chris-m

Hi, first time poster.
UK based.
I'm going to install a standard Ls1 into a kit car (Gardner Douglas T70 replica lola) and run it on a carb, using the edelbrock /msd conversion plug n play into the stock coilpacks/cam/crank sensors.

the question i need to answer if possible is what is a suitable carb size for my application? i need a manual choke, and the car is going to be used on track and for sprinting, maybe a few drag runs, but very little road use. i dont want it to be a pig to drive though!

the engine will have race type headers and a simple race type exhaust, quite free flowing.
initially i am sticking with a standard engine and heads/cam, as the car will only weigh around 900kg.

i sent this question to edelbrocks tech helpline and was given advice to use a 800cfm (electric choke!) carb, which doesnt look to be right?

I'm not sure what power to expect out of a stock ls1 on carb set up with decent headers/exhaust, but dont want to strangle it/oversize it with the wrong carb. I may in the future get a mild cam but leave the std heads on, so something with a little "headroom" for tweaking further might be best?

Also, anything to choose between say Holley or Edelbrock carbs in whatever size is recommended?
thanks in advance
chris

TJ

iTrader: (10)

depending on RPMS, you can prolly get the most efficient power from a nice 650 4bbl style.
i wouldnt go 800, IMO unless you need all out top end power. with stock cubes, the bigger carb will hurt you low and midrange.
750 max, but thats just me.
contact any carb shop and they can get whats right for your application.
good luck!

chris-m

cheers TJ. someone else had asvised that Holley may be preferred over edelbrock for a circuit /track car due to the fuel surge i'll encounter?

one question i also have is mechanical or vacuum secondary's? for a track based /lightweight car would mechanical be better?
cheers

bygblok

iTrader: (4)

I could see a big carb on a 6.0 but even at that it's not necessary. I know of an S10 with a 5.7 LS that has a 650, spraying 150 and goes deep in the 6's at our local track. I won't run more than a 750. Will probably go smaller.

TJ

iTrader: (10)

i prefer a holley, as ive never really tuned an edelbrock.
the carter clan will tell you that holley is junk and vise versa, but you may run into those problems with the carter style carb.
on a holley, you can lower the fuel bowl a bit and loop the vent tube to keep fuel from sloshing from the bowls. if you have a good fuel pump, you wont have to worry.
might have to adjust the idle or the transition circuit since there is less pressure forcing down on the orfices with the low fuel in the bowl.
might lean things out in a spot.

if i had a lightweight car, going around corners, i might want a vacuum secondary to pull the power in slowly not to shock the tires in a corner.
with decent power, a mechanical carb "hits" the power in a hurry once you put your foot in it.
those few tenth of a second delays may be enough to keep the tires planted.
its just a guess, but it sounds like a decent one.
there are adjustable diaphrams out there too, so you can bring the rear in sooner or later than your old school style secondary carb.

bill is right, matt runs a 650, but it is worked a lil bit. his is an AED performance eliminator carb, and he says its the best one he has ever owned.(and he has had many carbs, i can tell you)

good luck!

chris-m

cheers guys, much appreciated.

bczee

iTrader: (12)

I think there is no one answer to your question. This is one of those Depend answer... and Trial and error is the only real way of getting a answer or a tune for what you are using your car for.

My 2 cents..

I'd vote for the Holley, as many more mod's can be done to tune for your type racing.

For a stock engine.. try going with the 650 with Vacuum and then move up to a 750 if that doesn't work out or if your are looking for more. (I think that is were you will end up)

I think GMPP is marketing a LS1 Crate with there Carb mainfold and carb, You might want to look into this to see what HP rating and carb size.. maybe that will give you a good start.

A engine with a more open exhaust system as yours will run leaner than one with a stock system or smog'd down and you can get away with a larger carb.

I once ran my 57 Chevy with a 283cid and a 850 Double pumper.. that seem like over kill to most.. but I was running 4.88:1 rear gears and a 4sp. And it did come on at the top end great and was still liveable on the streets (but gas was 27 cent a gal for super then, yeah... giving away my age) !.. so, it depends !

holley505

iTrader: (1)

I run a AED 650 (rather a 680DP) Holley type carb on my 346 with a 224 comp cam, RPM intake and MSD system (currently pill 4)

It is sweet. Runs Strong... looks cool.

Andy1

Chris,

I don't want to derail the thread, but what kind of gearbox are you using behind the LS1? G50, UN-1, ZF, Audi, or?

BTW, is there a reason you prefer to not run the stock EFI?

Andy1

bczee

iTrader: (12)

From that Trans Pan.. I'd say TH350

Wnts2Go10O

iTrader: (12)

700cfm at least.. id only use the 800 if you went with a pretty radical h/c/i setup

Zedzag

iTrader: (7)

I'm going to use a holley 700dp on my 6.0 with a 228/232 cam. I'm using the edelbrock performer rpm intake and box. With the dual plenum intake and bellmouth boosters on the 700, I'm looking for great street manners and lots of torque. I thing anywhere from 650 - 750 cfm should do you fine.

Davy_Baby9

iTrader: (23)

I plan on running a 750 Mighty Demon on the LS6 that I'm building. 346, CNC Ls6 heads, MS4 cam etc. I thought it would do the trick.

chris-m

cheers for the answers again, looks like i'll go 650cfm to start with on stock heads and cam.

I'll be running a porsche G50 box (already have that) and a custom bellhousing adaptor to mate to the LS1.
reason for running carb is that its a replica of a 1965 Lola T70 spyder and i'd like authenticity to some degree, altho the originals ran weber carbs and trumpets i believe. I've also never had a big carb'd V8 and always wanted to play with one, current road car is jap turbo 4wd with a mappable ecu so this will be a change!

Holley 505- can i ask you a question, how did you find the rpm/msd kit worked on your install? is it a proper plug n play conversion as it looks?
cheers

chuntington101

hey chris, where in the UK are you?? nice to see another UKL guy on here

oh and i bet i will be a very nice car once done

Chris.

Vcious04

iTrader: (16)

My exact setup.. But I will be running a forger bottom end (approx 11.5:1 comp) with a 175-200 direct port..

chris-m - I would not run the msd box that edelborck includes due to it's limited capabilities (plug in timing chips).. Go with the MSD-6010 box that includes the pro-data+ software.. just my .02 and it's almost the same price seperate..

holley505

iTrader: (1)

Sure it works. But the new kit will work better with the software i am sure. You only get 6 pills. So with the new setup, you will be able to squeeze a few more ponies out of it.

BUT the base kit has good drivability and road manners... good power... no issues here. But if you want to MAX it out... get the new kit or RUN SOME NO-2...new KIT !!

holley505

iTrader: (1)

Vcious04 you make a good point, but

the base Kit works... and it comes with the manifold so you get a little savings... if you don't have the LAPTOP or SAVY to program it ? It could be a pain in the A$$ not to mention costs a little bit more.

Of course they have a hand held programmer also...

MO MONEY .... MO MONEY ....

TJ

iTrader: (10)

MSD has a handheld controller available for about 100 bucks if you dont have a laptop.
plug it in the side of the box and program timing, 2 step and reatard.
from what i understand, it works like a SCT tuner.

holley505

iTrader: (1)

TJ got any pics of your IROC-z ??



oops....

I am a sucker for 3rd gens.

check my old ride.