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View Full Version : In long corners, I starve my carb


mazspeed
09-23-2007, 04:15 AM
I needed to ask this question because of piece of mind. When I was testing my car, we would go into long fast corners, and my engine would die, due to not having enough fuel. I know my float bowls are set a little low, but how can this be fixed? I'm not getting the answers I want to hear (carbs are problems with g forces) and that sort of thing. I should not be stalling the car in or right after I leave a hard corner. Is it just a float level adjustment or something else? The rerason why the floats are low, was because of stopping the car fast would also kill it if I'm on idle, and when the car dies, so does my hydroboost, and that was a saftey issue. The carb shop rebuilt my carb for blower specs. I have a 3/8 inch line for fuel, and a return lie as well. What can we do?

chicane
09-23-2007, 11:16 AM
You need to install the correct floats... and probably install jet extensions on the secondaries.

Years ago I had the same issue. One day I just happened to be at GW picking up some parts and remembered that Brad Urbans "Carb Shop" was about 100 yards away. I walked over, talked to Brad, told him my issues and he sent me out the door with a set of road race floats.

http://www.customcarbs.com/carbshopcatalog.htm

I never had any issues with the carb after that.

mazspeed
09-23-2007, 11:52 AM
You need to install the correct floats... and probably install jet extensions on the secondaries.

Years ago I had the same issue. One day I just happened to be at GW picking up some parts and remembered that Brad Urbans "Carb Shop" was about 100 yards away. I walked over, talked to Brad, told him my issues and he sent me out the door with a set of road race floats.

http://www.customcarbs.com/carbshopcatalog.htm

I never had any issues with the carb after that.

Ok cool. Did this help with stopping fast as well, not killing it at idle? Thanks for the response.

Spiffav8
09-23-2007, 12:00 PM
Just to make you feel better....carbs are problems with g forces. :cheers:

mazspeed
09-23-2007, 12:01 PM
Just to make you feel better....carbs are problems with g forces. :cheers:
hehehe not much better. :thumbsup:

chicane
09-23-2007, 02:05 PM
Ok cool. Did this help with stopping fast as well, not killing it at idle? Thanks for the response.

Yeah... it sure did.

The problem with the engine during decel is a possibility of one or more things. The first is the vent tubes spilling over into the carb venturi... which is a common problem when you get to 'that' level of braking performance. Next, would be that the engine leans out from the primary jets being uncovered. When the fuel in the bowl climbs the front of the bowl itself, it uncovers the primary jets. Not to forget to mention that if you are using stock floats... it will close the needle and seat too soon and the fuel level in the bowl will be down.

What I did to alleviate myself from these problems is:

Carb Shop floats
0.120 Viton needle and seats, front and rear
Metering plate vents, front and rear
Jet extensions on the secondary main jets
Float adjustment right to the bottom of the threads in the window

Carbs do not have any issue with g-forces... its the idiot that doesn't know how to tune the carb correctly... that has the issues. :lol:

The next series of problem's I encountered... was with loss of oil pressure, under braking. The chassis stopped so well that the oil pretty much collected in the timing cover and uncovered the oil pick-up... even when it was run 1.5-2 qts overfull. Lets just hope you dont get there.

mazspeed
09-23-2007, 03:03 PM
Yeah... it sure did.

The problem with the engine during decel is a possibility of one or more things. The first is the vent tubes spilling over into the carb venturi... which is a common problem when you get to 'that' level of braking performance. Next, would be that the engine leans out from the primary jets being uncovered. When the fuel in the bowl climbs the front of the bowl itself, it uncovers the primary jets. Not to forget to mention that if you are using stock floats... it will close the needle and seat too soon and the fuel level in the bowl will be down.

What I did to alleviate myself from these problems is:

Carb Shop floats
0.120 Viton needle and seats, front and rear
Metering plate vents, front and rear
Jet extensions on the secondary main jets
Float adjustment right to the bottom of the threads in the window

Carbs do not have any issue with g-forces... its the idiot that doesn't know how to tune the carb correctly... that has the issues. :lol:

The next series of problem's I encountered... was with loss of oil pressure, under braking. The chassis stopped so well that the oil pretty much collected in the timing cover and uncovered the oil pick-up... even when it was run 1.5-2 qts overfull. Lets just hope you dont get there.

Wow, what great info. Ill forwarded this info to Kevin and the guys at the shop. I will make sure they do this very thing. The carb shop did rebuild the carb, but not sure to what level. I know it cost around $600 so I'm not sure what level that went to and what changes they made. The guys were saying that the car was stopping so fast that the fuel slosh was killing the engine. The car does pull serious g forces in corners and in braking and that's why I have it set up this way, and hate the fact that the carb was limiting what I was doing. Thanks again for this info.

Blown353
09-23-2007, 05:16 PM
There is a good chance your dying problem on hard decel is a result of rich-killing it. Does it belch a big black cloud when you restart it?

This is a typical problem with a blowthrough carb and the milled down choke horn. They also usually mill down the vent tubes too... and the now shortened vent tubes don't resist sloshing as easily and under hard braking you slosh fuel out the secondary bowl vent and drown the engine in fuel. If it really spits out a black cloud when you restart it you can pretty much conclude it's fuel slosh out the vents.

My blowthrough carb had the same issue. Take a really hard stop and it would die, and on restart it would absolutely billow black smoke from all the fuel. I re-extended the bowl vents up to almost the very top of my carb hat and the problem went away.

mazspeed
09-23-2007, 05:36 PM
I'm not sure if black smoke comes out. I have never checked for it. I do have a taller hat now, so making the vent tubes longer soundsl ike that would work as well.

Blown353
09-23-2007, 05:45 PM
I'm not sure if black smoke comes out. I have never checked for it. I do have a taller hat now, so making the vent tubes longer soundsl ike that would work as well.

Purposely do a hard stop and let it die. Then when you restart it pay attention to the rearview mirror or have someone who can jump out and watch.

If it puffs black it died because it flooded and the cause of your problem is most likely the shortened vent tubes.

chicane
09-23-2007, 05:47 PM
...Good point with the vent tube lengths.

The metering plate vents and jet extentions will help with this a little as well.

4mm
09-23-2007, 06:27 PM
I had the same problem in my Mustang. When I would corner/turn hard, the engine would start sputtering and start to die and I would have to slow down and pedal on the gas a bit to keep the engine running and from dying. Same thing when braking hard.

The carb had been rebuilt in spec to my engine but they failed to install the fuel baffles that help keep the gas from spilling from the vent tube.

andrewmp6
09-24-2007, 01:28 AM
if you dont have a carb spacer get one they are cheap and help alot.

mazspeed
09-24-2007, 09:20 AM
if you dont have a carb spacer get one they are cheap and help alot.

Problem with that is the hood clearence. Ill go down there today and see if that's working as they do want to put one on.

andrewmp6
10-02-2007, 07:40 PM
so did you fix the problem or still scratching your head.