speed (and readjust the timing & carburetor).

Take a test ride.

Finer adjustments for timing are nice (and can-be/should-be done later), but do the above first and go for a ride.

Thans tim just did that. Set timing back on advanced side of octane mark to obtain max vacuum. My radiator continues to gurgle. Could it be that the vinegar is eating away clogs and air is venting through top?

re adjusted timing. took it for test drive. Surges and backfires whern i get to 40 mph. When I retard timing it goes away. how much retard is to much. still dealing with temp issue. Waiting for vinegar to work and new thermostat to arrive. ANy suggestions?

to begin with, set the timing the way you are supposed to, using the ball and pointer. Completely disregard the octane selector, it really has no use. At least there is none that I have found, I have never touched it in 30 years. Once you set the timing with the ball and pointer, you can tweak on it with the vacuum gauge, although after the above mentioned 30 years I gave 'er a go with the vacuum gauge. It increased the vacuum slightly,(maybe 3 inches) but as far as I could tell there was absolutely no difference in performance. (if you can call that performance) It was however more difficult to start. Before I messed with it, all I basically had to do was stomp the starter pedal to the floor, let it up, and it was running. So I put it back using the factory recommended method.

You need to work one problem at a time. Disregard the coolant for now if it is boiling all the coolant out on the ground. If this is the case, clean the block and radiator first.

The octane scale is only for fine tuning after you get the timing really close. You really need a timing light for this. I too have never seen much success with setting timing with a vacuum gauge. If thats all you have, then make the best of it. Set for highest reading then back off a few degrees using the octane meter.

You are still on ported vacuum if it rises as you speed up the engine, manifold vacuum will fall as soon as you crack open the throttle. Be sure to check the vacuum advance for movement, it should rotate the distributor as you rev the engine.

Who knows what is going on in your block, why is vinegar in there? Why not use a actual block and coolant cleaner? If you see bubbles all the time, I would suspect the vinegar is eating away the crude. Exhaust leaks to the coolant would be blowing coolant out at a pretty steady rate. Add a vent hose to the overflow tube and submerge the end of the hose in a bucket of water. If the exhaust is leaking to coolant, you will a increase of bubbles the faster you run the engine. It will stop as soon as you shut it off.

ok talked to previous owner of truck. Seems radiator may be the culprit. he never changed it or cleaned it in the 5 years he had it. He bought truck in peces and put it back together. When I came home today the vinegar in the radiator has turned brown and is still gurgling once in a while. I think the radiator.cooling ports may be clogged. I am waiting on a thermostat. As soon as i get it (tomorrow) I will drain vinegar flush it put in thermostat and see what happens. If that does not solve it I will pull the radiator and see if it can be rodded. Also, does anyone know if the radiator from a 1951 GMC 1/2 ton will fit?

Now for the timing issue. I am going to set the timing with a timing light tonight. Hopefully that will help some with the cooling and surge issue.


Any and all advice appreciated.

You may want to flush the cooling system with some baking soda after you drain the vinegar out. It will neutralize the acid.

ok Joe H your advice was good. Put hose in bucket saw bubbles. Opened radiator and saw bubbles there as well. Maybe the vinegar loosened enough clog for me to final see the bubbles. Will deal with timing after head gasket is replaced. Thanks for the help.

will a box of baking soda be enough?

Yes, you can "Completely disregard the octane selector", as brokenhead recommends, or you can use it to fine tune the optimum timing for your application after setting the pointer on the ball. The final optimum timing setting is confirmed by test drive. Needle on the ball may well be it, maybe not. I use the octane selector to fine tune so that I can experiment different settings, and have the ability to easily go back to the original setting without having to hook up the timing light every time I need to make an adjustment. You can do your test drive with a wrench in hand, pull over to the side of the road, adjust the timing with the octane selector, and test drive it again until it is just right. I would call that "a real use".

ok here we go again. I tried to time with a light. Guess I don't know what the BB is supposed to look like.
I turned the octane selector to 0. Then loosened the clamp on the vacuum advance. turned it until what i thought was the bb lined up with the pointer.

Any thoughts or advice?

I know what you mean

try painting the ball and pointer white

...click...

I even painted an arrow so I knew what direction to turn the distributor