![]() |
![]() |
#1 |
Registered User
Join Date: Jan 2006
Location: Houston
Posts: 434
|
BB Valve Clatter
Removed the intake manifold to clean it up and replace the gaskets. Now that the work is complete, my valves clatter when I am on the highway and accelerating. Timing is at 8 degrees btdc without vaccuum. When running, the vacuum advance is connected to ported vacuum under the throttle on the carberator (no vacuum at Idle). The valves did not clatter before the removal. I did not check what the timing was beforehand. Any suggestions?
I did a search and the answers are all over the place regarding ported and non ported vacuum. Which tells me, if my timing is set correctly, advance can be hooked to either ported or nonported. So, how do I know when vacuum is correct? Do I advance it or retard it? Do I leave it on ported or, do I go to nonported? I do not know how to measure mechanical advance. Last edited by stope4; 03-29-2008 at 07:35 AM. |
![]() |
![]() |
![]() |
#2 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
|
Re: BB Valve Clatter
With the vacuum advance connected to port vacuum under acceleration the vacuum advance is fully advanced. Some vacuum advance units will move the timing 15 degrees or more.
I would try moving the vacuum advance hookup to the vacuum on idle port. Jim
__________________
1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
![]() |
![]() |
![]() |
#3 |
Registered User
Join Date: Jun 2002
Location: central pa
Posts: 1,525
|
Re: BB Valve Clatter
It sounds like an air leak. Factory vacuum on a BBC points dizzy is full vacuum. Ported and full ports provide the same vacuum while going down the highway. Ported takes the advance off the dizzy while idling for emissions. I run full even with HEI as it stops the stumble off idle and did improve my MPG.
If you didn't have ping/rattle before you pulled it I would start looking for a vacuum leak. Did you take the carb off the intake? Make sure all of the vacuum hoses are connected and not split.
__________________
72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne |
![]() |
![]() |
![]() |
Bookmarks |
|
|