Intake Manifold Gasket Question
Thread Starter
Advanced
Joined: Jan 2010
Posts: 65
Likes: 0
From: Houston TX
Intake Manifold Gasket Question
I'm installing an Edelbrock Performer intake on stock heads for my '75 L48. The gasket came with 2 thin metal plates that fit over the center ventilation(?) holes. Do I need to include these when I install the intake?
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
Do you have the heat riser on the exhaust manifold? If you are running headers plug the holes. The holes are to allow heat from the exhaust to pass through the intake and warm the carburetor for cold weather starts.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Some gaskets block the entire heat riser passage for performance which is what I do in Texas.
Some gaskets have a metal piece w/ a hole in it. If you are driving a lot in winter it helps warm up when cold.
Some gaskets have a metal piece w/ a hole in it. If you are driving a lot in winter it helps warm up when cold.
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
the heat riser is an emissions thing. the cooler you keep the intake the denser the charge of air fuel mixture is. the more air fuel you get into the cylinder the more power you make. The difference between street legal and not street legal heads is the street legal heads have the port that alows exhaust gas to flow under the carb and across the intake manifold via the heat riser heating the air fuel to cut down the amount of emissions the car puts out. I either plug them or run an intake manifold & heads that don't have them
Melting Slicks
Joined: Mar 2006
Posts: 2,465
Likes: 0
From: Orange Park Fl
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The heat riser is a "warm up the carb" thing. That design feature has been used at least since the 1930's to help warm the fuel in the carb so that it vaporizes more easily. On engines with a 'divorced' choke, that passage is used to heat the choke coil, as well.
Thread Starter
Advanced
Joined: Jan 2010
Posts: 65
Likes: 0
From: Houston TX
Ok, almost done. Two last questions (hopefully):
The distributor won't all the way down. I marked it. It has maybe 1/4" to go before it's all the way down. Suggestions?
Also, how long should I wait before I start the car from when the intake was tightened down?
The distributor won't all the way down. I marked it. It has maybe 1/4" to go before it's all the way down. Suggestions?
Also, how long should I wait before I start the car from when the intake was tightened down?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Burning Brakes
Joined: Mar 2010
Posts: 943
Likes: 15
From: Valdosta Georgia
If the distributor isn't seating fully, its not engaging the oil pump shaft. you will need to use a long flat blade screwdriver down in the dist. hole in the intake and move the slot in the shaft to align with the bottom of the dist. shaft. It may take a few tries, but its easy to do. Once it lines up, it will drop right in.
If you have the manifold torqued down, you shouldn't have to wait long to start the motor. By the time you get the dist. installed you should be fine.
If you have the manifold torqued down, you shouldn't have to wait long to start the motor. By the time you get the dist. installed you should be fine.
Last edited by Drawmain; Oct 9, 2011 at 12:20 PM. Reason: added stuff
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
I agree it's likely the distributor tang not aligning with the intermediate shaft...but there's an easier way to drop it.
Just set the engine to about 8-12 BTDC on compression #1, drop the distributor in so the rotor is about 1/4" behind the #1 tower and "bump" the engine until it drops. Recheck timing, and off you go.
Just set the engine to about 8-12 BTDC on compression #1, drop the distributor in so the rotor is about 1/4" behind the #1 tower and "bump" the engine until it drops. Recheck timing, and off you go.
Melting Slicks
Joined: Jul 2009
Posts: 3,264
Likes: 3
From: Vero Beach FL
I agree it's likely the distributor tang not aligning with the intermediate shaft...but there's an easier way to drop it.
Just set the engine to about 8-12 BTDC on compression #1, drop the distributor in so the rotor is about 1/4" behind the #1 tower and "bump" the engine until it drops. Recheck timing, and off you go.
Just set the engine to about 8-12 BTDC on compression #1, drop the distributor in so the rotor is about 1/4" behind the #1 tower and "bump" the engine until it drops. Recheck timing, and off you go.
I have even cranked the engine "by hand" and done this.
Thread Starter
Advanced
Joined: Jan 2010
Posts: 65
Likes: 0
From: Houston TX
I got the distributor and timiing squared away (had to find compression stroke and redo plug wires).
New problem: One of the metal plates covering the heat riser passage has cone loose (I'm hearing tinning metal clanging intermittently, even at idle). With this little piece of metal cause me problems flying around loose? Should I not drive the car at all until I retrieve it? Will I be able to retrieve it? Felling pretty stupid right now.
New problem: One of the metal plates covering the heat riser passage has cone loose (I'm hearing tinning metal clanging intermittently, even at idle). With this little piece of metal cause me problems flying around loose? Should I not drive the car at all until I retrieve it? Will I be able to retrieve it? Felling pretty stupid right now.
Thread Starter
Advanced
Joined: Jan 2010
Posts: 65
Likes: 0
From: Houston TX
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If you installed them properly, there is no way for them to come loose. They are 'trapped' by the intake manifold gaskets. If you installed them on the wrong side of the gasket, they would go into the exhaust manifold and no harm could be done...except for the rattling, and that will go away shortly when that little piece of aluminum will ball up and get blown out the exhaust system.
If it fell off the gasket as you were installing the intake manifold, it will drop into the valley below and probably just lay there. The worst thing it could do is to partially block off an oil return passage...but I think that is unlikely.
It's your call, but you aren't going to suffer a catastrophic engine failure because of that 'problem'.
If it fell off the gasket as you were installing the intake manifold, it will drop into the valley below and probably just lay there. The worst thing it could do is to partially block off an oil return passage...but I think that is unlikely.
It's your call, but you aren't going to suffer a catastrophic engine failure because of that 'problem'.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
No, you'll have to remove the intake 
If it's in the valley, it's a pretty active place
If it gets bollixed up in the cam or makes it's way into an oil passage you'll be doing a lot more more than an intake R&R. I can't see how it could end up in the crossover passages.
Tough call - but that's what I'd do.
If it's in the valley, it's a pretty active place
If it gets bollixed up in the cam or makes it's way into an oil passage you'll be doing a lot more more than an intake R&R. I can't see how it could end up in the crossover passages.Tough call - but that's what I'd do.
Last edited by billla; Oct 11, 2011 at 10:47 AM.
