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FF, thats a pretty well explained article. I don't see any reason that a man cannot apply the same thinking to a Ford ?:unsure: If I want to run manifold vacuum on a Ford, should I paint the valve covers orange ? Is that how the engines know whether to like full vacuum or not ? Maybe all of this is solveable with an orange can of paint !!:ROFLMAO: Many of us are not concerned with certification, but rather what works best in the here and now. LSG
 

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FF, thats a pretty well explained article. I don't see any reason that a man cannot apply the same thinking to a Ford ?:unsure: If I want to run manifold vacuum on a Ford, should I paint the valve covers orange ? Is that how the engines know whether to like full vacuum or not ? Maybe all of this is solveable with an orange can of paint !!:ROFLMAO: Many of us are not concerned with certification, but rather what works best in the here and now. LSG
LS Guy, that sure was a long road of you following my tail lights to say I was not mistaken.
 

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Ford spark valve, load o matic, DVCV and more use manifold vacuum and ported vacuum, making the GM method not valid for Ford. There is no Ford engine certification that uses that GM strategy. Ported vs. Manifold Vacuum
The Load-O-Matic/SCV system does NOT use "ported vacuum" (static vacuum above the throttle plate). The SCV "modulates" a vacuum signal generated by manifold vacuum and VENTURI vacuum (generated the velocity of the air as it passes through the venturi) to provide a vacuum signal to the advance diaphragm that varies between zero and approximately 4"hg. This allows the distributor vacuum system, alone, to control spark advance based on engine load (throttle opening) and engine speed (intake velocity).
 

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Because the carb is a SCV carb a few suggested that I run the distro vacuum line to the manifold vacuum port not the carb's port.
So after all this. Tom991. What is your outcome?
 

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The Load-O-Matic/SCV system does NOT use "ported vacuum" (static vacuum above the throttle plate). The SCV "modulates" a vacuum signal generated by manifold vacuum and VENTURI vacuum (generated the velocity of the air as it passes through the venturi) to provide a vacuum signal to the advance diaphragm that varies between zero and approximately 4"hg. This allows the distributor vacuum system, alone, to control spark advance based on engine load (throttle opening) and engine speed (intake velocity).
You are correct. The "port" is still above the throttle plate. Anything below the throttle is manifold. The engine is a air pump and there are several low pressure zones on the way to the piston. We can argue that forever.
Look, the OP had a 65 Mustang with six cyl and a 1976 system. My intent was to inform him about his question, not to tell him what he should do.
When Chevy artists start telling me I am mistaken when they are wrong, I will defend my position with proof, end of story.
 

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Earlier in this thread I said I would try changing from ported to manifold vacuum on the distributor advance. So three months later I finally got around to trying it.
Car is a '67 with completely stock 289 with about 2000 miles on engine. Distributor is stock and vacuum advance does function properly. Base timing is at 10 degrees. No over heating problems.
With manifold vacuum the idle obviously raised so I backed it off a bit. Took it for a drive and put it thru many different levels of acceleration. There was no pinging.
My take on it - I just didn't feel any seat of the pants difference. Matter of fact when I changed it back to ported I think it had just a bit more pep off idle to mid throttle. Or maybe I was just imaging it. Either way a stock 289 with auto won't be roasting the tires anyway. FWIW I didn't do any tweaking on the advance adjusting screw.
I'm not trying to discourage anyone from trying the change, just the opposite, give it a try. Things like this intrigue this gear head and I enjoy tinkering and I'm always open to new ideas.

PS- I definitely am not trying to re ignite the p***ing match from earlier in thread!
 

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Unfortunately what you did by changing from ported to manifold vacuum does nothing and proves nothing if it wasn’t done with tuning specific to that modification.
 

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I have a Holley 1940 non SCV carburetor and a distributor for a 68 on my 200. I went through having the distributor curved by Mustang Barn and the engine ran well. I switched to manifold vacuum and it really woke up the engine. Much smoother idle and great throttle response. Timing is set to factory specs of 12 BTDC. Only adjustment I did was idle speed.

For me, it works great!
 
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I agree that ported vacuum was for emissions. Distributor currently has 15 advance, 34 total, light springs so the mechanical comes in fast. I've found a lot of initial helps to eliminate low rpm bog. This setup has worked well for my big block, 347 small block and stock 351C 4V all with fairly mild cams. I use intake manifold vacuum. Has about 35 degrees at idle. Works really, really well. I've also run no advance at all with the above distributor setup and it worked fine also. Back in the day I tried 15 initial on a stock 302 (factory said 6) and it didn't help at all - just detonation. I don't know why it works so well now - maybe the gasoline.
 

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You will simply need to drive it both ways and explain to the wife what you are doing and let her drive it both ways
You can see which way the drivability is the bestmostly
The above posts are correct.
That said straight sixes never ran that good even on fuel made (formulated) for carburetors
So over the years Ford did it both ways and added wax valves PVS and delay valves Et al. to the circuit
I would find a delay valve and try manifold first
I would also run it thru a PVS or TVS so it does not hit until the engine is warm
Real hard to find those kind of parts these days
 

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Earlier in this thread I said I would try changing from ported to manifold vacuum on the distributor advance. So three months later I finally got around to trying it.
Car is a '67 with completely stock 289 with about 2000 miles on engine. Distributor is stock and vacuum advance does function properly. Base timing is at 10 degrees. No over heating problems.
With manifold vacuum the idle obviously raised so I backed it off a bit. Took it for a drive and put it thru many different levels of acceleration. There was no pinging.
My take on it - I just didn't feel any seat of the pants difference. Matter of fact when I changed it back to ported I think it had just a bit more pep off idle to mid throttle. Or maybe I was just imaging it. Either way a stock 289 with auto won't be roasting the tires anyway. FWIW I didn't do any tweaking on the advance adjusting screw.
I'm not trying to discourage anyone from trying the change, just the opposite, give it a try. Things like this intrigue this gear head and I enjoy tinkering and I'm always open to new ideas.

PS- I definitely am not trying to re ignite the p***ing match from earlier in thread!
What you'll find, from the change to full manifold vacuum, is the need to modify the mechanical advance curve slightly by reducing the initial static timing a bit while extending the total amount of mechanical advance back to where it was before the static timing was retarded. In other words, if your static timing was 12* and total was 36* above 2,500 rpm, and you reduce the initial static timing to 6*, you'll want to extend the mechanical advance from 12 distributor degrees to 15 distributor degrees so you'll add 30* versus 24* to attain a total advance of 36*. From there, you'll tailor the vacuum advance curve as needed to prevent an excess of spark advance at light throttle transitions, when vacuum is higher, that can produce a "ping". A REALLY anal engine builder can further tailor the vacuum advance by relocating the pin where the vacuum advance lever attaches to the breaker plate in or out from the distributor shaft to accelerate or decelerate the rate of vacuum advance.
 

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With manifold vacuum the idle obviously raised so I backed it off a bit. Took it for a drive and put it thru many different levels of acceleration. There was no pinging.
My take on it - I just didn't feel any seat of the pants difference.
What did you back off? The timing or curb idle? You say you found a difference so you weren't completely out of whack but some with the curb idle too high in the first place wont see a difference.
Just like a few degrees of timing, advance spring or weights or a carb jet there are no absolutes in this area. Factory, dead on specs aren't a;ways the absolute.
For mine, now, ported is the "best" because I like to be able to idle >600rpm with the curb idle just ever so minutely pushing the throttle blades. If it was "only because" of for emissions reduction I see it as a bonus.
 
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