TBucket Engine Project (Dart SHP)

True. My 302 Chevy (8000 rpm) has the distributor locked out and the timing set to 36 degrees.
But it has no problems starting because of the MSD 6AL ignition and it's built-in timing retard during cranking.
Or so I thought. I will have to verify this.

Well, I dug the old paperwork out and could not find any references to the 6A and 6AL boxes retarding the timing during cranking, but the 7AL2 does.
So it appears I was wrong about this. I must have confused the 20 degrees of multiple sparks below 3000 rpm and 20 degrees of cranking retard.
Thanks for pointing this out AutoWiz.
 
Well those look a lot better. I meant on page 11 of the thread you linked to me. Your post #214. Those plugs looked gnarly. and you were complaining of oil consumption.
At 10,101 miles I put in Royal Purple 10w30 break in oil and ran it for 498 miles. Then I went
back to the RP 10w30 HPS oil I have always used except when the engine was new during break
in I used Lucas 30w break in oil. The plugs shown above were taken when the engine had 13,598
miles. The smoke in the exhaust has cleared up. I don't have a good number oil usage at this time.
Miles on the engine now is 13,802.

https://www.amazon.com/gp/product/B001LTZ860/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1
https://www.summitracing.com/parts/luc-10630-1
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With whatever you have in your distributor now, just taking it from 16 degrees base and setting it to 8-10 degrees base and connecting the vacuum canister on the distributor to the full time vacuum port on your carb you will get all this extra timing at idle, but right there in that space you just pointed out, you will be at less timing. Without ever pulling the cap off of your distributor.

Because everywhere but idle will now have 6 degrees less timing.

The ignition timing was set at 12° advance at idle with vacuum plugged. When I changed to the blue stop
bushing reducing the mechanical advance by 4°, I increased the initial timing to 16° to compensate for
the change in the stop bushing. Total is now at 34° and the starter does not have any trouble turning the
engine over.

See link below for the post comments about ignition timing changes.

http://garage.grumpysperformance.co...ine-project-dart-shp.3814/page-148#post-89826
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Base timing is usually supposed to be set closer to TDC than that. To go up from 6 to 8 is nothing. To go from 6 or 8 to 12 is a jump. To go from 6 or 8 to 16 puts you at up to 10 degrees over most base timing settings. Base timing does not have to be your final idle timing. It is merely the first D in your 3D timing curve. And it needs to be the minimum timing advance you ever want your motor to see under any load or rpm or circumstance while it is running.
 
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So to go to 16 degrees ensures that you will never under any condition place or time or engine speed or load or afr be under 16 degrees of base timing. And for that I hope you are idling north of 1,000RPM.
No, I'm not over a 1,000 rpm, more like 800-850 rpm.
 
finding what works best on each unique engine in any ignition advance timing curves are a bit of trial & error
theres zero doubt that you can with experience make a darn good estimate on what will work,
but a dyno and data logger will be required to absolutely fine tune,
the result for near perfect results.
yes the old mechanics experience ,ear and seat of the pants,
reading spark plugs skills of the better and knowledgeable,
old school mechanic can get you surprisingly close...
but theres no substitute for sensors and a data log system.
you can,t always hear detonation that can eventually damage your engine,
that requires sensors and a good knowledge of spark plug reading,
and a fuel/air sensor and exhaust heat measurements ,
with an infrared temp gun and oxygen sensors,
in each exhaust header primary sure helps

this is the most consistently accurate I.R temp gun I've used for testing
42545.jpg

http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products

http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/


https://www.regulustlk.com/products...MIruyLtoH24gIVDvDACh2ExAivEAQYAiABEgIfZvD_BwE

https://autoplicity.com/5227964-hal...MI0e3lzYX24gIVDRgMCh1CwwA3EAQYBCABEgI9pPD_BwE


http://garage.grumpysperformance.com/index.php?threads/build-a-knock-detector.14441/
 
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So is the vacuum canister still attached to your distributor or have you removed it and locked it out with the correct plastic piece and screw from the same bag as the weights and springs?
 
So is the vacuum canister still attached to your distributor or have you removed it and locked it out with the correct plastic piece and screw from the same bag as the weights and springs?
Yes it's still connected, I believe that vacuum advance is a good thing for the street and cruising
down the highway for hours at a time. I've driven the TBucket on a 6 hour trip one way.

The spark plugs have never shown any aluminum specks, signs of detonation. The only signs were
when I could hear a change in the engine sound that indicated detonation when easing into the
throttle to climb a small hill or to accelerate by just a few mph. Ambient was 90°F plus.

What do you think???
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Base timing is usually supposed to be set closer to TDC than that. To go up from 6 to 8 is nothing. To go from 6 or 8 to 12 is a jump. To go from 6 or 8 to 16 puts you at up to 10 degrees over most base timing settings. Base timing does not have to be your final idle timing. It is merely the first D in your 3D timing curve. And it needs to be the minimum timing advance you ever want your motor to see under any load or rpm or circumstance while it is running.

Some good, clear, and easy-to-follow explanations here AutoWiz. I also liked the way you explained about getting the combustion back in the chamber instead of partially out the exhaust by changing the timing (#2963 above). Keep it coming.
 
Thanks for the suggestions AutoWiz!!!

I don't have a Green bushing, did you mean the Blue bushing by chance. It's the one I'm using now with 2 light blue springs.

View attachment 12376

How do you mean .... retarded timing? My initial is setting at 16° advanced now and 34° total.

You might have retarded ignition timing. You need more timing at idle. 16-20 degrees total. to start. And your motor will run cooler also as you bring the combustion process back into the combustion chamber. 20 degrees of base timing will not crank nice, so you need to have the distributor canister connected to full engine vacuum.

Whenever we hear someone describe or define something so specific as a proper engine calibration as a thing of opinion or preferences, we should run from that source of information. If you want to say the parts you use to build with are subjective to what you are looking for then great. But once all the pieces are bolted together there is most definitely a correct rod angle to be firing the spark plugs at and there is most definitely a specific afr we should be chasing. Calibrating engines is very much an exact science. Or at least it is to those of us with a dyno, anyways.

If I may Rick, because I'm learning too, and I had to read the above a couple of times to understand it, what AutoWiz means by "You might have retarded ignition timing." is the spark igniting the fuel/air mixture too late in the process, causing some of the flame to be wasted out into the exhaust (hard-to-cool engine), instead of in the combustion chamber where it should be - even though your "timing" is set at 16 degrees advanced as shown by the timing light.
He says set initial to 8 degrees (easy starting), then full manifold vacuum at the vacuum advance canister will kick in and pull the timing to about 20 degrees at idle (hot cams like this), and use the proper bushing to set your machanical advance to what the engine likes.
Did I get it right AutoWiz?
 
Rick has a pretty Hot fairly radical camshaft from Crower.
I used to think it was mild till Bob pointed out it has 72 degrees Overlap or so.
Almost a Race Cam but detuned slight.
I always had best results with hot street cam profiles or Full Drag Race with lots of initial advance.
15-17 degrees BTDC.
I like fast ignition advance curves.

You actually don't need much vacuum advance to get a big gain in fuel economy.
Just 4- 8 Degrees more.
I prefer ported vacuum off the carb throttle blades if using vacuum advance.
Crane makes adjustable vacuum advance cans to adjust rate in and positive setscrew stop for amount of advance you want. I have used on Street cars cruising work nice.
 
He says set initial to 8 degrees (easy starting), then full manifold vacuum at the vacuum advance canister will kick in and pull the timing to about 20 degrees at idle (hot cams like this), and use the proper bushing to set your machanical advance to what the engine likes.
Did I get it right AutoWiz?

Exactly. And when he is idling at a traffic light at 850rpm and the light turns green and he mashes the gas pedal to the floor the 20 degrees of timing will drop down to 8 as the vacuum goes away. And that is a much happier number to be at with the cylinder full of air and fuel at such a low rpm.
 
I always had best results with hot street cam profiles or Full Drag Race with lots of initial advance.
15-17 degrees BTDC.

Yes. Yes. YES. big cams love timing down low. Because ignition timing is the great compensator for an engine's inefficiency and the hotter the cam the more inefficient it is at idle. But NOT at wide open throttle off idle. And that is why we need to rely on full time vacuum to the distributor. So at idle when we mash the gas the timing can go DOWN as the cylinder fills with air before the RPM's come up. It's the right way to tune for a hot cam. You ONLY want all that timing at idle with the throttle closed.
 
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The L88 Corvette has no Vacuum advance.
Pure Race Car 1967, 1968, 1969.

1969 and 1970 Pontiac RAIV 400 On the understood emission decal Base initial timing is 15 Degrees BTDC .
 
Stock cams used in oem applications have to be efficient at idle because they have to blow clean smog. So because of this efficiency down low they can and do run a lower ignition timing and so the base timing can be close to or at the minimum allowed timing. The Hot cams that do not like vacuum advance are also horribly inefficient all over down low and those engines typically idle at a notably higher RPM and not used on the street just for this reason. To disable vacuum advance on anything but a race application is a choice we are all entitled to make. I personally prefer non mechanical timing control that I can tell individual cells a specific number I want to see.
 
Rick has been working on his T for a long time with Grumpy.
I add to when I can.

It's ready for action cruising.
Roll Bar made bolted in track battle.
 
The L88 Corvette has no Vacuum advance.
Pure Race Car 1967, 1968, 1969.

1969 and 1970 Pontiac RAIV 400 On the understood emission decal Base initial timing is 15 Degrees BTDC .

Yes, but didn't that go along with high octane leaded gasoline that is not available today?
 
The absolute beauty in my suggestion for better idle quality was that it was free and fast to try and quickly reversed. He could even mark the distributor base to the intake before he starts so he can put it right back to exactly where it was even faster.
 
So to be fair, my engine is not a custom build. It is a crate low compression LS3. I run a stock LS3 cam. 204/211 .551/.525 117 I have a modified LS3 timing map. So the specific map is for my C5 but this trend or basic shape to a 3d ignition map usually stays somewhat similar to this:



This illustrates well how ignition timing should go down as more air is allowed in the cylinder at any RPM.
 
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