454 TBI Timing Question, too much advance?

[BBBURB]

Hi all, ive done research on this and cant find the answer im looking for on my exact engine. Hoping someone can help me out...

I just set the timing, this is my first time. Ive never done this before. I unplug the brown timing wire to ECU . I have a timing light from Harbor Freight and my wife held it while I slowly spun the distributor around. The sweet spot sounded good at 13* BTDC. When I reconnected the brown wire it brought it up to 29* BTDC. The engine was warmed first before readings.

My question: Is 13* BTDC ok for the base timing? With only high quality replacement parts and no mods other than a good exhaust and cat and all fresh parts and rebuilt TBI? It runs like a champ now! Just worried if it might be too much timing. I dont want a detonation.

After reconnecting the timing ECU wire and disconnecting the fuses to the ECU and reconnecting them the ECU advanced the timing to 29* BTDC

I havent pulled the new plugs yet to see how they are doing. But its on my list to do. Also going to add a Bosch knock sensor and a O/2 sensor with a guage.

Thank you.

 

[Customblue]

Spark knock will sound like pinging in the motor when its under load. Try finding yourself a hill and loading the engine up at the lowest rpm possible, Ive found this is the easiest way to hear the pinging.

 

[QBuff02]

I was taught and always been of the mindset that there's "base" timing and then there's what the engine "wants" timing. On my engine before I rebuilt it, it was around 10*BTDC and it ran very well there. With the new engine combo it's at 16*BTDC and the new distributor has been set for an additional 20* all in by 2,400rpm. We moved it around a few degrees here and there seeing how it would respond and it just likes 16*BTDC. So that's where it lives. If yours runs good with no issues at that timing then run it.

 

[shanegtr]

Factory spec for base timing is 4* from memory, which is what mine has been set to since I got it. I haven't had a play around to see if it can be optimised at all so would also be interested in other experiences

 

[yevgenievich]

Tbi commands additional timing at idle and 13 base is likely to be too high. In the chip there is a table that tells it wat base is, usually 0 to 4. Bumping it a bit to 8 and at most 10 can help overall timing curve. Lower base timing helps with easy start. As mentioned above, putting it under the load and see if it pings.

 

[shanegtr]

yeah mine pings a fair bit on our 91RON fuel at WOT, but improves on 95

 

[olnick]

Check with the BIG Block guys! As a SBC fan and end user, I no longer check the idle timing! SBC's sweet spot is 36 deg BTDC with vacuum disconnected and mechanical all in by 3500 RPM. Set it once and forget it. Re connect vacuum and you are set to go. I have been using this method for the last 15 years on any SBC I work on and have zero complaints on lack of performance and no issues with detonation! If it works don't fix it...

Olnick

 

[BBBURB]

I found this nice write up on Timing the BBC engines: https://itstillruns.com/time-big-block-chevy-5716636.html

They say 18* BTCD is good at idle for BBC and a total of 32-34* BTDC @3500 RPM


***I know the factory says 4* but they are obviously wrong.

 

[yevgenievich]

I found this nice write up on Timing the BBC engines: https://itstillruns.com/time-big-block-chevy-5716636.html

They say 18* BTCD is good at idle for BBC and a total of 32-34* BTDC @3500 RPM


***I know the factory says 4* but they are obviously wrong.

Factory probably runs about 15.
4 is the base timing that computer references.

 

[Customblue]

Another question would be to hook up to ported vs. Manifold vacuum for the vacuum advance? Whats ya'lls thoughts?

 

[BBBURB]

Another question would be to hook up to ported vs. Manifold vacuum for the vacuum advance? Whats ya'lls thoughts?

My understanding is on the TBI the advance is to the Distributor is controlled by the ECM not the Vacuum. Vacuum is for Mechanical advance.

 

[BBBURB]

Spark knock will sound like pinging in the motor when its under load. Try finding yourself a hill and loading the engine up at the lowest rpm possible, Ive found this is the easiest way to hear the pinging.

All new spark plugs (hotter) and all new dist, cap and rotor, the whole spark system is new, everything. Rebuilt TBI. New free flowing exhaust and new highflow CAT

Ok so I paid a mechanic to check the base timing and he said it was correctly set at the factory Base 4* BTDC. But It was always running HOT and running poorly. So i reset the base timing to 13* BTDC (seemed like a sweet spot at idle) When I reconnected the brown wire to the ECM it brought the timing up to 29* BTDC at idle.

My old gas MPG was 7 MPG
Now with new timing my MPG is 9.5 MPG (with a heavy foot)

I have now put in Premium gas 92 and it seems to run even better yet.

I went to the steepest hills I could find nearby here in California... I dont thin I hear any pinging... Heres the video...

What do you guys think, any pinging?

(I still need to do a valve job)

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[Bextreme04]

All new spark plugs (hotter) and all new dist, cap and rotor, the whole spark system is new, everything. Rebuilt TBI. New free flowing exhaust and new highflow CAT

Ok so I paid a mechanic to check the base timing and he said it was correctly set at the factory Base 4* BTDC. But It was always running HOT and running poorly. So i reset the base timing to 13* BTDC (seemed like a sweet spot at idle) When I reconnected the brown wire to the ECM it brought the timing up to 29* BTDC at idle.

My old gas MPG was 7 MPG
Now with new timing my MPG is 9.5 MPG (with a heavy foot)

I have now put in Premium gas 92 and it seems to run even better yet.

I went to the steepest hills I could find nearby here in California... I dont thin I hear any pinging... Heres the video...

What do you guys think, any pinging?

(I still need to do a valve job)

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It sounds good to me. In my experience you would feel a drop in power and definitely hear it if you were getting detonation. To really test it you should be under a heavier throttle load. Low RPM and high throttle up the hill should be the worst case condition to induce detonation. You want as much throttle as you can get without causing it to downshift. It will sound like you are shaking up a paint can but a little more "tinny".