[1965tripleblack]

Originally Posted by oldbogie

Vacuum advance goes away as the throttle is open because the vacuum in the manifold reduces toward atmospheric pressure unless you're running a super charger of some sort.

With an idle vacuum of only 8 inches you wouldn't be getting much vacuum advance unless the advance can is adjustable or has been reworked with a different return spring pressure.

With 8 inches of idle vacuum, this is pulling a pretty good cam, big cams like a lot of initial advance because the effects of late closing the intake valves reduces cylinder pressure which causes a slower burn which needs more time, thus advance to get across the chamber. I don't think dialing back the base timing is the way to go, at least not if you don't put it into the centrifugal and perhaps bring it up faster.

Generally Vortec type chambers like about 34-36 degrees max. Aluminum often likes more advance and more compression to make up for the cylinders faster temperature loss because of aluminum's much faster heat transfer rate into the cooling system than iron. You can also stand to run the coolant temp 15-20 degrees to slow the heat transfer rate a little.

All this is tuning for the new conditions, it can take a while to sort out what works best.

Bogie

The engine is pulling the VAC to the stop at idle. The can is adjusted to its limit, which is to say that it's delivering full vacuum advance of 14 degrees at 7.5 in-hg (the engine idles at 1100-1200, or 9 in-hg, so there is SOME breathing room here before a stall condition develops due to feedback if idle vac drops below 7.5 in-hg). The can is adjusted so that vacuum advance goes to zero by about 4 in-hg.

The block's water jacket is 3/4 filled, to 1" below the decks, and runs an oil cooler. This takes a LOT of cooling load off of the radiator, which, as you know is marginal, even when brand new. There was VERY little extra cooling capacity built into them from the factory. Because of this, I'm able to run a 160 degree t-stat, AND ACTUALLY HAVE THE COOLANT STAY PEGGED AT 160............EVEN ON 100 DEGREE DAYS IN AUGUST!

I'll play around with the spark timing and, I agree with what you say about the big cam and cylinder pressure. When I was trying to dial it in with the iron heads 2 years ago, the thing was a dog until I took the initial up past 17-18 degrees. If I can hold initial at 20, or better, then I'll rework the advance slot in the distributor to limit WOT advance to what the combustion chambers like......which will (probably) be somewhere between 34 and 38 degrees, total.

[Saltfever]

The reason big cams need so much initial at idle is because they are LEAN even though they can smell pig rich. Lean AFR is a very slow burn and therefore needs much more idle advance. Look at your cam card. You have a total of 69 deg overlap! (int = 37 and ex = 32.) That is a big cam that has built-in EGR! Because of overlap the exhaust gas is contaminating (i.e., LEANING) the intake and you get lean AFR as a result. Give the motor whatever it wants at idle. I suggest you weld a bung into the exhaust and buy an O2 data logger to help with tuning.

http://www.innovatemotorsports.com/products/lm2.php

There is no magic number to give you for WOT. Every engine requires its own number and that is determined by experimentation. Look at all the suggestions so far. There are no two agreeing numbers and that is the way it should be. Every engine and environment is different. Look at all the variables like gas or E-85, winter gas, summer gas, cold morning, or hot, humid afternoon, raised compression but by how much? Look at all the suggestions and note the assorted numbers. Pick a conservative one and start testing and reading plugs. As soon as you see pepper on the insulator back off timing 2 degrees. Good luck and have fun.

[1965tripleblack]

Originally Posted by Saltfever

The reason big cams need so much initial at idle is because they are LEAN even though they can smell pig rich. Lean AFR is a very slow burn and therefore needs much more idle advance. Look at your cam card. You have a total of 69 deg overlap! (int = 37 and ex = 32.) That is a big cam that has built-in EGR! Because of overlap the exhaust gas is contaminating (i.e., LEANING) the intake and you get lean AFR as a result. Give the motor whatever it wants at idle. I suggest you weld a bung into the exhaust and buy an O2 data logger to help with tuning.

http://www.innovatemotorsports.com/products/lm2.php

There is no magic number to give you for WOT. Every engine requires its own number and that is determined by experimentation. Look at all the suggestions so far. There are no two agreeing numbers and that is the way it should be. Every engine and environment is different. Look at all the variables like gas or E-85, winter gas, summer gas, cold morning, or hot, humid afternoon, raised compression but by how much? Look at all the suggestions and note the assorted numbers. Pick a conservative one and start testing and reading plugs. As soon as you see pepper on the insulator back off timing 2 degrees. Good luck and have fun.

For some strange reason, Comp uses 0.015" valve lift when defining valve opening/closing events on some of its cam cards. To me, it would be better if they used durations at 0.050" as well as seat-to-seat (SAE J604d) durations. Crudely extrapolating the available durations, based on the very fast flanks of this cam (Extreme Energy), yields a rough estimate of the seat-to-seat overlap value of 77 degrees.

Yup. Got one of those with bungs in both collectors.
http://www.zeitronix.com/Products/zt2/zt2.shtml
Works great as long as you have a powered triggering device to replace points/condenser. Otherwise there's no input to read engine RPM. Although RPM not necessary, it makes tuning easier by providing a readout on 2 axes. Of course, having a good running, STABLE laptop is essential with the Zeitronix. Not so with the Innovate unit.

[IMG][/IMG]

What does "pepper" (black spots) on the insulator actually mean? Why does it indicate too much spark advance?

[Saltfever]

Good point about Comp’s use of .015” for duration and I agree with their reasoning. It has a lot to do with viscosity, turbulence, and flow. I am not a CFD guy but I’ll make a futile attempt to sum it up. When you push a fluid through a tiny orifice you reach such a high point in velocity that the turbulence generated slows, or even stops, any further increase in flow. (kind of a Bernoulli thingy). Comp is probably right in assuming there is little to no flow at anything less than .015” of the valve curtain. Thus mechanical duration is not the same as flow duration.

Sorry about my trivial treatment of detonation i.e., (pepper on the insulator). When a cylinder starts detonating the first thing that gets knocked off by the shock wave is any residual carbon or other crud that has accumulated in a dirty cylinder over time. These particles attach, or get imbedded onto the plug insulator. They usually look like tiny pepper flakes. They are a sure sign of detonation. If you are a racer and have clean cylinders due to frequent tear downs you will still see pepper flakes. In that case they are parts of your piston! The shock wave is hammering your piston and very tiny bits of aluminum are being blown away. While you would think they would be shiny and white because they are aluminum, usually they are not. AlO2 is naturally a grey color and combined with carbon from the rings the stuff still looks like pepper flakes but maybe without the extreme black color. The key is to look for small specs of anything on the insulator. That is a clear sign of detonation. By “specs” I mean particles not to be confused with other junk that can be accumulated on the plugs as well. That is why it is critical to be able to make a correct plug reading. Of course, if you are at the track and can make repeated runs you can just keep increasing timing until it starts to nose over. I have greatly simplified everything but you get the point. The engine will have it's very own WOT number and you have to test to get it right.

Thanks for the Zeitonix link . . . interesting.

[Saltfever]

For some reason the system will not let me post your quote.

Innovate makes this inductive pick-up for systems that don't have a RPM source. Will it help you get the RPM signal you need?

http://www.innovatemotorsports.com/x...cat=250&page=2

[1965tripleblack]

Originally Posted by Saltfever

For some reason the system will not let me post your quote.

Innovate makes this inductive pick-up for systems that don't have a RPM source. Will it help you get the RPM signal you need?

http://www.innovatemotorsports.com/x...cat=250&page=2

Don't know why you can't quote my post??? Try again as I was looking at it a few minutes ago.

The photo in my post above is an actual "screenshot" of the output from my Zeitronix unit. As you can see, mine is working OK. It wasn't happy when I was running points/condenser, but now the Pertronix trigger and 45 kv coil feeding the MSD box sends the Zeitronix unit a nice, clean square wave. It provides an RPM readout, which is the "X" axis, and the a/f ratio provides the "Y" axis in real time while testing.

The Innovate unit is complete and self contained, while the Zeitronix unit needs a laptop to provide readout. I looked at the Innovate unit, but liked the laptop idea...............and the cheaper price...................with the Zeitronix, so I bought one of those.

Again, mine works great. Thanks a lot for your concern, and the link.

Here's a link I just found when I Googled "spark plugs" and "pepper":

http://www.mindsciencemotorsports.co...LUG%20TECH.htm

Very interesting and much more complex than I've ever seen in other explanations. In agreement with what you said above. I never realized that you had to look way down to the base of the porcelain, with a flashlight and magnifying glass to really make an accurate appraisal of what's going on. Of course, that assumes fresh, clean plugs!


Joe

[Saltfever]

Originally Posted by 1965tripleblack

Don't know why you can't quote my post??? Try again as I was looking at it a few minutes ago. Edit . . .
The Innovate unit is complete and self contained, while the Zeitronix unit needs a laptop to provide readout. I looked at the Innovate unit, but liked the laptop idea...............and the cheaper price...................with the Zeitronix, so I bought one of those. Joe

OK the quote feature worked this time.

I apologize for “thread drift”. This O2 sensor stuff probably should be in another thread but I’ll make a comment here because others may be interested. Probably not relevant for you since you have already bought a system you are happy with.

If you have a laptop then the Innovate LC-1 would do the same as your ZT-2 but at a lower cost. $199 vs. $279. I am not plugging any product and I am not affiliated with Innovate in any way. I’m sure they both do a good job. This is offered here in case others are in “research mode”
http://www.innovatemotorsports.com/products/lc1.php

However, sometimes a laptop is a liability in a big way. If the car gets upset the laptop becomes a unguided missile. When high speed driving it’s difficult to manage or is a hassle. Some of the Innovate products use a CF card which is great. You just record and when testing is over you pull out the card and read it into any computer. You don’t need a laptop in the car and keeps everything clutter free.

http://www.innovatemotorsports.com/p...s/MTS_grid.php

[Saltfever]

Can't edit my post above!

In the post above I meant an SD card not CF (compact flash?). You know what they are . . .those tiny little thingies in cameras and such. Also regarding the laptop; they are a real PITA when tuning a motorcycle. The SD card is a great way to record data on a motorcycle.