Spark Plug Advice Needed

-
bobscuda67 said:
It's a 9.9:1 340 with magnum heads and a 650 Eddy Thunder carb stock calibration. The distributer is set at 34 degrees at 3400. Initial comes in at 16 degrees. The vacuum can is hooked to manifold vacuum. Exhaust manifolds are on it too. Cam is 220/226 Lunati. I use 87 octane with no spark knock.
Click to expand...
Gimmee a break, my very similar combo would idle with the Idle-timing down as low as 5 degrees, no problem. 12 to 14 is all I've ever run, cuz that is where my T-slots synced up at.

Lemmee splain something;
Your AFR at idle is created by the combination of transfer slot exposure underneath the primary throttle blades, PLUS idle-mixture screws, augmented by fuel-level. If you close the throttles to reduce transfer fuel, you will have to increase the mixture screw fuel. If you do not, the engine will idle poorly or stall. So then, there is NO POINT to shutting off the transfers!
In your case, with the transfers as good as shut off, it won't idle very well if at all, on just the mixture screws, so you HAVE to throw timing at it to help out.
But now, as soon as you step on the gas pedal and open the throttles, the transfers come back on line, and now the ENTIRE low-speed circuit is fat cuz of the fat mixture screws.
That's just how simple it is.


Here is your game plan, the very same game-plan I used on mine;
1) Take the carb off, drain it, and flip it over.
2) Making sure the throttle is closed, and using the speed screw, adjust the transfer slot exposure to dead square. After that is done, do not touch the speed screw.
3) Reinstall the carb and set the mixture screws to; in the middle of their operating range. The Edelbrock/Carter should be about 2.5 turns out
4) Fill the bowls with gas and start it up, then let her warm up.
5) Now, replumb the VA to the sparkport.
6) after she is warm, the idle at 16* initial will be too fast. RETARD the stinking timing until the in-gear idle-rpm is in the window of 650 to 550; and in Neutral is not more than 750.
DO NOT touch the curb-idle-speed screw!
7) twiddle the mixture screws for best stable idle.
8) shut the engine off. Go check where the the mixture screws ended up.
a) if they are open further than 3.0 turns, the engine wants more idle fuel, so open the transfers, using the speed screw, about a half a turn, reset the mixtures to 2.5, and go back to step 7
b) but, if the mixture screws are at less than 2.0, then the engine is getting too much from the transfers, so shut them up a half-turn on the speed screw, reset the mixture-screws and go back to step 7
9) AFTER you get the mixture-screws synchronized to the transfers, you can then set the IDLE-Timing anywhere you want.
10) IF your new setting creates a tip-in sag, (see note-1), timing will NOT eliminate it. Most likely, modest additional idle-timing will not affect it at all. Usually this happens because the T-slot to mixture screw synchronization is off, the transfers being too far closed. BUT, I just detailed how to set the sync, and if you did what I explained, then the sync is now right on, and DO NOT mess with it! If the sag is very minor, ok, with the speed screw, open the throttle 1/4 to 1/2 turn, twiddle the mixture screws back to best lean idle. then see what happens.
If you have to, increasing the WET fuel level, will make it easier for the fuel to climb up the mainwells.
11) to see how close your AFR is (obviously without a gauge),
here is the procedure;

>Determine exactly where your after-tune idle mixture screws are set at,
should be 2.5 turns out, +/- , 1/4 turn.
Warm up the engine,
rev it up to about 2000/2200, and set the fast-idle cam to hold it in that neighborhood.
twiddle the mixture screws lean, to obtain the highest rpm.
kick it off fast idle and shut off the engine.
determine where the mixture screws ended up.
a) if more than 2.5T, then the engine wants more fuel at the rpm of testing.
b) if less than 2.5T, then the engine wants less fuel at the rpm of testing.
c) once the load comes on, she will want additional fuel, perhaps 1/4 turn.
d) if the screws are within lemmee guess, say in the window of 2.25 to 2.75 turns out, then forget about it. But if say a full turn, then I would consider fixing it.
e) you only have a couple of options to change this, and this will affect the life of your plugs, your fuel economy, and if very fat, can shorten the life of your rings and cylinder walls.


Note-1
A tip-in sag occurs when the transfers are too far closed. In this condition, air passing by the throttles sorta evacuates the upper exposed section, and then when you gently open the throttles, it takes a split-second for additional fuel to get pulled up and over the top of the mainwell. This is felt as a slight hesitation. The further closed the transfers are, the bigger/worse the hesitation becomes.
Do not confuse this with an accelerator pump issue, and do not try to cover this sag with pumpshot! Doing so costs gas-money and engine-life; Fix the sync.

Note-2
AFAIK, all hex-shaped Chrysler VAs are adjustable.
Inside the nipple, there is an allen screw, that adjusts both the onset and rate of advance.
On the arm is a number that indicates, in distributor degrees, the amount of advance each can is calibrated to. I have seen anywhere from I think 4* to 15* which has to be doubled, to get crank degrees.
HOWEVER, the thing that sets this number is the large stops on the arm, which you are free to grind off, bit by bit, until you get whatever amount of advance that your engine wants, up to a maximum of 22/24 degrees.
It's so easy, anyone can do it.
Mine is set to bring all of it in, as quickly as is possible, no delay ...... which allows me to easily run 14* or less idle timing, even down to 5*, cuz as soon as that circuit wakes up, she brings up to 22* to the party.

Note-3
btw, if that cam of yours is on a 110 or less LSA, it has the potential to make great to fantastic hiway fuel economy.
With that cam in straight up, the power extraction is very long, compared to other cams of this size. By combining this long extraction period, with the high cylinder pressure of your 340, your engine has the potential, with optimized cruize timing, and coupled with an overdrive; to go deep into the 20mpgs, assuming that 340 is not pushing a brick..
However, the overlap period is generous enough, that with headers and good heads, it should continue to make modest power to past 5500.
---------------------------------------------------------
As an aside;
My Hughes 223/230/110 cam had very similar specs, and easily went deep 20s with overdrive and a manual trans. I used to mention that, on one particular trip, point to point, geared 65=1600, she made 32mpgs; and most everyone here seems to think that is impossible, pretty much calling me a liar......... so if you hear that, from somebody else, just know that it was done on a day-long trip, and we were not always doing just 65. By 85mph, that rpm had risen to 2100. The timing was optimized at cruise rpm, using a dash-mounted, adjustable, electronic timing module, with a range of 15 degrees.
My combo has never burned anything higher than 87, except for the time she went to the track, and ran four Eighth mile blasts, with a lil hi-test 91 dribbled in.
Furthermore;
that 223 cam, in my 11.3Scr/367 used the same plugs for 5 years, until one day the lobes fell off the cam. I replaced that cam with a 230/237/110 cam, and left those plugs in it.
Those plugs were new in 1999.
They have seen three cams, several intakes, several carbs, and three ignition systems ......... and they were still in there over 100,000 miles later. I finally installed new ones in fall of 2022, as a courtesy to the guy that wanted to buy the car. So those plugs were 23years old when I pulled them. Jus saying.
 
Last edited:
Your fine. No worries here.
RustyRatRod said:
My bad. I'll shut it down on my end then. Don't forget about the pump shot on that carburetor. Lots of times, when you lean one out it will get a stumble off idle, because it may need more pump shot so keep that in mind.
Click to expand...
The Edelbrock rods will be here tomorrow and I can get a better read on a hotter plug.
 
AJ/FormS said:
Gimmee a break, my very similar combo would idle with the Idle-timing down as low as 5 degrees, no problem. 12 to 14 is all I've ever run, cuz that is where my T-slots synced up at.

Lemmee splain something;
Your AFR at idle is created by the combination of transfer slot exposure underneath the primary throttle blades, PLUS idle-mixture screws, augmented by fuel-level. If you close the throttles to reduce transfer fuel, you will have to increase the mixture screw fuel. If you do not, the engine will idle poorly or stall. So then, there is NO POINT to shutting off the transfers!
In your case, with the transfers as good as shut off, it won't idle very well if at all, on just the mixture screws, so you HAVE to throw timing at it to help out.
But now, as soon as you step on the gas pedal and open the throttles, the transfers come back on line, and now the ENTIRE low-speed circuit is fat cuz of the fat mixture screws.
That's just how simple it is.


Here is your game plan, the very same game-plan I used on mine;
1) Take the carb off, drain it, and flip it over.
2) Making sure the throttle is closed, and using the speed screw, adjust the transfer slot exposure to dead square. After that is done, do not touch the speed screw.
3) Reinstall the carb and set the mixture screws to; in the middle of their operating range. The Edelbrock/Carter should be about 2.5 turns out
4) Fill the bowls with gas and start it up, then let her warm up.
5) Now, replumb the VA to the sparkport.
6) after she is warm, the idle at 16* initial will be too fast. RETARD the stinking timing until the in-gear idle-rpm is in the window of 650 to 550; and in Neutral is not more than 750.
DO NOT touch the curb-idle-speed screw!
7) twiddle the mixture screws for best stable idle.
8) shut the engine off. Go check where the the mixture screws ended up.
a) if they are open further than 3.0 turns, the engine wants more idle fuel, so open the transfers, using the speed screw, about a half a turn, reset the mixtures to 2.5, and go back to step 7
b) but, if the mixture screws are at less than 2.0, then the engine is getting too much from the transfers, so shut them up a half-turn on the speed screw, reset the mixture-screws and go back to step 7
9) AFTER you get the mixture-screws synchronized to the transfers, you can then set the IDLE-Timing anywhere you want.
10) IF your new setting creates a tip-in sag, (see note-1), timing will NOT eliminate it. Most likely, modest additional idle-timing will not affect it at all. Usually this happens because the T-slot to mixture screw synchronization is off, the transfers being too far closed. BUT, I just detailed how to set the sync, and if you did what I explained, then the sync is now right on, and DO NOT mess with it! If the sag is very minor, ok, with the speed screw, open the throttle 1/4 to 1/2 turn, twiddle the mixture screws back to best lean idle. then see what happens.
If you have to, increasing the WET fuel level, will make it easier for the fuel to climb up the mainwells.
11) to see how close your AFR is (obviously without a gauge),
here is the procedure;

>Determine exactly where your after-tune idle mixture screws are set at,
should be 2.5 turns out, +/- , 1/4 turn.
Warm up the engine,
rev it up to about 2000/2200, and set the fast-idle cam to hold it in that neighborhood.
twiddle the mixture screws lean, to obtain the highest rpm.
kick it off fast idle and shut off the engine.
determine where the mixture screws ended up.
a) if more than 2.5T, then the engine wants more fuel at the rpm of testing.
b) if less than 2.5T, then the engine wants less fuel at the rpm of testing.
c) once the load comes on, she will want additional fuel, perhaps 1/4 turn.
d) if the screws are within lemmee guess, say in the window of 2.25 to 2.75 turns out, then forget about it. But if say a full turn, then I would consider fixing it.
e) you only have a couple of options to change this, and this will affect the life of your plugs, your fuel economy, and if very fat, can shorten the life of your rings and cylinder walls.


Note-1
A tip-in sag occurs when the transfers are too far closed. In this condition, air passing by the throttles sorta evacuates the upper exposed section, and then when you gently open the throttles, it takes a split-second for additional fuel to get pulled up and over the top of the mainwell. This is felt as a slight hesitation. The further closed the transfers are, the bigger/worse the hesitation becomes.
Do not confuse this with an accelerator pump issue, and do not try to cover this sag with pumpshot! Doing so costs gas-money and engine-life; Fix the sync.

Note-2
AFAIK, all hex-shaped Chrysler VAs are adjustable.
Inside the nipple, there is an allen screw, that adjusts both the onset and rate of advance.
On the arm is a number that indicates, in distributor degrees, the amount of advance each can is calibrated to. I have seen anywhere from I think 4* to 15* which has to be doubled, to get crank degrees.
HOWEVER, the thing that sets this number is the large stops on the arm, which you are free to grind off, bit by bit, until you get whatever amount of advance that your engine wants, up to a maximum of 22/24 degrees.
It's so easy, anyone can do it.
Mine is set to bring all of it in, as quickly as is possible, no delay ...... which allows me to easily run 14* or less idle timing, even down to 5*, cuz as soon as that circuit wakes up, she brings up to 22* to the party.

Note-3
btw, if that cam of yours is on a 110 or less LSA, it has the potential to make great to fantastic hiway fuel economy.
With that cam in straight up, the power extraction is very long, compared to other cams of this size. By combining this long extraction period, with the high cylinder pressure of your 340, your engine has the potential, with optimized cruize timing, and coupled with an overdrive; to go deep into the 20mpgs, assuming that 340 is not pushing a brick..
However, the overlap period is generous enough, that with headers and good heads, it should continue to make modest power to past 5500.
---------------------------------------------------------
As an aside;
My Hughes 223/230/110 cam had very similar specs, and easily went deep 20s with overdrive and a manual trans. I used to mention that, on one particular trip, point to point, geared 65=1600, she made 32mpgs; and most everyone here seems to think that is impossible, pretty much calling me a liar......... so if you hear that, from somebody else, just know that it was done on a day-long trip, and we were not always doing just 65. By 85mph, that rpm had risen to 2100. The timing was optimized at cruise rpm, using a dash-mounted, adjustable, electronic timing module, with a range of 15 degrees.
My combo has never burned anything higher than 87, except for the time she went to the track, and ran four Eighth mile blasts, with a lil hi-test 91 dribbled in.
Furthermore;
that 223 cam, in my 11.3Scr/367 used the same plugs for 5 years, until one day the lobes fell off the cam. I replaced that cam with a 230/237/110 cam, and left those plugs in it.
Those plugs were new in 1999.
They have seen three cams, several intakes, several carbs, and three ignition systems ......... and they were still in there over 100,000 miles later. I finally installed new ones in fall of 2022, as a courtesy to the guy that wanted to buy the car. So those plugs were 23years old when I pulled them. Jus saying.
Click to expand...
Well AJ I pulled the carb and the transfer slot was a perfect square so no adjustment was needed.
I set the idle screws to the highest rpm and it was at 650 in drive. They were screwed out 1 3/4 turns same as before.
I backed off the timing a bit to get the 750 in park number and connected to port vacuum.
Vacuum reading is 18 inches.
I'll drive it around tonight and see if I can feel any difference.
IMG_2437.JPG
 
AJ/FormS said:
Gimmee a break, my very similar combo would idle with the Idle-timing down as low as 5 degrees, no problem. 12 to 14 is all I've ever run, cuz that is where my T-slots synced up at.

Lemmee splain something;
Your AFR at idle is created by the combination of transfer slot exposure underneath the primary throttle blades, PLUS idle-mixture screws, augmented by fuel-level. If you close the throttles to reduce transfer fuel, you will have to increase the mixture screw fuel. If you do not, the engine will idle poorly or stall. So then, there is NO POINT to shutting off the transfers!
In your case, with the transfers as good as shut off, it won't idle very well if at all, on just the mixture screws, so you HAVE to throw timing at it to help out.
But now, as soon as you step on the gas pedal and open the throttles, the transfers come back on line, and now the ENTIRE low-speed circuit is fat cuz of the fat mixture screws.
That's just how simple it is.


Here is your game plan, the very same game-plan I used on mine;
1) Take the carb off, drain it, and flip it over.
2) Making sure the throttle is closed, and using the speed screw, adjust the transfer slot exposure to dead square. After that is done, do not touch the speed screw.
3) Reinstall the carb and set the mixture screws to; in the middle of their operating range. The Edelbrock/Carter should be about 2.5 turns out
4) Fill the bowls with gas and start it up, then let her warm up.
5) Now, replumb the VA to the sparkport.
6) after she is warm, the idle at 16* initial will be too fast. RETARD the stinking timing until the in-gear idle-rpm is in the window of 650 to 550; and in Neutral is not more than 750.
DO NOT touch the curb-idle-speed screw!
7) twiddle the mixture screws for best stable idle.
8) shut the engine off. Go check where the the mixture screws ended up.
a) if they are open further than 3.0 turns, the engine wants more idle fuel, so open the transfers, using the speed screw, about a half a turn, reset the mixtures to 2.5, and go back to step 7
b) but, if the mixture screws are at less than 2.0, then the engine is getting too much from the transfers, so shut them up a half-turn on the speed screw, reset the mixture-screws and go back to step 7
9) AFTER you get the mixture-screws synchronized to the transfers, you can then set the IDLE-Timing anywhere you want.
10) IF your new setting creates a tip-in sag, (see note-1), timing will NOT eliminate it. Most likely, modest additional idle-timing will not affect it at all. Usually this happens because the T-slot to mixture screw synchronization is off, the transfers being too far closed. BUT, I just detailed how to set the sync, and if you did what I explained, then the sync is now right on, and DO NOT mess with it! If the sag is very minor, ok, with the speed screw, open the throttle 1/4 to 1/2 turn, twiddle the mixture screws back to best lean idle. then see what happens.
If you have to, increasing the WET fuel level, will make it easier for the fuel to climb up the mainwells.
11) to see how close your AFR is (obviously without a gauge),
here is the procedure;

>Determine exactly where your after-tune idle mixture screws are set at,
should be 2.5 turns out, +/- , 1/4 turn.
Warm up the engine,
rev it up to about 2000/2200, and set the fast-idle cam to hold it in that neighborhood.
twiddle the mixture screws lean, to obtain the highest rpm.
kick it off fast idle and shut off the engine.
determine where the mixture screws ended up.
a) if more than 2.5T, then the engine wants more fuel at the rpm of testing.
b) if less than 2.5T, then the engine wants less fuel at the rpm of testing.
c) once the load comes on, she will want additional fuel, perhaps 1/4 turn.
d) if the screws are within lemmee guess, say in the window of 2.25 to 2.75 turns out, then forget about it. But if say a full turn, then I would consider fixing it.
e) you only have a couple of options to change this, and this will affect the life of your plugs, your fuel economy, and if very fat, can shorten the life of your rings and cylinder walls.


Note-1
A tip-in sag occurs when the transfers are too far closed. In this condition, air passing by the throttles sorta evacuates the upper exposed section, and then when you gently open the throttles, it takes a split-second for additional fuel to get pulled up and over the top of the mainwell. This is felt as a slight hesitation. The further closed the transfers are, the bigger/worse the hesitation becomes.
Do not confuse this with an accelerator pump issue, and do not try to cover this sag with pumpshot! Doing so costs gas-money and engine-life; Fix the sync.

Note-2
AFAIK, all hex-shaped Chrysler VAs are adjustable.
Inside the nipple, there is an allen screw, that adjusts both the onset and rate of advance.
On the arm is a number that indicates, in distributor degrees, the amount of advance each can is calibrated to. I have seen anywhere from I think 4* to 15* which has to be doubled, to get crank degrees.
HOWEVER, the thing that sets this number is the large stops on the arm, which you are free to grind off, bit by bit, until you get whatever amount of advance that your engine wants, up to a maximum of 22/24 degrees.
It's so easy, anyone can do it.
Mine is set to bring all of it in, as quickly as is possible, no delay ...... which allows me to easily run 14* or less idle timing, even down to 5*, cuz as soon as that circuit wakes up, she brings up to 22* to the party.

Note-3
btw, if that cam of yours is on a 110 or less LSA, it has the potential to make great to fantastic hiway fuel economy.
With that cam in straight up, the power extraction is very long, compared to other cams of this size. By combining this long extraction period, with the high cylinder pressure of your 340, your engine has the potential, with optimized cruize timing, and coupled with an overdrive; to go deep into the 20mpgs, assuming that 340 is not pushing a brick..
However, the overlap period is generous enough, that with headers and good heads, it should continue to make modest power to past 5500.
---------------------------------------------------------
As an aside;
My Hughes 223/230/110 cam had very similar specs, and easily went deep 20s with overdrive and a manual trans. I used to mention that, on one particular trip, point to point, geared 65=1600, she made 32mpgs; and most everyone here seems to think that is impossible, pretty much calling me a liar......... so if you hear that, from somebody else, just know that it was done on a day-long trip, and we were not always doing just 65. By 85mph, that rpm had risen to 2100. The timing was optimized at cruise rpm, using a dash-mounted, adjustable, electronic timing module, with a range of 15 degrees.
My combo has never burned anything higher than 87, except for the time she went to the track, and ran four Eighth mile blasts, with a lil hi-test 91 dribbled in.
Furthermore;
that 223 cam, in my 11.3Scr/367 used the same plugs for 5 years, until one day the lobes fell off the cam. I replaced that cam with a 230/237/110 cam, and left those plugs in it.
Those plugs were new in 1999.
They have seen three cams, several intakes, several carbs, and three ignition systems ......... and they were still in there over 100,000 miles later. I finally installed new ones in fall of 2022, as a courtesy to the guy that wanted to buy the car. So those plugs were 23years old when I pulled them. Jus saying.
Click to expand...
What in the world is a transfer screw, speed screw?? Never heard of either of these until now
 
Dan the man said:
What in the world is a transfer screw, speed screw?? Never heard of either of these until now
Click to expand...
The transfer slot is down inside the primary throttle bore, on the front side, and is the primary source of fuel delivery from idle to roughly 30% throttle opening, (I'm guessing) when the Mainjet comes on line.
At idle, transfer-slot fuel is augmented by fuel coming from the Mixture screw ports.
 
bobscuda67 said:
Well AJ I pulled the carb and the transfer slot was a perfect square so no adjustment was needed.
I set the idle screws to the highest rpm and it was at 650 in drive. They were screwed out 1 3/4 turns same as before.
I backed off the timing a bit to get the 750 in park number and connected to port vacuum.
Vacuum reading is 18 inches.
I'll drive it around tonight and see if I can feel any difference.
View attachment 1716262060
Click to expand...
Dynomite!
But if the mixture screws are only 1.75T open, then you still have the option of trading away some transfer fuel to get some more idle mixture. It's an option. How she runs at cruising speed with just 1.75Turns out, will determine what to do next.
 
Last edited:
AJ/FormS said:
The transfer slot is down inside the primary throttle bore, on the front side, and is the primary source of fuel delivery from idle to roughly 30% throttle opening, (I'm guessing) when the Mainjet comes on line.
At idle, transfer-slot fuel is augmented by fuel coming from the Mixture screw ports.
Click to expand...
Just how important is this? I'm asking because I looked at my edelbrock carburetor tuning booklet and it's not even mentioned
 
Dan the man said:
Of the few people who I have known over the years that claimed to be engine tuners, I never once heard this term before
Click to expand...
Com'on, my friend, stick with me.
Name one part on a carb, or one circuit, that is redundant.
You said it yourself, namely; "claimed to be engine tuners".
There is a very strong possibility that your tuner acquaintances DO know about this, cuz it's darn near impossible to have a sweetheart of an engine, with a poorly-tuned low-speed circuit. All of us, as tuners, strive to do a good job cuz all it takes is one bad report circulating, to affect us negatively for a long time.

Time wise and miles wise, Ima thinking more than 90% of the life of your engine is gonna be spent on the Low-speed circuit, which, principally, is the transfer slots plus mixture screws.
How important is it to get this right?
Well,
if 90% of the time your low-speed circuit is rich, or lean, or not exactly correct; is that important?
How aggravating is a tip-in sag?
How aggravating is it when you put the trans in gear and you hear this loud clang from her, and the car jumps ahead against the brakes?
What if the engine is so far off AFR that the exhaust is burning the eyes of your neighbor who is trying to have breakfast on his deck, two doors down?
and/or several times each summer you gotta buy new plugs, or the oil turns black in less than a week, and your rocker-shafts look like crap
If you manage to cover the tip-in sag with pump-shot, how much is that gonna cost you, over the life of the engine?
All of that could, or most like would, originate in, the low-speed circuit.

Unless you are a buddy of a tuner, how likely is it that this is gonna come up in conversation? Most of us are gonna get this synced up in just a few seconds, and then move on to other things. If you're watching your guy, you may not even notice him do it. Really, once a tuner gets this figured out, the tip-in sag never lies. Well let me rephrase; IMO, the tip-in sag has never fooled me, lol. But I admit, I like to idle my engines down, down, down with idle-retard, and so, the tip-in sag simultaneously jumps out of the background, making it easy to find. Once found, sync it up, and put the idle-timing back, Badaboom! maybe 30 seconds, if the distributor is already loose.
Friend, it is not my intent to befuddle you, or belittle you; we all gotta start someplace. My intent is to give you something to think about, and ammo to come back at me with, lol. I love you, as friends do.
 
A few people are saying fix the carb first. They are 100% wrong. Timing at idle [ & more if IT BIS needed ] IS NOT A BANDAID. What it shows is that folks do not understand what is going on in the cylinders...at idle!!!
At idle, the air entering the engine is throttled [ almost closed t/blades have 'stretched' the air ] so that the air below the blades is less dense than the air above the blades. There is now a greater distance between air molecules.....so the flame front needs more time to complete the burn for MAXIMUM EFFICIENCY AT IDLE, ie, more timing is needed at idle. Then you have residual exh gas left inside the cyl, caused by reversion at the end of the exh stroke. Mixed with fresh fuel, it burns more slowly & needs more idle timing. Increase cam duration/overlap, & it gets worse, even more timing is needed to get the optimum burn TIME at idle.
Sure, you can use less timing than OPTIMUM at idle & use more throttle opening, but you will never have:
- the best idle quality that is possible
- the best fuel efficiency
- the highest vacuum
- the coolest running engine at idle/off idle
- because the engine is most efficient when it has the CORRECT timing, uses the least amount of fuel & produces the highest amount of HP.

So get the idle timing correct FIRST before you touch the carb, NOT THE OTHER WAY AROUND.
 
bobscuda67 said:
Your fine. No worries here.

The Edelbrock rods will be here tomorrow and I can get a better read on a hotter plug.
Click to expand...
Don't forget about the springs, too. You can change them as well.
 
The transfer slot. It is mentioned on p.2 of the Edel carb book.
 
I have .030 of exposed transfer slot exposed to vacuum and my mixture screws out 1 3/4 turns for best lean idle.
IMG_2440.JPG
IMG_2441.JPG
IMG_2443.JPG
 
I will install the fatter mixture rod. which won't help the idle, and try it with a hotter plug.
If that doesn't bring satisfactory results I'm going to switch to a AVS2.
My carb probably needs some drilling and sleeves in the idle circuit to lean it out.
 
Bewy said:
A few people are saying fix the carb first. They are 100% wrong. Timing at idle [ & more if IT BIS needed ] IS NOT A BANDAID. What it shows is that folks do not understand what is going on in the cylinders...at idle!!!
At idle, the air entering the engine is throttled [ almost closed t/blades have 'stretched' the air ] so that the air below the blades is less dense than the air above the blades. There is now a greater distance between air molecules.....so the flame front needs more time to complete the burn for MAXIMUM EFFICIENCY AT IDLE, ie, more timing is needed at idle. Then you have residual exh gas left inside the cyl, caused by reversion at the end of the exh stroke. Mixed with fresh fuel, it burns more slowly & needs more idle timing. Increase cam duration/overlap, & it gets worse, even more timing is needed to get the optimum burn TIME at idle.
Sure, you can use less timing than OPTIMUM at idle & use more throttle opening, but you will never have:
- the best idle quality that is possible
- the best fuel efficiency
- the highest vacuum
- the coolest running engine at idle/off idle
- because the engine is most efficient when it has the CORRECT timing, uses the least amount of fuel & produces the highest amount of HP.

So get the idle timing correct FIRST before you touch the carb, NOT THE OTHER WAY AROUND.
Click to expand...


Dude, slow down and think for once.

The carb is so fat at idle he’s jacking a bunch timing to it. That’s bullshit and you should know that.

You can’t honestly think with 9.9:1 compression and that little cam needs 30 DEGREES OF TIMING AT IDLE.

No way should it need that. But your god said in his book to throw a bunch of timing at idle when everything else is wrong.

Look at his plugs. Apart from being a bit too cold it’s pig fat rich and that’s WITH all that timing at idle.

The one who is getting it wrong and leading people down the merry path of bullshit tuning is you.
 
For starters get rid of those plugs and put the NGK equivalent of what ever plug the factory put in it that came out in that year. Most likely a NGK BP5ES. Also make sure the plugs you buy have no more resistance than 0.5 Ohms from the center electrode to the tip.

Those plugs are a resistor type plug.....not what you want in that engine and gap them according to what ignition system you have in the car. As always check the voltage at the alternator as an ignition system that doesn't fire correctly doesn't give reliable info concerning the tune.

WHAT IS A RESISTOR SPARK PLUG?

Since resistor type plugs actually “resist” some of the spark energy, non-resistor type plugs actually deliver a more powerful spark. It is for this reason that most racing plugs are non-resistor types.

I have seen a 0.5v drop in alternator voltage output make a perfectly good plug read change to a pig rich plug read without altering the the AFR what so ever.

Change the spark plugs to what they should be and then get back to us with more pics
 
You must log in or register to reply here.
-

Back
Top