Is My Timing Really 55 Degrees Advanced? - Team Camaro Tech
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post #1 of 71 (permalink) Old Mar 13th, 17, 04:19 PM Thread Starter
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Brett
 
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Is My Timing Really 55 Degrees Advanced?

I bought my 69 SS 396 from a guy (Guy#1) that let the car sit for 6 years. He bought it from another guy (Guy#2) that did the partial restoration. Guy #1 could not tell me anything about the restoration or the engine, other that it had been rebuilt and started, but had zero miles. Guy #2 moved to Las Vegas and I have been unable to locate him. Guy #1 is a used car salesman, so I cant trust anything he tells me, so I guess it was okay that he couldn't tell me anything about it. The 396 does have roller rockers, but just Hyd. lifters. I purchased a brand new Holley 650 double pumper. The engine seems to run real rich. It did not have a timing indicator on it so I bought a billet indicator and put it on Saturday. I was finally going to get to set the timing. I have one of those timing lights with the dial. A buddy told me to put the dial at "0", and then turn the dial until the timing mark lines up with the zero on the indicator. I started turning, and turning and all of the sudden, I saw the mark on the balancer coming closer and closer. It finally lined up with the "0" on the indicator. When I looked at the dial I about dropped the timing light! 55 degrees! 55 Degrees at idle. Is that possible? What am I missing? I know there are many more questions that need to be asked. I called my buddy and he said that the indicator is just in the wrong place. But 55 degrees?! That's a quarter of the way around the harmonic balancer. I have a high torque starter, but there seems to be no drag on the engine either hot or cold. There is some faint clattering up around the lifters. I noticed when I re-adjusted the valves (I wasn't sure if the valves were originally sett correctly, so I went through and re-set the valves in order- some of the lifters didn't seem to pump oil up through the push rods. I verified that the push rods were clear). I am concerned that the 6 years that the car sat in a paint & body shop, it got dust in everywhere, maybe even clogging up oil galleys. My oil pressure is a 50/60 psi.
When I tried to adjust the distributor, each way the car would want to die. It is right where it runs the smoothest. I re-adjusted the air/fuel screws (4) until the idle smoothed out and increased barley (they were in too far, and I backed the screws out maybe 1/4 turn).
Im not an experienced tuner, but my main question is can my 396 be actually running at 55 degrees advanced?

Thank you in advance!

Brett.....

https://youtu.be/ZZkd8O4xJK8?list=FL...SCk4TL0MP4t5sw
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1969 SS 396 X66 - RS Conversion - Paint Code 71-LeMans Blue

Last edited by Brettallen59; Mar 13th, 17 at 04:22 PM. Reason: added text
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post #2 of 71 (permalink) Old Mar 13th, 17, 04:28 PM
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Garth
 
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Re: Is My Timing Really 55 Degrees Advanced?

How did you find 'zero'? Since this is not a factory assembled engine you need to start all over with everything when it comes to timing and markers or pointers. Finding TDC with a piston stop is a good start.

Make sure you also have any vacuum advance disconnected if you have one.

Body dust should not be in the oil system if the engine was closed up.

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post #3 of 71 (permalink) Old Mar 13th, 17, 04:48 PM Thread Starter
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Re: Is My Timing Really 55 Degrees Advanced?

Starting over sounds like the smartest Idea. Can I be one tooth off with the distributor and rotated it over so much that it started? I brought the #1 piston up, and then stabbed the distributor pointing at #1 cylinder. The distributor is a centrifugal advance, carb is mechanical secondaries, mechanical choke...

1969 SS 396 X66 - RS Conversion - Paint Code 71-LeMans Blue

Last edited by Brettallen59; Mar 13th, 17 at 04:51 PM. Reason: added text
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post #4 of 71 (permalink) Old Mar 13th, 17, 05:15 PM
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Re: Is My Timing Really 55 Degrees Advanced?

Is it possible to have 55 degrees of advance at idle? With a BBC yes it is possible, but highly unlikely. I would guess first off that you have a capacitor ignition box installed. A CD ignition box can play havoc with some of the lower priced adjustable timing lights (though I have had remarkably good luck with a cheap one I bought from Sears years ago.)

Second issue is your bolting an indicator to the block and hoping it lines up with TDC. Stock indicators are often off a degree or two, and that is before any one modifies the motor.

As Garth stated above find TCD with a degree wheel and a piston stop. Once you have TDC marked with your bolt on pointer set to match the grove in the damper, find out by using a dial indicator and the degree wheel where your cam is installed (usually straight up is four degrees advanced with an off the shelf cam). You can use the degree wheel and the dial indicator to measure duration, and lift and calculate your overlap and LSA. You can then use the dial indicator to measure your duration at 0.050" lift to get all of the information that was printed on your cam card by who ever ground it.

As a final consideration check under the distributor cap to see if the vacuum advance has been disabled (locked out) or if the weights are not sticking out because a spring popped off, or the weight platform is so rusty that the weights are sticking.

Big Dave
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post #5 of 71 (permalink) Old Mar 13th, 17, 05:17 PM
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Mark
 
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Re: Is My Timing Really 55 Degrees Advanced?

To find the exact spot where the timing pointer should be see

When you check the timing, make sure you unplug the vacuum hose off the dist vac can and stick a golf tee in it. Otherwise you will be in the 50's.

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post #6 of 71 (permalink) Old Mar 13th, 17, 05:42 PM Thread Starter
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Re: Is My Timing Really 55 Degrees Advanced?

VERY Interesting video! Real intriguing that the Dampner can actually rotate on the balancer. That could be my problem. I do have a CD box. Another thing I recall. I put the weakest springs onto the weights. Don't know why, as it was a stupid move. I ordered a piston stop from Summit. Can I degree the cam with the timing cover on? Oh yeah, the indicator I purchased, bolted into two timing cover screws. The only thing it could be is if it was not made correctly, as there was no other place it would mount in relation to it intended locating place. It can not be mis-located. That doesn't mean that it's truly in the right place, I'm just trying to relay how it is mounted.
Thanks,
B...

1969 SS 396 X66 - RS Conversion - Paint Code 71-LeMans Blue
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post #7 of 71 (permalink) Old Mar 18th, 17, 06:37 PM Thread Starter
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Re: Is My Timing Really 55 Degrees Advanced?

Okie Dokie, I used a piston stop and verified TDC. It was actually only off from the original timing mark on the dampner by approx 3/8". I then looked at the rotor, and it looked like it was one tooth off from pointing at cylinder #1, so I pulled the distributor, turned the oil pump back a little, and re-stabbed the distributor to where it was closer to pointing to #1. Put it back together and fired it up. Seemed to run better after turning the cap a little. Then, back to the timing light. I set it to "0", then turned the dial until I hit 12 degrees. Now the timing is at 35 degrees advanced.

Please see if I am thinking about this right; Doesn't the firing of number 1 cylinder have to occur in relation to the cam? I mean, I'm moving the rotor, but I'm not moving the cam, and the cam is what is opening/closing the valves. This car with the old timing was running really rich. I moved the distributor one tooth (27.69 degrees) which is approx. what the dial moved when I re-checked it. It seems to me, if I move it one more tooth, then if I'm guessing right, will bring the dial down to 12 degrees, which will also synchronize the cam (valve opening/closing) closer to where it needs to be.

I apologize that I have not yet done the Degreeing of the cam yet, as I did print off a degree wheel. I know that you are going to say: "If you had done that, it would show you what your talking about", but if this sounds correct, and all I have to do is rotate the distributor back one more tooth, I would be excited to try it.

The fact that dropping one tooth back changed my amount of advance from 55 to 35 makes me wonder if I'm still off one tooth. I guess that is the main question I have.

Thanks guys!
Brett

And P.S; I just want to say Larger Dave, you are a wealth of knowledge. I am really focused whenever reading your replies wherever I run across them. Every time you speak....I listen (just takes me a little more time to do what you say! lol) Thanks for your input Big Dave.

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Last edited by Brettallen59; Mar 18th, 17 at 06:38 PM. Reason: added text
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post #8 of 71 (permalink) Old Mar 18th, 17, 07:56 PM
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Re: Is My Timing Really 55 Degrees Advanced?

The rotor in your distributor does move with the cam. It is driven by the gear on the end of the cam that you are stabbing those distributor teeth into. The cam turns at half of the crankshaft's rotational speed. So one cam revolution is equal to two complete revolution of the crankshaft, or 720 degrees. Luckily we are only interested in the first 90 degrees or so of the damper as that is the portion of the crankshaft's rotation that makes up the power stroke on cylinder number one.

You want to fire the cylinder before the piston reaches top dead center because gasoline burns (not explodes). It takes time to consume all of the fuel. As it burns the temperature in the cylinder rises (and from the ideal gas law we know that as the temp rises so to does the pressure in the cylinder). It is this equivalence of heat with pressure that makes the internal combustion engine work. By setting the gas to burning early (about 10-12 degrees at idle) the fuel is burnt before the piston starts down the cylinder propelled by the heat of combustion.

The higher the RPM the sooner you have to light the match because the gas still burns at the same rate, so ignition lead increases. Get to ambitious with ignition timing and the piston will be rising the final twenty degrees of crank shaft rotation as the flame front is consuming more and more of the available fuel trying to push it back down the bore. This cocks pistons (the rattle you hear with preignition) and really loads up the bearings promoting premature wear.

The more efficient the combustion chamber is in mixing and promoting flame front propagation the less ignition lead you need and the more power you can extract from the engine. This is the difference between a SBC 400 and the BBC 402. Both are the same size but the SBC will beat the 402 hands down in power to weight and take less ignition lead doing it. A modern Vortec fast burn head design in a SBC 400 will make nearly 1.5 horse on the street. You can throw a bucket of money at the SBC 402 but it won't come near that mark.

This is because the open chambered head design (opened up in 1969 to unshroud the intake valve in the LS-7 and L-88 race engine) is huge. This cavern is so large that even starting earlier (more ignition lead) the gas can not burn fast enough to be totally consumed before the piston is too far down the bore to contribute to making any power (pressure and volume are inversely related so as one increases the other decreases). Racers (Arias, Pat Musi, and Sony Leonard) designed BBC heads with twin plugs to help get the fires lit, but they are not a production item (fully hemispherical, and on a bigger bore center to obtain a larger bore size).

Recapping (as I have diverged thinking about the upcoming Gatornationals time trials) your rotor turns in sync with the cam which is in sync with the crank. Turning the cap on the distributor changes your initial timing. Inside the cap the weights and springs provide a mechanical advance in timing as a function of RPM (relies on Hooks law, so the curve is actually a line that is it is linear in it's advance) and there is a vacuum diaphragm that pulls even more advance in response to low manifold pressure to further accelerate your timing. Total of these three must not get ahead of the speed of the combustion of the gas in the chamber or you start top break parts.

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post #9 of 71 (permalink) Old Mar 19th, 17, 11:45 AM
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Re: Is My Timing Really 55 Degrees Advanced?

I read that you have a NON-COMPUTERIZED ignition system, and that you are using a DIAL-BACK feature on the timing light. THAT DOESN'T WORK. The ONLY place a dial-back feature works on is on computerized ignition systems, like EFI.

Strongly suggest leaving the timing light dial on ZERO, mark the balancer to read degrees. Go from there.

And, YES, I do this EVERY DAY, it is my business. I fix ignition system problems made worse by bad advice from all sorts of sources.
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post #10 of 71 (permalink) Old Mar 19th, 17, 12:57 PM
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Re: Is My Timing Really 55 Degrees Advanced?

When you talk about the rotor pointing to the #1 cylinder, are you talking about the physical location of number one or the rotor pointing to the #1 terminal on the cap? The vacuum advance should face just behind the right headlight

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post #11 of 71 (permalink) Old Mar 19th, 17, 02:25 PM
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Re: Is My Timing Really 55 Degrees Advanced?

Quote:
Originally Posted by dave ray View Post
I read that you have a NON-COMPUTERIZED ignition system, and that you are using a DIAL-BACK feature on the timing light. THAT DOESN'T WORK. The ONLY place a dial-back feature works on is on computerized ignition systems, like EFI.

Strongly suggest leaving the timing light dial on ZERO, mark the balancer to read degrees. Go from there.

And, YES, I do this EVERY DAY, it is my business. I fix ignition system problems made worse by bad advice from all sorts of sources.
I am a noob but could you explain why a dial back light does not work?
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post #12 of 71 (permalink) Old Mar 19th, 17, 03:21 PM
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Re: Is My Timing Really 55 Degrees Advanced?

Quote:
Originally Posted by dave ray View Post
I read that you have a NON-COMPUTERIZED ignition system, and that you are using a DIAL-BACK feature on the timing light. THAT DOESN'T WORK. The ONLY place a dial-back feature works on is on computerized ignition systems, like EFI.
Not sure where you read that, but it's a BS story. I come across alot of stories that are not true, even in books. Don't believe everything you read. I checked my timing using a non back dial light and a back dial light, and they time the same.


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post #13 of 71 (permalink) Old Mar 19th, 17, 03:39 PM
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Re: Is My Timing Really 55 Degrees Advanced?

Quote:
Originally Posted by dave ray View Post
The ONLY place a dial-back feature works on is on computerized ignition systems, like EFI
Please explain. My dial-back timing light works fine with points ignition.

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post #14 of 71 (permalink) Old Mar 19th, 17, 04:02 PM
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Dave
 
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Re: Is My Timing Really 55 Degrees Advanced?

With the addition of new heads, and a radical cam often your timing will change from the stock settings to reflect the additional RPM range your motor is capable of. Just as often when you attempt to time your car using the timing tab and scribe line on the balancer you run out of timing marks before you reach your desired initial timing plus mechanical advance.

A dial back light allows you to pre-set your total mechanical advance and after disconnecting the vacuum advance shoot the light at the timing mark. When the light shines on the zero degrees advance you have reached your preset timing limit that in effect you have dialed it back to zero degrees. This is only useful if you do not have a fully degreed harmonic balancer that has timing marks all the way around the outer periphery. If you have those timing marks, or you use timing tape glued to the balancer properly set at TDC then any timing light will work, and I personally think this is the most accurate way of doing it.

With a CD (Capacitive Discharge) ignition box the dial back frequently won't work because the ignition box fires the ignition four to five times at idle for every power stroke. This multiple stroke confuses the timing light's circuitry. There are dial back timing lights designed to work exclusively with a CD ignition box, but it has been my experience that most of the professional (Snap-On, Matco, New Britain, etc.) dial back lights will work with a CD box.

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post #15 of 71 (permalink) Old Mar 19th, 17, 04:44 PM
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Re: Is My Timing Really 55 Degrees Advanced?

Thanks Dave
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