The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 12-31-2013, 06:06 PM   #1
marquis
Registered User
 
Join Date: Dec 2013
Location: kailua hi
Posts: 8
Unknown line

Trying to figure out what this line is. The guy that had the truck before had it run into a pcv valve that connects to the manifold but didn't have the valve connected to the carb. It runs to the back of my transmission. Can anyone help me out?
Attached Images
 
marquis is offline   Reply With Quote
Old 12-31-2013, 06:09 PM   #2
tlawre87
Registered User
 
tlawre87's Avatar
 
Join Date: Jun 2012
Location: Meeker, ok
Posts: 146
Re: Unknown line

Its the vacuum modulator for the th350. It has to be hooked up for proper shifting. It should connect to the intake manifold.
__________________
Trevor
74 C20...work in progress.
04 Saturn Ion...Daily Driver
tlawre87 is offline   Reply With Quote
Old 12-31-2013, 09:24 PM   #3
marquis
Registered User
 
Join Date: Dec 2013
Location: kailua hi
Posts: 8
Re: Unknown line

The valve that it connects to has two ports. I'm assuming that I should keep the second one plugged and not connected to the carb?
marquis is offline   Reply With Quote
Old 12-31-2013, 09:53 PM   #4
cory d
Registered User
 
cory d's Avatar
 
Join Date: Dec 2011
Location: Arlington WA
Posts: 1,728
Re: Unknown line

thats the vacuum modulator valve on a th350. it helps control your shift points with your vacuum. shift earlier when just cruising of holds the gear long when wide open. if its not connected at all you will just shift off of the governer. if i recall correctly, i havent ran an automatic in a while
cory d is offline   Reply With Quote
Old 12-31-2013, 11:09 PM   #5
buddy_1
Registered User
 
buddy_1's Avatar
 
Join Date: Dec 2013
Location: Humble, Texas
Posts: 185
Re: Unknown line

That modulator in the pic looks like it is leaking fluid probably needs to be replaced. Got a pick of the valve that it connects to? The reason I ask is that you said it has 2 ports and the modulator needs vacuum to work correctly. If that valve isn't connected to the carb/intake that second port needs a hose hooked to a vacuum source.
__________________
I know the "VOICES" aren't real but they have some great ideas.
1978 GMC Sierra Classic C25
1983 Datsun 280ZX Turbo
1997 Chevy Cheyenne K2500
1999 Polaris Sport 400
buddy_1 is offline   Reply With Quote
Old 12-31-2013, 11:31 PM   #6
marquis
Registered User
 
Join Date: Dec 2013
Location: kailua hi
Posts: 8
Re: Unknown line

Yea I have to go over my transmission with a fine tooth comb because it think there's more than one leak. So I do need to hook the other port up to the carb?
Attached Images
 
marquis is offline   Reply With Quote
Old 12-31-2013, 11:42 PM   #7
875.3CHEVY
Registered User
 
Join Date: Sep 2008
Location: spinawheel sc
Posts: 108
Re: Unknown line

no thats hooked up right.straight vaccum off the monifold

Last edited by 875.3CHEVY; 12-31-2013 at 11:45 PM. Reason: clarification
875.3CHEVY is offline   Reply With Quote
Old 01-01-2014, 12:09 AM   #8
marquis
Registered User
 
Join Date: Dec 2013
Location: kailua hi
Posts: 8
Re: Unknown line

The pcv valve port being used is the one that goes to the transmission not the carb.
marquis is offline   Reply With Quote
Old 01-01-2014, 12:23 AM   #9
buddy_1
Registered User
 
buddy_1's Avatar
 
Join Date: Dec 2013
Location: Humble, Texas
Posts: 185
Re: Unknown line

I agree with 875.3, it is connected correctly. To help prevent the vacuum hose from collapsing, the nipple on the pipe is supposed to fit directly into the fitting on the intake with a hose over the union.
__________________
I know the "VOICES" aren't real but they have some great ideas.
1978 GMC Sierra Classic C25
1983 Datsun 280ZX Turbo
1997 Chevy Cheyenne K2500
1999 Polaris Sport 400
buddy_1 is offline   Reply With Quote
Old 01-01-2014, 12:46 AM   #10
875.3CHEVY
Registered User
 
Join Date: Sep 2008
Location: spinawheel sc
Posts: 108
Re: Unknown line

the fitting behind the carb with the orange line and the capped off port is not a pvc port.it just straight vaccum.that what the trans needs.pvc should come off the carb and should be 3/8 in size.hope this helps
875.3CHEVY is offline   Reply With Quote
Old 01-01-2014, 01:38 AM   #11
marquis
Registered User
 
Join Date: Dec 2013
Location: kailua hi
Posts: 8
Re: Unknown line

Thank you guys very much. I was very confused haha.
marquis is offline   Reply With Quote
Reply

Bookmarks

Tags
pcv valve, transmission

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 09:17 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com