![]() |
Register or Log In To remove these advertisements. |
|
|
![]() |
|
Thread Tools | Display Modes |
![]() |
#1 |
Senior Member
Join Date: Nov 2003
Location: Brookings, SD
Posts: 10,497
|
Where does my distributor vacuum go?
Does it hook up to the capped port on the front of my carb? The screwdrivere is pointing to the port I am referring to. This is the only vacuum port I can find on the carb.
Click on the picture for a bigger version.
__________________
Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs. Last edited by 71swb4x4; 01-07-2008 at 12:25 PM. |
![]() |
![]() |
![]() |
#2 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,647
|
Re: Where does my distributor vacuum go?
Pretty sure that's where mine is -- not easy to check right now with several inches of wet snow on the hood...
![]()
__________________
- Mike - 1972 K20 LWB 350/350/205 RIP El Jay Last edited by Stocker; 01-07-2008 at 12:42 PM. |
![]() |
![]() |
![]() |
#3 | |
Registered User
Join Date: Oct 2006
Location: Cheney, KS
Posts: 669
|
Re: Where does my distributor vacuum go?
Anywhere theres manifold vaccum
__________________
Quote:
|
|
![]() |
![]() |
![]() |
#4 |
Senior Member
Join Date: Jun 2006
Location: Oregon City, Or
Posts: 758
|
Re: Where does my distributor vacuum go?
You want it hooked to a port that increases the vac as the rpm's go up. If you hook it to a manifold vac port it will be at constant full advance in the timing. Just start the motor and use a vac gauge or hold your finger over the port. Raise the rpm it should increase the vac as you raise the rpm.
__________________
63 short fleet Patina build http://67-72chevytrucks.com/vboard/s...d.php?t=287751 Man I want another one. |
![]() |
![]() |
![]() |
#5 | |
Registered User
Join Date: Oct 2007
Location: Garageless, Missouri
Posts: 408
|
Re: Where does my distributor vacuum go?
Quote:
__________________
R.I.P ESLL Even as the body dies the spirit lives on in the people you touched Last edited by DavesRide; 01-07-2008 at 01:05 PM. Reason: Clarification |
|
![]() |
![]() |
![]() |
#6 |
Registered User
Join Date: Oct 2007
Location: Desert Southwest
Posts: 540
|
Re: Where does my distributor vacuum go?
None of the above is entirely correct.
What you need is to hook up to the vacuum post that DOES NOT (assuming everything is set up properly) have vacuum at idle. Once the throttle is opened slightly, the port will have vacuum. From there, the vacuum will be engine vacuum which changes depending on throttle position and engine load. The port you are pointing to looks to be the right place. You do not want straight manifold vacuum as you will have a hard time setting and keeping a consistent idle speed. |
![]() |
![]() |
![]() |
#7 |
Senior Member
![]() Join Date: Dec 2006
Location: Studio City, Calif.
Posts: 2,873
|
Re: Where does my distributor vacuum go?
Yes (to your question).
__________________
'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. |
![]() |
![]() |
![]() |
#8 | |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
|
Re: Where does my distributor vacuum go?
Quote:
It appears from the picture that he does have an HEI distributor, if so then my post is for informational purposes only. There are tuners that recommend using full manifold vacuum in all cases and claim better performance. I can not substantiate that so I will defer to the experts.
__________________
VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
|
![]() |
![]() |
![]() |
#9 | |
Account Suspended
Join Date: Sep 2005
Location: Monroe, WA
Posts: 3,815
|
Re: Where does my distributor vacuum go?
Quote:
![]() The simple answer to the question is that if you have a stock or near-stock cam, you should connect to ported vacuum as no additional vacuum advance is needed at idle. Ported vacuum is taken above the throttle butterflies, and so is less than manifold vacuum at idle. If you have an aftermarket cam that's a little warmer, connecting the distributor advance to manifold vacuum will provide additional vacuum advance at idle which can improve idle quality. Once the butterflies are open to any extent, manifold vacuum and ported vacuum will be virtually identical and so there is no performance/fuel economy/etc. difference - the only reason for additional advance at idle is to smooth out a lumpy cam. BTW, this has been hashed out a million times - search is your friend ![]() Last edited by Billla; 01-08-2008 at 05:36 AM. |
|
![]() |
![]() |
![]() |
#10 |
Registered User
Join Date: Oct 2006
Location: maple ridge, b.c., canada
Posts: 190
|
Re: Where does my distributor vacuum go?
I'm gonna have to agree with Billla
![]() |
![]() |
![]() |
![]() |
#11 | |
Registered User
Join Date: Oct 2007
Location: Desert Southwest
Posts: 540
|
Re: Where does my distributor vacuum go?
Quote:
I would expect that the full vacuum at idle would be in conjunction with all the smog controls and equipment that would be installed on the engine that the HEI would have originally been removed from. Since the engine looks to be more like a non-smog era type, I would still run the vac advance to the ported vacuum so it would operate as a stock type distributer would. |
|
![]() |
![]() |
![]() |
#12 |
Registered User
Join Date: Sep 2007
Location: Emporium,Pa
Posts: 248
|
Re: Where does my distributor vacuum go?
I have the vaccum advance hose connected to the vaccum port located underneath the fuel inlet line on the left hand side of the carb. As stated this is the ported vaccum for the Rochester QJet carb (I.e no vaccum at idle but pressure increases with engine RPM's) from my research this is where it is on as near as I can tell all stock engines with Qjet carbs until the middle 80's when the switch to TBI tock place. The PO of the truck had the hose hooked to a constant vaccum sorce on the carb causing absolutely NO advance at higher RPM's. Just my 2 cents.
__________________
"When you were born, you cried and the world rejoiced. Live your life so that when you die, the world cries and you rejoice." [Cherokee saying] 2001 Dodge Ram Sport 1500 4x4. (old ride) 1987 GMC V1500 Sierra Classic ("new" ride) |
![]() |
![]() |
![]() |
#13 |
Senior Member
Join Date: Jun 2001
Location: Shelbyville, KY
Posts: 3,269
|
Re: Where does my distributor vacuum go?
Kind of depends on the model of HEI, cam, carb. In any case you set your timing with the vac line bocked off --not connected to the distributor. If you time it to 8 deg advance - you may or may not have adequate idle so I've had my best results by setting initial timing, then with a vacuum gauge, hood up the vac advance to manifold vacuum and then refine the timing to maximize Vacuum at the gauge --also may need to tweek the idle mix settings. This has worked for me in every case. ___See GMC Pauls tech tips on timing via Vacuum____Huck
|
![]() |
![]() |
![]() |
Bookmarks |
|
|