I took the night to think about a recommendation for the op which does not require any dyno time or egt gauge. A simple 93 octane recommendation based on the compression of the engine, reasonable outcome expectations and certainly within the scope of this discussion.

You will of course, need a timing light, at least. I can't believe we are actually having this discussion about whether or not to use a timing light, but here it. You really need to get one if you don't have one, and nobody in the year 2016 should be forced to set their timing by ear.

Base timing at 7* full in 28* by 2800rpm, and cruise at 35*
with an idle at 15" of Hg with 1* per every 2" of vacuum advance is 5* base + 7* = 14* idle timing total.
the full 28* + 7* with 15" of cruise vacuum is 35* total vacuum advance cruise.
So you will adjust springs to allow full mechanical timing by 2800rpm, and adjust vacuum advance to give a total of 1* per every 2" of vacuum, and use the intake manifold vacuum so that it kicks up idle timing.

One more time:
idle at 7* base + 7* vacuum advance = 14* total idle timing
cruise at 28* + 7* vacuum advance = 35* total cruise
WOT timing of course at 0" Hg will give the total mechanical advance of 28*

This leaves headroom for additional vacuum during cruise (another 2" will give 36* cruise for example) and the same for idle + 1* will not hurt anything.

I would still recommend a $60 chassis dynometer pass in which total timing was reduced by 2* to determine the difference in torque curve/shape was significant. If less than 2% difference in torque (perhaps 10~ "ft lb") I would keep it there, minus that 2* as a permanent change.

If you wish we can discuss tuning timing with an EGT gauge, or with a dynometer, in more detail as well. However, this post is all about my personal feeling regarding the baseline settings, I have a "hunch" my initial settings are close to optimal without much "tuning" necessary. Recommendation assumes owner is at sea level 0psi and that the engine is running 185*F to 200*F coolant temps, 200-215*F oil temps, and vehicle weight is under 3400lbs, and transmission has a lockup converter with overdrive. If the converter/trans has no overdrive and no lockup, the engine will cruise at a higher rpm, and may pull more vacuum, but being less efficient, may require even more cruise timing. Cruise a/f ratio needs to be 14.5 to 14.9:1 for reasonable economy regardless, and a wideband needs to be installed, no question about that, approx 4 to 5' (feet) from the engine.

 

King, I did not guess on anything. I used a vacuum gauge to measure vacuum, a timing light to measure advance, a tachometer to measure engine speed, an a/f ratio gauge to measure the air fuel ratio from idle to cruise to wot. So, where is my guessing in how I tune my engine? I don't have a knock sensor so I rely on my human senses such as hearing for detecting any ping. If there is ping, I reduce timing a degree or two using a timing light, not by listening. Sheesh. Here's some reading on how to tune an engine:
http://www.burtonmachine.com/tech It's was my guide to tuning my engine and it worked. My dyno results prove it.

Btw, your timing curve is barely acceptable even for a smog motor. It's out to lunch for a performance timing curve plain and simple but if your happy to tune your car that way, enjoy.

 

Since you are running a MSD......I am going to offer up these snips from the instructions and how I have been doing it for years on MSD equipped Chevrolet V8 SBC and BBC.

I would use the silver bushing-light blue/light silver spring and dial in 12 degrees initial as a baseline....and go from there......it may like a degree or two more or less......this engine has a fairly mild cam and will like this.

Cams that are larger than 250 @ .050 or so I use the black bushing and dial in 18-19 for 36-37 total.....more cam....more initial.....when the cam get bigger than this most just lock it out.

Read the snipped pics....it really is that easy This will get you close if not spot on.......

BTW 69427 is on the money with his description........no mystery here just facts.

Jebby

Jebby

 

That's the info I used to dial in my MSD distributors when I bought them. It woke the engine up significantly on my '69 427 and on the 355 in my Z28. I hadn't even planned to get a distributor for the Z28 until I saw what it did for the 427. Work with the instructions and you'll be good to go.

 

http://www.superchevy.com/how-to/add...nition-timing/

 

Dins74 -

I have used the same approach as 69427 a few times - it is sound and it will get the average guy close enough with little to no real cost.

I will say that I agree 4 degrees base timing is very low - even these stock emission-tuned motors will like more advance than that. It takes some experimentation to find the sweet spot your car will like.

There are some very good timing posts from other members like Lars, BarryK and a few others. Do a search and read up, it's worthwhile. The sticky up top also has a good discussion with the folks I mentioned, as well as 69427.

You will pick up some very good, effective and inexpensive methods to get your timing set up. It sure won't cost you $60 to $80 an hour.

 

I've got a knock detection setup that I use on the 355 turbo in my C4. I used it and my WBO2 sensor while I was remapping the spark and fuel curves when I first put the engine in the car years ago. It's the wrong time of the year for doing a lot of C3 driving, but I'll offer up the loan of my setup if you ever have any interest in playing around with it. It's all genuine Delco parts (knock sensor and ESC module), with a harness to hook everything up, and some pulse stretcher/driver circuitry to monitor the knock pulses and then flash a damn bright remote LED to let the driver know each time knock occurs.
I've wanted to use this on my big block too, but the block designers decided to put the coolant drain plugs right under the motor mounts, and I can't fit a knock sensor in there (yet). Once I get caught up from a couple more urgent projects this winter I'm going to see if I can fabricate an odd looking motor mount that will give me enough clearance to thread in a knock sensor there.

 

This is your original post. The method for setting initial timing is valid because you mention a timing light. Essentially once you connect the timing light, the user will adjust the timing with the light, which rules out, or eliminates guess work.


This is the guess work. 'pinging' can be detected by a knock sensor long before it is audible. Audible ping is NOT an acceptable way of timing an engine, and should never the recommended approach. Secondly, audible ping is often undetectable over the noise of an engine. Just because you hear it at 36* doesn't mean it isn't audibly pinging at 33* where you cannot hear it, and furthermore, that doesn't mean that the engine isn't in-audibly pinging at 30* where a knock sensor would have detected it. The human ear is not tuned to frequencies specifically associated with the on-set of knock.


Also, there is no mention of using any of the other those tools you suddenly mentioned, such as a/f gauge. I was supposed to read your mind? I am not god, you know, and your post assumes I am.

 

I completely agree that it isn't necessary to use any dyno for low cost engines, or when they are inaccessible. However, the value of a torque curve with zero smoothing is worth $60 in my opinion, especially when this is 1%~ or less of the cost of an engine. The dynometer may reveal characteristics in the torque output of the engine which facilitate diagnostic procedures. An engine which seems to be running fine may reveal much more than can be revealed by any of the hundreds of diagnostic gauges/monitoring tools combined, by that one simple line called "torque". It isn't necessarily about picking up max output, it is more about ensuring that the output of the engine is reaching the tires effectively and smoothly.

 

Knock generally occurs at frequencies between about 4 kHz to 8 kHz. Anyone with decent hearing can hear that frequency range. The only issue is if the background noise (exhaust/tires) masks the knock noise.

Knock noise is not necessarily an indication of over-advanced timing or impending engine damage. Insufficient octane, high ambient temperature intake air, or low humidity can all encourage detonation, even though the timing was correctly set for 20* ATDC location of peak pressure (LPP). A good example of this, if anyone paid attention to it in the 80's and 90's, is several FWD models of GM cars with the 2.5 L "Iron Duke" engine. That engine was known for knocking on a steady basis in daily driving traffic. The noise was loud enough to hear from the insides of other vehicles. Those engines ran for a lot of miles despite that "abuse". While I don't advocate running a (more expensive) Corvette engine with that degree of audible knock, it's not a hyper dangerous issue, unlike pre-ignition, which will hole a piston reasonably quickly.

 

Based on the above statement disregarding my use of the vacuum gauge, I don't think you are qualified to critique my timing method.