LS-Vega

I'm currently running a 650 DP Holley with the Holley low rise intake (max. rpm 7000), have 1 3/4" headers, my cam is a Texas Speed MS4 .649/.600 lift 239/242 @ .050 on a 110 cl, PowerGlide trans, 4.30 gear, 28" slick...3080# race weight best et is 11.12, best mph is 119 anyone using a larger cfm carb. on their "similar" combo? Thanks.

LS-Vega

oh yeah, the heads are untouched 317's (except for springs)

speedtigger

iTrader: (16)

I think you will find a 750 CFM will pick up nicely. You might make even more with an even bigger carb, but sometimes the larger venturis have trouble metering fuel properly at lower RPMs on a 6 liter or smaller.

LS-Vega

Thanks, I don't have a 750 to try, but I have a newer 996cfm ProSystems carb I was using on my 406 gen1 SBC, I can at least jet it down and try it I guess. I'm going to give it a whirl sunday, I'll post results.

ZONES89RS

iTrader: (25)

Try it. I bet it likes the bigger carb more than you would think.

Doug G

Try the bigger carb with no changes first....more than a few of us carb guys have found that the bigger jetting is what the LS wants

I went up 6 jet sizes from my 406ci SBC in my 750 Mighty Demon.

LS-Vega

Here's the current combo, hopefully the larger carb will make her happier ??? We'll see.

speedtigger

iTrader: (16)

Love me some Vega!

Also, that camshaft that you have will want 7500 RPM shift and trap RPM and a 5500 RPM stall torque converter to be happy in that engine. If you are not running it setup like that, you could do a lot better on the camshaft.

LS-Vega

here's my concern...I have an 8" 6000 stall in her right now, I leave off the transbrake at 5100 rpm, shift at 7000 (powerglide w/1.76), cross the stripe at 6800. I was afraid the converter was way too loose, my 60' is only 1.62. I know this combo does't make the tq. or hp. my previous combo did, using the same converter/rear gear/tire/shock set up...my 60' was 1.48 e.t. was 9.7's different animal. I also understand this is a 9.6:1 motor, bone stock heads, untouched bottom end...pleased a cam and 4 bbl woke up a 300 horse truck motor. I know there's potential. Just want to see what i can obtain without diving into the long block right now. Also it's hard to figure out what the best timing to run is...seems to pull good at 27 degrees across the rpm band to 7200 from launch.

speedtigger

iTrader: (16)

The lack of compression and a camshaft with a fairly late IVC like that one is a recipe for no torque. But, with a 6000 Stall, that thing ought to be in the 1.4s for sure.

Here is a timeslip from my old Junkard 6 liter engine in a #3700 car with a 4000 RPM 9.5" stall:



How much does that thing weigh?

LS-Vega

with me 3080# . I'll try the carburetor this weekend, but I also have a new converter to try, it's the TCI #740913 for engines producing their power between 4700 and 7000

LS-Vega

what do you think about the timing?

speedtigger

iTrader: (16)

With that low cylinder pressure, I would try more and see how it responds. 317 heads?

LS-Vega

yes 317, the only modification so far to them are the springs that match the cam, I haven't had them off the engine yet.

racer442olds

iTrader: (2)

Whats junkyard? 10.80s at 3700 lbs? my 408 only went 11:30s at with a 10" stalling at 3800. 1.59 60fts, my car is 3600 lbs

LS-Vega

Well...put the 996cfm on, in the 88 degree heat and 70% humidity I always seem to run, the car picked up .280 in e.t (1/4 mile) , .06 in 60' 2 mph in 1/8, 3 mph in 1/4 that's from the 650 to the larger carb, I think there's more left with tuning the carb and timing, then I'll try a different converter.

speedtigger

iTrader: (16)

PM me and we can talk about it. I don't want to derail the OPs thread.

Nice! Now you are cooking.

toxic99

Nice! Now turn the timing up. It will pick up some more.