. Satan is a cool girl

[Midnight Special]

All,

...Anyway there was more than one reason for the two of us to get together. Hopefully I can walk through a doorway towards helping my son! Amazing how all this fits together sometimes. Almost by design…..

Rob

..."Divine Order". The GT/CS has long been an effective vehicle in more ways than one.

 

[somethingspecial]

Back to Satan. Ron’s radiator had been plugged by the stuff in her engine on the way up from California. We were able to get out her block plugs very easily and we flushed and flushed. Bottom up with direct hose pressure into the block drain and top down later. Trust me, Satan has a clean block!! Rob

Wow, That sounds great. Who knew it would take a NURSE to give Satan an ENEMA to straighten things out. LOL Mike

 

[franklinair]

Good work & Good info.
Boy would I like to get my hands on Satan's belly!! My '68 conv looked like that - maybe worse. Now it looks like factory 'new'.
Glad to hear of the progress.

Neil

 

[mechanicalguy48]

Yeah Rob if it was idling at 12 atdc you said you didnt drive it but it would have been pretty sluggish and doggy with that timing. Everyone should set their cars at the most advance they can tolerate, in most cases thats about 12 btdc. If you drive carefully and use good gas you might get another 2 degrees or so but if it pings back off on it. A comment on timing here: When you talk about total advance or when shops talk about it or magazines say you should run x number of degrees of total advance that means initial plus centrifugal(NOT vacuum),,,,and does not include part throttle or vacuum advance. Your centrifugal weights are usually marked in numbers like 10, 12 or 14. Thats distributor degrees and double that is crank degrees. So if your running a weight marked 12 and you have 12 btdc initial then whats your total timing .... 12+ 24 = 36 total degrees at WOT (wide open throttle). Part throttle spark is for gas mileage and part throttle response, it really improves an engines feel and response. Usually you will see vacuum diaphragms marked 6, 8 or 10 or 12 and that also is distributor degrees so if you had a vacuum advance marked 10 you can get another 20 degrees of spark advance and your engine might be running well over 50 degrees of advance unloaded(high vacuum). Thats where they run best at part throttle. Advancing your timing means higher peak cylinder pressure and more power per event. Course it has a limit and thats pinging,,,once you hear that back off. Mustang Monthly has had several articles that were wrong on timing and I have told them, but they dont listen. Mustangs and fords has had a good article and you can see it at http://www.fordmuscle.com/archives/2000/03/timing/index.shtml

Steve

 

[robert campbell]

Steve,
No we are talkin!!

I have always been a proponent of the max initial that a starter will handle and the engine in total will not ping. I shorten centrifugal curves in my “adjustable” distributors. Although old school (stock) distributors had the ability to adjust both the centrifugal and vacuum advance. Either with weights and springs or in the case of vacuum, with washers and springs. I did a demonstration on the newer vacuum advance diaphragms for our local Mustang club by cutting one in half so you could see how and allen wrench allows the ability to shorten and “delay” when vacuum advance comes in. Great for assisting mid-power pinging under half throttle loads.

You made a comment that I wanted to ask you about. When I check for total advance of a distributor with a vacuum advance I leave the hose “connected” to the diaphragm. I usually hold the engine at a 3,000 RPM to ensure that all centrifugal advance is in. This is of course at a very light throttle opening, as we are stationary in the driveway. So the engine has near maximum vacuum so the vacuum advance has completely pulled in. This gives you total advance, but certainly not what you have under full throttle which would have zero vacuum advance.

Anyway, please give me your thoughts on this. Should vacuum advance be out of the equation when speaking to total advance (unhook the hose) for a car using a distributor with a vacuum advance diaphragm?

This would solve a question that has been rolling in my head for years. Mostly I use the timing light for basic set up and then use “seat of the pants” (get it to ping and drop a couple degrees out) methodology to fine tune. Especially with aftermarket heads, cams, headers and such. My performance engines do not have a vacuum advance.

Thanks for weighing in! I be learnin!!!

Rob

 

[mechanicalguy48]

Well you and a lot of other guys have looked at total advance that way, I even see them doing that in magazines sometimes, but its not right. For Total advance which is usually around 36 (plus or minus a couple) total crank degrees for any engine,,,chevies included your talking about centrifugal and initial only so yes your vacuum advance should be plugged. The reason they do that is that vacuum advance is load dependent ,, at WOT you will not see any vacuum advance. It is important to find total advance(its just a term) on the dyno for an engine because on the dyno you make wot runs and you vary the timing until you get optimum torque(which is also optimum HP at that rpm) at all the given rpm ranges. Then the factory takes out a couple of degrees to be safe and calls it Total advance and they program their centrifugal advance to stay within that. When charted out its a fairly steep curve with all of it in by about 3000. When you design a spark curve you look at WOT runs for the best centrifugal spark and then you look at part throttle runs on the dyno to see of your in the ballpark for vacuum advance, but generally the curb on part throttle spark is "ping" ,,,and at the factory we referred to it as octane requirement. We would run octane requirement on a given engine and advance combination and they would come back and say 95 octane,,and we would have to start over cause thats too high. It cant all be done on the dyno. But there are other ways to affect octane also-we found that 10 degrees higher air inlet temp upped the octane requirement by one point and thats one big reason that we went to ducted inlet air,, to get away from engine heat.
A racing engine has no need for vacuum advance because you arent racing at part throttle anyway you racing at heavy loads and wot. IMHO every (old tech)street engine should have vacuum advance with the exception probably of blown engines like yours because blown engines are very sensitive to detonation and transient spikes from vacuum advance could do you in, and also your controlling your peak pressure by the blower so timing is less of a HP issue and more of a detonation concern. Another couple terms ,,,"ping" and "detonation" are two different things. Ping refers to a second flame front hitting the one already started by your spark plugs ,,,it causes that "ping" sound, thats the collision of two wave (pressure) fronts in the cylinder. Detonation on the other hand is when the cylinder charge fires on its own due to pressure and heat without the plug firing,,,ping is only mildy troublesome, detonation is bammm your piston is gone almost right away because the pressure is so high.
The newer generation of blown engines or turbo engines can use computers and ping sensors to sense too much spark advance quickly enough to knock it back before it becomes detonation. The new computers map all the possible combinations of engine load and throttle position and heat and can tell whether unburned Hydrocarbons are in the exhaust and adjust parameters so fast that its almost impossible for a carburetor to come even close to their efficiency.

sorry thats so long,,, ya get wordy as ya get old I guess

 

[Midnight Special]

Good work & Good info.
Boy would I like to get my hands on Satan's belly!! My '68 conv looked like that - maybe worse. Now it looks like factory 'new'.
Glad to hear of the progress.

Neil

Maybe you'll get your chance Neil. Rob and "mechanicalguy", what great info! Really enjoying the read! I've grown accustomed to setting timing by trial and "ear". With fuel different today than it was in '68 - how accurate are the factory recommendations for the stock engines?

 

[J.Bart]

ditto to that and congrats again!

Now with all the great experiences, success and new friendships that began with this car,.......

ok... Now that's funny!

 

[aemoo28]

Gosh Rob and MG/Steve,

If you could speak a little english so the girls understand...

Rob- I began in the neuro ICU as a new grad RN, but ended up in the ER where my bossy 'take charge' attitude worked out perfect. I'm honored to help you out with your son's quest.

You know this car has really worked its CS magic. With all of my new wonderful CS friends and stories, I could write my OWN book. Without you, I would've lit the car and burned it by now.

 

[mechanicalguy48]

Hey Tim glad you liked the read...... actually I think the factory specs are a little light, most of the time you will see the factory saying 6 deg btdc ,,,, and it will run fine at that. But you get better mileage and better power by advancing to the way you drive,,, if your a leadfoot who lugs down an engine then stay with 6 deg,,,but if you use the good gas and drive carefully I would say you can go to 12 easily and it will get you 1-2 mpg better. Like rob says, tuning by ear is the best because area and gas and driving habits differ, so when your hearing just a little bit of ping and the car walks out of it ,,, its set at the best setting. A little bit of ping isnt bad, just dont let it do that for extended periods.

 

[Midnight Special]

...Roger that and Thanks! The 351C seems the most sensitive. Especially on drives where dramatic elevation changes are a factor. I try to listen to what the motor is saying and treat it accordingly. It tends to be "pingy" in the valley and "boggy" in the mountains...

 

[case12]

OK, please forgive if this is a dumb question - but does all the timing and performance discussion in this forum apply if you are using electronic ignition like Petronix in your distributor? Of course, I can advance and retard by turning the distributor, but is the Petronix module compensating for certain of the items you have discussed. Again, I am not even a backyard mechanic, so my question may not make sense?? Casey

 

[franklinair]

I don't believe the Pertronix system versus conventional points & condensor makes any difference. If I am correct in my thoughts, the Pertronix system offers higher voltage at a lower current (spark plugs last longer!) Timing is adjusted manually by moving the distributor + or -.

Neil

 

[robert campbell]

Steve (MG),
Thanks for the info! I have always thought about the vacuum piece when working with total advance. You have confirmed what I have suspected. Thanks!!! You are a HUGE asset to this site!

Amy,
Sorry, but more Greek! But we are all over your problem. No worries!

What this all means to you is Rob will have another session with your car. I am confident we can hook up your “existing” distributor to the vacuum and tune it in. Mike Godwin had it hooked up exactly as it should. I will take it out to 12 degrees BTDC. And it will idle at about 6 BTDC with it all hooked up. Then we will test drive it and see if we get “pinging”. May move it a bit from there, but the above is a good baseline.

This should not have any affect on your heating what-so ever! And it will make it run better! I think we have the heating problem on the run now. I will also fine tune your air mixture screws, because we have moved you curb idle all over the place and this changes the position on the transfer slots in the carb. The transfer slots are and the air mixture screws are directly related and affected by each other.

The above is deep into the tuning of a carbureted engine.

Casey,
Your Pertronix is nothing more than electronic control of when the coil applies a charge to the spark plug. As with most aftermarket electronic distributors. If you are running a “stock” distributor with a vacuum advance, or any (most) aftermarket distributor with or without vacuum advance, all of the stuff in this thread applies to you. When you get to modern computer controlled electronic fuel injected cars, they compensate for you. Again to the best of my knowledge. There maybe some exceptions. I have a laptop programmable distributor on my blower engine, but it still does nothing to compensate. I can just “program” a lot of stuff you used to have to do manually.

By the way, I love to help people fine tune their cars!!!

Rob

 

[mechanicalguy48]

Yeah right, first off the cleveland because of its large chamber area is VERY prone to ping and one of the reasons it was dc so be careful that engine in timing. It was always a doggie low end engine because of its large runner and valve size(high rpm). The pertronix simply takes away the points, timing is an issue unrelated to that. Its true that pertronix is capable of providing more spark energy but one thing you have to remember is that you can put a 60,000 volt coil on there but its still only going to use whatever it takes to break down the plug gap. If it takes 14,000 thats all it will use. This is why you see plug gaps opened up after we started using electronic ignition. If you still use an .030 gap ,,then you really dont need a huge coil unless they are firing in oil or fouled badly. Your kidding yourself to put an expensive ignition on a stock 289, it will fire with the same voltage the old system did. The only benefit might be it wont go away until 7000 rpm , but who runs these old engines at that rpm.
Steve


Oh I guess I posted exactly the same time as you Rob,,,didnt see yours but yeah your right

 

[robert campbell]

I have had the same experience as Steve on Cleveland engines. I had a 70 quench head 351 Cleveland engine that was hotted up a bit and it was very sensitive to pinging. I had very short (4.56) gears in it so low end “sluggishness” was not an issue. I had a friend with a 1971 Boss 351. It was sensitive and had “run on issues” when being shut off when hot.

All and all a very sensitive engine to timing.

On spark plug gaps, I totally concur. Widening you gap very much has little or no “positive” effect to a stock engine. Even a mildly modified engine. I have a friend who worked on a pro stock car for two years. They found that even with high performance pro stock engines that widening the gap allowed for the spark to be sorta “snuffed” out at extreme rpm’s. Way more than any of us will ever see. So their gaps to his knowledge are not extremely wide. I have high energy electronics on both my cars, but the gap is still .034/.035.

Again, a couple peoples opinion.

Gee, now lets talk about the new “multiple” spark, spark plugs. I bet that will be lively. In a stock engine a big waste of money imo. Even in a modified engine, the spark jumps to the closest ground. Suppose they may lat a bit longer if they don’t get gooked up first.

Now plugs that try to “unshroud” the spark. The “v” tip in the ground. Maybe…

Steve?

Rob

 

[mechanicalguy48]

I have always stuck with the factory plugs and a .032 gap. The early factory system was plenty spark for a stock or modified engine with the proviso that it probably went away around 5500 rpm,,,, maybe a little higher but not much. When we started leaning out the engines in the early 70's we started having problems with getting a good spark because a lean engine runs hotter and needs a hotter spark. We got the first electronic ignitions in uhhhhh about 75 in california I think and then the next year in 49 states calibrations. We opened up the spark gap to .055 and it helped, and the new system had the voltage to fire it, I cant remember the exact figures but you just about double the voltage. A standard system like most of our early 289's fires at 14-17000 volts. We fooled around a little with Capacitive disharge systems but the spark duration wasnt long enough so at that time they didnt work well. Later with CD systems they tried to get over the short duration problem by using multiple firings like you said, but I never really saw a system in the early days that was any better then the factory was using.

 

[robert campbell]

Amy,
Steve (mechanical guy) and I kinda got off in timing and mechanics la la land. But boys will be boys and Steve is a treasure trove of knowledge!!! My wife calls it "hijacking" a thread. Anyway, later this month I would like to see Satan again to put the rest of the vacuum lines back on and fine tune her a bit more. This should take only a few minutes now that I have a better grasp of these "pollution" control distributors.

Not urgent as Satan should run just fine the way she is. But this may even smooth her out a bit more and I promise not turn her into a fire breathing monster again!

Weekend of the May 16th look good. We will talk more as we get closer or maybe hit a night after work when you are off.

Rob

 

[Mosesatm]

If I remember correctly the Pertronix 2 system does adjust the timing via changing the dwell at certain times. I think it's only at initial start-up. The original Pertronix system did not do this.

Those of you with points please note that changing your point gap, or dwell angle, changes your timing so always adjust the timing after adjusting the points.

At least I think that's how it works!

 

[mechanicalguy48]

What the new Pertronix ll does is change the dwell angle. Most factory systems do this also. The dwell angle is the angle that the distributor shaft moves during which the points are open. This is when the coil field collapses and fires thru the cap and to the plugs. As rpm gets higher that angle stays about the same(or a little less) on a points system but that means the time for the coil field to collapse goes down and along with it voltage which can cause misfires. By increasing the angle it increases the amount of time the coil field has to collapse and thus gives you a stronger spark at higher rpm. Ford actually had this in its second iteration of electronic ignition modules back around mmmm ,,,, ? ahhhhh about 1980. So its not new but a pr thing mostly. It does not materially affect timing.


Hijacked again ,,,lol