Carb problem, or ignition?
Thread Starter
Melting Slicks
Joined: Apr 2004
Posts: 2,083
Likes: 2
From: Montreal Qc.
Carb problem, or ignition?
(79 L48, 700R4, headers not much else)
The car runs great in the driveway, idle to 5000+ but under load it BOGS badly at part throttle, until the revs go up or the secondaries kick in (20mph, floor it, bog, kickdown, BANG! SIDEWAYS
) I'm pretty sure I have no vac leaks, everything not needed is plugged, even headlight stuff.
I'm thinking carb, cause I set up the timing the Lars way, 36 mechanical all in at 2800. (by the way, that was the first time I ever did the recurve, it was a piece of cake after reading 100 threads about it in the last year
) With vac I get a total of close to 50 at 2800-redline
What do I need to do to setup a baseline idle mixture? Right now I'm at: turned it till seated, then backed out 2 full turns. What other adjustments can I make without taking the carb apart? How can I disable the choke to take that out of the equation? I can probably get a vacuum guage if needed.
(carb rebuild is not possible at this juncture, I can't have any more "downtime" at my current parking place...the sister-in-law has put up with 3 months of Vette-In-Pieces already this year)
Thank in advance (haha)
-steve
The car runs great in the driveway, idle to 5000+ but under load it BOGS badly at part throttle, until the revs go up or the secondaries kick in (20mph, floor it, bog, kickdown, BANG! SIDEWAYS
) I'm pretty sure I have no vac leaks, everything not needed is plugged, even headlight stuff.I'm thinking carb, cause I set up the timing the Lars way, 36 mechanical all in at 2800. (by the way, that was the first time I ever did the recurve, it was a piece of cake after reading 100 threads about it in the last year
) With vac I get a total of close to 50 at 2800-redlineWhat do I need to do to setup a baseline idle mixture? Right now I'm at: turned it till seated, then backed out 2 full turns. What other adjustments can I make without taking the carb apart? How can I disable the choke to take that out of the equation? I can probably get a vacuum guage if needed.
(carb rebuild is not possible at this juncture, I can't have any more "downtime" at my current parking place...the sister-in-law has put up with 3 months of Vette-In-Pieces already this year)
Thank in advance (haha)
-steve
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
It sounds like the secondary air valve control spring might be adjusted too loose. Use a piece of wire to hold the secondary air valve closed during WOT. If this cures the bog, adjust the secondary air valve so that it opens a bit later. Trial and error testing will tell you when it is right.
Let us know the final results, whatever they may be.
Mike
Let us know the final results, whatever they may be.
Mike
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
If it falls on its face till the secondaries open then it is the primary jet size. At wide open throttle with the secondary air valve closed the carb is running on the main jets. If the engine is laying down in this area the main jets are too small. Come up a couple jet sizes. You will need to get new main metering rods to keep the part throttle cruise mixture correct.
Also be prepared to go a little leaner on the secondaries once you have the mains right.
BigBlockk
Later.....
Also be prepared to go a little leaner on the secondaries once you have the mains right.
BigBlockk
Later.....
