Fast 95 Z28

So heres the scoop. I built an LQ4 408 and its running very rich as you can see in the picture I attached. I'm wondering if anyone knows which size jets I should run? I'm not sure what jets are currently in the carb as I bought it used and just slapped it on the car. Not sure if my small air cleaner is causing the super rich condition its a 10" air cleaner. I'm only running a 10" cleaner, because thats all that fits in my shaker scoop. I'm at sea level the combo ran an 11.48 @116.64 second pass. I'm happy with the E/T just thought it would trap more MPH. Heres the specs...

2003 Lq4 408 stroker
10.8:1 SCR
8.5:1 DCR
.037" quench
Stock untouched LS3 heads 821 castings
Forged -8cc wiesco pistons
Forged callies compstar crank
Forged eagles 6.125" rods
ARP 2000 rod bolts
Clevite bearings
231/242 @.050" .617/.615" 110LSA cam
Lunati Gold Dual Valve Springs (.660 lift)
Untouched L92 Victor JR. intake manifold
Quick Fuel 750 cfm double pumper mechanical secondaries (Q750)
LS7 Lifters
7.400 hardened pushrods
1 7/8" Dynatech Long Tube headers
NGK TR55 plugs gapped at .050"
3" X pipe into 2.5" Sweet Thunder mufflers
3000 stall converter
TH400 Transmission
3.73 rear gear with 275/60/15 when racing
Shifting at 6800rpm, redline 7000rpm
Launching at 2600rpm foot brake.
34* degrees of timing.

Engine is in a 1970 firebird weighing probably 3300 pounds.

Heres the link of the 11.48 pass.

TXsilverado

iTrader: (18)

i'm a carb noob, but i'd call quick fuel and ask them what jets it comes from the factory with and start there. or just blow some nitrous through it to lean it up some

do you have a wideband?

89gmcs15

iTrader: (7)

Check your jets. No way to tell without checking them. Your tuning blind right now.

ZONES89RS

iTrader: (25)

You need a wide band and a jet kit and start getting that thing dialed in.

Doug G

Very close to the same combo here (except 408 to my 364) and guess about the same weight.
Post a copy of your slip.

And that plug looks pig rich.
See whats in there and drop 5 sizes with a new set of plugs at the track.
Make a pass and pull it on the turn off road. Little idling as possible.

speedtigger

iTrader: (16)

This is where you should start

Then this^^^. A wideband will save you a bunch of time.

That plug is black. That is extremely rich. Return the carburetor to its factory calibration. Next, set the idle mixture screws. Until you get your wideband, you can use the old school method of adjusting them to achieve best idle vacuum with the car in gear. (make sure you set the parking brake and block the tires). Now you are at least in the neighborhood. Read all the carb tuning threads you can find in here. The information is all there, you just have to read it all.

Next, lets talk about timing. Do you have a map sensor installed?
Same as the carb stuff, do some searches in this forum and read the stickies on timing settings. Start conservative with your total timing at about 30 degrees and increase it 2 degrees at a time at the track until you find the sweet spot.

Report back with your progress!

Fast 95 Z28

I'll try those tips and I do have a map sensor installed. Heres a picture of the slip. Just wondering once I get this thing running better what E/T do you think I'll be able to achieve? 11.0?

speedtigger

iTrader: (16)

Depending on your raceweight, that thing should have the capability to run into the 10s and well over 120 MPH.

Doug G

Get that 60' down.
Try adding another 2-3* of timing
I get my best 60's launching between 1200-1500 rpm and flashing the converter on the last yellow

Fast 95 Z28

What size converter do you have? I always live on the third yellow as well. My best 60' I want to say was a 1.660... leaving at 2600rpm. What do you run in the 60'?

Doug G

I cut mid 1.5's with this 8" 4500 converter and 4.10's on 28" tall tires.

6D9

iTrader: (1)

Hey Doug who's 8" 4500 are you running? how is the street manners?

BANDIDO79

Not related to this bit you should make your shacker functionable with a WFO or Blockers kits so you don't have to run them crappy air filters. That's what I'm gonna do to my 79TA

speedtigger

iTrader: (16)

I bet it will 60' quicker than that when you get it sorted out.

GC99TA

iTrader: (30)

OP, sounds like a cool combo you have coming together....but then again, I'm a little partial to the early 2nd gen F-bodies.

Sounds like you've already gotten some good advice on fixing your over fueling condition. What are your goals for this car? Is it a mostly street driven car that you occasionally take to the track for fun, or is it a mostly track car that you occasionally drive on the street for fun? If maximizing ET is on your "to do" list, I see a few things you could change in your combo to help out. You have a solid foundation for a consistent 10-second capable car on your hands.

If you have a chance to post them, I'd love to see some more pics of the car!

Fast 95 Z28

I built the car to be a street/strip car. Probably about 75% of the time on the street. I'm cloning the car to be a TransAm, I've always loved that look. I don't have to deal with smog since its a pre-1976 car here in California. I understand it would be ideal to have a bigger stall and more gear to get better ET's but that would be revving like crazy on the street. Some pictures of the car and build are below I still need to do body work on the car, but I only paid $2500 for it.

Heres the same 11.48 run outside the car.


Just for fun the old poncho 350 engine I replace turning a 14.58

Fast 95 Z28

Old engine...

Doug G

Redneck...out of business now I think. But on the street it feels fine....until you stand on it.
Cruises at 3300-3500 at 65 ....due to the 4.10s (3.73's should be 300-500 rpm less)

I can only hope

89gmcs15

iTrader: (7)

I dont think you need to know what jets came in the carb from them. You need to know what is in it now. Get a wideband and figure out what jets are in it and tune the wot from there.

speedtigger

iTrader: (16)

There are reasons that putting it back to factory calibration is a good idea. To start with, there are no guarantees that the jet spread is even correct. If he does not know the factory calibration, he will not know if it has the correct jet spread. So, he could end up with a carb that is too lean on the primaries and too rich on the secondaries or vice-versa. Then, there are the air-bleeds, if somebody started playing with those, he could have all kinds of irregularities and gremlins to play with.

For somebody who is new to carburetors, it is best to eliminate variables and keep it simple.