Carbureted LSX forum - big disapointment

Just got back from the track with my fresh carbed 370lq4

Build thread

http://www.thirdgen.org/techboard/organized-drag-racing-autocross/633045-project-10sec-lq4-91rs.html



Engine
2004 lq4
.030 with forged flattop pistons. Ls2 rods. Stock crank
821 (ls3 heads). Ported valve job and milled. 035". Flowed around 360 cfm at. .700 lift
eps custom grind 235*/251*@050" 621/632 lift 110+4 installed straight up
Jp roller timing set.
.040 head gasket
Prc. .650 spring kit titanium retainers
7.325"pushrods
Ls7 lifters with. 080" preload
1 3/4 primary 3 collector longtube headers. 3"duals.
Port matched l92 victor jr 1"spacer
850 proform carb. 80 jet primary with 6.5 pv. 88 jet secondary
msd 6010 set at 35* timing straight across.
Tr55's gapped. 040"
Holley black fuel pump set at 8psi


Specs
1991 Camaro
-Full suspension with drag springs and shocks
-th400 w/ brake. 8"converter 4500 stall.
- Moser 9" 4.11:1 locker
- 28 x10.5s x15 et drags with skinnies up front.
- est 3300 lbs
With the old mismatched solid roller 383 sbc it ran 11.52@ 116 mph with 1.525 60 foot. Only thing changed was engine over the winter.

Leaving off brake at 3700rpm


Best run was
60'. 1.657
330'. 4.963
1/8. 7.730
Mph. 88.78
1000' 10.112
1/4. 12.135
Mph. 111.17

Shifting between6500-7200 rpm had no effect on mph.

Feels like it doesn't like anything over 7000 rpm. It originally was cutting out at high rpm so I jetted up 4 sizes from 76/84 to 80/88 helped a lil as far as missing out up top but no help in mph or et.

Did a hot compression test

All cylinders 190-200 psi

What gives guys?

You are moving plenty of air with those heads and cam. Do you have a fuel pressure gauge? What does it read at the top end?

60' is great.

your eighth seems to match your quarter

quarter E.T. matches the quarter MPH

Power is down from your old combo (sorry to state the obvious)

i disagree, 60' is poor as well for a 4500 stall and a well setup chassis.


Running out of fuel pump is my guess, or something else going on. If timing is locked and plugs look good, you're down over 10mph easily.

Who specd your carb? Ive got a similar setup and my carb was specd between 980 and 1040 cfm (pro-systems). I have less compression, my heads (stock 821) flow less and my cam is 1 degree less on both sides. I do weigh 800 lbs less tho.

i disagree, 60' is poor as well for a 4500 stall and a well setup chassis.



He's not spinning much with a 1.6!!!!!!

Who specd your carb? Ive got a similar setup and my carb was specd between 980 and 1040 cfm (pro-systems). I have less compression, my heads (stock 821) flow less and my cam is 1 degree less on both sides. I do weigh 800 lbs less tho.

my shelf in my garage speced it for me lol. its what i have to work with

thanks for everyones suggestions. i have a game plan and a list of stuff i need to make sure is spot on.

going to run a new fuel feed set up 1/2 lines all the way to front with a nice flowing filter. ( currently running origional lines and canister filter) :emb:

also going to throw relays on everything. gotta make sure this stuff is getting a constant 12 volts!!!!

just had a dumbass moment!!!!!!

had the girlfriend jump in the car and hold gas pedel to floor. secondaries are about 1/8 of the way open. throttle stops when primaries are not quite all the way open and secondaries and just starting to open

just had a dumbass moment!!!!!!

had the girlfriend jump in the car and hold gas pedel to floor. the secondaries are only opening bout 1/4 of the way
Wouldn't be the first and won't be the last time. Always check full throttle!

Hey - you can brag that it runs 12.1 at part throttle!

Wouldn't be the first and won't be the last time. Always check full throttle!

installing throttle linkage and testing it happen to fall on a night when none of my buddies came over to drink all my beer!!!! :cheers:

I love a happy ending.

Hope it works out.

Woohoo! Ha, I was hopin for somethin simple. I was gettin disappointed myself, thinkin these builds ran faster than that. I was askin about the carb cuz they specd me a bigger one and I was worried its too big but im prolly fine. Good luck! Post a vid of the next run!

He's not spinning much with a 1.6!!!!!!

He's also not accelerating fast at all with that kind of number. :angel:

That car should go 1.49 or faster to the sixty. It has an 8" 4500 stall and 4.11's and slicks with lots of suspension goodies. Just remember to keep your tuning systematic j ;)

just had a dumbass moment!!!!!!

had the girlfriend jump in the car and hold gas pedel to floor. secondaries are about 1/8 of the way open. throttle stops when primaries are not quite all the way open and secondaries and just starting to open

I had the exact same problem with mine. This is what I would during the winter tear-down.

http://youtu.be/wAXicGT1Ow0

Look familiar? I've been messing with mine but I still can't get WOT.

Should mention I used my iphone to record the video while I hit the throttle. That's what I came up with since I work 99% of the time on my own.

I had the exact same problem with mine. This is what I would during the winter tear-down.

http://youtu.be/wAXicGT1Ow0

Look familiar? I've been messing with mine but I still can't get WOT.

Should mention I used my iphone to record the video while I hit the throttle. That's what I came up with since I work 99% of the time on my own.

Almost identical to that video. Lol

What linkage setup are you using? I have a lokar cable and stock pedal. My tv cable for my 700r4 was binding a bit and the throttle cable was flexing. Removing the tv cable gave me wot.

Stock camaro tbi cable. No kickdown cable running th400. I was able to get close to wot last night dicking around with it the primaries are vertical the secondaries are slightly less than vertical

if the primaries go vertical and the secondaries are still not all the way open, the linkage that goes to the secondaries needs to be shortened. you can do this by taking it off and bend it to a slight U-shape. this linkage is on the driver's side of the carb.

here's a picture of the linkage
http://i424.photobucket.com/albums/pp321/ford81stang/PB100302.jpg

Man, talk about a heart break till you saw that happened.

Friend of mine just did a 6.0 in his third gen since he liked the way mine ran, but he has better heads and is automatic so should run harder, he finished it and said t was not running right, told him my carb tune, and I get a text later, there was trash in the primary jets and he is blown away at the lack of traction he now has, lol.

Man, talk about a heart break till you saw that happened.

Friend of mine just did a 6.0 in his third gen since he liked the way mine ran, but he has better heads and is automatic so should run harder, he finished it and said t was not running right, told him my carb tune, and I get a text later, there was trash in the primary jets and he is blown away at the lack of traction he now has, lol.

U built a brpv blo thru carb yet?

Haven't had a chance to drive it yet. It should a lil less traction on the street !! Lol

Matt- thanks for the tip I will check it out!!!

U built a brpv blo thru carb yet?

Nope, when I go with the power adder, I will probably just end up with a blow through carb.

this thing is a rocket now. lol. runs a hellofa lot harder at wot. :drive:

this thing is a rocket now. lol. runs a hellofa lot harder at wot. :drive:

Glad you got it sorted out. When will you be taking it back to the track?

April 15th hopefully

Buddy of mine with a ls3 swap had the pedal calibrated wrong on the electric throttle body. Was only opening 64% at WOT. He re calibrated it and got it to open 98%. He went from a 12.4 to an 11.5.

Makes a pretty big difference I would say.

1.531 60' 6.991 @98mph
10.97 @ 124mph
Off transbrake
30 degrees timing shifting at 7200 rpm.

Need to lower instant center. Front end goes up imediately. Feels like it needs more forward push than going up.

1.2 second drop is insane. Hope your happy with the new setup.

hell yea I am. They dint even tell me to leave for nit having a roll bar lmao.

glad you got that figured out man... Looks like a hard runner now.

still need to work on that 60' but congrats on the 10sec pass

impressive turn around...congrats

Great news man, congrats.

WHOOOOT!!!!
CONGRATS on the 10!!, there's more in it with fine tuning for sure!!

1.531 60' 6.991 @98mph
10.97 @ 124mph
Off transbrake
30 degrees timing shifting at 7200 rpm.

Need to lower instant center. Front end goes up imediately. Feels like it needs more forward push than going up.Now that is more like it, grats..:nod: