Intake/head water ports????
Thread Starter
Le Mans Master
Joined: Nov 2000
Posts: 5,210
Likes: 104
From: Fort Worth TX
St. Jude Donor '06
Father & Son St. Jude Donor '09
Intake/head water ports????
I have my stock intake off and looking at the heads, there appears to be 3 water ports, front, middle and rear. However, the middle port is partially plugged up and doesn't look like it has had any water pass through it??? I'm confused and want to get this right before I put the intake back on. Any help would be appreciated.
Le Mans Master
Joined: Jul 2001
Posts: 9,622
Likes: 16
From: absecon nj
Re: Intake/head water ports???? (74-Roadster)
its not a water port its an exuast port for egr valve..heat riser..does it have carbon built up in it?
[Modified by pats406nitrovette, 7:27 PM 10/26/2001]
[Modified by pats406nitrovette, 7:27 PM 10/26/2001]
Racer
Joined: Sep 2000
Posts: 287
Likes: 0
From: Wildwood IL
Re: Intake/head water ports???? (74-Roadster)
Yep, the middle port is the exhaust crossover port for the EFE system which consists of a vacuum operated heat riser valve in the psngr exhaust manifold. When the engine is cold, the valve is closed which forces the exhaust through the intake to the left side and then out. This heats up the manifold quicker to provide better cold weather driveability and fuel burning for the first few miles. Its also an emissions device. Once the engine heats up, a TVS (thermal vacuum) switch in the thermostat cover closes off the vacuum and the heat riser valve opens. That TVS switch is triggered at a certain temperature. If you're using a low temp t-stat, you should disconnect the system by reversing the check valve in the vacuum line that runs from the carb to the TVS. Otherwise, you could end up with a heat-riser that opens and closes intermittently or never really closes. Not a good thing.
Anyway, that port will definitely get carbon build up and should be scraped out. Be sure to use your shop vac to suck it out while you clean. Also, when you re-install the intake with new gaskets, be sure to use the restrictor in the gasket port as directed (on the opposite side of the heat riser).
Hope this helps!
Tom
Anyway, that port will definitely get carbon build up and should be scraped out. Be sure to use your shop vac to suck it out while you clean. Also, when you re-install the intake with new gaskets, be sure to use the restrictor in the gasket port as directed (on the opposite side of the heat riser).
Hope this helps!
Tom
Racer
Joined: Sep 2000
Posts: 287
Likes: 0
From: Wildwood IL
Re: Intake/head water ports???? (trs77)
Just in case yer wondering... the exhaust going through the crossover does not go into any of the intake runners. It simply passes through the intake in its own passageway from one side to the other. EGR is the system that meters exhaust gas into the intake runners.
[Modified by trs77, 8:45 PM 10/26/2001]
[Modified by trs77, 8:45 PM 10/26/2001]
Thread Starter
Le Mans Master
Joined: Nov 2000
Posts: 5,210
Likes: 104
From: Fort Worth TX
St. Jude Donor '06
Father & Son St. Jude Donor '09
Re: Intake/head water ports???? (trs77)
Yes, all of your explanations help a lot. There is carbon build up on both sides, more in the driver's side. As for the EGR, I got an EGR block off plate from Summit Racing but it doesn't fit my manifold. How can I block the EGR off? Is a custom plate and homemade gasket my only option?
Le Mans Master
Joined: Jul 2001
Posts: 9,622
Likes: 16
From: absecon nj
Re: Intake/head water ports???? (74-Roadster)
you have the stock intake right?i made one for my older intake awhile ago i just took a piece of metal and used the egr gasket as a template then cut it out then drill 2 holes in it use a little copper gasket sealer and bolt it down had no problems with it.
Racer
Joined: Sep 2000
Posts: 287
Likes: 0
From: Wildwood IL
Re: Intake/head water ports???? (74-Roadster)
Its surprising that the Summit block off plate doesn't fit. Give 'em a call. Make sure you got the right one. But that's the only way to really block it off (with a plate that is). I thought EGR valves on these engines didn't change much over the years (70s that is, but I think 74 was the first year with EGR so it may have changed in 75). Since you're blocking off the EGR, you may as well block both crossover ports with the full restrictors that should come with new fel-pro gaskets. Just make sure that heat riser valve and actuator is removed or never allowed to close! ps... Need someone with a 74 to step in here. It may be slightly different than the setup on my 77.
:cheers:
tom
:cheers:
tom
Thread Starter
Le Mans Master
Joined: Nov 2000
Posts: 5,210
Likes: 104
From: Fort Worth TX
St. Jude Donor '06
Father & Son St. Jude Donor '09
Re: Intake/head water ports???? (pats406nitrovette)
you have the stock intake right?. . .then drill 2 holes in it use a little copper gasket sealer and bolt it down had no problems with it.
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
Le Mans Master
Joined: Jul 2001
Posts: 9,622
Likes: 16
From: absecon nj
Re: Intake/head water ports???? (74-Roadster)
i know what you mean... you could still make one also.
you have metal wire looking bracket holding it down right..
[Modified by pats406nitrovette, 11:02 PM 10/26/2001]
you have metal wire looking bracket holding it down right..
[Modified by pats406nitrovette, 11:02 PM 10/26/2001]
Thread Starter
Le Mans Master
Joined: Nov 2000
Posts: 5,210
Likes: 104
From: Fort Worth TX
St. Jude Donor '06
Father & Son St. Jude Donor '09
Re: Intake/head water ports???? (pats406nitrovette)
. . . you could still make one also. you have metal wire looking bracket holding it down right..
My other option is to tap new holes in to attach a simple plate. Either way it's a pain!
Thread Starter
Le Mans Master
Joined: Nov 2000
Posts: 5,210
Likes: 104
From: Fort Worth TX
St. Jude Donor '06
Father & Son St. Jude Donor '09
Re: Intake/head water ports???? (Pedro'74)
I've ended up putting my EGR valve back on and plugging it. A plate will be fabricated in the future.
Melting Slicks
Joined: Jun 2001
Posts: 2,340
Likes: 2
From: Moro IL
Re: Intake/head water ports???? (74-Roadster)
Evidently the big blocks have the same EGR setup in 73 and 74 as the samll blocks, since you descibed how mine was setup. I left my EGR valve in place, made a gasket for it without any holes, bolted the EGR valve back on and capped the vacuum line to it on both ends, so far so good. Haven't had any problems with this setup. Oh yea, I'm sure 74 is the same setup on the heat riser as 73 is, but your valve in the exhaust is setup with a coil spring similiar to the choke as it heats it opens, there sholdn't be any vacuum lines to it like on later models. I may be wrong here if they changed it over in 74, at least that's the way it's setup on my 73, or I should say was setup before the headers.
:cheers:
Pat Kunz
:cheers:
Pat Kunz
Safety Car
Joined: Aug 2001
Posts: 3,685
Likes: 202
From: Waterford Mi
Re: Intake/head water ports???? (73 LS-4)
The best way to solve your problem would be to buy a Performer #2101 (assuming you have a SB)intake. Not only do you loose the EGR valve hole, you also will increase you total performance from your engine.
:cool:
:cool:
