Recipe for breaking 12s with a 355

[stomis]

I've always had eyes for building a fast car but never got far enough along. Now that I have the 442 with a good 200r4 and an 8.5 3.73 rear in it PLUS a good 355 sitting in my unused lawn ornament truck I feel like I've got a chance in hell at getting this puppy going.

I'd really like to shoot for a car that breaks twelves. 12.8 would be great but the further in I get the better.

I've been doing alot of reading lately and theres certain people around the web that are optimistic of ETAs and some that are pessimistic but I want a real evaluation.

Heres what I have so far.

The car:
1986 442. 307/200-4r/8.5 rear

The motor I have:
1987 LO5 TBI 350 Truck Motor with 40,000 miles. Runs like a damn raped ape and pulled my truck on 36in tires with 3.73s like nobodies business. As far as I know its got nothing but a 420ish lift computer cam and long tube headers.

I have a line on both some sportman II heads and some 906 vortecs for $200. I know the sportmans can support nearly 500 ponies from research with the correct CI's, cam, etc. The vortecs I know will top out around 450hp and only breath on til about 6000rpms.

Heres the cam I was looking at: http://www.summitracing.com/parts/LUN-60103/

Its basically a dual pattern lunati version of the infamous comp 268.

I'm aware that with the vortecs I could follow a couple chevy mag builds to hit like 450 hp and 480 ft/lbs of torque which would feel great as the daily driver it will be but I'm wondering if going vortecs and limiting my top end is gonna hurt my 1/4 mile time due to the power band being lower.

As far as drivetrain it will be stock converter so figure between 2000-2400 stall, a shift kit, ratchet shifter to control the gears. The rear I'll keep the 3.73s and install a posi if I dont have one (only had the car for a few days 🙂

Thoughts? Comments? The infamous thats not enough motor to hit those times comments?


O and at some point in the future I'll be transferring the top end to a 406ci once the machinist I know yanks the tired one out of his truck.

 

[madmaxstyle]

If a stock corvette can do it with the 350 I think it can be done to a g body. With a little more tuning of course, because they are heavy.

 

[monte olrac]

Here's a recipe...your combo and about 300 shot NO2, you should be in the twelves, bad news is you may only make that run one time, on the other hand you need about 350 hp/trq to the rear wheel, able to hook, and you'll be pretty close to a 12 sec car. you'll probally need 4:10 or 4:58 gears since you have overdrive it will still be streetable you need to up that cam to something that make more power on the topend, next you'll probally need about 3000-3500 stall ...

all that just to say those vortec heads and low top end hp/trq isn't going to get you anything but good 60ft time IMO

 

[stomis]

If a stock corvette can do it with the 350 I think it can be done to a g body. With a little more tuning of course, because they are heavy.

O I know it can be done.

I read another build on using a roller cam to increase lift while keeping duration down and keeping it streetable. With a little machining to bring vortecs down to 58cc's they got 450/450 out of a stock bottom end roller vortec headed 350.

 

[stomis]

Here's a recipe...your combo and about 300 shot NO2, you should be in the twelves, bad news is you may only make that run one time, on the other hand you need about 350 hp/trq to the rear wheel, able to hook, and you'll be pretty close to a 12 sec car. you'll probally need 4:10 or 4:58 gears since you have overdrive it will still be streetable you need to up that cam to something that make more power on the topend, next you'll probally need about 3000-3500 stall ...

all that just to say those vortec heads and low top end hp/trq isn't going to get you anything but good 60ft time IMO

Thats my concern with the vortecs but I've also seen dynos stretching them out to 6400 rpms with good power (450hp)

 

[monte olrac]

were the vortec in stock form? I know there pretty good heads but from what i know they flow pretty good till about 5000 or 5500 rpm, but i could be wrong as hell to, best bet is to do some research, talk to a good machine shop and ask them about the vortecs, dont go on what super chevy dyno's engines at either, they are about getting the most power period and fluff it sometimes too.

 

[stomis]

were the vortec in stock form? I know there pretty good heads but from what i know they flow pretty good till about 5000 or 5500 rpm, but i could be wrong as hell to, best bet is to do some research, talk to a good machine shop and ask them about the vortecs, dont go on what super chevy dyno's engines at either, they are about getting the most power period and fluff it sometimes too.

No this was a build from popular hot rodding but I definitely hear ya on fluffing the numbers.

I'll probably port the runners myself and put that die grinder to use.

And no the vortecs they used in that build were large runner by EQ Lightning.

 

[monte olrac]

AHH, they were vortec stlye heads, one thing i heard from someone else is porting vortecs are a bad idea, something about boat anchors

 

[stomis]

AHH, they were vortec stlye heads, one thing i heard from someone else is porting vortecs are a bad idea, something about boat anchors

I've heard the same but about the bowl not the runners.

 

[khan0165]

My car has run a best of 12.9 @ 108mph. And it's good for low 13s on most days. In my signature are the build specs, and you'll notice it's a very "old fashioned" approach to getting good power... big solid cam, lots of compression, and a big stall on a low geared trans.

from lots and lots of reading and research, here's the combos that I found hit consistant 12s on a 355motor.

Obviously, a big cam helps. My solid cam with 0.495lift and 0.236dur was pretty radical a few years ago, but cam technology has exploded since then, and you can now find upwards of 0.530 lift on a streetable application. You'll always make more power with a solid over a hydraulic. But they wear quicker and it's a headache to lash and adjust every so often. But that's old school anyways, and I highly recommend you check out a roller valvetrain option.

Heads are HUGE! my engine was built on a budget, so the 54cc chambers on the L98 heads was a good option. But these heads don't flow great, even with port work. Edelbrock delivers awesome performance with their RPM heads. You can get them with 58cc chambers, very small port angles, and great flow numbers. Check it out...

When you're chosing pistons, make sure you do you math on compression ratios. Make sure they work well with your heads, and make you can run pump gas. Generally, 10:1 compression is comfy with today's low octane gas... 10.5:1 starts to push it.

To run a big duration cam and keep the car streetable, you simply cannot use anything lower than a 2800-3000rpm stall. It'll be a pig on the road and your brakes will just suck. Talk to the guys you are getting the cam from, they'll usually recommend what stall to run.

And keep your 3.73 rear gears. My 3.42s are great for the road, but only pull 5200rpm thru the traps... which is not in the powerband of my cam. Your 3.73s will pull you thru the traps with a good strong rpm.

Beyond this, it comes down to basics... Don't cheapout on the driveline. Make sure you buy quality low friction parts. Less friction in your rotating assembly means more power.

Experiment with weight reduction and transfer some load to the rear of your car. Suspension is another key element. Choose a tire size that works well... bigger is not always better. Beef up the rear springs, install a rear sway bar, and box your rear control arms. And when you're dragging, pulling off your front swaybar helps transfer weight to the rear at launch.

Anyways, I'm sure alot of this your know yourself... but for more tips, there's lots of smart guys on here that will help you out.