csysman

I had my friend drive the 67 L79 home from the BShop after they detailed and cleaned the car for its winter hibernation so its ready for me when I get a chance to bring it down to Florida (where I am now) and he was concerned about the surging and bucking when your foot was off the gas pedal also hard to hold an Idle (stalls)- as soon as your foot steps on the gas pedal... all was well ...let off and (in any gear - bucked and surged ... some backfire thru the side pipes does occur -( the car starts up with no issues at all but feather the gas to keep it running ) ... He thinks the distributor may be the culprit that it may have a vacuum leak, although he did not hear anything abnormal - i had experienced this myself ...thought it was a hotter cam the former owner had installed when the motor was rebuilt ..and was thinking of removing it and installing a stock one back in to correct this drivability issue - - it just runs perfect when fuel is delivered ... if any one can shed some insight please advise
Thanx as always
Charlie

Tampa Jerry

Charlie: I would put a vacuum gauge on the engine and see how it reads. Google engine vacuum and you will find a few websites that explain and demonstrate very well how to read the findings. It could be timing or a bad can on the distributer or a carb issue. Where in the sunshine state are you located?? Jerry

csysman

Jerry We are in Delray beach (thanx for the input)

Matt Gruber

sounds like the cam was changed and they neglected to change the vacuum advance to match the new cam. the cam has lower vacuum than stock EXCEPT when u let up, then it increases advance beyond what the new combo wants.

csysman

Thanx for the advise --- appreciate it

csysman

Sounds like it may be the cure - I will have that checked out
Happy Holidays to everyone

Matt Gruber

google:
lars vacuum advance
.
11 page paper gives all the details

MikeM

Once you get the idle speed established, I don't see any way a mis-matched can will cause the engine to stall at idle. It can cause other problems.

w1ctc

If the vacuum can is attached to manifold vacuum and is pulling the timing up, a little stumble will slow the engine down. If the can is on the edge the timing will drop slowing the engine and less vacuum etc.
The next thing could be a check of the power valve. When it idling can you see gas dribbling from the venturi?

csysman

Thanx to all that have replied - found the problem and it was solved when my friend retarded the timing (the distributor was to advanced ) set it back and the car runs great - no bucking or surging )he has not had a chance to check the timing but says he will before I get it shipped down to Florida - hope to have it in time for Kissimmee -its only about 3hrs away and would be great to drive it there
Happy Holidays to everyone
Charlie