dwell, timing, and rpm on a 462

essenz · Post by **essenz** » Thu Jan 01, 2004 3:56 pm

This is sort of a followup to my previous post. My 1966 coupe 462 does indeed have transistorized ignition.

So I decided to use my dwell meter and timing light and get everything set just right.

For starters, I installed a new ignition coil (Accel Universal #8140). Fired up the engine, let it warmed up. In park, idle RPM was 1200 and dwell was 31.5. To measure the dwell I attached my dwell meter leads to the tach block (not the dist and coil) - I assume this is proper way in transistorized systems. I am not sure what the timing is because the markers were too oil coated to read (next chance I get I'll clean it in order to get a timing reading). MM has dwell at 22-24 degress, timing at 10 BTDC, and neutral idle at 1600 RPM.

So, I took of dist cap, loosened breaker and moved it back a little to open up the points. Started the car up, and my dwell was now at 29.5. However my park idle RPM was only 750 and the car seemed to struggle a bit.

Question... When the dwell goes down, do you have to change the timing? With my timing unchanged, and dwell drop of 2 degress, is the drop in RPM expected? Other than dwell and timing, would I have to touch the carb in anyway?

Basically, I want to get my dwell to 22-24 and my timing to 10 BTDC, and this is my first time doing all of this - so I am a little unclear on certain things - tips and suggestions are welcome!

Thanks.
John

Dee · Post by **Dee** » Thu Jan 01, 2004 4:19 pm

The very first thing to get adjusted is the dwell. This affects timing and consequently affects the idle speed. The next thing to adjust is the timing and you may have to adjust the idle speed while you are doing this as you want the timing to be set at 10 degrees at around 650 rpm. After setting the timing check the rpm again and reset the idle speed if necessary. You should disconnect and plug the vacuum line while doing this. If you find that you get too much pinging at 10 degrees, try 8 degrees. The manual says this is alright to do but warns against retarding more than the 2 degrees. You then connect the vacuum hose and set your curb idle speed with the car in drive.

essenz · Post by **essenz** » Sat Jan 03, 2004 1:18 pm

Update:

I got everything set properly with the dwell and timing. Dwell is 23.5 (transistor) and timing mark is right on 10 BTDC.

However.... Now I believe I have some carb settings to work on. PARK/NEUTRAL RPM is 800, and when I put the car in drive, RPM drops real low - car struggles and will stall if I dont give it gas.

I tried tickering with my very-old and very dirty carb, and I could increase the PARK/NEUTRAL RPM to 950-1000 by moving to idle speed (or air mixture) screw outward. However, whenever I switch the car into drive, it struggles and stalls.

I noticed my fast idle linkage is a bit loose, and no matter what I do it always drops down. I have very little carb experience.

I have been thinking about getting an Edelbrock 600, should I waste my time tuning an old carb which might have other hidden problems? I am also thinking that it might be easier to tune a nice clean edelbrock.

-John

Dee · Post by **Dee** » Sat Jan 03, 2004 2:54 pm

Before buying another carb try some adjustments on yours. It could well be dirty inside and may have to be cleaned. Try adjusting the MIXTURE screws. The air idle screw and mixture screws affect one and other. Try starting the mixture screws at 1-1/2 turns out and the idle speed screw(center)at about 2 turns out. Adjust the idle speed ( in gear) to where you want it ( about 450 rpm). you need to adjust the mixture screws a little at a time to obtain smoothness. You will find that you have to work back and forth between the mixture screws and the idle air screw to obtain the desired smoothness and rpm. Once you set everything , the carburetor adjustment should last a long time. If the carburetor doesn't respond to these adjustments then I suspect that it needs to be cleaned and overhauled.The AFB carbs on these cars are really pretty trouble free.

Vitas · Post by **Vitas** » Sat Jan 03, 2004 6:16 pm

Try looking at page 9 - 28 of the service manual "Advance Characteristics" and page 9 - 14 "Vacuum Advance."

Modern vacuum advance units are screw adjustable; the insruction sheet for one says "This unit must be adjusted before installation. Turn screw located inside vacuum tube to clockwise stop using the appropriate allen wrench. Then turn the screw counter clockwise the indicated number of turns."

Dist. tag no

C6VYF-A (Conventional) or C6VF-B (Transisitor)

4 1/4 ccw turns

essenz · Post by **essenz** » Sat Jan 03, 2004 7:37 pm

Dee,

After I got the ignition stuff set, I reset the air and fuel mixture screws to specs, 3.5 turns and 1.5 turns. When I started the car with those settings, PARK/NEUTRAL RPM was 850 and rough. Drive RPM was reading 400 -600, it was all over the place struggling to stay alive - but would not stall. In NEUTRAL, I turned the speed screw outward, and was able to get RPM up to 900-950, but then when I switch to DRIVE it immediately stalls.

From what you are saying, by turning the speed screw out, and not touching the fuel screws, I was increasing RPM, but I was also leaning out the mixture, which would explain why it stalls in DRIVE right?

Vitas,

My manual doesn't mention anything about adjusting the vacuum advance via screws. Without special test equipment it will be difficult to see if it is advancing the correct amount. My current dist and vac advance look to be original (steel line type). I do have a modern vac replacement (slip-on tube type) and a new distributor. I was going to put on the new dist until I discovered how difficult it is to remove my current one. Took 15 min. of elbow grease just to rotate a degree or two!

-John

Vitas · Post by **Vitas** » Sat Jan 03, 2004 11:33 pm

John, there is a 3 part test to a Lincoln tuneup.

I've got notes somewhere, but until I find them give Steve at Baker's a call.

Believe it or not, Steve recommends 4 degrees BTDC timing, John Cashman recommends 6 degrees BTDC timing.

EDIT John's rationale is ability to use low octance fuel.

Steve's rationale is burning out the engine.

The Engineers are going to have to give us the real answer.

The vacuum advance test is a certain timing reading at a certain RPM; I don't think special tools are required.

As I recall, you don't want the vacuum advance unit leaking air, for starters.

danwhite · Post by **danwhite** » Sun Jan 04, 2004 6:13 am

Sounds like you either have some sort of vacuum leak or "as I suspect" you need to revisit your timing settings. your engine sounds like the ign. initial timing is way too late hence why it struggles to stay running in gear. 850-900 rpm on a big block V8 should be plenty to prevent stall once placed in gear.

<BLOCKQUOTE>quote:<HR>Originally posted by essenz:
Dee,

After I got the ignition stuff set, I reset the air and fuel mixture screws to specs, 3.5 turns and 1.5 turns. When I started the car with those settings, PARK/NEUTRAL RPM was 850 and rough. Drive RPM was reading 400 -600, it was all over the place struggling to stay alive - but would not stall. In NEUTRAL, I turned the speed screw outward, and was able to get RPM up to 900-950, but then when I switch to DRIVE it immediately stalls.

From what you are saying, by turning the speed screw out, and not touching the fuel screws, I was increasing RPM, but I was also leaning out the mixture, which would explain why it stalls in DRIVE right?

Vitas,

My manual doesn't mention anything about adjusting the vacuum advance via screws. Without special test equipment it will be difficult to see if it is advancing the correct amount. My current dist and vac advance look to be original (steel line type). I do have a modern vac replacement (slip-on tube type) and a new distributor. I was going to put on the new dist until I discovered how difficult it is to remove my current one. Took 15 min. of elbow grease just to rotate a degree or two!

-John<HR></BLOCKQUOTE>

Heavymetal · Post by **Heavymetal** » Sun Jan 04, 2004 9:38 am

Just to add: your timing should be set in 'Drive' or at a low rpm (500-600)so that you know your centrifugal isn't kicking in.A vacuum guage is a great tool to have for tuning.I tune my carbs by it.They're cheap to buy and give a ton of info.

Dee · Post by **Dee** » Sun Jan 04, 2004 1:04 pm

Set the timing at 450 rpm. It doesn't have to be in gear. The rpm is important because of the centrifical advance mechanism. If you set the timing at a high rpm you will end up with the timing retarded when you reduce the idle speed to the specified 450 rpm.

Heavymetal · Post by **Heavymetal** » Sun Jan 04, 2004 1:08 pm

What Motor Manual are you using? Isn't the dwell 26-31 degees like a 460? Just thinking out loud here.

essenz · Post by **essenz** » Sun Jan 04, 2004 2:04 pm

Update:

I definitely have to redo timing as it was done at a high NEUTRAL RPM. I will try to do this at 450 RPM with vacuum line disconnected.

Dee, how can I not be in gear? Isn't being in drive the only way to set timing at the low RPM?

On another note, I just got back from the car. It turned over fine, but PARK idle was really high (1850) and DRIVE was 1000 RPM. When I turned the car off it shaked a bit, gurgled, and then sprayed a white smokey fuel mixture out of the carb 3 feet in the air.

Here is what I am going to do: Set carb to default settings (3.5 turns, 1.5 turns), Hand crank to 8 BTDC , then manually rotate distributor with car off such that 8 BTDC has rotor exactly on Spark Cyl 1. That should be enough for me to "safely" start the car. Then I will get the timing fined tuned in DRIVE @450RPM with vacuum line disconnected.

The only other assumption I am making is that my timing marks accurately represent the engine state. If I wanted to, I guess I could verify if TDC is correct by sticking a little measuring stick down into the #1 cylinder via a spark plug hole.

-John

MarkIII · Post by **MarkIII** » Sun Jan 04, 2004 3:57 pm

<BLOCKQUOTE>quote:<HR>Originally posted by essenz:
Update:
On another note, I just got back from the car. It turned over fine, but PARK idle was really high (1850) and DRIVE was 1000 RPM. When I turned the car off it shaked a bit, gurgled, and then sprayed a white smokey fuel mixture out of the carb 3 feet in the air.-John<HR></BLOCKQUOTE>

Diesel! Idle speed way too high on shutdown. May have the primary butterfly opened up quite a bit.

I really don't remember setting timing on any car or truck while in gear. As Dee says, set the timing down around a decent idle speed. A fast idle can get the mechanical advance to start to come into play. After timing is set properly, then set the low (curb) idle in drive w/trusted companion holding the brakes on.

Did the 462 really curb idle down at 450 RPM? I was always used to about 550 or so for most V8's. But go back in time to the flathead, idle back then was something like 380-400. Of course the redline was a lot lower too!

essenz · Post by **essenz** » Sun Jan 04, 2004 9:42 pm

<BLOCKQUOTE>quote:<HR>Originally posted by MarkIII:

I really don't remember setting timing on any car or truck while in gear. As Dee says, set the timing down around a decent idle speed. A fast idle can get the mechanical advance to start to come into play. After timing is set properly, then set the low (curb) idle in drive w/trusted companion holding the brakes on.
<HR></BLOCKQUOTE>

Okay, now you are confusing me! When I set the timing I can either be in PARK/NEUTRAL or DRIVE.

Its obvious now that I need to set the timing at a low RPM with vacuum adv disconnected - and DRIVE provides the lowest RPM. If I set the timing in NEUTRAL, my RPM will be at least 1000 - 1200, causing centrifugal advance. Is there some other way of getting RPM done low in NEUTRAL for initial timing? Theoretically I could compensate for the centrifugal advance, and time accordingly, however I doubt that my distributor's centrifugal adv. characteristics are still calibrated as the manual indicates.

One other thing.... Timing effects RPM right? What causes RPM to increase, advancing or retarding?

Dee · Post by **Dee** » Mon Jan 05, 2004 12:03 am

I agree with Dan White. A vacuum leak or the timing should be revisited. Yes, the mixture screws need to be adjusted when you adjust the idle air screw. When you speed-up the idle with the idle air screw you should also richen up the mixture screws. You will find that the engine speeds up when you do this, buts runs smooth. There is some technique involved here but you can start reducing the idle speed with the air screw a little at a time and tweak the mixture screws( in) a tad as you go. Trying to maintain smoothness. If the timing is on, no vacuum leaks and you're running on all eight you should be able to get the car to idle down to about 450rpm in drive. hope this helps.

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