Timing for stock 350?

[dtch]

Can't find any info in my book on how much timing for a stock 350. Been watching videos and come up with between 8-12*BTDC. Can anyone confirm how much exactly?

84 350 C20, TH350, Fed Emission

 

[1987 GMC Jimmy]

That’s about the range you should shoot for. As long as it doesn’t ping and the plugs aren’t white after a while, that range should work for you. A stock 350 isn’t a high compression plant so it’s more flexible.

 

[maxtwms]

Alright, there are plenty more knowledgeable than me on here but let me give a try at helping all I can and take the beating where I'm wrong.

"Every engine is different" yada yada.. true but there is also a ballpark where you can make sense of things. As told, you will hear between 34-36deg BTDC total timing and I can agree with that.

For completeness, total timing is mechanical (distributor weights) plus initial (no vacuum advance).

You'll see 8-12deg initial for these engines and that's prob close BUT!

I'm a fan of knowing exactly what my motor likes. This is where I may get harrassed but if you connect a vacuum gauge you can at least have another data point for finding your timing. Here's my suggestion.

Remove vacuum advance tube and plug it. (I used to put hemostats on it while still plugged in both, not realizing I was preserving the vacuum on the vacuum can. but I digress)

Hook up your vac gauge to manifold, advance dizzy till you get Max vac, back off 2 inhg.

Tighten dizzy back down. Note initial timing (vac adv still removed). Raise rpm while watching timing and note highest reading. If initial was 12 and highest was 38..... Typically, lower your initial at least my 2 degrees. Remember for the most part, you want between 34-36 total. That much is very well established and 2 degrees of total timing is very tight tolerance all things considered.

On the same issue, say your initial was 10 and you plugged your vacuum advance back up and then observed an extra 10deg of timing... You got a good setup. You want to make sure all your vacuum advance (assuming your vac can specs are correct) is giving you all it's capable of at idle.

Again, I'm a novice but this is what I've assembled in my head. Please test it out for me and report back!



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[75gmck25]

You can generally run initial timing as high as 16 BTDC without any issues on a relatively stock engine. Measure it with the vacuum advance connected, and at a very low idle (650?).

Then you want the mechanical to add no more than 20, for a total of 36 max. A stock mechanical advance often comes in slowly and not reach 20 until 3000 rpm or more. Modifying the advance curve to get 20 mechanical by about 2000-2400 usually helps. There are standard kits that provide all you need to change the total advance and the curve for an HEI.

Stock vacuum advance may add as much as 20, and if you are already at 36 you might get some part throttle cruise pinging. This means you need a lower rated vacuum advance (e.g., 15 degrees), or you will have to dial back base timing or mechanical until you get rid of the pinging.

Bruce

 

[Rusty Nail]

Factory setting is 0°.

Hope this helps!

 

[maxtwms]

I should say that if all your emissions are hooked up, the sticker in front of your radiator will tell you the factory setting

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