|
|
|
|
| Author |
|
|
Registered
|
Help! Popping Carbs - Intake Manifold?
I took my 911 into the mechanic this morning with complaints of popping carbs, backfire and significant power stutter. Within seconds we found an issue with a missing cap on my intake manifold. The problem seems to be solved and I’m shocked on how simple it was.
That said, can some explain this to me? I’ve seen most cars DO NOT have this section of the manifold capped, is it better to just remove them? What exactly does this do and how did it solve the problem? The attached picture shows my intake manifold with two circles, the green circle shows the previously capped port and the red shows the one we replaced today. The additional photo shows the other manifold with no ports or plugs. Any help or advice would be appreciated!  
|
||
05-27-2023, 07:52 PM
|
|
|
Registered
Join Date: Aug 2007
Location: San Antonio, TX
Posts: 2,167
|
Those vacuum ports on one side were usually for Sportomatic cars. You have an MFI shroud, so I'm assuming the engine did not originally come with Webers.
|
||
|
05-27-2023, 09:51 PM
|
|
|
Registered
|
I did not convert this car to carbs nor is the engine original to my ‘72. Assuming MFI was the original set up. Is it better to cap these vacuum ports or leave them open?
|
||
|
05-28-2023, 04:39 AM
|
|
|
Registered
Join Date: Jan 2011
Location: Gulf Coast FL
Posts: 1,484
|
You have two choices if you don't want that to happed again
1. remove the nipple fittings from the manifolds and install solid metal threaded plugs 2. buy some molded rubber vacuum nipple plugs and make sure they are clamped (I would use oetiker clamps) Last edited by eastbay; 05-28-2023 at 05:19 AM.. |
||
|
05-28-2023, 05:17 AM
|
|
|
Registered
|
I’d much prefer to pull the fittings and install plugs. Is there a chance anyone knows the size off the top of their head?
|
||
|
05-28-2023, 05:50 AM
|
|
|
Registered
Join Date: Jul 2013
Posts: 1,104
|
I don't believe that the holes on the left / shown in green, are actually drilled through the casting. They are likely just blind holes.
|
||
|
05-28-2023, 07:32 AM
|
|
|
|
Registered
|
Yes agreed. It looks like I’ll only have to cap the right side.
|
||
|
05-28-2023, 07:52 AM
|
|
|
It's a 914 ...
Join Date: Jan 2008
Location: Ossining, NY
Posts: 4,697
|
Azio - any ports that go through into the intake runner do need to be plugged as noted, or your engine will be getting unmetered air and run lean (the popping you had). I'd feel better with something held on with a hose clamp, or as suggested, a pressed in plug.
|
||
|
05-29-2023, 04:29 AM
|
|
