12 Sec Car

[problemenko]

Alright guys, I'm fairly new to the game and my 79 L48 is in dire need of improvement. What I'm looking for is advice on HP/Tq numbers that will support a 12 sec 1/4 time. Assume I'm running, for now, a Turbo 350 with a 3.55 rear. I'll most likely keep the auto but can change rear end ratio at a later date if necessary. Also assume street tires on 15 in rims. Any advice?

 

[mike weyman]

all you need is money, and lots of it. these babies are 200 + or- h.p. hauling a 3400 lb.car.a proper set up may get you there, but it will be simpler to buy a built crate engine and drop it in. that way when you sell the car you can swap the old "original" engine back in and save the goodies for the next project.
you'll need about 400 h.p. to attain 12 seconds,plus the other goodies like a stall converter and a good flowing exhaust. mike
just say NAAAAWWS......

 

[problemenko]

Mike, thanks for the advice. I suspected that 400 ponies should be able to do it.

 

[problemenko]

I found this on the Engine Factory web site. The Engine Factory builds crate engines. I did speak with them from time to time but really don't know much about the quality of their work. They have been in business for quite a while if that is any indication of anything.

Figure your ¼ mile time. ​

​

Estimated Time Weight of Your Car in pounds​

2600 2800 3000 3200 3400 3600 3800 4000 ​

​

15.0 seconds 167 180 193 205 218 232 246 257​

14.5 seconds 186 200 213 228 242 256 270 285​

14.0 seconds 206 222 237 253 270 285 301 317​

13.5 seconds 230 248 265 283 300 318 335 353​

13.0 seconds 257 277 297 317 337 357 377 397​

12.5 seconds 289 311 334 356 378 400 423 445​

12.0 seconds 327 352 377 402 428 453 479 504​

11.5 seconds 372 400 429 458 486 515 543 572​

11.0 seconds 425 458 490 523 556 589 620 653​

10.5 seconds 488 526 563 600 638 677 714 751​

10.0 seconds 565 608 652 695 739 783 826 870​

​

This chart shows how much horsepower is needed at the flywheel to run an Elapsed Time in the ¼ mile. This chart is under optimal conditions. The entire car must be set up perfectly to run these times. Very few cars run 100% of their optimum. Wheelspin, slow shifting, clutch slippage, and other factors reduce the amount of usable horsepower. ​

 

[1979toy]

My best times so far with my '79 that used to be an L48 and Turbo 350 is a 12.80 on real street tires. Looking back on it I would have to agree with the above suggestion to buy a crate engine. My current setup is a 406 small block that shows 480 HP on Desktop Dyno. We have to deal with a lot of drivtrain power loss through the automatic transmission and IRS so the numbers posted above will be a bit skewed for a Corvette.
Above all, don't forget that your vehicle is a package. You need to insure that the rest of your package is prepared to handle the amount of horspower that you are putting in it.

 

[Glensgages]

I agree 100% with 1979toy; look at the ENTIRE car as a package, and don't just build as much HP as you can (altho that never hurts...)

With a starting-point being the L-48, it'll be that much tougher, with 8.2:1 CR:
even with 64cc heads, you're still only about 9.3:1 CR.
If you'd start with the 8.9:1 CR L-82, you'd be close-to 10:1 with small-chamber heads.

I'd think that 3.55s might only result in 12s if you run a long-arm 383", or a 400":
if you intend on running the L-48 short-block, I think you'll need 3.90s at least, and probably 4.11s.
With the 3.48"-stroke, I'm guessing close to 6000 RPM shift-points, and probably a converter:
it sounds like 1979toy can offer a good combination.

Hell, I'm interested in hearing more!!!!

I have a '79 Z28 that runs 'easy' 12.80s/105 on pump-gas 355" SBC at 3800 lbs (slicks, 4.11s, 8" converter, etc.):
if you'd like the specifics, please E-mail me.

Glen.

 

[1979toy]

OK, here's what got me to 12.80 at 109 MPH.

ENGINE
400 cubic inch small block bored .030 with 4 bolt mains
Edelbrock Performer RPM cylinder heads
Cylinder heads port matched and bowls blended
Manley pro-flow valves with reduced stem diameter
5.7 inch connecting rods
KB flat top pistons
1.6 / 1.5 ratio full roller rockers
Lunati solid lifter camshaft 300/310 duration
Air-Gap intake manifold
Barry Grant Speed Demon 750 carburetor
MSD 6A ignition
Accel distributor
Poly engine mounts
MSD 8.5 mm plug wires
Moroso 7 quart oil pan
Black Hooker headers with sidepipes
DEI header wrap
Homemade baffles for Hooker sidepipes
Flex-a-Lite dual electric fans
4 core radiator
L-88 air cleaner and hood


DRIVETRAIN
Turbo 350 transmission, shift kit from B&M
B&M transmission oil cooler
Chance 3000 RPM stall torque converter
Poly rear transmission mount
Poly forward differential bushings
VB&P differential crossmember reinforcements
Spicer heavy duty U-joints




CHASSIS
VB&P front mono spring
VB&P lower A-arms
VB&P front spreader bar
VB&P 330 pound fiberglass rear spring
1 1/8th inch front sway bar
5/8th inch rear sway bar
Poly bushings everywhere
Braided stainless steel brake lines
Monroe front shocks / KYB rear shocks
Hydroboost hydraulic brake booster

The engine parts came AFTER completely rebuilding the suspension, steering and brakes. Some of the parts listed do not help the car at the drag strip but I was building a street car and ran it as such.

The street tires that I used to run 12.80 was a set of Goodyear Eagle GTII's size 255-60/15. My 60 foot times reflected the serious lack of traction and my limited understanding about how to make the car hook with so much power. The same tires that got 2.00 60 foot times with my more or less stock L48 could only manage a best of 2.55 when power was added.

 

[problemenko]

Very nice build! I suppose that we should remember that our Vettes are sports cars. 12.80 is around what C&D reported the C06 can run the quarter mile in (12.70). I think that I'll end up with around 400-425 HP once I finish the suspension and break builds. I'm in the same camp as you, before putting all that HP in a car there is a significant amount of work to be done to handle the extra ponies. Thanks for the reply.

 

[iron cross]

Heres One Way

Money first though. This got me to 11.42 ET at 119 mph with 1.6 + or - 60 foot times. Box stock crate LS7, TI ignition from a 75 Chevy, Hooker Comp headers, 67 L88 intake, {the LS7 didn`t come with one}, 850 Holley, 4.56 gear, Manual shift Turbo 400, 3500 converter, and 9 in. slicks. The rest of the car is completely stock as is the LS7. Mostly all basic GM stuff, nothing trick. I`m not into that fancy aftermarket bolt in or on junk thats prone to break at the most inopportune times. Most of that garbage can really make you look bad. :L I don`t think I left anything out. HP?, dont really know or actually care. But probably quite a bit or at least maybe a bunch of um.

 

[titan81]

You will definitly have to rebuild that 350 trans, have one too in my 81

rebuild, use a 2500-2800 conv. transgo shiftkit,
that rear end gear needs be in the 3.73-4.01 range
An exhaust, heads, long tube headers, aggressive cam, (any came after 74 is sad compared to what could have gone in), A higher flow maybe 700cfm carb

A crate would be a much better way to go, also dont forget brakes and susp
can save weight there equals better hp-lbs = faster

 

[Glensgages]

Probably the easiest way to a honest 12-second C3 is swapping-in the ZZ502 with a THM400 transmission.
A guy at my local track has one in his '75 with side-pipes, 10" converter, 3.90 gears and 29" x 11" slicks (motor is box-stock) that ran 12.03 @ 112 (observed), with almost no burnout or high RPM launch, before busting the I.R.S. on his second run that day (car had been run before at the strip, with similar ET/MPH, and parts-breakage).
Even with the 29" tall tires, he said it was 'nosing-over' before the traps, so 3.55 gears might be even better.
567 ft/lbs of torque, keeping the RPMs below 5600, with a GM warranty, on 'junk' pump-gas, for less-than $8000 ain't too shabby.

 

[problemenko]

Lots of choices. All it takes is money and a dream. Tuition payment went out last month so the dream contiues.:L

 

[titan81]

Well if you dont care about having it 12 sec all the time get a
350-385hp crate, and add a shot of nos. Nitrious is soooo cheap for the horspower.
Just built the car to handle a spray and shoot 100, and bam easy.
Some guy has a 1986 vette L98, no puts out 350+ cant recall exact, adds 100 NOS
bam 10.93 1/4 @ 128ish.

 

[problemenko]

I really didn't consider nitrous but makes for a compelling arguement of when power is needed. I would assume that engine internals would need to be beefed up somewhat maybe the pistons and rings. Forged or hypereutectic? Anybody have thoughts on this?

 

[Glensgages]

Have never persoanlly messed with giggle-gas, but those who have suggest building a strong bottom end (forged pistons, better rods, steel crank, etc.) in an effort to let it 'live'.
They say that a 500+ HP SBC is taking abuse, whether it is 12:1 with a roller cam, or if it's an LT-1 with 150 of spray added, so build it accordingly to handle the abuse.
Injecting copious amounts of air and fuel into a n/a motor hasta play havoc on the internals of an engine...

 

[redc4corvette]

You want power spray it,I spray mine 125 shot stock lt1 msd 6AL retard box

fuel pump and nitto drag radials 315/17 turn 11.20 with 1.67 60 ft times 119 to 121.00 mph stock a slugg 13.60's total cost 800.00 or so.

 

[titan81]

You'll want to add beefed up
pistons/piston rings(exspeciallY)
valve springs, harder push rods, rocker arms ect...
If you plan to use nos alot/ more than 3-4 sprays
I'd just get a new crate built with the stronger materials
already. Hook the system up bam. instant power.

 

[curtis]

Everything I read tells me with frequent large NOS doses you should have forged pistons and forged crank and a compression ratio less than 10 to 1

 

[redc4corvette]

I have been spraying 6 bottles a month for a year 125 shot on stock lt1,With only about 3 mistakes, loose plugs once ,mixed up the jets and there are only 2. I forgot to retard and burnt plugs

If you spray any larger shot yes the engine needs to be forged top to bottom.

My Lt4 1986 is a 300 shot but that is built to the max and 300 is only good for about a year the rings do not hold up.

 

[76 Sting]

I have been spraying 6 bottles a month for a year 125 shot on stock lt1,With only about 3 mistakes, loose plugs once ,mixed up the jets and there are only 2. I forgot to retard and burnt plugs

If you spray any larger shot yes the engine needs to be forged top to bottom.

My Lt4 1986 is a 300 shot but that is built to the max and 300 is only good for about a year the rings do not hold up.

BEST BANG FOR THE BUCK!! I am installing the Snipper version in my 76 in about 2 weeks. For under $400 you can have a 150HP shot of NOS with very little engine tweeking PER HOLLEY! Installation can be easily done within 4 hrs.
Read it yourself

http://www.holley.com/HiOctn/ProdLine/Products/NOS/GenInfo/InstlReq.html