Help with Edelbrock 1406 install

[jtinpdx]

Hi All,
I have the 350 HO Turn Key crate engine from GM. It came with a Holley carb that was installed by the shop. I switched it out to an Edelbrock but I'm not sure I have the vacuum lines set up properly. The engine came with an HEI distributor, which I can't find the part number for so I don't know what advance that's configured with.

I currently have a vaccum line from the transmission going into the left side vacuum port on the Edelbrock. That might be wrong. And I have the front central port connected to the brake booster. That's right I think.

But the Holley had a hose running from the manifold. I have that currently plugged. Truck runs now. Not sure it's running optimally. Please see pics below. Any help would be much appreciated!

Thanks,
Jeff

[YoungPup1977]

Transmission modulator would need full manifold vacuum, it does not look from the placement of the hose for the trans its not getting full manifold vacuum... its above the throttle plate which would be ported vacuum. Just my guess....

[rharris]

Transmission line should have manifold vacuum. The left side of carb (small) is for timed vacuum advance on distributor. Back of carb or manifold T for brake booster. Front of carb big port for PCV. I put a 3 port fitting in the rear of the manifold for transmission, power brakes, and vacuum gauge.

[Wrenchbender Ret]

There is an outlet in the manifold in back of the carb that is generally used for the power brake & trans. modulator. with the proper fitting. Like the guys say, that is the wrong place for a trans. mod.
George

[truckster]

Your PCV needs to be connected to the large port in the front of the carb. Vacuum boost for the brake and the vacuum modulator for the transmission should be hooked up to full manifold vacuum - usually a port in the manifold directly behind the carb. Make sure there's a check valve between the manifold and your brake booster.

As for the vacuum advance - ported vacuum (Edelbrock calls it "timed vacuum") was an early component of emissions control. The purpose behind it was to retard the spark at idle so the fuel/air mixture would be burning as it exited the exhaust ports. That was intended to increase exhaust temperature to burn off more hydrocarbons, but all it really accomplishes is burning excess fuel. Do yourself a favor and block off the ported vacuum and connect your vacuum advance to manifold vacuum. You'll get quicker response and better fuel economy.

[AcampoDave]

Originally Posted by truckster

Your PCV needs to be connected to the large port in the front of the carb. Vacuum boost for the brake and the vacuum modulator for the transmission should be hooked up to full manifold vacuum - usually a port in the manifold directly behind the carb. Make sure there's a check valve between the manifold and your brake booster.

As for the vacuum advance - ported vacuum (Edelbrock calls it "timed vacuum") was an early component of emissions control. The purpose behind it was to retard the spark at idle so the fuel/air mixture would be burning as it exited the exhaust ports. That was intended to increase exhaust temperature to burn off more hydrocarbons, but all it really accomplishes is burning excess fuel. Do yourself a favor and block off the ported vacuum and connect your vacuum advance to manifold vacuum. You'll get quicker response and better fuel economy.

I don't necessarily disagree with this advice about the advance port, but when i tried it my enginge "loaded up" in heavy traffic so I switched it back.

[jtinpdx]

Thanks All. Much appreciated. I'll look for the right fitting for the back of the carb and set it up that way.

-Jeff

[rharris]

Originally Posted by jtinpdx

Thanks All. Much appreciated. I'll look for the right fitting for the back of the carb and set it up that way.

-Jeff

I used this on the manifold behind the carb. 3/8” npt, 3/8” barb and 1/4” barb for the power brakes and transmission line.

[jtinpdx]

Originally Posted by rharris

I used this on the manifold behind the carb. 3/8” npt, 3/8” barb and 1/4” barb for the power brakes and transmission line.

Just bought from Summit. Thanks!

[jtinpdx]

Originally Posted by rharris

I used this on the manifold behind the carb. 3/8” npt, 3/8” barb and 1/4” barb for the power brakes and transmission line.

I got this in the mail and have installed it. I have the trans modulator and the brake booster running to it. I'll send new pics when I get a chance.

[68 P.O.S.]

Originally Posted by AcampoDave

I don't necessarily disagree with this advice about the advance port, but when i tried it my enginge "loaded up" in heavy traffic so I switched it back.

It probably loaded up because you only switched the hose and had too many degrees of advance in the vac can. The vac advance needs to be restricted to 10-15 degrees for manifold vacuum, depending on your engine.

[68 P.O.S.]

Originally Posted by truckster

As for the vacuum advance - ported vacuum (Edelbrock calls it "timed vacuum") was an early component of emissions control. The purpose behind it was to retard the spark at idle so the fuel/air mixture would be burning as it exited the exhaust ports. That was intended to increase exhaust temperature to burn off more hydrocarbons, but all it really accomplishes is burning excess fuel. Do yourself a favor and block off the ported vacuum and connect your vacuum advance to manifold vacuum. You'll get quicker response and better fuel economy.

This^^^ I couldn't agree more

[geezer#99]

Your pcv valve is normally on the drivers side with a breather on the passenger side. You might want to fix that up too.

[jtinpdx]

Originally Posted by geezer#99

Your pcv valve is normally on the drivers side with a breather on the passenger side. You might want to fix that up too.

Will do. Thanks.

[Dead Parrot]

Lots of threads on manifold vs timed for the vacuum advance. End results seem to be that most motors like manifold but some prefer timed. Sounds like yours might be in the timed column. Once you get everything dialed in better, might be worth a retry on the timed vs manifold ports.

If you have the vacuum operated doors for your climate system, it will need a manifold source as well. Usual place is the manifold port behind the carb.

If you are planning on using a OEM type cleaner cover, it might interfere with the fuel inlet. Mine did. Fix was switching to a banjo fuel inlet.

[jtinpdx]

Originally Posted by Dead Parrot

Lots of threads on manifold vs timed for the vacuum advance. End results seem to be that most motors like manifold but some prefer timed. Sounds like yours might be in the timed column. Once you get everything dialed in better, might be worth a retry on the timed vs manifold ports.

If you have the vacuum operated doors for your climate system, it will need a manifold source as well. Usual place is the manifold port behind the carb.

If you are planning on using a OEM type cleaner cover, it might interfere with the fuel inlet. Mine did. Fix was switching to a banjo fuel inlet.

In terms of advance, the vacuum advance port was already capped off at the distributor. Stock GM distributor. Is that also wrong?

[jtinpdx]

Originally Posted by Dead Parrot

If you are planning on using a OEM type cleaner cover, it might interfere with the fuel inlet. Mine did. Fix was switching to a banjo fuel inlet.

Yep, have the banjo and a gauge on it. Still a tight fit but works. Pic later in the thread. Thanks!

-Jeff

[Tom]

Wrong compared to stock sure. You don't have a stock setup. Whats the timing like in the distributor?
Also, why switch the carbs to begin with?

[jtinpdx]

Originally Posted by Tom

Wrong compared to stock sure. You don't have a stock setup. Whats the timing like in the distributor?
Also, why switch the carbs to begin with?

That's part of the issue. I can't find a part number or any specs on the distributor. It came as part of the GM Performance 350 HO Deluxe Turn Key package. Think it should be vacuum advance connected to the vacuum advance port on the carb (or manifold behind the carb, but those are now spoken for with the brake booster and transmission modulator)?

[rharris]

Originally Posted by jtinpdx

That's part of the issue. I can't find a part number or any specs on the distributor. It came as part of the GM Performance 350 HO Deluxe Turn Key package. Think it should be vacuum advance connected to the vacuum advance port on the carb (or manifold behind the carb, but those are now spoken for with the brake booster and transmission modulator)?

Correct. I’d use the drivers side port on front of carb (non-timed) for distributor.

[jtinpdx]

Originally Posted by Tom

Wrong compared to stock sure. You don't have a stock setup. Whats the timing like in the distributor?
Also, why switch the carbs to begin with?

Switched carbs because I had a freshly rebuilt Edelbrock in the garage along with a gauge and regulator ready to go. And the Holley that it came with always ran poorly. But maybe for some of the reasons we're finding now. The guys that set it up could never get it right. It had a monumental stall when you hit the gas pedal.

[rharris]

Good engine by the way. looks like the same one I had in my 71 GMC. should be about 330HP if memory serves me correctly

[jtinpdx]

Originally Posted by rharris

Good engine by the way. looks like the same one I had in my 71 GMC. should be about 330HP if memory serves me correctly

Yessir. Or should do after I get the carb set up.

[Tom]

First I would check initial timing with a timing light. If its high, go with ported vaccum to start. If its low go with manifold to start. Just T one of your current lines. If it doesn't feel great then switch to the other port and see what happens.

[Dead Parrot]

Hook the vacuum advance to one of the two small ports on the front of the carb, that is what they are for.

Once you have things properly connected and the engine runs decent, fairly easy to get a rough idea of the distributor setup. You will need a tach, borrowed is fine.

For testing, set initial timing to zero, with vacuum advance disconnected and port plugged and idle set slow. Then connect the dizzy to the manifold vacuum port. Motor should speed up and timing advance. Read the advance. That will be your vacuum advance. Disconnect the dizzy and plug the port.

With the initial timing still at zero, slowly feed in more throttle. At some point, your timing will start to increase. Note the RPM. Keep adding throttle until advance quits increasing. Note this RPM. You now know when your mechanical starts to come in and when it is all in.

Reset your initial timing back to what the motor really wants and reconnect the dizzy to whatever port your motor likes best.