If you are running rich, check your fuel Pressure!! • The Dodge Challenger Message Board

by **insuranceguy** » 08 Sep 2004 16:17

One again I am trying to spend as much money as possible for a small fix. I have been running an Edelbrock Thunder AVS series carb (800 cfm) and trying to tune it. It has always run rich, no matter how many different jet combo's and metering rods I have tried.

So genius that I am, I bought a new Holley 4160 Electric Choke 750 with a 4150 conversion so I can use jet's for and aft rather than metering plates. Found a neat chrome dual fuel line with a built in pressure gauge as well. Got the exact specs from Mopar performance for what jetting they recommend for my crate 402/435.

Put it all together, and viola! I have 13 pounds of fuel pressure! Way too much! Bought a $40 pressure regulator, installed it, set to 6 pounds. Now it runs great!

Bet the Edelbrock would have worked with the regulator as well.. :oops:

Live and learn!

by **dave-r** » 08 Sep 2004 17:17

Yes folks! ALWAYS use a regulator with a non-standard or performance fuel pump.

Set the pressure to 6.5-7.5 lbs on a Holley depending on how big and how powerful your engine is. I think the Edelbrocks like less pressure?

by **Christer** » 08 Sep 2004 18:01

Thanks for the useful tip!!!! Bigger isn´t always better then.... :wink:

by **insuranceguy** » 08 Sep 2004 19:20

The good news is that if I ever supercharge the motor, I have some spare fuel pressure to play with :wink:

by **spitfire9137** » 09 Sep 2004 1:28

Thats like my 318, i have like 9.5-10psi and it runs rich all the time. Im debating still whether I want to buy a regulator for a engine that wont be in there permantly.

by **dave-r** » 09 Sep 2004 7:23

You guys do realise that flooding the carb with high fuel pressure will kill your engine?

The carb does not just run rich. You get raw wet fuel dripping (running?) into your engine. It washes the oil off the cylinder walls (wearing the cylinders and destroying the rings) and it runs into the oil making it thin.

If your fuel presure ever goes over 7 or 8 psi you MUST use a regulator.

by **spitfire9137** » 10 Sep 2004 1:34

It alsoo burns hotter burning the oil away.

by **Christer** » 12 Sep 2004 16:37

spitfire9137 wrote:It alsoo burns hotter burning the oil away.

I don´t fully agree with you, spitfire (or maybe I have misunderstood you?) From what I have learned, a too rich mixture (too much fuel) will cool the engine.

by **dave-r** » 13 Sep 2004 8:17

Too much fuel can cool or heat depending on how much you are talking about. A lot of liquid fuel will cool as it evaporates.
Also a slightly richer mixture might be cooler but I am not sure on that point.

But I think a very rich burning mixture can heat more because it burns for longer. In particular the exhaust valve, cylinder head and exhaust can get very much hotter. That is my understanding and I have come across situations where that seemed to be the case.

by **Christer** » 13 Sep 2004 9:20

Thanks! That sounds logical to me.