Slant Six Forum :: Possible Vacuum Leak

: Hi Everyone,
: I just completed my conversion over to the
: Super six and Dutra Dual exhaust setup along
: with a new
: dual exhaust system. Everything went together
: great but, I suspect I may have a vacuum
: leak somewhere around the 'infamous'
: manifolds..!! The engine is lopping when I
: adjust the idle speed on the BBD. The carb
: was totally rebuilt by a great shop and is
: doing fine. Questions...What do you
: recommend I spray around the manifolds and
: carb to see if I can located the leak..??
: Also, should I look at re-timing..?? Please
: give me as many ideas or tips to begin to
: get the idle smoothed out..!! The car runs
: great under load and there is not apparent
: backfiring under compression... I installed
: the manifolds per Doug's recommendations and
: torqued all bolts per specs...Thanks for you
: comments.
: 66 Dart

: Any type of carb cleaner will do the trick, if
: you spray it on a leak area, you will hear
: the idle speed change.
:
: Also check the timing, try a few different
: settings to see if that helps any.
:
: Also try blocking the PCV valve / hose to see
: if that smooths-out the idle. I have seen
: these cause a lean / rough idle condition.
: If it still runs rough after blocking the
: PCV, try slowly closing the choke butterfly,
: a littly at a time. If there is a vacuum
: leak or other lean condition, you will find
: a place where the idle smooths-out with a
: partially closed choke flap.
:
: It could still be a problem inside the carb.
: but let's get through these tests first,
: then go from there.
: DD

: Thanks for the input guys...
: Doug, your duals went on great and the muffler
: shop did a beautiful job on custom making
: the exhaust system. I will have to get some
: digital pictures taken of the entire
: conversion and show them to you..!! I went
: out tonight and adjusted the idle speed to
: stay at approx. 800 rpm. It is still lopping
: and the rpm's flucuate up and down from 600
: to 800 to 1000 back down to 800 etc....I
: reset the timing down as low as I could to
: approx. 3 degrees btdc. I can't go any lower
: without pulling and resetting the
: distributor..!! I drove it for awhile and it
: pulls good when accelerating but definitely
: flucuates when coasting or decelerating..!!
: Sometimes when coming to a stop, the idle
: will be back up around 1200 and won't kick
: down..Maybe there is something still needing
: adjustment on the Carb..!! I will try
: blocking off the PCV valve and your choke
: idea and see what happens...Thanks again for
: you time and ideas..I'll let you know what
: happens...
: 66 Dart

Author:	66Dart [ Wed Jul 11, 2001 5:09 pm ]
Post subject:	Possible Vacuum Leak - Need Advice
Hi Everyone, I just completed my conversion over to the Super six and Dutra Dual exhaust setup along with a new dual exhaust system. Everything went together great but, I suspect I may have a vacuum leak somewhere around the 'infamous' manifolds..!! The engine is lopping when I adjust the idle speed on the BBD. The carb was totally rebuilt by a great shop and is doing fine. Questions...What do you recommend I spray around the manifolds and carb to see if I can located the leak..?? Also, should I look at re-timing..?? Please give me as many ideas or tips to begin to get the idle smoothed out..!! The car runs great under load and there is not apparent backfiring under compression... I installed the manifolds per Doug's recommendations and torqued all bolts per specs...Thanks for you comments. 66 Dart msimpson@whpacific.com

Author:	Doctor Dodge (Doug Dutra) [ Wed Jul 11, 2001 7:11 pm ]
Post subject:	Re: Possible Vacuum Leak - Need Advice
Quote: : Hi Everyone, : I just completed my conversion over to the : Super six and Dutra Dual exhaust setup along : with a new : dual exhaust system. Everything went together : great but, I suspect I may have a vacuum : leak somewhere around the 'infamous' : manifolds..!! The engine is lopping when I : adjust the idle speed on the BBD. The carb : was totally rebuilt by a great shop and is : doing fine. Questions...What do you : recommend I spray around the manifolds and : carb to see if I can located the leak..?? : Also, should I look at re-timing..?? Please : give me as many ideas or tips to begin to : get the idle smoothed out..!! The car runs : great under load and there is not apparent : backfiring under compression... I installed : the manifolds per Doug's recommendations and : torqued all bolts per specs...Thanks for you : comments. : 66 Dart Any type of carb cleaner will do the trick, if you spray it on a leak area, you will hear the idle speed change. Also check the timing, try a few different settings to see if that helps any. Also try blocking the PCV valve / hose to see if that smooths-out the idle. I have seen these cause a lean / rough idle condition. If it still runs rough after blocking the PCV, try slowly closing the choke butterfly, a littly at a time. If there is a vacuum leak or other lean condition, you will find a place where the idle smooths-out with a partially closed choke flap. It could still be a problem inside the carb. but let's get through these tests first, then go from there. DD

Author:	Craig [ Wed Jul 11, 2001 7:55 pm ]
Post subject:	Re: Possible Vacuum Leak - Need Advice
I've had those brass idle fuel pick-up tubes fall out of the diecast part they are pressed into in the venturi cluster assembly of those late BBD carbs. Does not idle worth a @^$%&%$ when that happens. cfield@ll.net

Author:	66 Dart [ Wed Jul 11, 2001 9:31 pm ]
Post subject:	Re: Possible Vacuum Leak - Need Advice
Quote: : Any type of carb cleaner will do the trick, if : you spray it on a leak area, you will hear : the idle speed change. : : Also check the timing, try a few different : settings to see if that helps any. : : Also try blocking the PCV valve / hose to see : if that smooths-out the idle. I have seen : these cause a lean / rough idle condition. : If it still runs rough after blocking the : PCV, try slowly closing the choke butterfly, : a littly at a time. If there is a vacuum : leak or other lean condition, you will find : a place where the idle smooths-out with a : partially closed choke flap. : : It could still be a problem inside the carb. : but let's get through these tests first, : then go from there. : DD Thanks for the input guys... Doug, your duals went on great and the muffler shop did a beautiful job on custom making the exhaust system. I will have to get some digital pictures taken of the entire conversion and show them to you..!! I went out tonight and adjusted the idle speed to stay at approx. 800 rpm. It is still lopping and the rpm's flucuate up and down from 600 to 800 to 1000 back down to 800 etc....I reset the timing down as low as I could to approx. 3 degrees btdc. I can't go any lower without pulling and resetting the distributor..!! I drove it for awhile and it pulls good when accelerating but definitely flucuates when coasting or decelerating..!! Sometimes when coming to a stop, the idle will be back up around 1200 and won't kick down..Maybe there is something still needing adjustment on the Carb..!! I will try blocking off the PCV valve and your choke idea and see what happens...Thanks again for you time and ideas..I'll let you know what happens... 66 Dart msimpson@whpacific.com

Author:	Mike P [ Thu Jul 12, 2001 8:49 am ]
Post subject:	Re: Possible Vacuum Leak - Need Advice
Quote: : Thanks for the input guys... : Doug, your duals went on great and the muffler : shop did a beautiful job on custom making : the exhaust system. I will have to get some : digital pictures taken of the entire : conversion and show them to you..!! I went : out tonight and adjusted the idle speed to : stay at approx. 800 rpm. It is still lopping : and the rpm's flucuate up and down from 600 : to 800 to 1000 back down to 800 etc....I : reset the timing down as low as I could to : approx. 3 degrees btdc. I can't go any lower : without pulling and resetting the : distributor..!! I drove it for awhile and it : pulls good when accelerating but definitely : flucuates when coasting or decelerating..!! : Sometimes when coming to a stop, the idle : will be back up around 1200 and won't kick : down..Maybe there is something still needing : adjustment on the Carb..!! I will try : blocking off the PCV valve and your choke : idea and see what happens...Thanks again for : you time and ideas..I'll let you know what : happens... : 66 Dart Set your timing with a vac guage and monitor vac as RPM changes. Advance to peak vac. then back off 1 or 2 degrees.

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Author:	Chad [ Thu Jul 12, 2001 3:11 pm ]
Post subject:	Re: Possible Vacuum Leak - Need Advice
Quote: : Thanks for the input guys... : Doug, your duals went on great and the muffler : shop did a beautiful job on custom making : the exhaust system. I will have to get some : digital pictures taken of the entire : conversion and show them to you..!! I went : out tonight and adjusted the idle speed to : stay at approx. 800 rpm. It is still lopping : and the rpm's flucuate up and down from 600 : to 800 to 1000 back down to 800 etc....I : reset the timing down as low as I could to : approx. 3 degrees btdc. I can't go any lower : without pulling and resetting the : distributor..!! I drove it for awhile and it : pulls good when accelerating but definitely : flucuates when coasting or decelerating..!! : Sometimes when coming to a stop, the idle : will be back up around 1200 and won't kick : down..Maybe there is something still needing : adjustment on the Carb..!! I will try : blocking off the PCV valve and your choke : idea and see what happens...Thanks again for : you time and ideas..I'll let you know what : happens... : 66 Dart hmmmmmn, methinks worn throttle shaft. beardliz@msn.com

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