[murph3204]

I'm in the process of finishing up a 69 400 and I need some assistance. I have an auto car that's being converted to a 4 speed car and have a question regarding the manifold vacuum switch and how it would hook up to an HEI distributor. I have a stock points distributor that I want to replace with an HEI. The vacuum hose kit for the 4 speed has two lines that hook up to either side of the stock 2-port vacuum advance on the points distributor. The HEI distributor only has one port on the vacuum advance. How do I match up the 2 switch lines to the single line HEI?

[LATECH]

Cant tell much from the picture.Pretty grainy.
Just use a ported source from the base of the carb.Dont run manifold vacuum to the distributor advance. I am sure there will be someone who chimes in and says just the opposite.
Reason you want ported is you want vacuum at part throttle to help with mileage at cruise rpm (and it improves power for pulling hills).If you run manifold vacuum, as soon as the motor turns vacuum is made and the timing advances, making it hard to start.
Your distributor should have mechanical advance of about 20 degrees (allin by around 3000) and the base timing should be around 12-14. Giving a rough total timing of 32 degrees.
Having a ported source will give you more timing at cruise rpm when mixtures are lean and you aren't looking to make full power, helping the already lean mixture by igniting it ealier to give it more lead time to burn.
Cruise rpm is roughly between 2250 and 2600 rpm.The mechanical advance wont be "all in" by then and the small amount the vacuum will pullin (around 5-7 degrees) is where you want to be.
I have a 9.5 to one389 (punched to 400) .My distributor is set at 14 degrees intial, has 20 degrees mechanical and 8 degrees vacuum advance at 7 inches Hg. It is flawless . When I come to a hill (mountain here in Pa) I don't have to press the gas , she just goes.

[murph3204]

Thanks for the valuable info. Basically my points distributor has two vacuum ports. My HEI has only one. What do I do?

[Will]

Don't worry about it. Hook the one vacuum port on your HEI to a ported vacuum source on the carb and go drive the snot out of it.

The whole ported vs. manifold vacuum thing has been beaten to a juicy pulp of fetid horseflesh, dried under a raging sun of controversy, ground to a fine powder by the millstone of internet bluster, and finally used to powder the bellybuttons of differing opinions.

I like ported vacuum and have always used it on my street cars because I find doing it that way produces a more stable idle and makes tuning the advance curve easier, especially on an HEI that generally has a fairly limited range of advance. YMMV. Try manifold vacuum if it floats your boat. Either way you don't need two different vacuum sources.

[dmac]

Two vacuum connectors at distributor? Hook one to source from carb, probably whichever is physically closer to the carb/intakes Plug the other. When setting initial timing, disconnect and plug line to carb.

What year is the distributor?

[Cliff R]

If you are replacing a stock points distributor with an HEI, it will need FULL voltage, not reduced voltage thru a resistor or resistor wire like the points unit.

In most cases an HEI will also need to have the advance curve adjusted, and less timing applied by the vacuum unit. Most HEI's will provide WAY too much advance for older higher compression engines, and too much additional timing via the vacuum unit. At a minimum I would have it set up like the points unit, or custom tuned for exactly what you are doing by someone who knows what they are doing.

As for the dual-vacuum advance thing, it is not used on the HEI, or needed. No mention of what carb is being used, but if the stock 1969 Q-jet is still in service it has a dedicated vacuum port for the distributor, and it will be ported vacuum to the advance. The source location on the factory carb is precisely located to apply FULL manifold vacuum to the distributor right off idle, so you will enjoy all the benefits of FULL manifold vacuum to the distributor at light throttle cruising for best engine efficiency, and no additional timing applied when coasting or at idle.

That is the way those engines were set up, as they do not want or need any additional timing at idle if it is a "stock" engine or still sports a decent compression ratio and well chosen camshaft......Cliff

[rohrt]

The TVS is purely for emissions. I know that the 68 bird had a push pull vacuum can didn't realize the 69 did too. I thought it was eliminated then. Going by memory here; If I remember right the TVS doesn't open until 210 deg. It was to help lower emission at idle by retarding the timing which heated up the engine. Then the TVS would switch and advance the timing and allow it to cool back down. Someone correct me if I'm wrong here but that was how I remember it. There is more info in the 67-69 FB archives on the TVS.

If your wanting to keep a stock look you can still use it. May need to do some testing and plug one of the hoses. I think on mine I swapped a couple of lines.

[murph3204]

Originally Posted by rohrt

The TVS is purely for emissions. I know that the 68 bird had a push pull vacuum can didn't realize the 69 did too. I thought it was eliminated then. Going by memory here; If I remember right the TVS doesn't open until 210 deg. It was to help lower emission at idle by retarding the timing which heated up the engine. Then the TVS would switch and advance the timing and allow it to cool back down. Someone correct me if I'm wrong here but that was how I remember it. There is more info in the 67-69 FB archives on the TVS.

If your wanting to keep a stock look you can still use it. May need to do some testing and plug one of the hoses. I think on mine I swapped a couple of lines.

Sounds like I can eliminate the TVS system along with the vacuum switch located near the thermostat, plug the hole where tha vacuum switch was and run the vacuum source for the HEI from a ported source on the carb?

[rohrt]

Originally Posted by murph3204

Sounds like I can eliminate the TVS system along with the vacuum switch located near the thermostat, plug the hole where tha vacuum switch was and run the vacuum source for the HEI from a ported source on the carb?

Many people do this. Only reason to keep it is if you going for that stock look.

[steve25]

Murph, while your wiring up the new flame thrower I would also wire in a 15 amp toggle switch under the dash somewhere.
These come in handy should the internals in the distributor get stuck as they sometimes do in the above idle advance position or when you yourself have put in too much timing,which will make a hot motor near impossible to restart.
Having the switch will let you get the motor cranking over and then you can flip on the spark.
It also makes a nice anti thieft guard if you hide the switch under the dash.
A buddy of mine put one in his Cuda some years ago due to where he parks this car when he takes it to work, then one day when he did not take the car to work he comes home and then wants to take it for a drive.
He finds it will mot start and is reaking of gas smell. Come to find out his 15 year old son had gotten hold of his spare set of keys and was going to take it for a joy ride, of course his son did not know of the ignition kill switch installed 3 days before! Lol

[murph3204]

Originally Posted by steve25

Murph, while your wiring up the new flame thrower I would also wire in a 15 amp toggle switch under the dash somewhere.
These come in handy should the internals in the distributor get stuck as they sometimes do in the above idle advance position or when you yourself have put in too much timing,which will make a hot motor near impossible to restart.
Having the switch will let you get the motor cranking over and then you can flip on the spark.
It also makes a nice anti thieft guard if you hide the switch under the dash.
A buddy of mine put one in his Cuda some years ago due to where he parks this car when he takes it to work, then one day when he did not take the car to work he comes home and then wants to take it for a drive.
He finds it will mot start and is reaking of gas smell. Come to find out his 15 year old son had gotten hold of his spare set of keys and was going to take it for a joy ride, of course his son did not know of the ignition kill switch installed 3 days before! Lol

Good idea Steve.

[murph3204]

Originally Posted by Cliff R

If you are replacing a stock points distributor with an HEI, it will need FULL voltage, not reduced voltage thru a resistor or resistor wire like the points unit.

In most cases an HEI will also need to have the advance curve adjusted, and less timing applied by the vacuum unit. Most HEI's will provide WAY too much advance for older higher compression engines, and too much additional timing via the vacuum unit. At a minimum I would have it set up like the points unit, or custom tuned for exactly what you are doing by someone who knows what they are doing.

As for the dual-vacuum advance thing, it is not used on the HEI, or needed. No mention of what carb is being used, but if the stock 1969 Q-jet is still in service it has a dedicated vacuum port for the distributor, and it will be ported vacuum to the advance. The source location on the factory carb is precisely located to apply FULL manifold vacuum to the distributor right off idle, so you will enjoy all the benefits of FULL manifold vacuum to the distributor at light throttle cruising for best engine efficiency, and no additional timing applied when coasting or at idle.

That is the way those engines were set up, as they do not want or need any additional timing at idle if it is a "stock" engine or still sports a decent compression ratio and well chosen camshaft......Cliff

Cliff, the carb is a #7042251. I've got your book and disassembled the carb but that's as far as i've gotten. It's a 69 400 +.030, zero decked, stock intake, #16 non-ported heads, 2802 cam. lobe separation is at 112 with ICL @109. According to my calculations, the CR should be around 10.5