#1  
Old 03-15-2020, 02:55 PM
tripowergp tripowergp is offline
Member
 
Join Date: Apr 2007
Location: wonder lake il.
Posts: 48
Default Low vacuum

After a center carb rebuild, I am only getting 8" of vacuum from the fitting that is on the carb base. The carb does have the hot idle compensater. Only change I made was I switched from the base gasket with open center to the one with the 2 holes. Would this gasket change cause this problem? 65 setup, Thanks

  #2  
Old 03-15-2020, 03:30 PM
Goatracer1 Goatracer1 is offline
Ultimate Warrior
 
Join Date: Oct 2003
Location: NH
Posts: 3,768
Default

Easy enough to check. Just install the original type gasket.

  #3  
Old 03-15-2020, 04:10 PM
Kenth's Avatar
Kenth Kenth is offline
Ultimate Warrior
 
Join Date: Feb 2003
Location: The Kingdom of Sweden
Posts: 5,457
Default

Small base 2 GC w/HIC may use this throttle body gasket.
Attached Thumbnails
Click image for larger version

Name:	-65 2G bowl gasket.jpg
Views:	144
Size:	41.3 KB
ID:	534537  

__________________
1966 GTO Tri-Power
1970 GTO TheJudge
http://www.poci.org/
http://gtoaa.org/
  #4  
Old 03-15-2020, 04:19 PM
tripowergp tripowergp is offline
Member
 
Join Date: Apr 2007
Location: wonder lake il.
Posts: 48
Default

I might of Mis-spoke, I changed the gasket between carb base and manifold

  #5  
Old 03-15-2020, 04:22 PM
Kenth's Avatar
Kenth Kenth is offline
Ultimate Warrior
 
Join Date: Feb 2003
Location: The Kingdom of Sweden
Posts: 5,457
Default

Open or 2 hole flange gasket will not affect the vacuum signal.

__________________
1966 GTO Tri-Power
1970 GTO TheJudge
http://www.poci.org/
http://gtoaa.org/
  #6  
Old 03-15-2020, 04:30 PM
tripowergp tripowergp is offline
Member
 
Join Date: Apr 2007
Location: wonder lake il.
Posts: 48
Default

Thanks for the info

  #7  
Old 03-17-2020, 11:32 PM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,387
Default

Did you have good vacuum before the carb rebuild? If so, there is likely something plugged in the idle circuit, probably the venturi cluster. Idle tubes, idle bypass restrictors, are the ones with small holes that could be plugged. If you give us the parameters of the engine--cam, C.R., cubic inches, etc., we can tell you what the idle circuit orifice sizes need to be. A moot point if it ran OK before the rebuild. PM if you need to.

Also, I've had low vacuum with a carb-to-manifold gasket with holes in it outside the two throttle bores. The base of the carb will not seal to the manifold with the "Chev" style gasket. You need to use a solid base gasket with only throttle bore holes and carb mount holes. As Kenth pointed out, the open or closed gasket makes no difference.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'99 Bonneville SE Sedan
  #8  
Old 03-18-2020, 04:23 PM
jotrout jotrout is offline
Senior Chief
 
Join Date: Feb 2002
Location: San Ramon, CA
Posts: 459
Default

OP: Sorry to hijack your post.

Hello Dick,
Is the 66 center carb gasket the same requirement; with just venturi and post holes? I suffer from low vacuum for the front disk brakes and this maybe the cause. I run the tripower with a 455 with a big thumper cam. .560 lift.

Thanks
Joe

  #9  
Old 03-18-2020, 11:42 PM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,387
Default

Has the center carb been calibrated for your cam? Let us know your engine parameters and we’ll tell you how to modify your center carb for decent idle, which equates to higher vacuum.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'99 Bonneville SE Sedan
  #10  
Old 06-16-2020, 10:44 PM
jotrout jotrout is offline
Senior Chief
 
Join Date: Feb 2002
Location: San Ramon, CA
Posts: 459
Default

Hello Dick,
I've been away from the site for awhile and just picking up your message. Thank you for your offer. I'd like to take a raincheck as I'm working on putting her all back together with trim and badges from a new paint job. Then new tires and rims. Then I can concentrate on the tripower.

Once again I appreciate the offer on guidance. Joe

Reply

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 02:30 PM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017