Edelbrock conversion

[richnan]

Also posed this on tech. page ....

Hi
Am putting a 1403 edelbrock on my 62 289.. Need to know which side to put the dist. vacuum line on.. I should have checked whether i have full vac at idle or at timed vacuum advance..Also any suggestions for a good spot for the choke wire hookup...
Thanks Dick

silver hawk

[Mike Van Veghten]

You can do it either way.

Mounting above the butterflies will give you "ported" vacuum, and below the butterflies will give you OEM (full) vacuum.

Each one has benefits and drawbacks. Just as "no" vacuum does. All three require slightly different tuning...overall timing wise.

My thought to you is...try both ported and non-ported, see which you like best for your type of driving.

Sorry this isn't a "do it this way" answer.
To get the most of your car and the way you drive...try'em both. Even with no vacuum works. Again...each requires a different tuning method. I currently do not use the vacuum side of the advance mechanism on my 259 powered Lark.

Mike

[Mike Van Veghten]

You can do it either way.

Mounting above the butterflies will give you "ported" vacuum, and below the butterflies will give you OEM (full) vacuum.

Each one has benefits and drawbacks. Just as "no" vacuum does. All three require slightly different tuning...overall timing wise.

My thought to you is...try both ported and non-ported, see which you like best for your type of driving.

Sorry this isn't a "do it this way" answer.
To get the most of your car and the way you drive...try'em both. Even with no vacuum works. Again...each requires a different tuning method. I currently do not use the vacuum side of the advance mechanism on my 259 powered Lark.

Mike

[Guest]

Mike

I was wondering if I could get you to dive a bit deeper into your response. Why do you run no vac on your Lark? What is the advantage/disadvantage? Also, the same with timed and untimed port use.
Thanks



Randy Wakefield

1955 President

"For the future that we wait..."

[Guest]

Mike

I was wondering if I could get you to dive a bit deeper into your response. Why do you run no vac on your Lark? What is the advantage/disadvantage? Also, the same with timed and untimed port use.
Thanks



Randy Wakefield

1955 President

"For the future that we wait..."

[bige]

I would also be interested in that reasoning...once the throttle is opened then both ports are subject to the same vacuum. Full vacuum at idle could result in increased hydrocarbon emissions and difficulty in setting curb idle properly. No vacuum advance and cruise mileage and tip in response could suffer unless static is set very high or distributor is custom curved; even then I don't think it would accomplish what a properly working vacuum advance would do.

ErnieR

quote:Originally posted by 55pres

Mike

I was wondering if I could get you to dive a bit deeper into your response. Why do you run no vac on your Lark? What is the advantage/disadvantage? Also, the same with timed and untimed port use.
Thanks



Randy Wakefield

1955 President

"For the future that we wait..."

[bige]

I would also be interested in that reasoning...once the throttle is opened then both ports are subject to the same vacuum. Full vacuum at idle could result in increased hydrocarbon emissions and difficulty in setting curb idle properly. No vacuum advance and cruise mileage and tip in response could suffer unless static is set very high or distributor is custom curved; even then I don't think it would accomplish what a properly working vacuum advance would do.

ErnieR

quote:Originally posted by 55pres

Mike

I was wondering if I could get you to dive a bit deeper into your response. Why do you run no vac on your Lark? What is the advantage/disadvantage? Also, the same with timed and untimed port use.
Thanks



Randy Wakefield

1955 President

"For the future that we wait..."

[richnan]

Thanks Much Too All For The Info ..... Dick

silver hawk

[richnan]

Thanks Much Too All For The Info ..... Dick

silver hawk

[Mike Van Veghten]

I'll try to keep this short and not too boring...

Full vacuum - The highest "normal" vacuum reading will be at idle. Then at flat land (no up or down hill) cruise speeds. The "highest overall" reading will be going down hill and the throttle closed or partially closed. The lowest reading will be at full throttle...untill the engine speed catches up with the throttle opening...or as you get to the speed you want to achieve.

Ported vacuum - Is almost the exact opposite of full vacuum. With the engine at idle, there will be almost "no" vacuum at the port in the carburetor. As the throttle is depressed, the differance in the vacuum above and below the throttle blades is the greatest, therefore, the vacuum goes up when the pedal is pushed and slowly comes back down to a low value at cruse speeds. Ported Vacuum is a little more sensitive to cam and carburetor size thAn the full vacuum is...not a lot small amount.

No vacuum - All of the timing is controlled with the mechanical advance only. So the initial advance must be altered and the mechanical (sprung wieghts) must match the desired control.

The "ported" (above the throttle blades) came about during the late 70's early 80's..smog years. This is because the timing is controled slightly different, it (the timing) goes "up" when the power is desired, vs. full vacuum, the timing goes "down" when the throttle is pressed...but comes back up during cruise mode...bad for NOX emissions. The full vacuum provides it's highest vacuum at cruise speeds and drops during acceleration, where the ported provides its highest readings during acceleration then backs down during cruise speeds.

As I noted in my first post...all three have good and bad in them. If you live in a mountain or hilly area...maybe the ported would work the best. More flat driving might like full or no vacuum better.
The three different methods require different initial timing requirements. For the "BEST" results...only you and your car can come up with that final method.
Many people will say...well mine works best with...do it this way or do it that way. There IS NO SINGLE BEST WAY of getting the best performance from your timing/engine system. It all works as a package deal. From the car, to the way you drive, to the landscape you drive in...it's a package you need to finish to satisfy both you and the engine driving the car.

Hope this hasn't been too hard to follow and somewhat helpfull.

Mike

[Mike Van Veghten]

I'll try to keep this short and not too boring...

Full vacuum - The highest "normal" vacuum reading will be at idle. Then at flat land (no up or down hill) cruise speeds. The "highest overall" reading will be going down hill and the throttle closed or partially closed. The lowest reading will be at full throttle...untill the engine speed catches up with the throttle opening...or as you get to the speed you want to achieve.

Ported vacuum - Is almost the exact opposite of full vacuum. With the engine at idle, there will be almost "no" vacuum at the port in the carburetor. As the throttle is depressed, the differance in the vacuum above and below the throttle blades is the greatest, therefore, the vacuum goes up when the pedal is pushed and slowly comes back down to a low value at cruse speeds. Ported Vacuum is a little more sensitive to cam and carburetor size thAn the full vacuum is...not a lot small amount.

No vacuum - All of the timing is controlled with the mechanical advance only. So the initial advance must be altered and the mechanical (sprung wieghts) must match the desired control.

The "ported" (above the throttle blades) came about during the late 70's early 80's..smog years. This is because the timing is controled slightly different, it (the timing) goes "up" when the power is desired, vs. full vacuum, the timing goes "down" when the throttle is pressed...but comes back up during cruise mode...bad for NOX emissions. The full vacuum provides it's highest vacuum at cruise speeds and drops during acceleration, where the ported provides its highest readings during acceleration then backs down during cruise speeds.

As I noted in my first post...all three have good and bad in them. If you live in a mountain or hilly area...maybe the ported would work the best. More flat driving might like full or no vacuum better.
The three different methods require different initial timing requirements. For the "BEST" results...only you and your car can come up with that final method.
Many people will say...well mine works best with...do it this way or do it that way. There IS NO SINGLE BEST WAY of getting the best performance from your timing/engine system. It all works as a package deal. From the car, to the way you drive, to the landscape you drive in...it's a package you need to finish to satisfy both you and the engine driving the car.

Hope this hasn't been too hard to follow and somewhat helpfull.

Mike