Carb problem ? or something else...
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 816
Likes: 1
From: Finland
Carb problem ? or something else...
During heavy braking when coming fast towards red lights in traffic my engines (-73BB with Holley850dp and TH400) idle rpm drops from normal 650 to very low and fights to survive and sometimes even dies away. It helps if I push a bit the accelerator during the last bit of braking. The A/F meter reads around 0.9 all the time so it does not seem to be due to lean or rich condition. In the morning I did open the sight plugs (engine off) - in front all ok but in back plenty of gas come out...screwed the adjustment bar one turn up but that maybe brought the situation even worse...must continue later today...how can you see if the gas level is too high or if the needle/needlevalve is bad...can this anyway cause the engine to die away during braking?
Last edited by Vesa; Sep 21, 2005 at 06:39 AM.
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 816
Likes: 1
From: Finland
Originally Posted by TheKomoman
I'll repeat what seems something of a mantra around here.... most carb problems are timing problems. Have you checked out Lars paper on timing on corvettefaq.com?
Last edited by Vesa; Sep 21, 2005 at 08:07 AM.
Instructor
Joined: Dec 2004
Posts: 216
Likes: 1
From: Lapeer Michigan
Safety Car
Joined: Jul 2002
Posts: 3,770
Likes: 3
From: St Louis MO
During braking, gas in the secondary bowl will pile up on the metering block and if the float level is high, there will be enough gas in the bowl to find it's out into the boosters, causing a bog. Fix this by lowering the float level 1/4 turn until the symptom goes away.
Safety Car
Joined: Jun 2004
Posts: 4,652
Likes: 80
From: Lakeland Florida
My Holley carb book states that somthing called "pullover" is a condition that may cause fuel to spill through discharge nozzles and vent into the carb. air inlet on ABRUPT STOPS OR TURNS to cause over rich air/fuel mixture. The engine will then run erratically or stall.
kdf
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 816
Likes: 1
From: Finland
Originally Posted by 1BAD80
Float need to be set correctly.
http://www.holley.com/TechService/Library.asp
http://www.holley.com/TechService/Library.asp
That adjustment instruction paper with pictures on Holley home pages is great! The picture showed me that yesterday when trying to cure the problem by turning 1/2 turn I managed to figure that I need to turn it counterclockwise - and that made the symptoms even worse - but now after seing that picture I turned it back 1/2 clockwise + an additional 1/2 turn to fix the original problem - and yes when opening the sight hole nothing comes out and the level is just there almost starting to come out. And the road test with hard brakings went well, there was no symptoms at all left
