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Old 05-14-2008, 06:50 PM   #1
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How to time by ear

i have been playing with my timing and i think i have it close but im not sure... my question is what is the best way to "time by ear" or figure out timing without a timing light due to the fact that there are no marks on my balancer and i dont have that timing tab.
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Old 05-14-2008, 07:16 PM   #2
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Re: How to time by ear

impossible- you will never know what you are at. get tab and timing light, there is a way to mark your balancer but i forget how do a search possibly good luck
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Old 05-14-2008, 08:00 PM   #3
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Re: How to time by ear

true, i will check into that but i have heard you can get it real close by advancing it until it starts to break down then retard it just enough so it runs normal, or something like that, i just dont know exactly how...
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Old 05-14-2008, 08:10 PM   #4
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Re: How to time by ear

Thats not necessarily true. With the ESC disconnected, my car runs like **** with the timing Exactly right. If I turn the distrubutor and advance the timing, the motor runs smoother and smoother. However, if I were to drive it like that it would be undrivable with base timing at like 8* advance.

Get a cheap timing light. They are like $30 and well worth it. I just have the basic "actron" light with no advance or anything. That is all you need, because you can use the tab on the motor for advance.
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Old 05-14-2008, 08:17 PM   #5
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Re: How to time by ear

Old school way was to advance the timing until it started pinging under load then retard it a few degrees.

Although that will work, it will be nowhere near to the best timing.

Base timing is just a base timing when the engine is idling and not under load. It's a starting point. Sometimes it's low, sometimes it's high. If too high, it makes it hard to start the engine.

Advance timing can be mechanical with vacuum and with computer controlled engines, electronic advance.

Electronic is all controlled by the computer and is based on where the base timing is set.

Mechanical advance controls how much and at what rpm the advance timing comes on. A good performance setup will be at full advance by 3000 rpm. The base timing plus the mechanical advance give a total timing. Changing the base timing will change the total timing. Playing with the weights and springs can change the mechanical advance.

Vacuum advance is only for part throttle operation.

Now, all you're concerned about is base and total. As I mentioned, total can be just about anywhere. Lets say you use 10* BTDC as a base timing. Engine starts and idles fine. Now the total timing is where the power is made.

Total timing depends a lot on the specific engine. Timing that one engine may like will not be the timing for another. Where an engine likes it's total timing can't be guessed at. The engine either needs to be on a dyno or by using dragstrip tuning to find the best timing which gives the best MPH. Being off by one degree can change the engine 10-20 hp. Once the best timing position is determined, no tuning changes to the engine such as jetting, plug gap, valve lash etc will affect where that engine wants it's timing.

Lets say you had a base timing of 10*. Checking the total timing gives you 32*. If you advance the timing to 16*, the total will be 38*. If you make more power at 38*, you may find the 16* base timing is now too much. 32-10 = 22* of mechanical advance. To maintain 10* base and 38* total, the mechanical advance needs to be changed to 28*

Now if your distributor is computer controlled, the best thing you can do is set the base timing to the factory specs and let the computer control the distributor. There has to be a mark somewhere on the balancer. If not then you'll never get a correct base timing. Change the balancer to one with a timing mark.
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Old 05-14-2008, 08:19 PM   #6
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Re: How to time by ear

how do you hold the tab on the motor? you still need the lines on the balancer right? this is all new to me, I have never done this before.
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Old 05-14-2008, 08:37 PM   #7
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Re: How to time by ear

ok I am understanding more now... so for peak hp all i am worried about is mechanical advance, my car isn't computer controlled, how do you adjust how far the mechanical advance advances it? I am leaning more and more to getting it dyno tuned, i will be making some trips to the drag track sometime tho...
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Old 05-14-2008, 09:40 PM   #8
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Re: How to time by ear

The large cap HEI distributors have weights and springs inside them. They also have a center cam which activates against the weights. These all control the mechanical advance.

How far the weights move determines how much mechanical advance is in the distributor. The springs control how fast the weights will advance. The lighter the springs, the faster the weights advance. This is what controls the rpm that the advance engages at.

Changing all this is considered recurving the distributor.

The tab on the motor? A factory timing chain cover has a timing tab welded onto it. Aftermarket covers may or may not have a tab welded on. Aftermarket timing tabs are bolted on with the timing cover bolts.

Most GM engines have the timing tab at roughly the 2 o'clock position and have a balancer with the timing mark in the same place when #1 or #6 cylinder is at TDC. Some engines have the timing marks at 12 o'clock. Using a balancer from one with the timing tab from another will be impossible to set the timing.
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Old 05-14-2008, 11:04 PM   #9
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Re: How to time by ear

you could try a vacuum gauge to set your timing. you're timing is set pretty good when you have maximum smooth deflection on your gauge. Make sure you are using manifold vacuum, not modified.

cheers,
trev

edit: im pretty sure it should read near then 15 mark at idle, some vacuum gauges come with a red/yellow and green band to help you with setting your timing.
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Old 05-15-2008, 08:03 AM   #10
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Re: How to time by ear

so i should put pretty light weights in there so i get advance pretty quick right? as for the weights i need to figure out where the engine runs the best then use weights to get it there? I have an aftermarket timing cover with no tab on it, so what should I do about the balancer and tab?
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Old 05-15-2008, 08:28 AM   #11
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Re: How to time by ear

A quick and fairly accurate way to set initial timing without a light:

- Buy some timing tape for your balancer
- Buy a piston stop
- Buy a timing tab
- Masking tape
- Marker

Procedure:

- Disconnect battery
- Remove two timing cover bolts and install timing tab
- Remove #1 spark plug
- Insert piston stop
- Rotate crankshaft until piston makes contact with piston stop
- Apply masking tape around the balancer
- Use the marker to draw a line on the tape in line with the timing tab on
your timing chain cover
- Rotate the crankshaft the opposite direction until the piston hits the
piston stop
- Draw another line on the masking tape in line with the timing tab

You now have two lines on your masking tape about 1/2" apart.

Use your best judgement to draw a line in between these two lines.

- Remove the piston stop
- Align the middle line on the masking tape with the Zero marker on the
timing tab
- Remove the masking tape
- Install the timing tape on the balancer
- Rotate the crankshaft to the desired timing advance on the timing tape

- Install your spark plug
- Draw a line on your distributor base in line with the #1 spark plug post
- Remove the distributor cap, and loosen the base clamp
- Align the distributor rotor with the line drawn on the distributor base

- Tighten the distributor base clamp
- Install the distributor cap

YOu have now phased the rotor with the #1 spark plug post and it is timed
to the amount of advance you have set according to the timing tape.

This will get you fired up and idling. You will still need a timing gun to set
the full advance, or recurve the distributor.

Also note, this is the 'poor man's degree wheel' method. By no means is the
piston at true TDC...but it's close, and the initial timing will be close enough
as well.
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Old 05-15-2008, 08:41 AM   #12
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Re: How to time by ear

When you use the piston stop, what protects the piston from being scratched up? also how do you turn the crank? After you find tdc how do you align that mark with zero on the tab? does the tab have slots so it slides back and forth?
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Old 05-15-2008, 08:52 AM   #13
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Re: How to time by ear

Quote:
Originally Posted by brodysZ28 View Post
When you use the piston stop, what protects the piston from being scratched up?
Piston stops are made of soft metals and they are rounded at the tip.
There is no chance of scratching the piston. Just rotate the crank slowly

Here's a pic of a piston stop:
http://www.scooterwest.com/files/ite.../67/toolps.JPG

Quote:
also how do you turn the crank?
You can rotate it via the flex plate/flywheel using a tool like this:
http://www.competitionproducts.com/p...umber=PFM67462

You can also rotate it with the crank bolt and a long wrench (torque wrench,
or breaker bar, etc.) , but you should remove the spark plugs to reduce resistance. The crank bolt strips fairly easily

Quote:
After you find tdc how do you align that mark with zero on the tab? does the tab have slots so it slides back and forth?
I'm not sure what you mean by this, but you can rotate the crank by
hand and use your best judgement to line up the mark on balancer tape
with the timing tab.

The timing tab doesn't move, it's bolted to the timing cover. Make sure
you have the timing tab in place and secured before you start this entire
process. This is your reference for everything.
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Old 05-15-2008, 09:03 AM   #14
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Re: How to time by ear

from underneath the hood, hold the throttle at about 2500 rpms. turn the distrubitor until the engine reaches its peak rpm at that throttle position.
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Old 05-15-2008, 09:20 AM   #15
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Re: How to time by ear

the reason i ask about the piston stop is because when i degreed the cam i used a piston stop and it wasnt rounded and scraped the piston a little so i smoothed it out with a file.

The engne is in the car everything installed so i cant use the fylwheel, I have heard of using a pipe wrench in the power steering pump, will that work good?

I understand now about the timing tab, i was thinking the timing was already set at that point...

now how does a timing gun work? i have never used one, and how would you adjust the timing lets just say 5 degrees, using the tape and the gun?
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Old 05-15-2008, 09:42 AM   #16
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Re: How to time by ear

I dont' know about the power steering pump, most of the engines I work on/build
don't have power accessories

YOu can try it...not sure if the belt will slip?

There are two types of timing guns that you can buy: an advance strobe light, and non adjustable strobe.

I highly recommend the advance type because it will allow you to see
what is happening when you measure full timing at high RPM.

The advance light has a dial that delays, or advances the strobe in relation
to the spark wire signal.

So...instead of using the timing tab gradations, you will use the zero mark
on the timing tab and adjust the advance dial on the timing gun.

You then look to the zero mark on the timing tape.

EDIT:

Adjust the dial on the timing gun for 5 degrees advance.

Move the distributor base until the ZERO mark on the balancer tape
lines up with the ZERO mark on the timing tab.

Does that make sense? It's tough to explain on here, but very easy once
you have the timing gun to watch it all work.

EDIT:

I forgot to say, you need to move the distributor base to align the zero marks!

Last edited by lukn4trbl; 05-15-2008 at 09:54 AM.
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Old 05-15-2008, 09:55 AM   #17
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Re: How to time by ear

i will probably have to read it about 5 times but i think i will get it...
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Old 05-16-2008, 08:44 AM   #18
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Re: How to time by ear

ok so how does the timing gun work? do you hook it up on the distributor somehow so it knows when the #1 cylinder has ignition? and to adjust the timing you just turn the dist until you get it where you want it, and the timing gun wil tell you what your timing is the whole time? it must be pretty hard to turn the dist 1 degree exactly isnt it? how is this gun?

http://store.summitracing.com/partde...5&autoview=sku
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Old 05-16-2008, 09:01 AM   #19
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Re: How to time by ear

Quote:
Originally Posted by brodysZ28 View Post
ok so how does the timing gun work? do you hook it up on the distributor somehow so it knows when the #1 cylinder has ignition?
Sort of...

You attach the inductive pick-up (which is the red rectangular object in
the photo) to the #1 spark plug wire.

Click the image to open in full size.

When the spark plug 'fires', it sends a pulse through the wire, and the
timing gun picks up this pulse and flashes the strobe light.

Quote:
and to adjust the timing you just turn the dist until you get it where you want it,
Yes.

Quote:
and the timing gun wil tell you what your timing is the whole time?
Yes. As you rotate the distributor, you will change the timing of the
spark in relation to the balancer mark.

When the strobe flashes on the light, you will see the timing marks
on the balancer in reference to the timing tab.

If you were to rotate the distributor counter clockwise (advance the timing),
the strobe light will flash sooner and you will notice the timing mark on
the balancer appear to move.

Quote:
it must be pretty hard to turn the dist 1 degree exactly isnt it?
Actually, it's fairly easy. You will get the hang of it quickly.


It's pretty decent and well priced. Go for it!
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Old 05-16-2008, 09:13 AM   #20
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Re: How to time by ear

i am sort of confused how you say you will see the timing tape change in relation to the timing tab because how can you see it when its spinning at whatever rpm?

i thought turning the dist counter clockwise was retarding it? the rotor spins clockwise right?

what do the black and red clamps go to? battery?
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Old 05-16-2008, 09:39 AM   #21
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Re: How to time by ear

Quote:
Originally Posted by brodysZ28 View Post
i am sort of confused how you say you will see the timing tape change in relation to the timing tab because how can you see it when its spinning at whatever rpm?
It's tough to explain, but if you have ever seen a person move in a dark
room with a strobe light flashing you can better imagine what is happening
with the strobe on the timing gun.

Just remember that the strobe light on the timing gun flashes when the
number one spark plug fires.

If the spark timing happens sooner, then the strobe will flash sooner.

You will then see the line on the timing tape sooner in relation to the
timing tab.

Quote:
i thought turning the dist counter clockwise was retarding it?
No. See below.

Quote:
the rotor spins clockwise right?

Yes. Look at this diagram. The rotor on the distributor (gray triangle)
spins clockwise.

The red arrow represents the #1 spark plug post. if you rotate the
distributor base counter clockwise, you also move the distributor cap
and posts clockwise.

This means the rotor passes the #1 post sooner in relation to the
crank position.

Check out the left and right diagram and notice how the timing mark
appears sooner when the distributor base is rotated counter clockwise.


Quote:
what do the black and red clamps go to? battery?
Yes, you got it!
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Old 05-16-2008, 10:15 AM   #22
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Re: How to time by ear

Subscribing to this thread.

Regarding stephen's response post #5, i have 2 questions.

1) I have certain fuel delivery issues for which i cant go full throttle, or itll bog the engine down and hold it at a constant rpm past half throttle. Can i still change the springs at the dragstrip and gauge the MPH and which springs are best, EVEN if im not at full throttle? (the RPM's will reach roughly 3000-4000 in this condition, higher if i stay in lower gear).

2) Im going to be ditching my Mr. Gasket curving kit, and opting to go with the ACCEL version, and im also going to be getting the "adjustable vacuum" canister. Im not sure exactly what its called, but you pull off the hose and adjust it with an allen key. How does this change the timing?
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Old 05-16-2008, 10:32 AM   #23
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Re: How to time by ear

I don't know if your question is directed to Stephen, or everyone in general,
but here are my thoughts:

#1
I wouldn't bother tuning your motor if you have fuel volume, or pressure
issues. Get that figured out first. Besides the risk of leaning out and damaging the engine, the timing
curve and air flow through the motor is not representative of what's happening
at 5500-6500 RPM ranges.

Changing the timing in this case under part throttle, or different engine
loads (gear change) is not going to be optimal.

#2.
The vacuum cannister adjust allows you to change the reaction of the
diaphram is relation to engine vacuum. You can roll off the vacuum sensitivity to pull timing and allow the mechanical and base timing to
tailor the curve.

In effect, by changing the vacuum advance curve, you can dial in more
mechanical advance without losing performance. A higher diaphram
pressure requires more engine vacuum to overcome...so in essence,
the vacuum curve reduces/delays as RPM and throttle angle increase.

With non adjustable systems, you are forced to back off the initial and
mechanical advance to keep the part throttle and idle timing within a
reasonable amount.

This hurts wide open performance because the vacuum advance portion
goes away at wide open throttle (vacuum signal drops to nearly zero).
You are then left with Base + mechanical which is conservatively set.
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Old 05-16-2008, 11:49 PM   #24
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Re: How to time by ear

So it looks like you have to take all the accesories off the motor to do the procedure above? does this mean the accesories have to be off to check/adjust timing? I couldnt see a spot where you could get the light to the harmonic balancer... am i missing something here?
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Old 05-17-2008, 04:30 PM   #25
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Re: How to time by ear

Nothing needs to come off to check timing.

Normally you can get a direct shot to the balancer from above the water
pump, or off to the sides by standing near either front tire.

Find a spot to install the timing tab that is easiest to work with for your
engine bay.
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Old 05-17-2008, 04:58 PM   #26
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Re: How to time by ear

Quote:
Originally Posted by lukn4trbl View Post

#2.
The vacuum cannister adjust allows you to change the reaction of the
diaphram is relation to engine vacuum. You can roll off the vacuum sensitivity to pull timing and allow the mechanical and base timing to
tailor the curve.

In effect, by changing the vacuum advance curve, you can dial in more
mechanical advance without losing performance. A higher diaphram
pressure requires more engine vacuum to overcome...so in essence,
the vacuum curve reduces/delays as RPM and throttle angle increase.

With non adjustable systems, you are forced to back off the initial and
mechanical advance to keep the part throttle and idle timing within a
reasonable amount.

This hurts wide open performance because the vacuum advance portion
goes away at wide open throttle (vacuum signal drops to nearly zero).
You are then left with Base + mechanical which is conservatively set.
Ive always struggled with this concept. I was referring to anyone who can answer my question.

Also, what do you mean by "pull timing"? and im assuming what you have described would let a car with a radical cam idle at its best, but still give you performance up top?

I have a failry lopey cam, and it has roughly 10-12 in-Hg of vacuum. I found with my current distributor (never curved) i have two choices. Either advance it like crazy, where it idles AMAZINGLY, i could swear it was fuel injected. However, at this setting, there is no top end power, and the car knocks like crazy past 2500rpm of load.

The other extreme is to retard the timing, where at idle it has a very "rhytmic" tune, but as soon as you get on the throttle, it smoothes out, and pulls up top like a bat outa hell.

So how would a adjustable vacuum canister help me?

Also Brody

I gotta go to a wedding right now, but when i get back, ill snap a few pix for you on my car to give you an idea of where the tab is. Its really not that hard, you just point the light and make sure the mark ends up where you want.

We can help you figure out where it should end up, and thats the tough part.
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Old 05-17-2008, 07:39 PM   #27
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Re: How to time by ear

Let's see if these drawings help you understand what's going on:

This drawing applies to those using a manifold vacuum port (manifold reference).
Notice how the vacuum line connects to a port that is below the throttle
blade of the carburetor.


When the throttle blade is closed (idle), or part throttle (cruise), the vacuum
signal is strong at the distributor. This advances the timing which is added
to the initial and any mechanical advance.

As the throttle blade opens, it exposes the port and allows the air to flow
through the main venturi with less restriction. Fluids and gas will flow to
the path of least resistance; therefore the vacuum signal gets weaker as
the throttle blade opens and vacuum advance timing is essentially "pulled".
That's what I meant in the previous post.

Let's say that your particular engine runs best with 36 degrees advance.
You would set your initial timing and full advance timing for best power
and the curve might look something like the solid red line in the graph
below.



You want to add vacuum advance to help with fuel economy
and keep EGTs low while cruising around, etc.

The problem is, the engine is going to add the Initial + vacuum + mechanical
together. This could send the total timing well over an efficient point.
With a stock cannister, the curve might look like the yellow solid line.

If you add the solid red and solid yellow line together at 4500 RPM, you
get over 60 degrees. This is too much, so without tuning the vacuum
curve, you are forced to back down the inital timing to about 6 degrees
and the total drops to 32 degrees.

Now you're screwed when you go wide open on the accelerator, because
if you recall from above, the vacuum signal to the distributor is lost as the
throttle blade opens.

If you have a distributor with a tunable cannister, you can adjust the
vacuum advance to 'roll off' sooner (like the green solid line). With that
curve, you can bump up the initial and restore the total mechanical
timing for best power and get the best of both worlds.

Now when you add the timing at 4500 RPM, you are left with mechanical
only ~ 36 degrees.
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Old 05-18-2008, 11:29 AM   #28
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Re: How to time by ear

alright those pics would be good, are all stock canisters non adjustable? I have been having a problem with my car stalling usually when i give it a little gas then let off it stalls. does this sound like a timing issue? i bumped up the idle but idk whether or not it will still stall.

As power is concerned it seems to have pretty good low end power, i havnt brought up the rpms very (still breaking in the cam) but it doesnt really pull that hard at lk 3 grand. What should i do about this? advance or retard? also what if it starts hard?
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Old 05-20-2008, 10:37 AM   #29
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Re: How to time by ear

lukn4trbl;

That is incredibly helpful. I think im starting to get it. Still a little fuzzy, but that can be sorted out in practice. I saw your description of the vacuum port location. It might be a little too advanced for this post, but would you know how the holley "timed vacuum" port works on a 4150 series?

In any case, thanks for takin the time to explain.


Brody:

All stock canisters are non-adjustable. The stalling issue can be a mixture of things. Usually its the carb. As for power, it cant be solved just by timing. It may just be the engine combo you have.
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Old 05-20-2008, 11:34 AM   #30
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Re: How to time by ear

Quote:
lukn4trbl;

That is incredibly helpful. I think im starting to get it. Still a little fuzzy, but that can be sorted out in practice. I saw your description of the vacuum port location. It might be a little too advanced for this post, but would you know how the holley "timed vacuum" port works on a 4150 series?

In any case, thanks for takin the time to explain.
Actually, you're in luck. The 4150 uses the same principle (as do many carbs)
for this port. The diagrams above can be used to describe pretty much any
design.

As for the advanced function of pressure, I'll explain briefly and you can
fire back with any more questions.

The throttle blade acts like a pressure regulator, or pressure valve. It is
used to change the pressure in the manifold with respect to the atmospheric
pressure around your car.

With the engine off, and the throttle blades closed (or open) the pressure in
the manifold equals atmospheric because the pistons are not creating any
sort of vacuum. Pistons are stopped, therefore no pressure change.

When you start up the motor, the pistons begin to move and the pressure
changes in the manifold.

Pressure moves from high to low areas. This applies to gasses and fluids.
Without a differential in pressure, you have zero flow.

With the throttle blade closed, the atmospheric pressure cannot "mix"
with the manifold pressure (much). You therefore have a sub atmospheric pressure
in the manifold and we call that "vacuum".

Atmospheric pressure is about 14.7 PSI at sea level.

If you were to put a gauge on the intake manifold, it would read something
below atmospheric.

IE: 12 in./hg. (inches of Mercury)

When you convert inches of Mercury to PSI (Pounds per Square inch), you
get about 5.89 PSI below atmospheric.

14.7 PSI - 5.89 PSI = 8.89 PSI

This means air is flowing from outside the carb into the engine. That little
bit of airflow allows the engine to idle.

The pressure difference acts on the distributor diaphram, brake booster, etc.

As you open the throttle blade, the intake manifold is no longer blocked
from the outside atmosphere and "vacuum" begins to drop...and the
manifold pressure raises closer to 14.7 PSI

Ideally, we would want 14.7 PSI (or more like boost) to help fill the cylinders.

Now with the vacuum rolling off, and high pressure in the manifold present,
the vacuum advance on the distributor is pretty much gone.

Instead of having a vacuum at the port where you connect the distributor,
you have a high pressure pushing the diaphram in the opposite direction.

That takes away the timing advance originally given by the vacuum cannister.

Last edited by lukn4trbl; 05-21-2008 at 07:46 AM. Reason: spelling
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Old 05-20-2008, 06:24 PM   #31
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Re: How to time by ear

i got a timing tab, one that sits right around 12 o clock, and the guy who is going to be timing it for me said to just mark the groove on the balancer with a yellow crayon since timing tape doesnt last long. a also got a curving kit, what do you guys think i should run for springs? will the lightest be too light? also it came with different colored bushings that go in the weights, are these different weights too? which one should I use? oh ya, and i got some full synthetic oil to change out, should i change the filter too, even though it only has 500 miles on it, or not worry about it? thanks...
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Old 05-20-2008, 07:49 PM   #32
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I've run timing tape for years on a balancer with no problems. The key is getting the damper completely clean before applying the tape.

Change the filter when you change the oil. No need to contaminate the synthetic oil with what's in the filter.
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Old 05-21-2008, 07:33 AM   #33
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Re: How to time by ear

ya, thats what i figured, how did you clean it? run sandpaper on it while the motor is running?
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Old 05-21-2008, 07:42 AM   #34
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Re: How to time by ear

Quote:
how did you clean it? run sandpaper on it while the motor is running?


Engine off will be just fine and much safer!

You can use sand paper if it's bad enough. Acetone and a rag works really
well once you get all the crap off.

Start off with the heaviest weights until you have the initial and full advance
where the engine is happiest.

Swap in progressively lighter springs while listening for/monitoring knock.

You can also get a good idea of the appropriate spring by 60 foot times,
or a dyno if you happen to do some tuning.

Changing the springs will be something you can feel; the timing curve
really differs between pairs/mixed sets.
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Old 05-21-2008, 08:56 AM   #35
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Re: How to time by ear

so use the heaviest weight, then play with the springs? i will probably start with the medium spring... what does knocking sound like? i have a header leak so i am hearing a ticking sound all the time...will that mask the knock?
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Old 05-21-2008, 09:13 AM   #36
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Re: How to time by ear

Quote:
what does knocking sound like?
Like shooting tiny rocks at a tin can...or small rocks shaking around in a glass jar.

Quote:
i have a header leak so i am hearing a ticking sound all the time...will that mask the knock?
Possibly, it depends how loud the leak is.
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Old 05-21-2008, 09:57 AM   #37
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Re: How to time by ear

alright, sounds like i would notice it if it was doing it, how loud is it? and does it either knock or not knock or does it gradually get worse?i know that sharp edges or burrs can cause this too right? but is it pre-ignition, where the timing is too far counter clockwise, or advanced?
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Old 12-03-2008, 11:35 PM   #38
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Re: How to time by ear

Quote:
Originally Posted by brodysZ28 View Post
but is it pre-ignition, where the timing is too far counter clockwise, or advanced?
Yes, that brings the point on the cap to the rotor sooner as it rotates clockwise.
Alternately, as you retard(remove timing) you will rotate the cap clockwise so that the rotor will come to the point on the cap later in the cycle.

The pre-ignition(I would call it ping or detonation so it's not confused with knock from piston slap, loose bearings, or dry lifters) is the combustion cycle(power) coming as the piston is still traveling up on it's compression stroke.
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Old 12-03-2008, 11:53 PM   #39
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Re: How to time by ear

Since this thread has been brought back, I'll add something.

A mechanic at work had his new 383 on an engine dyno last weekend. He did 18 pulls with it to get a good tune. He found out it makes it's best power at 36*. If it was off by one degree either way, it lost 20 HP. It only peaked at 450. He's going to change a couple of things and try again. He wants 500 dyno HP. It's not going into a street car.

Guessing at 37, 35 or anything else will work but without dyno information, you'll never know how much you're losing by guessing at the best timing.

I have my distributor locked out at 37*. Am I making the most power? Probably not but I'm also a bracket racer. I just change the number on my windows to match the times I'm running at the time. I need to get my car on a chassis dyno some day.
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Old 12-03-2008, 11:53 PM
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