What is this hose for?
Thread Starter
Pro
Joined: May 2015
Posts: 572
Likes: 21
From: Milford, CT
What is this hose for?
On my 77 4spd, there is a junction built into the thermostat housing on my manifold. It has 3 ports on it. Can they be blocked off? I don't have to go through emissions in Connecticut so that's not an issue. I know one of them goes to the EGR valve and I plan on installing a block off plate for that hose. The other one goes into the front of the carburetor and it has a valve in it. Can I block that one off too? What is it for? I want to install a chrome thermostat housing with no vacuum ports in it.
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,482
From: Southbound
Cruise-In II Veteran
The fitting is a TVS switch and part of the emissions hose routing. There's a page in the AIM showing how the various hoses connect and the color codes. You can remove these and plug the open ports if emissions testing isn't a problem.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
The one in the first photo is for EFE and should not pull a vacuum on EFE when the engine is warm. The other is EGR/EVAP and only pulls a vacuum on EGR and the EVAP canister when the engine is warm.
Thread Starter
Pro
Joined: May 2015
Posts: 572
Likes: 21
From: Milford, CT
My EVAP canister is connected directly to the carb with a long hose. Its not connected to either of the ports on the manifold. So... with that said.. since I no longer have any emissions or smog parts I can just block off both the EFE and the TVS switches on the manifold and on the carb? I assume from "the old days" before EGR valves and emissions of any kind the only hoses I need connected to the carb are the PCV valve, the vacuum advance and on this car... that fuel vapor canister that's in the drivers side fender well. Does that sound correct? Regarding the manifold the only vacuum ports I think I need are for the brake booster and the headlights. My car no longer has heat or air conditioning and it doesn't have cruise control or the stock exhaust manifolds or the stock air cleaner. Am I on the right track??
Thread Starter
Pro
Joined: May 2015
Posts: 572
Likes: 21
From: Milford, CT
So just so I am clear on this. The only hoses and vacuum lines I need connected to my 1977 motor with no heat or AC in a state that doesn't have emissions are...
Upper and Lower radiator hoses
Fuel Charcoal canister to carb
Distributor Vacuum Advance to carb
Vacuum hose from brake booster to manifold
Vacuum hose from headlights to manifold
PCV valve to carb
Upper and Lower radiator hoses
Fuel Charcoal canister to carb
Distributor Vacuum Advance to carb
Vacuum hose from brake booster to manifold
Vacuum hose from headlights to manifold
PCV valve to carb
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