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

[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.

[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 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.

[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!

[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?

[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?

[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 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)?

[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.

[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]

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.

[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.

[Andy4639]

Here is my new Elderbrock on my 64 Impala. It runs great after tuning it. Right port is power glide vacuum module. Center is PVC valve and left is vacuum advance on distributor. Vacuum for the brakes is in back.

[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

[68 P.O.S.]

First of all, it’s not as easy as slapping the carb on there and cruising. Job number one is to verify the timing. If your timing isn’t correct right off the bat, nothing else will be correct either and you’ll be chasing your tail. That engine has vortec heads, so your timing number is 32 degrees total timing. That distributor has springs in it that allow the full advance of 32 degrees at 4000 rpm, which is too high for a daily driver. You want the full advance to fall between 2500-3000 rpm. Get the spring kit from Crane Cams and use 1 blue spring and 1 silver spring, and that will allow full advance at about ~2700 rpm. Everything else about that distributor is perfect for that engine, just take the blue cap off of the vacuum advance canister so it will function. Easiest way to set your total timing is to pull the springs out of the distributor (be careful, don’t lose ‘em) and just rev it to around 1500 rpm and set timing for 32 degrees. Without the springs, the weights will swing out fully at low rpm, so you won’t have to run it at 4000 rpm with your head under the hood lol. After the timing is advanced to 32 degrees total, put the springs back in and you can move on to the carb.

There’s 3 things you need to buy when installing an Edelbrock carb. First thing is either a fuel pressure regulator set to 5.5 psi or a fuel pump that produces 6 psi max. (like the Edelbrock fuel pump). Edelbrock carbs flood with any more fuel pressure than that. Also, adjust your float levels to the specs in the instructions, or they will make the carb flood as well. The floats are never set correctly out of the box due to shipping and handling. Secondly, you need a heat insulating gasket between the carb and intake, like the Edelbrock 9266. Edelbrock carbs are notorious for percolating fuel after engine shut down, which causes hard starting issues. A heat insulating gasket will cure that. Third, you need the Edelbrock 1487 calibration kit to properly select the best rods, jets, step-up springs, etc. for your engine.

Once the engine is timed correctly, pull the carb off and the transition slots need to be adjusted next. Here's a link to a great thread from Gregski that shows the transition slots: http://67-72chevytrucks.com/vboard/s...=713728&page=2. He begins to talk about it on post 37 and the following posts. The whole thread is worth a read, especially if you decide to go back to the Holley. After the slots are correctly adjusted, do not really use the idle adjustment screw anymore, as that will undo the work you just did. Slap the carb back on and set the idle mixture screws, with a vac gauge, for highest rpm. Ensure the vacuum advance and vacuum gauge are plugged into manifold vacuum when you do this. Turning the screws clockwise leans the mixture, turning counter clockwise richens it. Turn the screws all the way clockwise to bottomed out, then back out 1.5 turns, and start from there. Here’s a good video from Jegs outlining the setup: https://www.youtube.com/watch?v=wR_AfQjyT-A&t=3s.

As everyone else has pretty much said, and as shown by rharris’ picture, the back of the intake needs a connector with 2 or 3 ports on it to supply manifold vac. The trans modulator needs to be connected to that. The brake booster connects to the rear port on the carb (make sure the check valve at the booster is good and not leaking), PCV hose on the front large middle port routed to drivers side valve cover (not sure if it truly matters which side), cap the ported/timed port on the passenger side front because you have no need for it, vacuum advance plugs into the driver’s side port. Next, go for a ride!

[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.