I give up. '83 chevy base timing.

[brown82]

I have used this "advance" search on thus board long enough.

Can someone please link me to a thread(if one even exists) or a site that has a walk through on what steps to PROPERLY set your base timing for a 350 gas?


Thank you.


James


I know "A" vaccum line needs pulled and motor needs to be warm. I just dont know what vaccum line and other possible details that maybe important to know.

[notallthere]

1. Warm up the motor.
2. Pull the vacuum line to the distributor and plug it off.
3. Loosen the distributor hold down only about a turn to a turn and a half.
4. I used a digital gun with a digital timing indicator for the first time and I am addicted to it. Anyways hook up the timing light.
5. Point the gun at the harmonic balancer to set the timing. Depending on the engine timing is set from 4 degrees to 12 degrees.
6. If you have a tachometer you will have to adjust timing to maintain about 750 rpm.

Leave the truck in park. (not an insult but you would be surprised how many people do not know this.)

[brown82]

OK. There is not anymore steps? Like raise it up to 3,000 rpms o check actual timing or something like that?

[notallthere]

I have never done that. Once I set it and lock it down I do go for a test drive.

[donut]

http://67-72chevytrucks.com/vboard/s...d.php?t=290498
FAQ in the "Engine & Drivetrain" section.

Only need to raise rpm if you want to know or adjust your centrifugal advance.

[brown82]

Thanks to both of you. I went into the FAQ and searched for base timing. It told me "no results"

[rich weyand]

Some notes:

Bear in mind that, for a given engine setup, the distributor base timing setting is basically a horsepower adjustment. Any hot rod guy will tell you to advance the timing 2 degrees at a time until you get knocking (pinging) when lugging up a hill or getting on it hard, then back off that last 2 degrees. Most Gen I 350s will take 16-20 degrees of base timing and another 20 degrees of centrifugal advance.

You don't need to block off the vacuum line to set base timing. As long as the engine runs, you're good, having the right mixture doesn't matter, as it is purely a mechanical adjustment. You do need to disconnect the vacuum line to the distributor to keep the vacuum advance disabled.

You can check total timing (base timing + centrifugal advance) by revving the engine up to 3000 rpm and reading what you have. This is also done with the vacuum advance disconnected. For the standard Chevy HEI distributor, the centrifugal advance ought to be 20 degrees, so if you have 16 degrees BTDC base timing, the total timing should measure at 36 degrees or so. If you don't get that or close to that, your vacuum advance may be shot or stuck (or was modified along the way during the vehicle's life).

Make sure you tighten down the distributor clamp when you are done, or the rotation of the shaft will drag the distributor body to a retarded timing value over time.

[natedogg]

I had a had a problem trying to set the timing on the 305 in my 85 recently. When pointing the light at the balancer I couldn't see the mark anywhere near the timing tab. My truck has a aftermarket timing tab mounted at the 2:00 position. After some research I found that the stock timing cover for a 305 had the tab around the 12:00 position. That's why the mark on the balancer was off. I was told to find TDC and put a new mark on the balancer lined up with the zero on the tab and set timing from there. Any opinions on that?

[donut]

Originally Posted by natedogg

I had a had a problem trying to set the timing on the 305 in my 85 recently. When pointing the light at the balancer I couldn't see the mark anywhere near the timing tab. My truck has a aftermarket timing tab mounted at the 2:00 position. After some research I found that the stock timing cover for a 305 had the tab around the 12:00 position. That's why the mark on the balancer was off. I was told to find TDC and put a new mark on the balancer lined up with the zero on the tab and set timing from there. Any opinions on that?

Do it. As an alternative, you could go buy a balancer with the correct groove in it. Unless you need to change the balancer, sounds like a good way to throw some $ out the window.

Something to be aware of when timing the sbc, find what the engine likes. My last couple liked 16+*, but the starter didn't like more than 14*.
I would back lash the starter, long before I'd "ping", but that may just be my combination.

[franken]

I may get beaten for mentioning it, but if you play with the distributor you can get a feel for the timing. Turn it back a hair from where the RPM is the highest and it'll be very close.

With the RPM highest (vacuum connected) it will be too advanced, and pretend the battery is low when starting.

[rich weyand]

Chevy used three different harmonic balancers, with three different timing tab locations, 12:00, 2:00, and 2:30. But you can dial this in with your timing light if you have the adjustable ones.

The crankshaft keyway at #1TDC is at 45 crankshaft degrees clockwise from straight up on all Chevy small blocks: call it 1:30 o'clock looking at the front of the engine. The three timing tab locations are 40* counterclockwise from the keyway (5* total off vertical, called 12:00), 10* counterclockwise (35* total off vertical, called 2:00, though it's more like 1:00 really), and 2* counterclockwise (about 43* off vertical, called 2:30, though it's more like 1:30 really).

Note: These are all crankshaft degrees, not camshaft degrees.

If you have the 2:00 tab with a 12:00 balancer: Set your digital timing light to 30* advance. If the timing is set at 0*BTDC, the light will flash 30* after the spark on #1 cylinder, and put 0* BTDC on the 12:00 balancer under 0* BTDC on the 2:00 tab. If you really want, say, 12* BTDC, then set the timing light to 42* advance, and adjust the distributor to align 0* on the balancer to 0* on the tab.

Having the 12:00 timing tab and the 2:00 balancer is tougher. If you could set your timing light 30* retarded, it would fire when the balancer and tab agreed at 0* BTDC. But timing lights can't be adjusted retarded. However, the #8 cylinder fires 90 crankshaft degrees after #1. So if you can set your timing light to 60* advanced (most of them go to 60*), and hook the timing light on the #8 spark plug wire, the balancer and the tab will agree on TDC. You probably can't set the advance on the timing light any higher, but you can set your timing to 12*BTDC by using the hash marks on the tab and harmonic balancer.

All that being said, the timing marks and all is just a quickie way of getting the engine timing sort of right for the factory people and service people. Adjusting the engine so it has what it wants -- the most advance that does not result in knocking under load -- is trial and error, but it's worth it, because that is where the best performance and mileage is.