454 smog pump
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Joined: Dec 2005
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From: Lakewood Colorado
454 smog pump
Need advice on '74 454 smog pump/ pulley.
Need to fix smog pump up to pass emissions, but in need of diverter and pulley. Is there only one diverter and pulley that fits on 454 pump, or can I interchange parts from other units (like 350) to accomplish this interim fix?
Any advice is appreciated.
Need to fix smog pump up to pass emissions, but in need of diverter and pulley. Is there only one diverter and pulley that fits on 454 pump, or can I interchange parts from other units (like 350) to accomplish this interim fix?
Any advice is appreciated.
Le Mans Master
Joined: Sep 2002
Posts: 5,235
Likes: 898
From: Myrtle Beach SC
Originally Posted by vettecrazy88
Need advice on '74 454 smog pump/ pulley.
Need to fix smog pump up to pass emissions, but in need of diverter and pulley. Is there only one diverter and pulley that fits on 454 pump, or can I interchange parts from other units (like 350) to accomplish this interim fix?
Any advice is appreciated.
Need to fix smog pump up to pass emissions, but in need of diverter and pulley. Is there only one diverter and pulley that fits on 454 pump, or can I interchange parts from other units (like 350) to accomplish this interim fix?
Any advice is appreciated.
Now the pump on the LS4 7801149 was used on all 1974 Corvette motors and used from 1970 through 1977...lots of applications. The diverter served (if I recall correctly) to vent hot exhaust gas away from the pump that may backup from the combustion process and therefore was tuned to cubic inch and horsepower. So all diverter valves mount the same to the pump. To get by emissions I suspect any valve would do if originality does not matter. Bill Hodel is used by many as the emission system guru in restoration work and advertises in the NCRS Driveline.
The AIM for 74 will shows these part numbers as well as the pulley.
Le Mans Master
Joined: Mar 2004
Posts: 7,455
Likes: 1,482
From: Little Rock AR
The diverter valve works on a vacuum signal from the carb. On high vacuum it will divert the air coming from the smog pump and send it back out to the atmosphere. On low vacuum conditions the valve will allow air from the pump to flow to the inside of the exhaust manifolds to help burn any left over combustibles leaving the combustion chamber.
The reason the diverter valve was used is because if you sent air from the pump into the exhaust manifold all the time, you would get a backfire when you get off the gas quickly, such as shifting etc. These are periods of high vacuum. If you have a blown diverter valve, you probably already know what I am saying.
-Mark.
The reason the diverter valve was used is because if you sent air from the pump into the exhaust manifold all the time, you would get a backfire when you get off the gas quickly, such as shifting etc. These are periods of high vacuum. If you have a blown diverter valve, you probably already know what I am saying.
-Mark.
Burning Brakes
Joined: Nov 2001
Posts: 1,191
Likes: 1
The diverter served (if I recall correctly) to vent hot exhaust gas away from the pump that may backup from the combustion process and therefore was tuned to cubic inch and horsepower.
Bill Hodel is "the man" when it comes to smog systems. You might search the archives, including the FCR board, for contact info if you don't have access to the NCRS publications.If originality isn't important, and once you price original components you might reconsider, then you can hit the NAPA store for pumps, but I think they are iffy on diverter valves.
