ASJ1960

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?

Nowhere Man

Did you check the floats and fuel levels in the front bowl

Frankie the Fink

Not nearly enough info. Is the car stock with the stock WCFB ? Is your curb idle/mixture set properly ? Did it do this before your changes ?

ASJ1960

My mechanic has been tweaking/tuning the carbs since they were rebuilt, but they seem to be working fine.

ASJ1960

The car is not stock, no. The carbs may not be original, but are appropriate for the engine/car.

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.

Frankie the Fink

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 ?

GTOguy

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.

Westlotorn

Good advice

ASJ1960

Thanks for the input. I'm not trying to be coy when I say "appropriate", but there's 45 years worth of work on the car that I can't vouch for. The engine is 270/283, but from a car a few years older. The transmission is also not the original, but is the right part. I believe the carbs are Holly, but don't know if they are actually original or just the right parts for the car.

ASJ1960

Thanks for the advice; will certainly have that looked at. But given that the problem predated the rebuild of the carbs, does that still sound like a possible cause?

Frankie the Fink

Guaranteed non-original carbs if they are Holley - originals would be Carter WCFBs. And, I agree, the float level is highly suspect...

GTOguy

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.

Westlotorn

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.

ASJ1960

Ha! Can't see myself re-adjusting the float every time I go down a hill, so hopefully I can find a small tweak like you did that can keep me from stalling without making a mess of the rest of my ride.

ASJ1960

Question, please...can you explain why lowering the float would increase the fuel supply when on an incline? That seems counter-intuitive to me, but that's to be expected from someone completely ignorant of how the thing works.

Westlotorn

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.

Frankie the Fink

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....

ASJ1960

Dumb question, but certainly not my first...I'm assuming that the sputtering and drop in RPMs is starving for fuel, not flooding. But how would I know? How would a flooding engine behave in that situation? Sharp decline, slow to a near-stop at a stop sign, RMPs drop from 900 to 500 or worse, threatening to stall.

One more thing...after it stalls in that situation, it has trouble starting again. So maybe it IS flooding after all...?

ASJ1960

They are Carter carbs, just rebuilt about two weeks ago. But again, no idea of their history re: how long they've been on the car.

Frankie the Fink

Well then, a few things:

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.