AMC360 Vacuum help

[Theduke]

1989 Jeep Grand Wagoneer.
Rebuilt the AMC360 back in 2008.
K8600 Cam
Edlebrock aluminum intake
Edleborck 4 barrel carb 1406 Performer 600cfm (non EGR for all components)
doug thorley headers
HEI distributor

I yanked out all the Emissions control stuff in 2008.
I sold the jeep in 2011 and just bought it back (sentimental) in February so I'm not sure what I did vs what the other owner did. They said they never drove it but did have their mechanic look at it. It was still sitting on the tires I put on it in 2008. It has new tires now.

It was running fine up until I sold it.

My carb has 4 ports. 3 front, 1 rear.
Rear large port goes to the PCV and just above the PCV there is a T with a smaller line running up and connecting to a Y just past a vacuum reservoir (round bulb) mounted to the firewall. This reservoir powers the 4wd, heater and cruise control.
The front center port large port goes directly to the brake booster.
The manifold vacuum port is capped and the ported vacuum port goes to the distributor.
That's all I've got. Is it the minimum or was it taken to far.
The vapor canister is gone (not sure who did it, might have been me). So I don't know where the gas tank is currently venting.

I've read a bunch and looked at more schematics than my brain can handle.
Any advice would be helpful.

Also I'm getting 10" (not 17-22") from the manifold to the brake booster or anywhere else.
Timing is currently set to 11.4 degrees at around 700 rpm. Any lower and it stalls out.
No leaks found yet.
One of the pictures shows a fitting behind the carb with 2 blocked off cut hoses. Buddy already told me to plug that with a new brass pipe fitting.
Also one picture was taken mid-diagnosis so disconnected vacuum line with vice grip

[Theduke]

Update. Between idle set screw and advance I've managed to get it to 12 degrees at 700rpm. Not sure what it should be with a k8600. However, ported vac line measures 5" at idle. Manifold measures 10" at idle.
Still way to low.

[Lincoln7]

Often debated but I always run my vacuum advance off manifold vacuum. Better idle quality and stronger vacuum that way.

But to check your idle ignition advance you must disconnect/plug the vacuum line to the distributor. That initial timing should be 'around' 10*. I have mine set at 12* initial, 34* total, and with manifold vacuum hooked up to distributor it gives me about 24* timing at idle.

[rocklaurence]

The vacuum on a good old motor should be at 14-ish. My power valves are 9's. So, either your rings are shot or timing is way off. Hopefully, its the timing.

[Theduke]

Timing is 12 degrees at 700rpm.
I disconnected every vacuum line from the carb and put plugs on them. Except the pcv which is a pain to remove so I clamped it closed. I put the vacuum gauge on manifold and read 10". I swapped it to the ported side and got 5". Why would I read 5" ported at idle?

[MReno]

The question I have is on my Edlebrock Performer manifold there is a 2-hose connection port that I have capped (circled in RED on attached), but I am not sure its purpose? 2nd, in addition, I am wondering where I should be connecting my vacuum gauge to the manifold to check vacuum? The attached image has what I thing should be the correct point to attach vacuum gauge, but it is currently capped with a brass pipe fitting.

Can anyone provide some guidance? Thanks.

[Dr.Bob]

The question I have is on my Edlebrock Performer manifold there is a 2-hose connection port that I have capped (circled in RED on attached), but I am not sure its purpose? 2nd, in addition, I am wondering where I should be connecting my vacuum gauge to the manifold to check vacuum? The attached image has what I thing should be the correct point to attach vacuum gauge, but it is currently capped with a brass pipe fitting.

Can anyone provide some guidance? Thanks.

OK, just saw your pictures.

So, manifold vacuum should be drawn from that port you circled in red on the back runner of the intake-manifold, with that fitting that has the two vacuum nipples. That is where you should measure manifold vacuum. It also is where the vacuum reservoir on the firewall should be routed to, as well as the vacuum motors to control the flaps on the air-cleaner.

The power-brake booster should be attached to the big port on the front of the base of the carburetor, as you have it.

One possible reason you are seeing that vacuum from the ported vacuum source at idle is that you have adjusted your throttle-opening stop-screw too far in order to obtain the proper idle-speed, instead of adjusting it properly through the mixture screws.

[Dr.Bob]

You also don't need any caps or vacuum lines on that blue thermostatic switch on the back-side of the air-cleaner; that is for the EGR valve, which you don't have. It isn't a vacuum source, so it can be left uncapped. The air-cleaner flaps should be connected to that manifold vacuum source at that fitting at the back of your intake; that only does good things (if you run a preheat hose down to around your exhaust manifold). The vacuum should go from that manifold source, to a "T", one which goes directly to the inner flap vacuum-motor, and the other that goes through a check-valve, into the thermostatic switch in the base of the air-cleaner, then to that outer flap vacuum motor (I see you have the vacuum delay valves already in-line; leave those there).

These are some of the things I go over in excruciating detail in my vacuum line replacement video series, starting at about 14:30 in the first episode:

https://www.youtube.com/watch?v=GReFi9Z59cA&t=1s

[MReno]

Dr.Bob, thanks for the input. Many of the components you referenced I will need to look up so I can locate them in order for me to reroute the vacuum lines properly. I'll watch your video and see if it helps me.

[MReno]

Is the Jeep J20 you work on in the video have the same vacuum set up as my '89 Grand Wagoneer, even though I running a 4bbl carb?

[MReno]

I guess I should also add, that I'm in a state where I'm not bound to have emissions system operational, so I want to keep that crap off the vehicle as much as possible. I am also not using the OEM air filter system, rather just a round K and N filter.

[Dr.Bob]

Is the Jeep J20 you work on in the video have the same vacuum set up as my '89 Grand Wagoneer, even though I running a 4bbl carb?

Basically, yes; the only difference will be you won't need the external manifold vacuum source going to the power-valve, and the ported vacuum-port locations may be in different spots. The components you may include, or delete, are basically the same on all these engines.

[MReno]

Where is the power valve?

[Dr.Bob]

Front center bottom of the carburetor

[MReno]

When you say, power valve, you referring to the Power Brake Booster? If so, I believe I have that hooked up properly.

[letank]

When you say, power valve, you referring to the Power Brake Booster? If so, I believe I have that hooked up properly.

Different Power devices: the power valve (PV) is part of the carburetor at its bottom front, it elivers extra gas when the manifold vacuum drops below a sudden vacuum level such as during pedal to the metal event, thru its proper carburetor channel.

as a matter of fact the brake booster is also connected to the intake manifold at the same port as the power valve hose in the front of the intake behind the oil filler pipe in the standard OEM config, hoses have different size.

the fat hose behind the yellow vacuum switch upfront is for the brake booster

[MReno]

Anyone wish to provide some input on how my engine is running, and possible issues to look into by watching this video https://youtu.be/NfgWa55pJFc

[Dr.Bob]

Anyone wish to provide some input on how my engine is running, and possible issues to look into by watching this video https://youtu.be/NfgWa55pJFc

There are a lot of guides out there to interpreting vacuum-gauge readings, but here is a pretty good one:

https://www.crankshaftcoalition.com/wik ... _diagnosis

You could need new spark-plugs, or valve-guides, with that minor flutter at idle.

[MReno]

Plugs are new and gapped properly. Thanks for the video link, will watch that later.

[letank]

Anyone wish to provide some input on how my engine is running, and possible issues to look into by watching this video https://youtu.be/NfgWa55pJFc

Great video, it sounded better on a desktop than a phone... light flutter, how is the power when you take it for a run...? you could turn the mixture screw a tad rich 1/8 of a turn and observe, do one side at a time, and do the other side... Ideally you know how much from lightly seated the mixture screws are set to? the usual is 1 1/2 turn from lightly seated for the motorcraft, not familiar with this edelbrock version.

Also remove the oil filler cap and open the throttle briefly , like a nice tug to rev up the engine and see if you have a cloud of smoke coming of the oil filler tube

Also new plugs, which ones and #?