1971 LS-5

Ever since I bought my stock LS-5 454 all I've heard is "if want to make the car fast you'll have to get rid of that stock hood." But then I found out Chevy stuck an LS-6 in the Corvette in 1971 under the same hood I'm using. I've read road tests of them running high 13's in the quarter. That's with stock exhaust manifolds and mufflers. With today's technology it should be easy to duplicate this motor and easily shave a second or more off of that time. Chevy axed the LS-7 at the last minute in 1970 rated at 450-465 HP, not sure what hood they had planned for that, but there is some documentation of two of them being made with stock big block hoods. And what about the '68-'69 427/435. Reports say 13 seconds stock under a big block hood. Who out there is running fast (N/A) under a stock hood?

baxsom

I wouldnt say that mine is anywhere near the fastest but I have a 72 454 with the stock hood and a LS6 intake and it did 440hp and 500 lbs of torque on the engine dyno after it was rebuilt and modernized with a roller cam. Never got a chance to put it on a chassis dyno but the butt dyno feels it go sideways when the passing gear goes in.

Easy Mike

My advice: stop listening to the folks who are telling you this.

qwank

I bet there's a ton of people running good times wit a stock hood

1971 LS-5

My intent on starting this thread was to see how successful folks were at getting there cars to run fast, with out nitrous, under a stock hood. so far baxom is the only vette to chime in with a very respectable 440/500. Probably able to run in the mid to low 13's with those numbers. Any body else out there???

roadblock69

I have a Chevelle specification LS-6 in my '72 with the stock hood. I am very happy with the performance. I had headers on the car for a short time too. There was some power increase as a result of that but, the gain simply did not justify the clearance issues that were created by the headers. I have never had the car on a dynamometer. Just much more fun to drive than with the LS-5.

calwldlife

OP, what reason do these people say it needs another hood?

427Hotrod

Do a search on some of the Chevelle Super Stockers. There's been tons of 10 sec and a few 9 sec passes with the "pancake" intake. Certainly a better intake helps...but you can do well anyway. Cam choice can help a lot. You have to think about *where* the restriction is...carb, intake, heads....which one is the worst? Then think about some of the old Busch motors...great heads and intake...strangled carb. Cam choice for that allowed for a pretty short duration (considering power level) because whatever got through the carb could easily be handled by the intake and heads. They wanted to create all the "pull" on the carb they could.

The intake on your motor would be the largest restriction if you had say an 850/950 CFM carb on it. The heads will flow whatever gets through the intake...the carb can certainly flow whatever the intake is going to allow. Now you have to start thinking of adding duration to get some more airflow through there. Of course major porting on the flat intake would help too. Or even use something like the Torker II and port it too.

Anyway, a better intake is the best answer..but with restrictions you have to make allowances and tweeks. Same thoughts on exhaust side...."where" is the restriction? Heads, manifolds/headers, pipes, mufflers?

JIM

1971 LS-5

Good info Jim. What your saying is the approach that needs to be taken when building an N/A motor. Find the weakest link and build to your best advantage to strengthen the weakness. I guess the trouble begins when the weakness cannot hang with the other mods and makes for a bad combination.
My thinking is if I can run a goal of low 12's on street tires through mufflers, high 11's on slicks,with a short intake, why go through the expense of putting a different hood on to allow for a taller intake manifold. I'm just looking for that combination recipe that will allow me to reach those goals. I will have to research those Chevelles that are running fast with pancake intakes. Tho I have a feeling they are doing so with high compression necessitating race gas which is out of parameters for me. Must be pump gas. Maybe this is the topic for a new thread.

1971 LS-5

I've been running 2" Hedman long tubes for a few years and have not came close to having clearance issues. My car sits low, not jacked up at all. Is it possible your suspension needs attention?

1971 LS-5

The simple fact of being able to have a choice in taller intakes which makes it easier to put together a high horsepower power plant. But look at the expense. Initial cost of hood $400-$500, prep and paint another $400-$500. And if you want to make it functional another $200-$300. That's $1000-$1300 just to run a taller intake. Plus I love the look of the stock hood. It's a piece of art.

calwldlife

yeah i see that now. I guess I missed in the OP where the car
is for racing.
Or that racers were giving advice on 1/4 mile runs.

garygnu

with a ls6 engine and a well built air pan ,you could run low 11s with proper suspension and trans components..I made 500/500 with a GM ls6 crate motor and a small crane solid cam ,and a 800 DP.

1971 LS-5

Interesting. So when you say ls6 I asume your talking 454 big block? So does that mean you achieved those numbers with the low rise, square port intake? I'm not sure what an air pan is?

gungatim

I am making 507 hp with stock hood. just a lil' L-89 motor...
Never raced a 1/4 mile but I would guess 12 seconds if the tires would ever stop spinning...

Specs:
442 CID, 507HP @ 6100 RPM, 482 ft/lb @4800 RPM
Short Block:
Block bored .060 over
custom JE pistons (4.3135 bore)
502/502 7/16 rods
Polished Crank
Comp Cams roller lifters (mechanical)
Roller cam 282/292 street performance
Cloyes dbl roller timing set
Aluminum Heads, winters snowflake
Crane roller rocker arms stud mounted aluminum
Crane valve springs 99893-16
Intake Holley carbs 3 x 2 bbl
Aluminum intake, winters snowflake, rectangular ports
Stock exhaust manifolds
4spd close ratio, 3.70 rear

holley505

I had to dump my Stock hood to fit a LSX with a CARB...

But I am 3 seconds faster than 13s

1971 LS-5

Point well taken holley505.

Gungatim those are impressive numbers especially if done through stock exhaust manifolds. I was wondering if anyone would post running 3 deuces.

Does anyone know any flow numbers to compare tri-power w/ square port heads, to LS-6 w/ square port heads, to Torker II w/ oval heads?

vette427-sbc

http://forums.corvetteforum.com/c3-t...-mufflers.html