1969 superbee 383 rough idle and low vacuum

[josephqatarcarguy]

Hey , my superbee which should have a mostly stock 383 engine has a rough idle and dies in gear . The engine is stock except edelbrock aluminium heads , firecore distributor and ecu , edelbrock avs2 650cfm carb , it has really low vacuum 5 ..6 .. I can get it to idle but the engine js vibrates alot , the idle mixture screws do nothing if adjusted , can turn it all the way in and the engine still runs , vacuum leak ? Timing is at 14 initial

What should I check?

Thanks guys

 

[Don Frelier]

Sounds like a vacuum leak.
Broken pcv valve, loose carb, bad brake booster.
Maybe intake.
Eliminate all the rubber hoses temporarily connect one at a time and test.
A unlit propane torch waived around potential leaks or carb cleaner can help find if you have a leak.

 

[BSB67]

Hey , my superbee which should have a mostly stock 383 engine has a rough idle and dies in gear . The engine is stock except edelbrock aluminium heads , firecore distributor and ecu , edelbrock avs2 650cfm carb , it has really low vacuum 5 ..6 .. I can get it to idle but the engine js vibrates alot , the idle mixture screws do nothing if adjusted , can turn it all the way in and the engine still runs , vacuum leak ? Timing is at 14 initial

What should I check?

Thanks guys

When did this problem begin?

 

[josephqatarcarguy]

When did this problem begin?

After 7..8 months of not driving her

 

[BSB67]

So it was running perfectly fine when it was parked 7 months ago, and it started with this problem when you pulled it out?

How long have you owned it?

 

[josephqatarcarguy]

So it was running perfectly fine when it was parked 7 months ago, and it started with this problem when you pulled it out?

How long have you owned it?

About a year and a half , no it's been running kinda rough all ehile long , I could get her to idle alright around 850 rpms then switch her off and let her cool for 10..15 mins and start her back up and idlee surges to 1200 rpms .

Think there's a vacuum leak on the intake gasket? Should I just pull the intake?

 

[gtxrt]

what intake is on there ?

 

[josephqatarcarguy]

what intake is on there ?

The stock intake

 

[hofferwood]

Secondary's might be cracked open a bit.

 

[josephqatarcarguy]

Secondary's might be cracked open a bit.

The idle screws do nothing, I can turn them both fully in on the eddy and the car still runs , have tried advancing the timing to back down idle screw to no luck , what should I do?

 

[hunt2elk]

Do you have the vac advance hooked to manifold vacuum by chance?

 

[josephqatarcarguy]

Do you have the vac advance hooked to manifold vacuum by chance?

Vacuum advance is hooked upto ported vacuum on the passenger side

 

[Fran Blacker]

Before pull lntake get it running spray carb cleaner at intake cyl head mating surface. If engine rpm changes look there.

 

[josephqatarcarguy]

Before pull lntake get it running spray carb cleaner at intake cyl head mating surface. If engine rpm changes look there.

alright , i also installed a firecore distributor and ecu, car starts right up , could it have to do anything with it?

 

[Don Frelier]

Double check your firing order

 

[josephqatarcarguy]

Double check your firing order

Checked and confirmed

 

[Mick56]

A good way to find a vacuum leak is to use a smoke machine. Many U-Tube videos on how to make one.

 

[71Beeper]

If the idle mixture screws do not respond, then the engine idle needs to be reduced until they do.
Usually the idle rpm should be about 700 rpm's.
If you can't bring the idle down to that, then you may have a vacumn leak.

 

[Road Grabber]

A lot of good things suggested. Before removing parts I would disconnect all vacuum lines one at time and plug them to see if anything changes. Plug them at the carb and intake. You could have a leaking hose that is not visible. Something that major could be the PVC or power brake booster hose.
Like mentioned above you should also make sure you are using the idle circuit and not opening the throttle plates to compensate. That would explain the lack of response from your mixture screws.
If this is a growing problem it could be the intake but I would rule out anything mechanical by checking that all plugs are sparking and you do have uniform compression.
If you have a bad EC UNIT and not all of your cylinders aren’t firing you won’t get good vacuum. Check your plugs too and see if they look new and not firing.

I like to rule out mechanical. It doesn’t take much time to do it. If the compression is good then as long as you have good ignition and fuel with no leaks it should run fine. If you’re not running on all eight it shows in your vacuum. Basics….

You are placing the wires on the cap in the right rotation? Just saying. Assume nothing…