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Correct ignition timing

If it's going to reliably sit in the same position at low speeds. It's common for them to gum up, but yours looks pretty much new. It's possible they machine them a little looser than the OEM to ensure you get the performance from the curve, but I'm just guessing. It could be an issue with the pick up coil or module, but if it's choosing the wrong zero crossing you would jump off by a bunch of degrees (sorry, too lazy to do the math right now).
 
Ok, you lost me at zero crossing. I dont know what that is. What would you suggest I try next ? Module, pickup, recurve kit ?
 
I would suggest as Rene’ mentioned….with the vacuum advance hooked up and driving normally (cruising) in high gear, listen for the knock under load while keeping it in high gear. Check the timing number with vacuum advance unhooked and plugged and start retarding the timing back a couple degrees at a time, then hook up vacuum advance and drive again to listen for knock under load. Keep doing this procedure to where it’s doesn’t knock under load while keeping it in high gear. Note where the timing is on the tab with vacuum unhooked (regardless of what the number is, use this as your base timing) then see what the increase in timing is by holding the engine at about 3000rpm. See how much mechanical advance is coming in at that point. Probably somewhere between 12-20* of mechanical advance. Note that number. This is your base + mechanical advance. Plug in the vacuum advance and see where you’re at now. This is total timing. Probably in the 40-50* range. If it surges while cruising, that may be too much vacuum advance, and may require an adjustable canister to retard it some.
It would also help to use a vacuum test gauge to become familiar with how much vacuum changes when the vacuum advance is plugged in.
When you get those parameters set, start adjusting your carb to idle where it sounds happy (depending on cam, this may be 600-900 rpm) watch your vacuum gauge as you make idle speed and mixture changes, and try to achieve the highest vacuum at a reasonable idle.

A well respected head guy once told me a lot of carb problems are in reality related to the ignition system.

Good luck!
 
Just a question... Because I'm not very good at this part. But, can't a lean condition cause pinging too?

Maybe the timing is ok, but it's lean in them spots is what I was thinking... :dunno:
 
shady said:
Just a question... Because I'm not very good at this part. But, can't a lean condition cause pinging too?

Maybe the timing is ok, but it's lean in them spots is what I was thinking... :dunno:
Click to expand...
Maybe, but it's done this with 2 different carburetors. The one I have on there now was running ridiculously rich at idle. Idk how to tell what it's doing under load without an afr gauge and wideband 02 sensor.
 
ping and detonation have many components. High compression with poor or low octane fuel, the quench area, an issue I think I have with my 350. Air fuel ratio can contribute, as well as spark plug heat range.
Valve that have to thin edge margins, even carbon deposits.

To answer your question, no changing springs will not alter your total mechanical advance, only the shape of the weights and the center bar can do that.
Some where in my thread I documented my tinkering with the HEI in 77 https://ck5.com/forums/threads/wess-burb-build-update-maintance.336847/post-4397996
 
I just went through this on my truck, it’s a 1982. I had a vacuum leak on carb gasket then fixed that. Then found leak under egr valve gasket so I fixed that. I have my timing set to around 12-14 degrees initial and rpm’s set to 800, I do have a 383 stroker in truck. The distributor is an msd street fighter and it advances 20 degrees. Hope this helps in an any way.
 
those appear to be iridium ? If so you may want to try plain copper. Sometimes Iridium just doesn't work in older stuff.

edit might be left fouled from other carb.
 
So my truck appears to be built out of 2 different blazers, 1988 engine and chassis, 1985 body.
Is it possible that the balancer from the 85 5.0 was put on the 88 5.7 motor, and that would give me an incorrect timing reading ?
According to oreillys website, the balancers are different.
 
Yes, this can happen, but usually that makes the marks way off, like 90 degrees. It never hurts to verify physical TDC to the mark.
 
So, I have verified tdc. But it seems like I can turn the crank quie a few degrees( U haven't measured it) before the piston starts moving back down again.
 
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