Carb'd LSX, what are these holes for?

[spitfire980]

Hi Guys

I got these holes that i dont know what they are for,

Any help would be appreciated

Its an LS1 with a Edelbrock 71187 Performer RPM Dual Plane Intake Manifold

The hole on the side of the intake, whats this for?


The passanger side valve conver has 2 vent tubes, should i block them off?



The driver's side valve cover, whats this for?

[homemade87]

the one in the side under the carb looks to be one for a MAP sensor . If you are running something like a msd controller I would recommend taking the time to learn how to run a map with your operating system .

The ones in the valve covers are for your PCV system . Could google it to learn more about the routing and see how you want to run it .

[spitfire980]

Originally Posted by homemade87

the one in the side under the carb looks to be one for a MAP sensor . If you are running something like a msd controller I would recommend taking the time to learn how to run a map with your operating system .

The ones in the valve covers are for your PCV system . Could google it to learn more about the routing and see how you want to run it .

Im running an MSD 6014, according to the instructions:
"The LS Ignition controller includes a built-in 2.5 Bar MAP sensor that can be used with Naturally Aspirated or boosted applications. This allows for timing advance or retard based on the intake manifold pressure. It is recommended that you use it, but not required unless you are using forced induction."

Ill get the car running and driving then ill plug it in later and start learning how to full utilize it.

What about the one on the driver's side valve cover? whats that for?

[homemade87]

Can you run without the map , you sure can . Will it perform at part throttle cruise or idle as well, most likely not . The map does the same thing the vacuum canister did on the distributor on the first gen engines . It gives you timing advance on idle & part or light throttle . Makes the engine more efficient under these conditions . If all you want is wot . No need for it .

As for the hole in the valve cover . That hole is for the PCV valve .

[crazy longhorn]

Agree with all on the pass side, I did a 90 degree hose , with a small cone shaped filter (autozone part). On the dr side, understand that the LS engine did not have a pcv.....no internals, it was just a restrictor. I opted to run a pcv in my carbed setup, just plum it to the front of the carb, bottom center. Longhorn

[71cadc10]

the hole in the intake is for any manifold vac source needed...if you don't need then just plug it...its NPT thread.

For the valve covers....the pass side trucks did have 2 ports there. One was typically routed to the filtered intake air...so that is basically the 'fresh air in' port.
Driver side there is a restrictor / sort of PCV valve in that large grommet, and that runs to the top of the plastic OEM manifold. That's your suction side.

my opinion, mount a breather to the front nipple pass side. block the rear nipple.
slip a PCV in that large grommet driver side rear, and run it to a manifold vac source (bottom of carb or over to that hole in the intake manifold on passenger side. This will give fresh filtered air in on the pass side, and suction on the driver side to clear moisture out of crank case.

Looks like your valley plate is smooth, so you don't have any ports there correct ?
if your valley plate has a nipple at the front, you can also have that be your "suction side" and then run breathers on both valve covers. The valley cover is a good place to pull the crankcase vapor from

another note: those grounds I would recommend running to the bolt holes on the back of the heads. not the coil pack bracket like shown. valve covers have a rubber seal under them and I'm not thinking you will get a great ground to the block that way