Carbureted LSX forum - Not Enough Carb for H/C/I LQ9???

been tuning on our LQ9 setup and I dont know if we have enough carb with the Holley 850 DP on it!!!

Been tuning on it since we put the new 5500 Coan stall in and the car seems really lean!! with the older 4000 GER converter the car was running great with a 82 Front 91 Rear jet setup, put the new stall in and got consistent cutting out and popping under a load. Since then we've bumped all the way up to a 95 Front 103 Rear and the spark plugs are still chalk white!!!

Does anyone think we need to go to a 950???

Currently running 91 octane pump gas, 7psi pump, 3/8's fuel line, Percy's Adjust-A-Jet in the rear....

Never been much into the Carb stuff, as I prefer Fuel Injection!! My father talked me into running a carb since this car is 99.9% Track only!

http://i245.photobucket.com/albums/gg48/06x6spdGTO/2012-05-06_11-12-57_320.jpg

ive got a prosystems/holley 4150 4bbl on my lq9/ls3 combo. it flowed in between 980 and 1040 actual cfm after machine work. it drives good once i got the fine tuning down.

My 750 keeps my 6.0 happy to 7200, making afr at 12.7-13.0.

Heres some video of the issues.

1st time out on GER 4000 Stall: (82 Front 91 Rear) 12.7 AFR
http://www.youtube.com/watch?v=tfjTYN3ZX90&feature=relmfu

2nd time out with Coan 5500 Stall: (Wideband is out!)
http://www.youtube.com/watch?v=gHQNf8HSiKU&feature=relmfu

Most recent 3rd time out with MAJOR jet changes last pass @ night is a 95 front 103Rear
http://www.youtube.com/watch?v=llWlPeGqKFo&feature=youtu.be


^Wideband is still down....

Here are some basic tuning aid questions:

Have you played with the float level?
- If the floats are too low, it can cause a lean condition.

Power installed or blocked?

What CC of accelerator pump shot are you running?
- Your car might like a 50cc pump, or a different pump cam

What size shooter?

Have you thoroughly checked for vacuum leaks?

Float level adjusted everytime the bowls were off and Mains changed, Using a blocked power valve, 50cc Accelerator, #30 shooters and white pump cams

Any stumble?

Only once in awhile coming off the Trans Brake. and if you listen to the video again in the Low-High shift...

A larger carb is going to move more air, but not necessarily more fuel. Sounds to me like you aren't moving enough fuel. What size pump? I'm guessing no regulator, just a regulated pump? Are the filters clean and all fuel fittings the high flow type? No noticeable restrictions? Do you have a pressure gauge and what does it read under load?

By the way, is that a plumbing T on your temp sensor? Pretty unique solution.

A larger carb is going to move more air, but not necessarily more fuel. Sounds to me like you aren't moving enough fuel. What size pump? I'm guessing no regulator, just a regulated pump? Are the filters clean and all fuel fittings the high flow type? No noticeable restrictions? Do you have a pressure gauge and what does it read under load?

By the way, is that a plumbing T on your temp sensor? Pretty unique solution.

Yep plumbing "T" Its not a show car by any means!!
Got all the fittings for the T from the local hardware store in a town with a population of 900 people so it was easy enough to find if something was to get broke.

I believe the pump is a Carter 80GPH 7psi Internally regulated pump. I havent checked the filters, so that will be a good spot to check next... Only restriction we might have is a 90 degree elbow up to the carb.

I just find it odd that the carb setup worked great until we changed the converter!!

pumps can go bad, junk can come loose from the tank and clog the filters. Doesn't have to be related to the converter. Of course maybe you kinked a fuel line

Anybody else think that pump sounds kinda small for that kind of combo? I'd think a 140gph pump would be what he wants on that kinda of setup.

The first thing I would do is monitor the fuel pressure at the carb during a pass.

Ordered a 110GPH Holley with the regulator and guage today.... Also going to switch to 4.30's in an attempt to get the car to pull a little harder on the big end and 60'ft better

been tuning on our LQ9 setup and I dont know if we have enough carb with the Holley 850 DP on it!!!

Does anyone think we need to go to a 950???

This may sound a little bizarre, but the Holley 950 HP is actually a smaller carburetor (read small venturi diameter) than the 4781 series Holley mechanical secondary carbs.

If you want a larger carburetor, you need to go to the Holley 1000 CFM 4150 series.

But, like I said before, you need to monitor your fuel pressure at the carb for the a whole pass. Even with they new fuel components you are purchasing.

When I had fuel supply issues (not enough pump) it was like the new car speed limiters....just lost all power, but if you pumped the gas peddle it would surge.

I feel you're sucking air somewhere under load....find your vacuum leak.

It's not the carb size IMO

I'm not an expert on carbs but I bought a Holley blue 140gph pump for my 5.3/750 build....I didn't believe when I read you have an 850 dp with monster jets and you only had a 90gph pump?
If I was you I would run half inch fuel line to the regulator at least with that motor...you can always turn pressure down at regulator...good luck man nice car!

With a blocked off power valve, you will need at least 10 jet sizes from what was originally in the carb. Have you pulled a plug to see if it's lean?

for one, put the power valve back in there, you're missing 6-8 jet sizes on the primary with it missing or square up the jetting so primary and secondary is identical since neither has a power valve

Yeah, plugs were still tend to be reading LEAN when I checked them out..

Isnt the Holley Blue Pump 110GPH???

for one, put the power valve back in there, you're missing 6-8 jet sizes on the primary with it missing or square up the jetting so primary and secondary is identical since neither has a power valve

Good catch! I missed where he said he removed his primary power valve. Yep, either put it back OR raise the front jetting to match the rear.

With no power valve you definitely need some type of wideband to set the primary and secondary balance correctly. Like said above the power valves is worth a good 10 jet sizes.

But the fact it ran OK before swapping the converter says you have a problem that isn't with the power valve because I assume it was working that way before the swap.

The type of fuel system you hook up affects the size of the pump you need. Return style regulators need less pump to flow more fuel, as does larger fuel line/less restrictive plumbing. Here is a good guide

http://www.1bad69.com/fuel_system/index.htm

110 GPH with a return style regulator and 3/8 or better yet 1/2 fuel line will serve just about anything you can do N/A.

With the old converter and jetting i was getting 12.6:afr with the old pump and no power valve. After the converter swap is when things started to get worse. Unfortunatley we couldnt run the wideband all the time becuz of an alternator issue that we have finally resolved.

But from the wideband being unheated for multiple passes the sensor is trashed. Next outing i would like to have a brand new sensor to log afr.