# fuel/air/ignition advises



## Chris-Austria (Dec 23, 2010)

Hi!

Tomorrow my GTO will be adjusted regarding ignition and carburators. The mechanic asked me to find out all needed values for this adjustment.
What will he need? Ignition timing? And something with 6-8°?? I don't know what's needed, but can you give me all needed values for a complete adjustment? I think the carburator will be adjusted with a measuring device for proper fuel/air delivery?

The engine is a 428cui with a Tri Power setup.
Are there any differences compared to the original 389cui Tri Power in the setup?

I have a MSD ignition control module (6 series), headers and a 3" exhaust.. if you need any more information, I'll try to find it out 

I'll use premium fuel (100 octane), platinum spark plugs and I have a aluminium 3" radiator. Don't want to get problems with heat!

Thank you!!!
Chris


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## dimitri (Feb 13, 2009)

I pretty sure you said you have a manual trans. 

Idle is 950 rpm manual transmission
Timing is 9 deg Before Top Dead Center with vacuum hose disconected and plugged at the distributer at idle.
Air fuel ratio is 15:1
Our engines do not like platinum plugs or E3 plugs or Bosch plugs. They love AC Delco regular copper core resister type plugs gapped at .045" of an inch. NGK regular plugs work good also. Just change the plugs every 10,000 to 20,000 miles. Start looking at them at 10,000 miles. If they look bad replace them.

Make sure all of this is done with a air cleaner on.


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## Chris-Austria (Dec 23, 2010)

I also checked my owners manual, they write:

Spark Plug Gap: 0,033" to 0,038"
Hot Idle Speed 4 Speed Manual: 700rpm
Ignition Timing: 6° (with vacuum line disconnected and manifold opening covered)
Distributor Dwell Angle: 28 to 32°
Point Gap: 0,016"

But this is for the 389cui tri power, I thought maybe my engine needs some other values or maybe I need some changes because of the headers...

Is this everything thats needed for a good engine adjustment?
I'll change the plugs, but are you sure that I should use a bigger gap than recommended? I couldn't find AC Delco plugs for my car at Rockauto, do you have a part number?

And are you sure about timing? 3° more than in the manual?


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## dimitri (Feb 13, 2009)

I thought you had a HEI distributer? Do you have points? If you do, follow what it says in the book.


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## Chris-Austria (Dec 23, 2010)

The MSD box is a HEI distributer? In that case I have one 
But I don't have a book for this MSD box! I'll search for one at their homepage.


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## dimitri (Feb 13, 2009)

Spark plug gap with HEI is .045".
Set eveything else as per book.
I do not know the part number for the spark plugs.


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## Chris-Austria (Dec 23, 2010)

If it makes a difference.. I have the MSD 6AL 6420.
Okay, I'll order some non platinum plugs with a 0,045" gap, thank you!
The settings as per book can't be improved? I thought maybe I need some changes because the engine isn't the one from the book (428cui instead of the 389cui) and there are some modifications like exhaust system, headers...


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## BearGFR (Aug 25, 2008)

Chris-Austria said:


> If it makes a difference.. I have the MSD 6AL 6420.
> Okay, I'll order some non platinum plugs with a 0,045" gap, thank you!
> The settings as per book can't be improved? I thought maybe I need some changes because the engine isn't the one from the book (428cui instead of the 389cui) and there are some modifications like exhaust system, headers...


There's not a lot to be gained from "fancy" ignition and plugs on a stock engine. Either it's sufficient to "light the fire" or it's not. The plugs need to be the correct heat range so that they burn hot enough to stay clean but not so hot that they become "hot spots" that can cause detonation. The power the engine makes comes from burning the fuel, not the spark that lights it. If you have access to a chassis dyno, one thing you can play with is total ignition timing under load at full throttle. Most Pontiacs with iron heads tend to "like" something in the neighborhood of 32 to 36 degrees total advance for max power, the variance being mostly due to subtle differences in combustion chambers and how well the heads "work", as well as head material (iron tends to be more efficient than aluminum and therefore doesn't need as much advance). Cubic inch displacement doesn't make much if any difference. The way to do it would be to run your car on the chassis dyno, varying the amount of total advance on different runs until you find the one that makes the best power. Once you know that, then use a timing light to measure whatever initial advance setting at idle that turns out to be so you'll know how to "get back there" on future tuneups.

Bear


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## geeteeohguy (Feb 2, 2008)

Ok......platinum plugs are made because they last a long time and are for engines that have emissions warranties and have hard to get at plugs. Regular copper core is fine. The "ideal" fuel/air mixture for emissions controlled, modern engines is 14.7:1. 15:1 is too lean. For your 428, you adjust the mixture and idle speed LAST. You first set the points dwell to 30 degrees (if you have points), then your ignition timing, then yur idle mixture, and then your base idle speed and you're done. Base timing is 6 degrees BTDC or a little more. As said, total advance is what is important. 34 degrees max. You can set that and then see what your base is when you return the engine to idle. I like about a 650 rpm idle with a stockish cam. I also like connecting the vacuum advance to manifold vacuum as Pontiac designed it,rather than ported vacuum. Manifold vacuum advances the timing at slow speed and idle and keeps the engine COOL. It has no affect on total timing if connected as designed. To adjust the carburetor mixture without an exhaust gas analyzer, you let the engine idle, warmed up. There are two screws at the bottom of the center carb. Turn one screw in slowly, clockwise, until the engine rpm starts to drop and the engine starts running a little rough. STOP. Now turn the screw counter clockwise very, very slowly until the engine smooths out. Do the same with the other screw. I've been using this method for decades, and when I hook up the analyzer, the car is always in specs for tailpipe emissions. Now, lastly, set your base idle speed. A Pontiac of your vintage will want a slight righ mixture at idle, especially if it has a bigger cam than stock. Good numbers to shoot for on a gas analyzer are about 200ppm HC and 2 percent CO. If you have high hydrocarbons and low co, you're too lean or have a misfire, and if your CO is too high, you are too rich. This is a simplification, but it'll work here. If you have a big cam, you may have higher readings on both HC and CO. Good luck.


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## Chris-Austria (Dec 23, 2010)

@geeteeohguy

Thanks for your advises! I'll copy them, translate them and provide my mechanic with the information. He has a exhaust gas analyzer, so I hope he will set everything as good as possible.


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## Chris-Austria (Dec 23, 2010)

My mechanic told me that I have also a MSD Distributor and he can't adjust it to 6° BTDC. There are springs on the distributor, he said maybe other springs will change the timing?! I also don't have this vacuum line, isn't it possible to connect it with the MSD distributor? 
The old spark plugs are not very good, he thinks they need to be changed. The HC and CO are too high now as well.

I don't know exactly what I have to do now...

And which spark plugs exactly should I order? (at ebay, rockauto...) AC Delco 44S or AC Delco 43 are listed in my manual, but they don't have the correct gap. Heat Number?! should be 5? I can buy NGK plugs at the local store, if you can provide me the part number.


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## BearGFR (Aug 25, 2008)

Chris-Austria said:


> My mechanic told me that I have also a MSD Distributor and he can't adjust it to 6° BTDC. There are springs on the distributor, he said maybe other springs will change the timing?! I also don't have this vacuum line, isn't it possible to connect it with the MSD distributor?
> The old spark plugs are not very good, he thinks they need to be changed. The HC and CO are too high now as well.
> 
> I don't know exactly what I have to do now...
> ...


Hi Chris,
First, don't panic. It depends on which type of MSD distributor you have and whether or not you also have an MSD ignition box in the system as well, and how all those components were set up by whoever installed them. Go to this web page  and see if you can use it to identify which distributor you have - the "ready to run" or the "pro billet". You can also look at the details on both of them and use the "instructions" tab for each to get more information. 
It's possible that whoever set up the MSD system set it up for racing and has "locked out" the centrigual advance, but all that is reversible and it *is* possible to properly set the timing to 6 degrees initial. If you also have an MSD "box" as part of your ignition system you should be able to find instructions for it on that same web site.

AC 44S plugs (or whatever is equiivalent from another manufacturer) are probably correct for your engine, you can adjust the gap to whatever works best with the rest of your ignition system. I'm running those plugs in my 461, gapped to .035". I'm using a Proform HEI ignition.

First things first though. Figure out what you actually have in your ignition system, then we can take it from there.

Bear


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## Chris-Austria (Dec 23, 2010)

Hi Bear!

I have the MSD 6420 ignition box and one of those distributors you mentioned. I will have to check it tomorrow, but I think it was the one with the none-polished steel shaft (Ready to Run).
I could find out that this one should have the option to connect the vacuum hose. If I can connect this, will the ignition timing be advanced at idle and slow driving?
And to set it to 6°.. what will I need? Or is it adjustable?
I saw some springs and a timing module with the part number 8680, but this one is pretty expensive. With that I can adjust the timing from inside the car from 0-15°?!


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## BearGFR (Aug 25, 2008)

Chris-Austria said:


> Hi Bear!
> 
> I have the MSD 6420 ignition box and one of those distributors you mentioned. I will have to check it tomorrow, but I think it was the one with the none-polished steel shaft (Ready to Run).
> I could find out that this one should have the option to connect the vacuum hose. If I can connect this, the ignition timing will be advanced at idle and slow driving?
> ...


For normal driving, connect and use the vacuum advance if you have it. At idle and at part throttle operation, it helps with efficiency and fuel economy to add a little more advance than the engine would be able to tolerate at full load WOT. You want to disconnect it and plug the line for the purposes of setting the timing, but it should be connected otherwise. 

Rather than try to write about it, here's a link to a 



 that shows the process and how to do it. This video uses a small block (cough cough) Chevy instead of a Pontiac, but the principles are the same.

Some MSD boxes do have the ability for you to "fine tune" the timing "curve" from inside the vehicle, but for street driving it's not something you normally need to do. It's certainly not a "must". Understand that setting the intial timing is just that - the initial or "starting point" for timing. The mechanism of weights and springs inside the distributor will gradually add more "timing" advance as the engine rpm increases. How much advance is added and how quickly it "comes in" is what is referred to as the "advance curve". Changing the weights for heavier/lighter ones, changing the springs for heaver/lighter ones, or changing to different size "limit bushings" to control how much advance is possible are all ways of customizing the advance curve.
Some MSD (and other) ignition boxes can control all of these variables electronically, so in such systems the mechanical advance mechanism in the distributor is disabled or "locked out" so the advance curve function can be taken over by the ignition box instead.

Bear


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## Chris-Austria (Dec 23, 2010)

So I'll have to check, if my msd box can change ignition timing electronically. I'll read the instruction sheet, but cannot find information about timing options with the box.
I'd only be able to connect the timing control module to it.

But I found the distributor instruction sheet which explains how to set timing by using weights, bushings and springs. One good setup would be enough, but I don't have these parts.. I'm not sure if I should order them or if I should order the module which can change timing electronically. Second sounds much easier and I'd be able to connect it by myself.. 

Good Video, I think I now understand what ignition timing is about. Now I only need to use this information on my car 

Another question... I'll mark my spark plug wires before I remove them tomorrow, but what happens if you connect 2 wires wrong to the distributor? Will the engine run smooth? Or will it run not at all? Of simplified.. will you be able to recognize that something is wrong connected? Or will it just silently work but damage the engine?


Edit:
I found a picture, is this how my wires should be connected to the distributor? If so, I don't have to mark them.. looks quite simple to me 










Edit #2:
I was now searching for spark plugs like the AC 44S... I can't find a good one. Are "Accel" spark plugs good? And what's the heat range I should use with my setup? The original AC plugs have a heat range of 4 I think, the mechanic told me to use 5. But many plugs have 6-7, even in the cross reference chart of the AC 44S.
I'm a little bit confused. In my garage there are 8 new Bosch Platinum+ plugs which I will not use like you told me, but I don't want to order wrong plugs a second time...

Edit #3:
I checked my distributor, it is the Pro Billet (8563). The wires are connected as seen on the picture. Spark Plug wire #8 seems to be bad, where it is plugged into the distributor, the contact is white. I cleaned it up and see, if it will become white for a second time. Maybe cylinder #8 didn't work as supposed because of the wire?
The spark plugs which are currently installed are "Accel 137". These are titled "race plugs" on the webpage.. I think the pre-owner wanted a racing setup.. So I won't use such plugs again, I think they are heat range 7, which maybe to much?! They also are none-resistor plugs.. I don't know whats the difference to resistor plugs.. but "dimitri" wrote I should use plugs with resistor.
Why are the Accel 137 listed in cross reference to AC 44S? Accel heat range is 7 and AC heat range is 4. Which heat range will be good for my car? Original they used 5 max I think.


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## BearGFR (Aug 25, 2008)

Hi Chris,
That's a good diagram and is correct for Pontiacs. One thing it doesn't show, is the location of the vacuum diaphragm on the distributor (if yours has one). If it does, the correct orientation for the vacuum diapragm, using your graphic as a guide, would be to have the hose connection pointed "straight up" --- or directly towards the drivers side of the car.

It sounds like you might be a little confused about timing and advance, still, because you're still asking about changing it with electronics in the "box" or by changing springs in the distributor. You may not need to do either of those at all. Regardless of the means you use to get there, what you're really trying to do in all cases is to set things so that the total amount of ignition advance makes the engine the "happiest" when it's under load, at full throttle, and into the "meaty" part of the torque/power curve. For factory iron head Pontiacs that's usually somewhere in the neighborhood of 32-38 degrees.

(One thing since you've got that MSD distributor, is you need to know how it's currently set up. Before you start, check out my comments about that under "alternative 2" below. If it's currently "locked out", then you'll have to address that first.)

Here's what I would do in your case, I'm going to describe two alternatives.
If you (or your mechanic) has access to a timing light that is capable of measuring total ignition timing/advance (here's an example of one), then I would do this:
(alternative 1 - the "best" way)
1) Disconnect the vacuum advance line from the distributor (if it has one) and plug the line.
2) Loosen the distributor hold-down clamp bolt "just enough" that you can turn the distributor body with some effort, but not so much that it turns easily.
3) Start the engine, run and hold it at a steady 2600-2700 rpm.
4) Set the "timing" to 34 degrees while the engine is running at 2600-2700 rpm.
5) Re-tighten the distributor hold down bolt, then re-check the timing at 2600-2700 rpm to make sure it didn't "move". (repeat until you're able to keep the setting with the bolt tight)
6a) Reconnect everything, drive the car, make sure the engine gets up to normal operating temperature and that you don't have any "knocking" under load (like when going to full throttle, uphill, in high gear, from about 2500 rpm)
If it feels good, drives good, doesn't knock --- you're done. Enjoy the car.
If you have knock, then repeat all the above, except reduce the timing to 32 degrees, and re-test. If you get down to 30 degrees and still have knock, then it'll be time to talk about changing the advance curve like you've been asking about (electronics and/or changing springs/weights)
6b) If you DON'T have knock at 34 degrees but think the car "wants/needs" more power, then reset it to 36 degrees and re-test again. If you find the point where either it starts to knock or doesn't seem to be making any more power, then go back to your previous setting - you're done, enjoy the car.
7) Once you find the "happy spot" for your car, then you can disconnect and plug the vacuum line again, and "read" the initial timing setting you have with the engine idling and using a 'normal' timing light. You won't be changing anything, this is just to find out what initial setting corresponds to the total advance "happy spot" you found. That will make it easier to set it properly in the future. 

(alternative 2)
If you DON'T have access to a light that can measure total advance at 2600-2700 rpm, then do this:
Since you don't have the factory distributor we really don't know how much centrifugal advance is "in" your MSD distributor yet. Since you now know you have the 8563 pro billet, you need to know if it has been "locked out" (page 4 figure 7 in the instructions), which advance bushing it has (page 4 figures 5 and 6 in the instructions), and which springs it has (page 3 figure 3 in the instructions). You can identify all this by removing the cap and rotor without having to remove the distributor from the car. (use a mirror to look "underneath" on the back side of the advance mechanism to see which bushing it has. It would really be better to remove it from the car and take it to a shop that has a distributor testing machine. They'll be able to tell you how exactly how much centrifugal advance it has and how fast it "comes in", but we can get close enough without doing that. Once you know all the above, then you can figure out where to set your intial timing. For example, lets say that your MSD distributor has the 'silver' bushing, so it has 25 degrees centrifugal advance. In that case you'd begin your series of tests using an initial timing setting of 9 degrees (25 + 9 = 34) in order to have a total advance of 34. (25 + 9 = 34). If it has the red bushing (28 degrees centrifugal) then you'd start with 6 degrees initial (28 + 6 = 34). If it has the black bushing (18 degrees) then you'd start with 16 degrees initial (18 + 16 = 34). Get the idea?
If your distributor has been "locked out", then you'll either need to remove it and "unlock it" and also install advance springs if they aren't there, or we'll have to control the complete advance curve from the MSD box.

Assuming it's not locked out, (or you unlock it) then begin by setting your initial timing (engine idling, vacuum advance line disconnected and plugged) to whatever intial setting in degrees will give you 34 degrees total (depends on the bushing from the steps above) going through steps like the did on the video.
Then repeat all the "testing" steps above until you find the "happy spot" for your engine.


For the "testing" part, it's better if you can do it on a chassis dyno, or on a race track with elapsed time clocks, or with something like this because being able to accurately judge performance using just "seat of the pants" can be difficult.

If you can't get your ignition timing "dialed in" using one of these methods (you can't get rid of "knock" or you can't get "enough" power), then it'll be time to consider "fiddling" with the electronics or with the springs/weights - but I wouldn't "go there" if I didn't have to - at least not at first.

It's a process. Everything is connected to everything else. Dialing in the timing can have an effect on what idle mixture setting and/or which carb jet size your engine likes, requiring a change - and then that change might result in the engine now being "happier" with a slightly different ignition setting. If you're wanting to optimize it, you'll probably go through several iterations of "sneaking up" on the settings that do that by repeatedly making small changes and then testing. That's part of what makes it fun though.

Once you get everything optimized, if you then want to hunt for more power, then you can consider playing with the advance curve by changing the weights and/or the "box" to bring the advance in "faster" or "slower", or maybe changing things so that there is "more" or "less" advance that gets added with rpm (requiring a corresponding "less" or "more" amount of initial timing in order to get the same total advance "happy value"). You might also have to do things like that if you have a knock you can't get rid of in other ways ---- but the point is, do the simpler/easier things first.


Spark plugs: You can go through a similar process. Having the "wrong" heat range plug for your engine is not going to cause instant irreparable harm. Start with what you have (they're new, right?), drive the car under normal conditions for a few days or a week, then pull some or all of them and see how they look. There are many web sites that have examples, here's one.. Based on what you see, you should be able to tell lots of things about what's going on in your combustion chambers including whether your plugs are too hot, too cold, or "just right" (sort of like Goldilocks's porridge ). Like with fuel mixture and ignition timing, your engine will tell you what it likes and what it doesn't. The trick is in learning how to listen.

A note on that timing video... ::cough:: Chevy distributors spin the "wrong" way - clockwise. Pontiacs turn the "right" way - counterclockwise.  So when they talk about rotating the distributor body to either advance or retard the timing, keep in mind that it's done in the opposite direction on a Pontiac. Also, the timing marks on a Pontiac are on the passenger side of the front cover, down by the edge of the harmonic balancer on the crank shaft.

Make sense?

Bear


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## BearGFR (Aug 25, 2008)

Dang! Did I really write all that?? 

I guess you can tell I've been at home all week, working out of the house due to the icy conditions in Dallas. I gotta get out.... :willy:

Bear


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## Chris-Austria (Dec 23, 2010)

Hi Bear!

It makes sense now! 
My mechanic has a timing light, but he thought that he can't set timing by moving the distributor. I'll tell him what you told me and start with 34° and optimize it if necessary like you explained to me.
There is no vacuum advance on this distributor!

Will a correct setup and other spark plugs make better HC and CO values?

The Accel 137 plugs are old, I'll need to change them anyway, but I have only Bosch Platinum+ plugs at home which are not good for my engine. Shipping is more expensive than 8 plugs, so I don't want to order different ones every week  With the old Accel 137 (heat range 7) the car runs pretty good, maybe I should order the same spark plugs that were used until now and replace them with new ones.

I made a list of parts for my ignition system which I think may work:

1. Moroso 72550 - Moroso Blue Max Spiral Core Custom-Fit Wire Sets 8mm
2. ACCEL 0137 - ACCEL U-Groove Performance Spark Plugs
3. MSD Ignition 84335 - MSD Distributor Cap and Rotor Kits
4. MSD Ignition 8464 - Distributor Springs, Bushings
5. MSD Ignition 8628 - Distributor Weight, Kit

When I think of what you told me, I might check first if I really need 4 and 5. And like I said.. I'm not sure of heat range 7 plugs. I will check the old plugs to find out if they get too hot or too cold and if the get to hot, I should use plugs with lower heat range? Or is it just opposite?

Thank you again for spending so much time helping me with my engine!


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## Chris-Austria (Dec 23, 2010)

Another question.. spark plug wires...
Is it better to have less ohm? Maybe the deliverd power to the spark plugs is higher with less ohm than with more ohm wires?
I can chooose between the Moroso 72550 and the Mallory 926M Pro Sidewinder. The Mallory have 300ohm, the Moroso have 800ohm. What's the better choise?


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## BearGFR (Aug 25, 2008)

Chris-Austria said:


> Another question.. spark plug wires...
> Is it better to have less ohm? Maybe the deliverd power to the spark plugs is higher with less ohm than with more ohm wires?
> I can chooose between the Moroso 72550 and the Mallory 926M Pro Sidewinder. The Mallory have 300ohm, the Moroso have 800ohm. What's the better choise?


Hey Chris,
My opinion is that it doesn't matter much. Remember power comes from burning fuel, not from electrial energy. Either you've got enough "juice" to light the fire or you don't.

I've been looking at the NGK web site, and they call out their XR5 or XR5IX plugs as being correct for Pontiac. That got me to thinking though, which heads does your engine have? To correctly ID them, you need both the date code which will be located either here or here, along with the head code that's located here.

Getting everything set "correctly" including your idle mixture should help the HC and CO readings, but be aware that if the motor has a stronger-than-stock cam in it, it's just going to be pretty 'dirty' at idle because of the increased overlap period in the cam.

Bear


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## Chris-Austria (Dec 23, 2010)

The date code may be behind the valve cover, the head code is "670". If the other code is needed, I'll have to remove the valve cover. Will it seal without leaking if I remove it and install it without using a new gasket?

I only was thinking about the spark plug wires because I read at the Moroso page "for use without HEI" and I have HEI. So I'll take the Mallory! Only wanted to know if 300ohm instead of 800 will make things worse instead of better!

I thought I have to use copper electrodes, so I didn't check all iridium and platinum plugs. My mechanic also told me not to use platinum just like dimitri did. So I'm searching for matching copper resistor type plugs with heat range 5 to 7. (if I don't find the perfect spark plug, I'll order new accel 137 and replace them with my old accel 137 )


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## BearGFR (Aug 25, 2008)

Chris-Austria said:


> The date code may be behind the valve cover, the head code is "670". If the other code is needed, I'll have to remove the valve cover. Will it seal without leaking if I remove it and install it without using a new gasket?


Jackpot... no you don't need any other codes. Those heads were only used on 1967 GTO's. They're the last of the Pontiac "closed chamber" heads. They have screw in studs, pushrod guide plates, and the larger size valves. They flow pretty well, but they don't have the best chambers for flame propagation. Because of that, to optimize them you may wind up needing 36 degrees of total advance or more.



Chris-Austria said:


> I thought I have to use copper electrodes, so I didn't check all iridium and platinum plugs.


I wasn't aware of that, but then I'm not really a spark plug expert either. There's certainly nothing wrong with what you're planning to do.

Bear


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## Chris-Austria (Dec 23, 2010)

Good to know, so I'll make it like you said in alternative one, but start with 36°
I think I'll place my order at summit and take 2 different spar plug sets, one with heat range 7 and one with heat range 5. If the 7 don't work well, I can change them.

I'm glad having a plan now 

Edit:
I found out that heat range isn't the same by every brand. Some have high numbers for "cold" plugs and some have high numbers for "hot" plugs. 
The cross-reference to AC 44S (original GTO spark plug) is the Accel 0137 which I have now, but need to replace them because they are too old. Heat range 4 by AC is the same as heat range 7 by Accel.
I've placed my order and will get everything I need in about 2 weeks. (spark plugs, wires, distributor cap, springs and bushings for the case I need them and a spark plug gapper)

By the way, my choke works now great. I push the pedal one time, the choke plate closes, I turn the key and the engine starts up like a new one  The bi-metal spring wasn't correct mounted, now it works just perfect! I also oiled the whole linkage system with my graphite spray and the mechanic adjusted the links so that all 3 carbs work as they should.


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