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 Initial and Total timing?
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Chavez
Two Feathers

USA
58 Posts

Posted - 30 Apr 2018 :  12:10:47 PM  Show Profile  Reply with Quote
Just wanted to know where should timing be on a rebuilt 400? Edelbrock performer intake, lunati voodoo cam(219/227 @ .050 and .468/.489 lift). Also need to know the basics on how to time. I do have a dial back timing light. No timing tape. Do i set initial first, then total? It's all confusing. Thanks for help guys

Bill Boyle
Horse Feathers (Charter Member)

USA
5091 Posts

Posted - 30 Apr 2018 :  2:17:16 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Steve--

HEI will typically put in about 20 degrees of mechanical advance. Your engine's total timing should be 34-38 degrees or so. It will be more with the vac advance at part throttle, cruising on the highway.

Set your initial at 14 degrees. This should give the engine around 34 or so. This is done with no vacuum involved. Attach vacuum line to a ported vacuum outlet on that carb and see how it runs. Idle should be 750-800 rpm with ported vacuum providing zero help on the mechanical.

BTW, moving the distributor counter clockwise will advance the spark. Once you get 14 degrees, lock down the distributor bolt.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Chavez
Two Feathers

USA
58 Posts

Posted - 30 Apr 2018 :  4:23:14 PM  Show Profile  Reply with Quote
Ok. So when I set initial timing to 14 degrees that automatically sets total to 34 so I don't have to set that also? You said idle should be at 750-800 rpm, is that with vacuum line connected? If not, should i use manifold vacuum instead?
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Chavez
Two Feathers

USA
58 Posts

Posted - 30 Apr 2018 :  9:39:33 PM  Show Profile  Reply with Quote
I set it to 16 but when I hooked vacuum advance to ported vacuum on carb, rpm stayed the same
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Bill Boyle
Horse Feathers (Charter Member)

USA
5091 Posts

Posted - 01 May 2018 :  07:16:18 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Ported vacuum provides no advance to the HEI at idle. In contrast, manifold vacuum is present at idle. Stick with ported vacuum.

With the initial set at 16, the mechanical advance, the weights in the distributor will spin and move the advance up to 20 degrees. So, the HEI should provide up to 36 degrees total mechanical advance.

Now there is no way to determine that total advance unless you have dial back timing light or a tape on the balancer correctly marked.

What I am telling you is that the standard HEI should provide 20 degrees of mechanical advance. So, 16 initial, plus 20 degrees mechanical = 36 total mechanical timing.

When the vac canister is attached to a ported vac source there will be no additional advance at idle. Vac advance will assist under part throttle some rpm above idle. It could provide advance to the HEI unit before all the mechanical is in. It could also provide advance after all the mechanical is in.

Let's say, you are cruising along on the highway at 70 mph. Your engine is turning 3000 rpm. The springs in the HEI have caused a leveling off of mechanical advance so it stops there. The vacuum advance is providing enough draw at part throttle to provide 6 more degrees of advance (for example). So, instead of having 36 degrees total, the HEI is now yielding a little more, bumping the total advance to 42 degrees. This is good because of the engine rpm and helps the combustion process become more efficient at part throttle. Efficiency helps the engine provide cruising mpg and will help the engine from overheating.

This is all simplified. There are a lot of other factors but this will give you a good foundation on what is going on.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Chavez
Two Feathers

USA
58 Posts

Posted - 02 May 2018 :  12:00:06 PM  Show Profile  Reply with Quote
Thanks Bill. I set timing at 16 but I noticed when I hooked up vacuum to manifold, it idled better. Is distributor suppose to have a gasket?
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cortcomp
Coyote

USA
5438 Posts

Posted - 03 May 2018 :  09:40:34 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
There is a small thin gasket for the distributor.
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Chavez
Two Feathers

USA
58 Posts

Posted - 03 May 2018 :  10:45:12 PM  Show Profile  Reply with Quote
Thanks cort. Bought one and installed it.
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Chavez
Two Feathers

USA
58 Posts

Posted - 03 May 2018 :  10:48:06 PM  Show Profile  Reply with Quote
Set my initial at 16 but when I checked total timing, I'm at 45. Not 36. Did I do something wrong? Also hear some ticking under valve covers. I'm guessing valves need adjusting. How do I do that. I do have lock nuts
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Bill Boyle
Horse Feathers (Charter Member)

USA
5091 Posts

Posted - 04 May 2018 :  06:54:38 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Without seeing it, I believe you have your vacuum advance hooked to manifold vacuum. It needs to be hooked to ported vacuum that provides no vacuum advance to the engine at IDLE (between 700 to 1000 rpm).

When you set initial timing the vacuum advance must not be in play. The vacuum line must not be connected to the HEI. The source of the vacuum must be capped otherwise you will get a false idle reading.

Manifold vacuum, also available at the carb, will show anywhere between 9 and 20 Hg at idle. Ported vacuum source will show '0'. Borrow or buy an inexpensive vacuum gauge to know
what your source is doing.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Chavez
Two Feathers

USA
58 Posts

Posted - 04 May 2018 :  11:36:07 AM  Show Profile  Reply with Quote
I plugged up vacuum advance like everyone said when i set initial. I only have two ports coming from carb. One is for vacuum advance and the other i have it going to get valve. Maybe i have a leak somewhere. An actual manifold vacuum that i do use is for the transmission.
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Bill Boyle
Horse Feathers (Charter Member)

USA
5091 Posts

Posted - 04 May 2018 :  2:05:17 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
When you plug in the vacuum while the car is idling, what happens to the engine rpm?

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Chavez
Two Feathers

USA
58 Posts

Posted - 04 May 2018 :  2:21:33 PM  Show Profile  Reply with Quote
When i plug to ported vacuum on carb, nothing happens to rpm. When I plug to manifold vacuum, rpm goes up. But I've been sticking with ported vacuum like everyone suggests
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Chavez
Two Feathers

USA
58 Posts

Posted - 04 May 2018 :  2:23:36 PM  Show Profile  Reply with Quote
With ported vacuum, my total is at 45 and initial at 16 at around 700 rpm
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Blued and Painted
Chief PONTIAC

USA
3505 Posts

Posted - 05 May 2018 :  12:24:39 PM  Show Profile  Reply with Quote
Remember, ported and manifold vacuum signal is exactly the same EXCEPT at idle.
When using larger than stock camshafts with low intake vacuum, the stock vacuum cann on the distributor may give erratic timming at idle when using manifold vacuum, especially when cold. When vacuum drops off, idle speed may spiral down to a stall. Adjustable vacuum cans are available.
Intake vacuum is sometimes used as a crutch or bandaid for deficencies in the carb idle circuit with a poor idle. It's tuff to fix a carb calibration issue with ignition adjustments.

Polls at other sights show the carbureted with vacuum advance community is split on the vacuum source debate.
Manifold vacuum was used almost exclusively by all makes and models up until the heavy emission controls starting in the late 60's

So, use which ever source, in your opinion, works best for your combo.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 05 May 2018 12:31:20 PM
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Miles
Cochise

Canada
209 Posts

Posted - 05 May 2018 :  12:32:35 PM  Show Profile  Reply with Quote
That's 29 degrees of mechanical advance, at what rpm do you get 45 degrees of timing?

I'm not and expert, this is just my opinion and don't want to start an argument, but I would use the manifold vacuum source, not stepped/ported.

Cars used manifold vacuum from the very start of use of vacuum advance. Only when the attempts to lower emissions with the use of the A.I.R. and such systems, did the manufacturers switch over to stepped vacuum source. The idea was to burn the emissions in the exhaust with the air from the A.I.R. pump. To do so the timing was retarded enough to have the fuel air charge still burning as it left the exhaust port. That caused a drop in efficiency and over heating problems.
The carburetor throttle blades had to be opened up to get the cars to idle. The caused more fuel consumption, overheating, run-on/dieseling, and other problems. But emission levels did go down, along with gas mileage. To combat the dieseling a throttle solenoid was employed. If you have a completely stock smog car and want to leave it completely stock, then use the stepped vacuum source, if not I would advise the manifold source.

Your rpm increases when you change from stepped to manifold vacuum because the timing at idle increases and your engine is running more efficiently. You can then back off the idle speed screw to lower your idle to the desired rpm, 600-700, and adjust the mixtures for the highest vacuum. Closing the throttles at idle will increase the vacuum and give a cleaner, more efficient idle.

Try getting a dial back timing light and checking, with the vacuum advance plugged, at what RPM you're getting your highest mechanical advance. Depending on the timing curve of your distributor you should get all the mechanical advance at around 3000 rpm. That is just a general ball park number, but a lot of Pontiacs run most efficiently with the mechanical all in by then.
You would have to get your car onto a dyno or do a lot of testing to find what is just right for your engine, but generally about 30 to 35 degrees of total timing at 3000 rpm is a good starting spot. Your 29 degrees of mechanical seem a bit high to me. I think most are closer to around twenty degrees. If you indeed have 29 degrees of mechanical maybe lower the initial a bit, say to 10-12 degrees or lower, that will lower your total closer to 40 from the 45 you have now, when you add the vacuum advance you will, depending on the advance can, be getting about 50-55 degrees at cruise. That will give you and efficient cruise. Put your vacuum advance hose onto the manifold port and you will be at about 25 or so degrees at idle.

On the dyno, my engine got the most power and torque at 29 degrees total timing all in by 3000 rpm. To get the 29 degrees I had to set my initial to nine degrees, that would be way too low for idle, but having the vacuum advance connected to manifold gave me a 29 degree idle timing. I was able to lower the idle rpm to 500. At cruise I had 9 initial, plus 20 mechanical plus 20 vacuum for a total of 49 degrees. When I opened the throttles the vacuum advance dropped and I had the optimum, for my engine, 29 degrees.

Just my opinion, I'm not an expert.
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Chavez
Two Feathers

USA
58 Posts

Posted - 11 May 2018 :  3:31:32 PM  Show Profile  Reply with Quote
Thanks Miles. I'm getting 45 degrees total at 700 rpm. I'm going to adjust it again this weekend and see how my bird reacts.
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tjs44
Crazy Horse

USA
527 Posts

Posted - 11 May 2018 :  5:21:51 PM  Show Profile  Reply with Quote
IMO do away with the vac advance untill you get the timing ironed out.Did I miss CR and what heads?I usually set my engines up with 12 init and 34-38 total with 9.5 CR and iron heads on 91 gas.I have all my timing in at 2500.When I get those parameters setup and alls well I then play with vac advance.With large cams I usually dont run any vac advance.FWIW,Tom
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Bill Boyle
Horse Feathers (Charter Member)

USA
5091 Posts

Posted - 11 May 2018 :  6:51:41 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
45 degrees at 700 rpm! That's crazy. How did you determine that?

How much manifold vacuum do you have at idle? 15, 17, 20? Is it steady?

If you set initial at 10 degrees most vac canisters yield 20 when fully engaged. That's 30 degrees of advance if the HEI is hooked to a manifold vac source. You should have no mechanical advance at idle and if you do, you have the wrong springs in place.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Chavez
Two Feathers

USA
58 Posts

Posted - 12 May 2018 :  3:28:53 PM  Show Profile  Reply with Quote
I Have 6x4 heads. Not sure on CR. I set initial to 16. I wanted to check where i was at total so i revved up to 3000 RPM and dialed light till Mark on balancer hit zero. Dial read 45. That's how i came up with 45 at total. Did I do that right? I did all this without vacuum hooked up. Last time i checked with a guage how much manifold vacuum i have at idle, it read around 12 but fluctuating. Thinking i might have a leak somewhere. I do have light springs in my distributor.
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Chavez
Two Feathers

USA
58 Posts

Posted - 14 May 2018 :  03:52:21 AM  Show Profile  Reply with Quote
Ok I've adjusted initial to 12. Total is at 39 if I'm checking right. Manifold vacuum according to guage is fluctuating between 15 and 16
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tjs44
Crazy Horse

USA
527 Posts

Posted - 16 May 2018 :  6:40:29 PM  Show Profile  Reply with Quote
39 is a lot of total IMO.Tom
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Miles
Cochise

Canada
209 Posts

Posted - 18 May 2018 :  09:36:53 AM  Show Profile  Reply with Quote
I agree, that's 27 degrees of mechanical advance. Must have some strange weights to get that.
You said you had 45 degrees total at 700, I'm sure you meant at 3000?

I think you have to start from the beginning again.

First take off your distributor cap and check that there is nothing loose or broken on the distributor. Check that the springs are attached to the weights and the weights are not stuck. If you have a vacuum pump, pump the vacuum advance can and check that the thing is working and the plate rotates back when the vacuum is released. You may be able to get it to move by sucking on the hose like a drinking straw.

If everything under the distributor cap looks good reinstall it and proceed. Plug both the stepped and the manifold ports on your carb. Start your engine and let it warm up, check your timing at idle. Your idle timing should be between 10 and 18 degrees. A good place to start is 12 degrees at idle, this is your initial timing. Slowly rev you engine until the distributor quits advancing, note the rpm and the timing when this happens. It may quit advancing anywhere from 25 to 35 or so degrees. Doesn't matter for now what it is, but take note of the rpm and the timing. A ball-park for our engines is about 32 degrees at about 3000 rpm, whatever the timing is that is your total timing. The initial plus the mechanical advance is your total. Say you did start with 12 and you ended up with 32 you would have 20 degrees of mechanical advance.

If indeed you set it to 12 and then you got 39, you have 27 degrees of mechanical advance. That's a bit much, in my opinion. But if you do have that much- rev the engine to the rpm you were at when you reached the highest timing and then turn the distributor to reduce the timing back to a lower number, say 35 degrees. That will result in an initial of only 8 degrees, but your total will be in a better spot to avoid detonation. You will most likely have to readjust the idle screw to retain the 700 rpm idle.

Now let the car idle at whatever the resulting initial timing is and connect the vacuum advance to manifold vacuum. Recheck the timing. The timing at idle now is the initial plus the vacuum advance. If after you adjusted the total you did end up with 8 at idle, then connected the vacuum advance and now get say 26 at idle, you have a vacuum can that gives you 18 degrees of advance.

After you know exactly what your distributor will give you in terms of mechanical advance and vacuum advance, and you have your total at a safe number, you can then start to tune to your specific car. You need to know what total timing your car runs best at and where it is safe detonation wise. Every engine is different. You need the base line first.

Just my opinion, I'm not an expert.


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Bill Boyle
Horse Feathers (Charter Member)

USA
5091 Posts

Posted - 18 May 2018 :  2:33:46 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
I have worked on dozens of HEI distributors and have yet to see one yield 27 degrees of advance in stock form. Usually, they provide 19 to 20, based on my observations.

What center plate and weights are in you HEI Steve? There should be numbers stamped on them. Did you switch out the springs?

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Chavez
Two Feathers

USA
58 Posts

Posted - 19 May 2018 :  3:19:13 PM  Show Profile  Reply with Quote
I switched out the springs for lighter ones. I also messed with vacuum advance canister. Don't know if that matters since i plug it when setting timing. I used an Allen wrench in vacuum port and turned all the way clockwise then came back two turns.
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Chavez
Two Feathers

USA
58 Posts

Posted - 19 May 2018 :  3:23:37 PM  Show Profile  Reply with Quote
Thanks for the info Miles. I'll try again. Just want to make sure I'm doing this right, i find total when ok rev up engine tool it stops, then dial up timing light till Mark reaches zero. Once reaches zero, what ever number dial reached, that's total correct?
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Bill Boyle
Horse Feathers (Charter Member)

USA
5091 Posts

Posted - 19 May 2018 :  4:24:09 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Yes that is the total at that rpm. It doesn't mean that you reached the plateau ands the mechanical advance is leveling off at that rpm, it could be higher. You have to watch and see the rpm and the dial back and know when the advance stops moving (plateaus).

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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