What is this Port for (Intake Manifold) PIC - The 1947 - Present Chevrolet & GMC Truck Message Board Network

gmcbob · 01-17-2005, 08:25 PM

So, what's this port for? It's in the middle of the intake, on both sides.

From my '78, 350.

I'm thinking it's for oil, but not sure. If so, I assume that it's pressurized at the same pressure reading of my oil pressure guage? I've got oil gathering on top of the intake, and I think this is where it is coming from. Thanks!

(Hopefully the Pic works)

Bob "gmcboc"

Russell · 01-17-2005, 08:37 PM

Nope, thats your exhaust crossover

Your heads allow some exhaust gas to pass through that crossover so you have something to heat up the automatic choke for your carburator. It is also used for EGR valves as well, when the EGR valve opens up, it allows some exhaust gas into the air / fuel mixture from that passage, reducing allowing you to run more timing, and improving emissions

Oil collecting on the top of the intake would likely be due to bad intake gaskets(likely the front or rear seals), bad valve cover gaskets, or possibly a bad distributer gasket

bluex · 01-17-2005, 08:48 PM

Or possibly coming through a few of the bolts. Put some silicone on the threads before you reinstall your bolts. Not sure how much oil your getting, but it could be coming from that, maybe even a bad PCV valve.

gmcbob · 01-17-2005, 09:23 PM

Well, I guess I learned something new

Thanks for the help guys. So I'll be re-setting the intake this weekend.

Here's a few pics of the problem.

Thanks again,

Bob "gmcbob"

Russell · 01-17-2005, 11:09 PM

I'd agree with bluex -- Thats oil seeping up your bolt threads... before you reinstall the bolts, run a tap down the holes to clean them up, and a tie down the bolts to clean the threads, then put some silicone down the hole / on the bolt before re-installing it to seal them up from leaking again, as well as making it less likely that the bolts will come loose / loose their torque

gmcbob · 01-17-2005, 11:55 PM

Sounds great, appreciate the advice. Sounds like that should take of it!

Bob "gmcbob"

01-17-2005, 08:25 PM	#1
gmcbob Registered User Join Date: Mar 2000 Location: Phoenix, Arizona Posts: 57	What is this Port for (Intake Manifold) PIC So, what's this port for? It's in the middle of the intake, on both sides. From my '78, 350. I'm thinking it's for oil, but not sure. If so, I assume that it's pressurized at the same pressure reading of my oil pressure guage? I've got oil gathering on top of the intake, and I think this is where it is coming from. Thanks! (Hopefully the Pic works) Bob "gmcboc" Attached Images __________________ Bob 1978 GMC Sierra Classic K15 Shortbed, 350/350/NP203, 31's on Rally's, Restored to Stock Condition. Two-tone Russett Metallic / Buckskin. 1987 GMC Sierra Classic V1500, Longbed, 350 TBI, NP205, 33’s on Chrome Spoke with 4” Suspension Lift. Black. 2014 GMC 2500HD 4x4 Duramax Crewcab

01-17-2005, 08:37 PM	#2
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Nope, thats your exhaust crossover Your heads allow some exhaust gas to pass through that crossover so you have something to heat up the automatic choke for your carburator. It is also used for EGR valves as well, when the EGR valve opens up, it allows some exhaust gas into the air / fuel mixture from that passage, reducing allowing you to run more timing, and improving emissions Oil collecting on the top of the intake would likely be due to bad intake gaskets(likely the front or rear seals), bad valve cover gaskets, or possibly a bad distributer gasket __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

01-17-2005, 08:48 PM	#3
bluex Registered User Join Date: Jun 2004 Location: Spartanburg, SC Posts: 1,963	Or possibly coming through a few of the bolts. Put some silicone on the threads before you reinstall your bolts. Not sure how much oil your getting, but it could be coming from that, maybe even a bad PCV valve. __________________ Paul '78 GMC Serria 15 Heavy Half. 361/NV3500/3.73. Former LWB NV3500 swap Trailing arm swap '98 ECSB Z71 daily driver -traded '03 burb. Family cruiser http://upstategmtrucks.com/

01-17-2005, 09:23 PM	#4
gmcbob Registered User Join Date: Mar 2000 Location: Phoenix, Arizona Posts: 57	Well, I guess I learned something new Thanks for the help guys. So I'll be re-setting the intake this weekend. Here's a few pics of the problem. Thanks again, Bob "gmcbob" Attached Images __________________ Bob 1978 GMC Sierra Classic K15 Shortbed, 350/350/NP203, 31's on Rally's, Restored to Stock Condition. Two-tone Russett Metallic / Buckskin. 1987 GMC Sierra Classic V1500, Longbed, 350 TBI, NP205, 33’s on Chrome Spoke with 4” Suspension Lift. Black. 2014 GMC 2500HD 4x4 Duramax Crewcab

01-17-2005, 11:09 PM	#5
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	I'd agree with bluex -- Thats oil seeping up your bolt threads... before you reinstall the bolts, run a tap down the holes to clean them up, and a tie down the bolts to clean the threads, then put some silicone down the hole / on the bolt before re-installing it to seal them up from leaking again, as well as making it less likely that the bolts will come loose / loose their torque __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

01-17-2005, 11:55 PM	#6
gmcbob Registered User Join Date: Mar 2000 Location: Phoenix, Arizona Posts: 57	Sounds great, appreciate the advice. Sounds like that should take of it! Bob "gmcbob" __________________ Bob 1978 GMC Sierra Classic K15 Shortbed, 350/350/NP203, 31's on Rally's, Restored to Stock Condition. Two-tone Russett Metallic / Buckskin. 1987 GMC Sierra Classic V1500, Longbed, 350 TBI, NP205, 33’s on Chrome Spoke with 4” Suspension Lift. Black. 2014 GMC 2500HD 4x4 Duramax Crewcab



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