I was bored, so I made a cold start video!

[1972BlueC20]

I just talked to the shop that did my install....they said they just used my old coil wire and hooked it straight to the HEI....FML....

It's insane....this is a restoration shop and shop that's been there since 1977

[mechanicalman]

Originally Posted by 1972BlueC20

I just talked to the shop that did my install....they said they just used my old coil wire and hooked it straight to the HEI....FML....

It's insane....this is a restoration shop and shop that's been there since 1977

Replace that wire all the way to the fusebox with a 12 gauge wire. I like these trick pigtails so the wire does not fall out of the distributor and makes wiring a tach easy.
http://www.summitracing.com/parts/sum-g5211/overview/

[1972BlueC20]

Originally Posted by mechanicalman

Replace that wire all the way to the fusebox with a 12 gauge wire. I like these trick pigtails so the wire does not fall out of the distributor and makes wiring a tach easy.
http://www.summitracing.com/parts/sum-g5211/overview/

Thanks man!

So what do I do with the yellow wire that's currently hooked to my dizzy? Do I just tape it up and leave it back there?

The connector end they are using now is just like the connector used on the positive side of the electric choke.

Funny though, before I read your comment. I went by another mechanic shop that I've used before to ask them. There was an old timer working there. He offered to check the voltage for me. It was getting 10.9 with the key in the run position. He said that was plenty and once started it would be getting atleast 12v. Does that make sense? I thought it should have atleast 12v at all times running or with the key on. Correct?

[mechanicalman]

Originally Posted by 1972BlueC20

Thanks man!

So what do I do with the yellow wire that's currently hooked to my dizzy? Do I just tape it up and leave it back there?

The connector end they are using now is just like the connector used on the positive side of the electric choke.

Funny though, before I read your comment. I went by another mechanic shop that I've used before to ask them. There was an old timer working there. He offered to check the voltage for me. It was getting 10.9 with the key in the run position. He said that was plenty and once started it would be getting atleast 12v. Does that make sense? I thought it should have atleast 12v at all times running or with the key on. Correct?

You are correct, a little over 12V key on then around 13.5-14 engine running.

Not sure what wire that is, but if it's only 10.9V that would indicate the wire has a lot of resistance or you have a dead cell on your battery (doubt that). Trace that wire to the fusebox, remove, and install your new 12ga wire there, then cut off any part of the wire you can see to avoid confusion in the future.

Did you look at the accel pump lever on your carb to see what hole it is in?

[1972BlueC20]

Originally Posted by mechanicalman

You are correct, a little over 12V key on then around 13.5-14 engine running.

Not sure what wire that is, but if it's only 10.9V that would indicate the wire has a lot of resistance or you have a dead cell on your battery (doubt that). Trace that wire to the fusebox, remove, and install your new 12ga wire there, then cut off any part of the wire you can see to avoid confusion in the future.

Did you look at the accel pump lever on your carb to see what hole it is in?

No I haven't checked the accel pump yet. Will do that tomorrow.

So let me just be clear....so they checked the voltage at the dizzy without the truck running (just with key on) and it was around 10.9 volts....the mechanic said that was fine and it would be at least 12v when running.....so was he incorrect in his statement?

The electric choke is running off the dizzy too and i just checked it and its getting slightly over 12v.

My battery is putting out over 12v too.

I may be wrong, but I thought the yellow wire that's currently hooked to my dizzy came off the starter....I may be wrong.....I think it was originally coming off a bundle of wires coming from the starter area...one of the wires also was the wire that runs to the oil pressure sending unit.

[mechanicalman]

Originally Posted by 1972BlueC20

No I haven't checked the accel pump yet. Will do that tomorrow.

So let me just be clear....so they checked the voltage at the dizzy without the truck running (just with key on) and it was around 10.9 volts....the mechanic said that was fine and it would be at least 12v when running.....so was he incorrect in his statement?

The electric choke is running off the dizzy too and i just checked it and its getting slightly over 12v.

My battery is putting out over 12v too.

I may be wrong, but I thought the yellow wire that's currently hooked to my dizzy came off the starter....I may be wrong.....I think it was originally coming off a bundle of wires coming from the starter area...one of the wires also was the wire that runs to the oil pressure sending unit.

Well he was incorrect to say that 10.9V on that wire engine not running was fine (for HEI), and incorrect to say that 12V when running is normal although it would be sufficient if it never dropped below 12V.

The yellow wire does come from the starter and provides a full 12V when cranking to the dist because it's designed for the points to be able to fire when cranking. It's only supposed to get 12V during cranking then it only gets whatever comes through the orange and purple wire. Read VetteVet's explanation and look at the schematic.
http://67-72chevytrucks.com/vboard/s...d.php?t=454737
http://67-72chevytrucks.com/vboard/a...1&d=1300860073

OK what I told you previously will not work because you did not tell me that you were running the choke and the dist off the same wire.

Get out your wiring tools and get to work. Go to the fuse block and remove the orange/purple wire and run the 12ga wire to the HEI. Go to the fuse block "ign unfused" spade and run 14ga wire from there to your choke.

[1972BlueC20]

Originally Posted by mechanicalman

Well he was incorrect to say that 10.9V on that wire engine not running was fine (for HEI), and incorrect to say that 12V when running is normal although it would be sufficient if it never dropped below 12V.

The yellow wire does come from the starter and provides a full 12V when cranking to the dist because it's designed for the points to be able to fire when cranking. It's only supposed to get 12V during cranking then it only gets whatever comes through the orange and purple wire. Read VetteVet's explanation and look at the schematic.
http://67-72chevytrucks.com/vboard/s...d.php?t=454737
http://67-72chevytrucks.com/vboard/a...1&d=1300860073

OK what I told you previously will not work because you did not tell me that you were running the choke and the dist off the same wire.

Get out your wiring tools and get to work. Go to the fuse block and remove the orange/purple wire and run the 12ga wire to the HEI. Go to the fuse block "ign unfused" spade and run 14ga wire from there to your choke.

Awesome man!!

My choke wire is either coming off a different place on dizzy or it kinda looks like the mechanic did sort of a t off from the yellow wire and then went from there to the choke then to the dizzy off the yellow feed.

Here are some pics!

The coiled up red wire is going to nothing currently....its ran to the fuse block....thats how I had my choke ran on my old engine....it was keyed 12v

[dirtyjim]

I can check it out this weekend. I have the correct Packard 56 terminals and crimper to run you a new wire from the firewall block to the disributor if it needs it

[1972BlueC20]

Originally Posted by dirtyjim

I can check it out this weekend. I have the correct Packard 56 terminals and crimper to run you a new wire from the firewall block to the disributor if it needs it

you're the man!!

[mechanicalman]

Originally Posted by 1972BlueC20

Awesome man!!

My choke wire is either coming off a different place on dizzy or it kinda looks like the mechanic did sort of a t off from the yellow wire and then went from there to the choke then to the dizzy off the yellow feed.

Here are some pics!

The coiled up red wire is going to nothing currently....its ran to the fuse block....thats how I had my choke ran on my old engine....it was keyed 12v

That coiled up red wire-is it 12ga? Bigger than the yellow wire? If so, save yourself some work and try it on the distributor and keep the yellow wire on the choke if it has 12V and works to your satisfaction.

HEY why is your vacuum advance not hooked up? That's one reason your mileage is down.

[1972BlueC20]

Originally Posted by mechanicalman

HEY why is your vacuum advance not hooked up? That's one reason your mileage is down.

This is from the instruction sheet that came with my crate engine :

"Set spark timing at 32º before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the
distributor disconnected and plugged. This setting will produce 32º of total advance at wide open throttle
(WOT). The HEI vacuum advance canister should remain disconnected. This engine is designed to
operate using only the internal centrifugal advance to achieve the correct timing curve."


The shop that did my install told me that they set the timing according to the instructions above.....I checked it the other day at idle and it's 12 BTDC.
I don't know how to check it at 4000 RPM so I only can verify the idle timing.

If I was to hook up the vacuum advance, what should the idle timing be if I want a total advance of 32 ?

[mechanicalman]

Originally Posted by 1972BlueC20

This is from the instruction sheet that came with my crate engine :

"Set spark timing at 32º before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the
distributor disconnected and plugged. This setting will produce 32º of total advance at wide open throttle
(WOT). The HEI vacuum advance canister should remain disconnected. This engine is designed to
operate using only the internal centrifugal advance to achieve the correct timing curve."


The shop that did my install told me that they set the timing according to the instructions above.....I checked it the other day at idle and it's 12 BTDC.
I don't know how to check it at 4000 RPM so I only can verify the idle timing.

If I was to hook up the vacuum advance, what should the idle timing be if I want a total advance of 32 ?

What they are saying is to leave the vacuum dis-connected for the procedure and that it has nothing to do with the mechanical timing curve, and it don't. Vacuum advance is for cruise and light load only and is not part of the "timing curve"; it's designed to maximize gas mileage and has no effect on the engine when under heavy throttle conditions. It's a confusing instruction and I wish they would re-word it.

Didn't you install the degreed balancer? If not, you would need timing tape or dial type timing light to check total timing.

Just use your timing light and rev it till it stops advancing and the light will flash on whatever number line on the balancer that aligns with the pointer zero mark. I'm pretty sure you ordered the degreed balancer but maybe I'm wrong. The instructions say to go to 4,000 because you will be all in by then just to avoid confusion, but you only need to go till it stops advancing and you need to know when it stops advancing as well. I'd like to see your distributor all in by 3,000 but I expect that dist is right for that engine.

Hook up your vacuum pod to "timed vacuum" (don't worry about the emissions thing this is what you want to do). It will not affect your idle timing. See the picture below.

[1972BlueC20]

Originally Posted by mechanicalman

What they are saying is to leave the vacuum dis-connected for the procedure and that it has nothing to do with the mechanical timing curve, and it don't. Vacuum advance is for cruise and light load only and is not part of the "timing curve"; it's designed to maximize gas mileage and has no effect on the engine when under heavy throttle conditions. It's a confusing instruction and I wish they would re-word it.

Didn't you install the degreed balancer? If not, you would need timing tape or dial type timing light to check total timing.

Just use your timing light and rev it till it stops advancing and the light will flash on whatever number line on the balancer that aligns with the pointer zero mark. I'm pretty sure you ordered the degreed balancer but maybe I'm wrong. The instructions say to go to 4,000 because you will be all in by then just to avoid confusion, but you only need to go till it stops advancing and you need to know when it stops advancing as well. I'd like to see your distributor all in by 3,000 but I expect that dist is right for that engine.

Hook up your vacuum pod to "timed vacuum" (don't worry about the emissions thing this is what you want to do). It will not affect your idle timing. See the picture below.

Cool deal. My balancer is a factory Gm pre installed unit. It's marked with etchings.

I have a cheaper timing light with no options. I also don't have a tachometer so I wouldn't know what rpm I'm at. All I could do is rev it till it stops advancing and I'd know what my total advance is.

So since my timing is 12 btdc now at idle....if I hooked up my vacuum advance, what wouild that do to my timing?

[mechanicalman]

Originally Posted by 1972BlueC20

Cool deal. My balancer is a factory Gm pre installed unit. It's marked with etchings.

I have a cheaper timing light with no options. I also don't have a tachometer so I wouldn't know what rpm I'm at. All I could do is rev it till it stops advancing and I'd know what my total advance is.

So since my timing is 12 btdc now at idle....if I hooked up my vacuum advance, what wouild that do to my timing?

It will have no effect on your idle timing if you hook it up to the "timed vacuum" port in the picture.

Vacuum advance NEVER has any effect on your timing curve or total mechanical advance setting.

"Timed" vacuum only activates after you start opening the throttle, and goes away under moderate and heavy load low vacuum conditions.

Vacuum advance is only for cruise and light load so you can get better gas mileage.

[1972BlueC20]

Originally Posted by mechanicalman

It will have no effect on your idle timing if you hook it up to the "timed vacuum" port in the picture.

Vacuum advance NEVER has any effect on your timing curve or total mechanical advance setting.

"Timed" vacuum only activates after you start opening the throttle, and goes away under moderate and heavy load low vacuum conditions.

Vacuum advance is only for cruise and light load so you can get better gas mileage.

Ok so I should hook it up and it won't change my timing at all on any condition? It should net me better mpg?

What does the vacuum advance do that causes better mpg?

Sorry for all the questions, just wanting to learn.

You have been a GIANT help btw....

[mechanicalman]

Originally Posted by 1972BlueC20

Ok so I should hook it up and it won't change my timing at all on any condition? It should net me better mpg?

What does the vacuum advance do that causes better mpg?

Sorry for all the questions, just wanting to learn.

You have been a GIANT help btw....

Base timing=idle timing, no mechanical advance yet, no vacuum advance.

Total timing=full mechanical advance, no vacuum advance.

Overall timing=mechanical advance + vacuum advance.

It adds to the mechanical advance timing on cruise and light load conditions only and that gives the fuel mixture more time to burn thus more complete burn thus less throttle needed thus better gas mileage.

It has no effect on the mechanical advance timing curve setting. It will add to the overall timing but only under light load and cruise conditions where vacuum is high.

Ideal overall timing for cruise efficiency for your engine would be 50'-55' but that's ONLY when full vacuum advance and full mechanical advance. AND you would have to be cruising at an RPM where you had full mechanical advance and that's rare unless you are geared low. They have adjustable vacuum pods that allow you to maximize how fast you get or lose vacuum advance to minimize ping and maximize mileage.

Nothing you do to your vacuum advance will affect how you set your base timing or total timing. Read this.
http://www.setyourtiming.com/timing_settings.html

[1972BlueC20]

Originally Posted by mechanicalman

Base timing=idle timing, no mechanical advance yet, no vacuum advance.

Total timing=full mechanical advance, no vacuum advance.

Overall timing=mechanical advance + vacuum advance.

It adds to the mechanical advance timing on cruise and light load conditions only and that gives the fuel mixture more time to burn thus more complete burn thus less throttle needed thus better gas mileage.

It has no effect on the mechanical advance timing curve setting. It will add to the overall timing but only under light load and cruise conditions where vacuum is high.

Ideal overall timing for cruise efficiency for your engine would be 50'-55' but that's ONLY when full vacuum advance and full mechanical advance. AND you would have to be cruising at an RPM where you had full mechanical advance and that's rare unless you are geared low. They have adjustable vacuum pods that allow you to maximize how fast you get or lose vacuum advance to minimize ping and maximize mileage.

Nothing you do to your vacuum advance will affect how you set your base timing or total timing. Read this.
http://www.setyourtiming.com/timing_settings.html

Sweet, thanks for the info!

I hooked up my vacuum advance on the timed port as you said....it may be my imagination, but it seemed to accelerate more smoothly slowly off the line and the transmission seems to shift a little softer on low throttle cruising...is that just my imagination?

I will be interested in seeing if my MPG gets better by the end of the week as I just re-fueled last night!!

Also, I was reading some other posts and people were saying to hook up the vacuum advance line to the non emissions port.....I keep getting conflicting advice on this.....what's the thinking behind using the one you said versus following the instructions from Edelbrock which to my understanding looks as if they are saying to hook it up to the right side since it's a non emissions C20 in my case.

Thanks in advance!

[1972BlueC20]

Ok I think i figured it out for myself by reading online and with your help, but i'll still wait for your chime in and tell me if i've learned this correctly.

So the reason you want to used ported or timed vacuum for the vacuum advance canister is because by using that port it will not effect your initial timing at idle. It will only kick in once the throttle blades open and only from that moment up until the vacuum drops away once a higher rpm is reached. Vacuum advance also will never affect your total timing because once the vacuum drops off the mechanical advance takes over.

Using manifold vacuum for the vacuum advance canister would increase the timing at idle because you would be getting a vacuum signal at idle with using that port.

You want to have extra timing coming into play while cruising at moderate to low RPM via using the vac advance on a timed port because more timing is needed to get an efficient burn at cruising speeds.

The only thing that effects the WOT total advance timing is the mechanical portion of the timing.

Am I correct?

[mechanicalman]

Originally Posted by 1972BlueC20

Ok I think i figured it out for myself by reading online and with your help, but i'll still wait for your chime in and tell me if i've learned this correctly.

So the reason you want to used ported or timed vacuum for the vacuum advance canister is because by using that port it will not effect your initial timing at idle. It will only kick in once the throttle blades open and only from that moment up until the vacuum drops away once a higher rpm is reached. Vacuum advance also will never affect your total timing because once the vacuum drops off the mechanical advance takes over.

You want to have extra timing coming into play while cruising at moderate to low RPM via using the vac advance on a timed port because more timing is needed to get an efficient burn at cruising speeds.

The only thing that effects the WOT total advance timing is the mechanical portion of the timing.

Am I correct?

Answer:

Mostly, vacuum advance is not very RPM sensitive, it's mostly load sensitive via vacuum signal. While accelerating, the engine has to "catch up" with itself, when MPH levels off regardless of RPM vacuum signal increases as the throttle blades close somewhat as compared to where they were while accelerating (loading the engine). It's hard to understand unless you have driven a car with a vacuum, or "gas mileage" gauge. To better understand visualize that the carburetor or throttle body butterfly needs to not be very far open to develop vacuum.

The only time you COULD develop usable vacuum at WOT would be if the carb or throttle body was too small for the engine.

The only time you would NOT develop usable vacuum at light and part throttle would be if the carb or throttle body was too big. That's why too oversized carbs don't work well, especially mechanical secondaries.

"Using manifold vacuum for the vacuum advance canister would increase the timing at idle because you would be getting a vacuum signal at idle with using that port".

True, but to expand on that realize that both the timed port and the manifold port EQUALIZE as soon as the throttle blades clear the timed port and that's really quick. I've heard some people say that the transition port affects this but trust me it does not, it's not associated with timed vacuum it's only for part throttle fuel enrichment.

So to sum that up the vacuum advance works exactly the same with timed vacuum and manifold vacuum except at idle. AND, the only thing you will achieve using manifold vacuum at idle is higher emissions, stinky tail-pipe and wasted fuel at idle. Having said that, I probably have started WWIII. But it's only sensible to realize when you go manifold vacuum, as I have tried, the idle speeds up and you have to close the throttle blades to restrict air, then the tailpipe emissions go up. 2+2=4. Wasting fuel, using less air thus less avail O2 to burn idle fuel.

"But they did it this way until 1966, and it was OK then" said the naysayer. It was OK to pollute the environment and waste fuel before 1966, according to the law anyway. Duh. LOL

You have had a tough time with people feeding you mis-information, like the old timer that told you 10.9 volts was OK for the HEI. I know you are critical of all information you receive, and you need be but it has made you a tough student for me.

But now I can see light at the end of this tunnel, LOL.

[1972BlueC20]

LOL....I feel like I'm really starting to understand things and it's a good feeling. My next classic vehicle will be much easier to deal with thanks to what I've learned.

So my truck definitely idles smoother,accelerates smoother and cruises smoother since I've hooked up the vacuum advance. Atleast it really feels like it.

I have another issue that's happened only a few times now. A few times when I went to shut off the truck, The engine wants to keep running for like a second. Almost unnoticeable and doesn't do it every time. Do you know what could be causing this?

[mechanicalman]

Originally Posted by 1972BlueC20

LOL....I feel like I'm really starting to understand things and it's a good feeling. My next classic vehicle will be much easier to deal with thanks to what I've learned.

So my truck definitely idles smoother,accelerates smoother and cruises smoother since I've hooked up the vacuum advance. Atleast it really feels like it.

I have another issue that's happened only a few times now. A few times when I went to shut off the truck, The engine wants to keep running for like a second. Almost unnoticeable and doesn't do it every time. Do you know what could be causing this?

You should see a mileage improvement at least with the vacuum advance.

After you shut it off, you mean, running like running normal, or "dieseling"?

What is your idle speed?

Did your engine come with spark plugs?

Can you relate this to how you manipulate the ignition key?

[1972BlueC20]

It's more of a stumble like...blup...blup....then it's completely off. It doesn't keep running like normal otherwise I'd think ignition switch.

Not sure on my exact idle speed since I don't have a tach but it seems about right the way it sounds and feels if that makes any sense.

As for turning the key. Just a normal quick turn to off.

[mechanicalman]

Originally Posted by 1972BlueC20

It's more of a stumble like...blup...blup....then it's completely off. It doesn't keep running like normal otherwise I'd think ignition switch.

Not sure on my exact idle speed since I don't have a tach but it seems about right the way it sounds and feels if that makes any sense.

As for turning the key. Just a normal quick turn to off.

Read this:
http://www.badasscars.com/index.cfm/...prod/prd94.htm

It's dieseling. You have to have air/fuel, and heat to ignite it to diesel. The air/fuel comes from the carb, the heat comes from the combustion chamber and/or carbon deposits. You usually have to cut down air to stop dieseling.

Are you running 91 octane? Is there old fuel left in there from before?
"Gasoline with a higher octane rating does not self-ignite easily". So, poor octane fuel self-ignites easier and diesels worse.
http://engineering.mit.edu/ask/what%...gular-gasoline

You can shut it off while still in gear, then go to park.

Try turning the idle speed down a small amount if it will tolerate that.

But in the end you may have to install one of these.
Idle Compensator KIt
Maintains correct idle speed when air conditioner is on. Includes 12-volt solenoid and mounting bracket for all Edelbrock square-bore carburetors. - 8059
You would turn your main idle screw down to about 500RPM, then use this to control your desired idle speed, then when you shut the engine off it would collapse and revert to the regular idle screw and not have enough air to diesel.
http://www.edelbrock.com/automotive/...-service.shtml

What spark plugs are you running? Wrong length thread plugs will cause carbon build-up and contribute to the problem, if not yet then surely in the future.

And last IN THIS CASE if you can stand the tailpipe stink, we may need to convert to manifold vacuum for the vacuum advance in order to close down the throttle blades (idle speed will increase with manifold vacuum and necessary to turn idle speed back down) and stop the dieseling.

[1972BlueC20]

Originally Posted by mechanicalman

Read this:
http://www.badasscars.com/index.cfm/...prod/prd94.htm

It's dieseling. You have to have air/fuel, and heat to ignite it to diesel. The air/fuel comes from the carb, the heat comes from the combustion chamber and/or carbon deposits. You usually have to cut down air to stop dieseling.

Are you running 91 octane? Is there old fuel left in there from before?
"Gasoline with a higher octane rating does not self-ignite easily". So, poor octane fuel self-ignites easier and diesels worse.
http://engineering.mit.edu/ask/what%...gular-gasoline

You can shut it off while still in gear, then go to park.

Try turning the idle speed down a small amount if it will tolerate that.

But in the end you may have to install one of these.
Idle Compensator KIt
Maintains correct idle speed when air conditioner is on. Includes 12-volt solenoid and mounting bracket for all Edelbrock square-bore carburetors. - 8059
You would turn your main idle screw down to about 500RPM, then use this to control your desired idle speed, then when you shut the engine off it would collapse and revert to the regular idle screw and not have enough air to diesel.
http://www.edelbrock.com/automotive/...-service.shtml

What spark plugs are you running? Wrong length thread plugs will cause carbon build-up and contribute to the problem, if not yet then surely in the future.

And last IN THIS CASE if you can stand the tailpipe stink, we may need to convert to manifold vacuum for the vacuum advance in order to close down the throttle blades (idle speed will increase with manifold vacuum and necessary to turn idle speed back down) and stop the dieseling.

Interesting!

Yes I'm running 91 octane since the engine instructions said it was required.

On second thought the idle speed did seem high. So I turned it down, and it hasn't done it again yet since. We shall see. I feel the idle could still come down, but my idle in gear would drop too low. Is there a way to adjust the in gear idle seperate from the park idle?

I really would like avoid changing to manifold vacuum advance if at all possible. I like the way it's running currently and it definitely seems to be running less rich. I'm hoping just messing with the idle will take care of it. And again, it only barely spuddered twice.

[1972BlueC20]

Oh and to answer your question regarding the spark plugs. They came with the engine and they are gapped as recommended in the instructions

R44LTS - .040 gap