carb problem autocrossing
 

Hey guys,

My current setup is:

street ported 12a
racing beat header
custom exhaust
holley blue fuel pump set at 7 psi
holley street port carb setup

I run in SM2 on Hoosiers... the problem I'm having is that the car cuts out in corners... I am sure that it has to do with the carb, because I didn't have a problem before the holley.... any ideas? suggestions?

Dan

Fuel slosh causing the jets to over/under flow?

Don't know anything about your particular carb but fuel starvation in corners is a classic sign of the float sticking.

If the problem is lack of fuel caused by fuel slosh i would suggest that you build a surge tank. This will ensure that you allways have fuel in the system!

alot of old school hot rodders told me to rotate the Holley carb so that the front and back fuel bowls are facing towards you rather than parallel get me?? because in the holley install instructions it says the carb should face a certain way wich has the fuel bowls on each side , so when in a sharp turn or something amoung that nature it causes all your Fuel to go to rush one side causing it to either cut out or a studder , Ok rotate it so that your throttle linkage is either on your Right or left (depends on you) .....so if your carb looks like this from the front of your Car ----->{[ ]} rotate it ......lol ill try to get a picture , But all i know is that helped me out with your problem

Do you have center hung holley float bowls or side hung holley floats?

The basic Holley side float will definitely cause problems when cornering. You need to get the center hung float bowls.

Also jet extensions might help. On a rotary, the Holley is mounted 90* from its intended orientation, thats the cause of the problem. You cant mount it the other way cause of the primary/secondary setup. That and the center hung bowl as speedturn suggested is about all you can really do. Its a band-aid, but I dont think you can do anymore than that.

http://www.yawpower.com/racecarb.html

http://www.yawpower.com/techindx.html


Here's noted carb builder Paul Yaw's site, with his technical articles. If you can look past his understandable bias against your Holley (he mods Mazda Nikki carbs for racing), you'll find a wealth of information about carburetors.

So do I. I'm biased for purely technical reasons, but Im always willing to help any 7 owner with a carb, even a holley. :)

That's cool. I just posted the links 'cause that's where I learned about 90% of my carb knowledge from. Hopefully it was helpful, if only for understanding what happens inside a carb under cornering.


Myself, I'm biased towards computerized fuel injection, but I do love the mechanical brilliance of a well-performing carburetor - and Nikkis are damn fine peices.


p.s. The stock intake manifold on my S5 has Nikki cast on the bottom...

No offense taken at all. :beerchug: Yaw is very knoweledgable on these carbs, and has written some excellent stuff that should be read by anyone wanting to mess with their Nikki.


Also some info on the Nikki can be found at my partners site. www.sterlingmetalworks.com

I tinkered with Holleys for years (my dad owned a speed shop and we did a lot of drag racing), and yeah you are having fuel slosh problems. The jet extensions will help, they are aluminum tubes that are pressed into the jet. Some Holleys could have a 'stuffer' put into the float bowl, it was a foam or plastic block which would keep the fuel from sloshing up into the top of the bowl under hard acceleration or cornering. Another trick is a high volume (not high pressure) fuel pump, the stock RX7 pump can't flow enough to keep the bowls truly full. I see you are using a Holley blue pump, that should take care of any flow issues you might have. Are you by chance still using the stock return line to the tank, and if so are you using the check valve? If the check valve isn't there, it could be flowing too much back to the tank.