[C1] Engine sputtering on sharp decline
Thread Starter
Cruising
Joined: Feb 2006
Posts: 13
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Engine sputtering on sharp decline
Hi, guys. I have a 1960 Vette (not original parts, but all appropriate). Recently replaced the fuel pump and had the carburetors rebuilt.
But...on a steep decline, especially when braking, I really lose RPMs to the point of near-stalling or stalling. One intersection in particular, with a stop sign at the bottom of a steep decline, gets me almost every time.
Might that be the pick-up tube in the tank?
But...on a steep decline, especially when braking, I really lose RPMs to the point of near-stalling or stalling. One intersection in particular, with a stop sign at the bottom of a steep decline, gets me almost every time.
Might that be the pick-up tube in the tank?
Thread Starter
Cruising
Joined: Feb 2006
Posts: 13
Likes: 0
And yes, the idle always struggled on a sharp decline. That's what makes me think it has nothing to do with the carb rebuild & new fuel pump.
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,145
Army
On a stock dual quad car most find that the idle has to be bumped up to ensure a smooth, consistent idle. I run my dual quads (or I did before I sold my car this week) at 850RPM - pretty typical.
Out of my 9 years on the forum I think this is the first time I've heard of this problem with a C1 - it is not common inotherwords. Prob related to your non-stock 'appropriate' configuration.
I don't know what 'appropriate' means for your car....let's make it simple what engine/carbs are in the car ?
Out of my 9 years on the forum I think this is the first time I've heard of this problem with a C1 - it is not common inotherwords. Prob related to your non-stock 'appropriate' configuration.
I don't know what 'appropriate' means for your car....let's make it simple what engine/carbs are in the car ?
Race Director
Joined: Apr 2015
Posts: 17,571
Likes: 3,460
From: Fresno California
Rough running/stall out at an angle or incline when the car runs fine otherwise is indicative of a float level problem. If it were the fuel pump or pickup in the tank, the car would have to run a couple of minutes at least to deplete the gas in the carbs and filter bowl. So, I'd have the float level and float drop checked.
Le Mans Master
Joined: Feb 2008
Posts: 6,462
Likes: 1,888
From: Folsom CA
Rough running/stall out at an angle or incline when the car runs fine otherwise is indicative of a float level problem. If it were the fuel pump or pickup in the tank, the car would have to run a couple of minutes at least to deplete the gas in the carbs and filter bowl. So, I'd have the float level and float drop checked.
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Thread Starter
Cruising
Joined: Feb 2006
Posts: 13
Likes: 0
On a stock dual quad car most find that the idle has to be bumped up to ensure a smooth, consistent idle. I run my dual quads (or I did before I sold my car this week) at 850RPM - pretty typical.
Out of my 9 years on the forum I think this is the first time I've heard of this problem with a C1 - it is not common inotherwords. Prob related to your non-stock 'appropriate' configuration.
I don't know what 'appropriate' means for your car....let's make it simple what engine/carbs are in the car ?
Out of my 9 years on the forum I think this is the first time I've heard of this problem with a C1 - it is not common inotherwords. Prob related to your non-stock 'appropriate' configuration.
I don't know what 'appropriate' means for your car....let's make it simple what engine/carbs are in the car ?
Thread Starter
Cruising
Joined: Feb 2006
Posts: 13
Likes: 0
Rough running/stall out at an angle or incline when the car runs fine otherwise is indicative of a float level problem. If it were the fuel pump or pickup in the tank, the car would have to run a couple of minutes at least to deplete the gas in the carbs and filter bowl. So, I'd have the float level and float drop checked.
Race Director
Joined: Apr 2015
Posts: 17,571
Likes: 3,460
From: Fresno California
Yes. I HAVE run into the elusive wire that sways in the breeze and shorts out only under certain conditions and angles, but it's about a million times rarer than a messed up float level. Depending on the degree of slope, you may just have to live with it. My carbureted '83 Toyota 4x4 floods out on super steep slopes....the angle is too much for the carb design.
Le Mans Master
Joined: Feb 2008
Posts: 6,462
Likes: 1,888
From: Folsom CA
My friend and I installed a small block Chev in a Landcruiser and after getting all the bugs out of it took it on the famous Rubicon 4x4 Trail in the Lake Tahoe area. It was a two day trip on extreme 4x4 trail. The first day we could hardly keep the engine running even though it ran perfect on flat ground. We kept lowering the float level as day one went on, external adjusting floats on the Holley Carb, finally by day end we had it dialed in perfect and Day 2 went smooth as silk. Did not have to adjust them back up once on flat ground again it still ran perfect. Day one was a mess. Float adjustment can really mess you up on grades.
Thread Starter
Cruising
Joined: Feb 2006
Posts: 13
Likes: 0
My friend and I installed a small block Chev in a Landcruiser and after getting all the bugs out of it took it on the famous Rubicon 4x4 Trail in the Lake Tahoe area. It was a two day trip on extreme 4x4 trail. The first day we could hardly keep the engine running even though it ran perfect on flat ground. We kept lowering the float level as day one went on, external adjusting floats on the Holley Carb, finally by day end we had it dialed in perfect and Day 2 went smooth as silk. Did not have to adjust them back up once on flat ground again it still ran perfect. Day one was a mess. Float adjustment can really mess you up on grades.
Last edited by ASJ1960; Jul 26, 2016 at 01:57 PM.
Thread Starter
Cruising
Joined: Feb 2006
Posts: 13
Likes: 0
My friend and I installed a small block Chev in a Landcruiser and after getting all the bugs out of it took it on the famous Rubicon 4x4 Trail in the Lake Tahoe area. It was a two day trip on extreme 4x4 trail. The first day we could hardly keep the engine running even though it ran perfect on flat ground. We kept lowering the float level as day one went on, external adjusting floats on the Holley Carb, finally by day end we had it dialed in perfect and Day 2 went smooth as silk. Did not have to adjust them back up once on flat ground again it still ran perfect. Day one was a mess. Float adjustment can really mess you up on grades.
Last edited by ASJ1960; Jul 26, 2016 at 02:10 PM.
Le Mans Master
Joined: Feb 2008
Posts: 6,462
Likes: 1,888
From: Folsom CA
Ours was flooding out killing the engine when we went uphill or downhill.
Adjustment was tedious because we did not wish to run out of fuel so we did it slowly till we were dialed and it worked. The engine was so exposed it was easy to give it a pretty quick float adjust and get back on the trail.
If yours is starving for fuel that is the opposite of our issue.
If you are flooding on hills Lower your Floats.
Adjustment was tedious because we did not wish to run out of fuel so we did it slowly till we were dialed and it worked. The engine was so exposed it was easy to give it a pretty quick float adjust and get back on the trail.
If yours is starving for fuel that is the opposite of our issue.
If you are flooding on hills Lower your Floats.
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,145
Army
I would wonder if perhaps the floats were sticking (hitting side of float bowl) which improperly positioned floats in the original WCFB very tight float bowls are notorious for....which is why its important to give the configuration details of your setup. I didn't ask capriciously.
It could still be a problem with Holleys I guess. Sometimes there are characteristics you just learn to live with. Barry Grant made a carb that would nearly always stall out on a panic stop...when a friend called them describing a problem the response was that panic stops aren't a normal situation. Hmmmm....
It could still be a problem with Holleys I guess. Sometimes there are characteristics you just learn to live with. Barry Grant made a carb that would nearly always stall out on a panic stop...when a friend called them describing a problem the response was that panic stops aren't a normal situation. Hmmmm....
Last edited by Frankie the Fink; Jul 27, 2016 at 08:00 AM.
Thread Starter
Cruising
Joined: Feb 2006
Posts: 13
Likes: 0
Ours was flooding out killing the engine when we went uphill or downhill.
Adjustment was tedious because we did not wish to run out of fuel so we did it slowly till we were dialed and it worked. The engine was so exposed it was easy to give it a pretty quick float adjust and get back on the trail.
If yours is starving for fuel that is the opposite of our issue.
If you are flooding on hills Lower your Floats.
Adjustment was tedious because we did not wish to run out of fuel so we did it slowly till we were dialed and it worked. The engine was so exposed it was easy to give it a pretty quick float adjust and get back on the trail.
If yours is starving for fuel that is the opposite of our issue.
If you are flooding on hills Lower your Floats.
One more thing...after it stalls in that situation, it has trouble starting again. So maybe it IS flooding after all...?
Last edited by ASJ1960; Jul 28, 2016 at 10:40 AM.
Thread Starter
Cruising
Joined: Feb 2006
Posts: 13
Likes: 0
I would wonder if perhaps the floats were sticking (hitting side of float bowl) which improperly positioned floats in the original WCFB very tight float bowls are notorious for....which is why its important to give the configuration details of your setup. I didn't ask capriciously.
It could still be a problem with Holleys I guess. Sometimes there are characteristics you just learn to live with. Barry Grant made a carb that would nearly always stall out on a panic stop...when a friend called them describing a problem the response was that panic stops aren't a normal situation. Hmmmm....
It could still be a problem with Holleys I guess. Sometimes there are characteristics you just learn to live with. Barry Grant made a carb that would nearly always stall out on a panic stop...when a friend called them describing a problem the response was that panic stops aren't a normal situation. Hmmmm....
Last edited by ASJ1960; Jul 28, 2016 at 04:15 PM.
Team Owner
Joined: Aug 2007
Posts: 58,061
Likes: 7,145
Army
Float height and a PRECISE positioning of the float in the bowl is hyper-critical on these carbs so I hope your rebuilder was savvy on those points. There is a "left turn stall" fix that has been a known problem in these carbs for years. Fuel can slosh over into a passage and essentially flood the car to the near stalling point.
Its a simple fix but generally the issue only occurs on left turns but any inclines can exaggerate it...
So, to answer your question, yes the stumbling could easily be a flooding condition, in fact, I would give that a high probability.
Last edited by Frankie the Fink; Jul 28, 2016 at 04:56 PM.