vacuum question
Thread Starter
Intermediate
Joined: Apr 2006
Posts: 28
Likes: 0
From: Milwaukee WI
vacuum question
I'm currently changing my 1971 original 350cid engine for a 383cid engine including all ancillary parts such as tuff stuff starter, mallory electronic dist, mallory coil, proform carb, air gap intake, PM alternator, and so on.
Q: The original engine set up had two vacuum lines (one small and one large) running from the front of the carb to I don't know where. What are these for????
BR,
Rod
Q: The original engine set up had two vacuum lines (one small and one large) running from the front of the carb to I don't know where. What are these for????
BR,
Rod
Burning Brakes
Joined: Jun 2004
Posts: 872
Likes: 3
From: Cortlandt Manor New York
The vaccum lines off the manifold control many operations on your Corvette. Included are headlights, windshield wipers, power brakes, carburator, distributor advance, TCS system and others. Before you install you need to find out if your new setup will produce enough vaccum for you to drive your Corvettes accessories.
Thread Starter
Intermediate
Joined: Apr 2006
Posts: 28
Likes: 0
From: Milwaukee WI
The vaccum lines off the manifold control many operations on your Corvette. Included are headlights, windshield wipers, power brakes, carburator, distributor advance, TCS system and others. Before you install you need to find out if your new setup will produce enough vaccum for you to drive your Corvettes accessories.
Rod
Le Mans Master
Joined: Jan 2006
Posts: 8,319
Likes: 7
From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
I'm currently changing my 1971 original 350cid engine for a 383cid engine including all ancillary parts such as tuff stuff starter, mallory electronic dist, mallory coil, proform carb, air gap intake, PM alternator, and so on.
Q: The original engine set up had two vacuum lines (one small and one large) running from the front of the carb to I don't know where. What are these for????
BR,
Rod
Q: The original engine set up had two vacuum lines (one small and one large) running from the front of the carb to I don't know where. What are these for????
BR,
Rod
the big one is for PCV
the small one is for the distributor
Thread Starter
Intermediate
Joined: Apr 2006
Posts: 28
Likes: 0
From: Milwaukee WI
Rod
Team Owner
Joined: Jun 2001
Posts: 23,367
Likes: 1,061
From: Virginia USA
I'll take some shots tonight. Actually now that you mentioned it I beleive I have 3 vac hoses too. Yes, one is for the advance can on the distrubutor. My car was originally a 270hp base engine 4-speed.
Le Mans Master
Joined: Jan 2006
Posts: 8,319
Likes: 7
From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Please, that would be great! You don't mean the vacuum advance on the distributor do you? My old set up had 3 vacuum lines coming off of the front of the original carb. 1 small hose and the pcv hose pair off and go to the drivers side and then I don't know where they go??? Then the 3rd hose went to the distributor. The 2 that pair off and go to the drivers side are the 2 that I'm not sure about.
Rod
Rod
Hosed goes to PCV off valve cover
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Thread Starter
Intermediate
Joined: Apr 2006
Posts: 28
Likes: 0
From: Milwaukee WI
Carl, those are the two hoses that I'm talking about. What is that canister that they go to? When I look at the bottom of this canister it looks like some sort of mesh. My new Proform cabuerator doesn't have the same number of vacuum ports as the original had.
The old and the new set up had 2 vacuum lines running out of the intake manifold. 1 for the vacuum canister, and 1 for the transmission.
The old and the new set up had 1 vacuum line running from the back of the cab to the brake booster.
the old set up had 3 vacuum lines coming from the front of the carb. 1 was for the vacuum advance. 2 (one small and 1 large to the can mentioed above. My new Proform carb only has 2 vacuum ports; 1 is metered and 1 is full vacuum. I have used the full vacuum port for the distributor vacuum advance. Now what to do with the 1 sm and the 1 lg lines mentioned above????
The old and the new set up had 2 vacuum lines running out of the intake manifold. 1 for the vacuum canister, and 1 for the transmission.
The old and the new set up had 1 vacuum line running from the back of the cab to the brake booster.
the old set up had 3 vacuum lines coming from the front of the carb. 1 was for the vacuum advance. 2 (one small and 1 large to the can mentioed above. My new Proform carb only has 2 vacuum ports; 1 is metered and 1 is full vacuum. I have used the full vacuum port for the distributor vacuum advance. Now what to do with the 1 sm and the 1 lg lines mentioned above????
Pro
Joined: Oct 2004
Posts: 624
Likes: 24
From: Shoreline WA
From what I understand, the canister is a charcoal filter although I've never had mine out to check. I believe most all of my car is original and it's probably time to look into changing this (if needed).
I don't have it up off the deck but the canister bottom feels solid with a semi-loose center plate. There's a short large-bore rubber hose exiting the bottom.
Really cramped quarters in there!
I don't have it up off the deck but the canister bottom feels solid with a semi-loose center plate. There's a short large-bore rubber hose exiting the bottom.
Really cramped quarters in there!
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
With your new carb you can do this.
3/8" line from pcv to large port on carb (no tee)
Be sure to have breather tube on other valve cover.
Small line from dist to metered (port vacuum) or manifold vacuum (your choice) plug the other unused.
Tranny line to anywhere on the manifold
Pbrake to anwhere on the manifold
Pbrake and tranny can be tee'd together.
The charcoal cannister can be disconnected from the carb with no ill effects. The gas tank will still be vented thru it but in not as positive a manner.
The worst case is that you might smell gas a bit once ina while when parked in a tightly sealed garage. Mine has been this way and never smell gas though.
3/8" line from pcv to large port on carb (no tee)
Be sure to have breather tube on other valve cover.
Small line from dist to metered (port vacuum) or manifold vacuum (your choice) plug the other unused.
Tranny line to anywhere on the manifold
Pbrake to anwhere on the manifold
Pbrake and tranny can be tee'd together.
The charcoal cannister can be disconnected from the carb with no ill effects. The gas tank will still be vented thru it but in not as positive a manner.
The worst case is that you might smell gas a bit once ina while when parked in a tightly sealed garage. Mine has been this way and never smell gas though.
Team Owner
Joined: Jun 2001
Posts: 23,367
Likes: 1,061
From: Virginia USA
Here are your pictures. Stock (Not anymore it's a ZZ4) setup for a 1971 270HP Q-jet. The big tubes go to the charcoal canister in the driver fender below the vacuum can. I tried to get a picture of that but they were not turning out good. Hope this helps.
