Intake Crossover Passage Blocking Questions
Thread Starter
Instructor
Joined: Feb 2010
Posts: 150
Likes: 8
From: Pelham Alabama
Intake Crossover Passage Blocking Questions
I've decided that I'm going to block the intake crossover passage to prevent heat soak to the carb from boiling the gas out into the intake and for maybe for that whole extra 1/2hp. I'm only going to be driving the car during the summer so long warm-ups aren't a major concern. I'm concerned about keeping things cool to avoid detonation... so every little bit counts right?
So... I'm using the "correct" intake gaskets on my 1969 427 oval-port heads with a factory aluminum intake. The passageways up to the carb from the crossover have been threaded and plugged. Is this itself enough?
I figure that I'll need to make something to block the passage.
Any ideas or experience with doing this? I'd like something that will last (chemical/thermal resistant) and not cause leaks? I've heard of everything from old steel beer cans to sheet metal. What about stainless steel? Also what thickness should be used?
Anything else that I need to be concerned about when doing this... aside from a slow-to-open choke?
Thanks!!
So... I'm using the "correct" intake gaskets on my 1969 427 oval-port heads with a factory aluminum intake. The passageways up to the carb from the crossover have been threaded and plugged. Is this itself enough?
I figure that I'll need to make something to block the passage.
Any ideas or experience with doing this? I'd like something that will last (chemical/thermal resistant) and not cause leaks? I've heard of everything from old steel beer cans to sheet metal. What about stainless steel? Also what thickness should be used?
Anything else that I need to be concerned about when doing this... aside from a slow-to-open choke?
Thanks!!
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
NO gasket will do the job, period, end of conversation on that score...BTDT for decades....
what does work, remove the intake mani and clean out the heat riser/crossover....oil/carbon free.....then fill with PLASTER OF PARIS, use tape on one side and fill from the other side, let it soak in good, ram home with a wood dowel/etc....get all the bubbles out, IF it was a EGR manifold, that should block off the EGR stuff also.....
let it set up over night, then install in the AM with normal spec gaskets...
NOW, to realize this will stop ANY heat riser for your choke, and if you have a hot tube choke or a choke 'stove' on the top, you need to get the set up converted to a electric heated choke....
and disable any heat riser off the typical passenger side pipe/manifold, that simply MUST be open at all times,
what does work, remove the intake mani and clean out the heat riser/crossover....oil/carbon free.....then fill with PLASTER OF PARIS, use tape on one side and fill from the other side, let it soak in good, ram home with a wood dowel/etc....get all the bubbles out, IF it was a EGR manifold, that should block off the EGR stuff also.....
let it set up over night, then install in the AM with normal spec gaskets...
NOW, to realize this will stop ANY heat riser for your choke, and if you have a hot tube choke or a choke 'stove' on the top, you need to get the set up converted to a electric heated choke....
and disable any heat riser off the typical passenger side pipe/manifold, that simply MUST be open at all times,
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
A piece of .020 stainless steel will work too. Just cut it slightly bigger than the opening and stick it under the gasket. (between the gasket and the head.) I've done it with aluminum too, but always kind of wondered if the aluminum would really hold up.
Drifting
Joined: Aug 2005
Posts: 1,443
Likes: 65
From: Wauconda IL
Edelbrock sells steel plugs to put into the cross over ports in the heads- At least they do for Oldsmobiles, I would assume Chevy would be real popular. They only cost about $12. A little easier than pouring plaster down your heads IMO. Then use some intake gaskets with the cross overs blocked and you're in business!
Elm
Elm
Le Mans Master
Joined: Oct 2010
Posts: 6,930
Likes: 845
From: melbourne florida
2023 C3 of the Year Finalist - Modified
we used to was up pieces of aluminum foil and pack them in there. i have even poured molten aluminum in there that's as permanent as it gets. living in central Florida i remove the choke too.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
NO gasket will do the job, period, end of conversation on that score...BTDT for decades....
what does work, remove the intake mani and clean out the heat riser/crossover....oil/carbon free.....then fill with PLASTER OF PARIS, use tape on one side and fill from the other side, let it soak in good, ram home with a wood dowel/etc....get all the bubbles out, IF it was a EGR manifold, that should block off the EGR stuff also.....
let it set up over night, then install in the AM with normal spec gaskets...
NOW, to realize this will stop ANY heat riser for your choke, and if you have a hot tube choke or a choke 'stove' on the top, you need to get the set up converted to a electric heated choke....
and disable any heat riser off the typical passenger side pipe/manifold, that simply MUST be open at all times,
what does work, remove the intake mani and clean out the heat riser/crossover....oil/carbon free.....then fill with PLASTER OF PARIS, use tape on one side and fill from the other side, let it soak in good, ram home with a wood dowel/etc....get all the bubbles out, IF it was a EGR manifold, that should block off the EGR stuff also.....
let it set up over night, then install in the AM with normal spec gaskets...
NOW, to realize this will stop ANY heat riser for your choke, and if you have a hot tube choke or a choke 'stove' on the top, you need to get the set up converted to a electric heated choke....
and disable any heat riser off the typical passenger side pipe/manifold, that simply MUST be open at all times,
Keep the shiny side up!
Scott
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Drifting
Joined: Nov 2002
Posts: 1,688
Likes: 201
From: Loveland, CO
As I recall, every intake manifold gasket set I have bought had the metal blocking plates included in the kit. They were shaped to fit the hole in the gasket itself, and had little extensions to bend over and hold in place.
But, I'm getting old and my memory isn't what is used to be.
Ralph.
But, I'm getting old and my memory isn't what is used to be.
Ralph.
