Corey_68

Having a friendly discussion in which I stated a decent duration cam, intake, and headers would net 350hp. I was told "No way", not I relaize the compression was 8:2 maybe if the heads were shaved one thousandth, and a thinner gasket installed to raise compression might do it?

So you L48 owners, what did/does it take to make 350-400hp??

carl a

my l-48 was tore down and turned into a 383 motor ,10.5 to 1 comp,488 lift cam,, preformer intake,, 670 holly , intake valves opened to 2.02 intake /165 exh

MotorHead

You will not get there with stock L48 heads, you need better heads and 10:1 CR, cam, intake, exhaust and carb, basically the whole nine yards

SteveG75

Now, my combo is:

L-48, .030" over for 355 cubes
Edelbrock RPM heads with 64cc chambers, approx 10:1 compression
Edelbrock 2101 Performer (my chokepoint) with Lars' tuned Q-Jet
Hooker sidepipes (primaries are a little on the large side)
Cam: Crane hyd roller 214/222 @.050", .488/.509 lift

Car pulls hard from 2000 and I limit myself to about 5500/6000 rpm.

BTW: Desktop Dyno says 430 HP at 6000 rpm and 430 ft/lbs at 4000 rpm. I'll be conservative and say I have 375 or so.

45ACP

An Edelbrock Performer RPM package or its equivalent.

I went the "or its equivalent" route (I can go into greater detail if you want, but the RPM package is what it amounts to) and figure I'm at 400 or so at the flywheel. That number is just a guess, but I'll have to say that it makes for a lively ride that I've been happy with for quite some time.

mandm1200

First, look at what the 350hp engines had. That should be a good starting point. "Bigger' cam, better heads, and more compression.
Swap out the heads for the Vortecs which are an improvemnet over the old double humps. They will also raise the compression. For more compression a thinner head gasket could be used and it should come up in the to 10:1 range. Change the cam as well as the intake which is required for the heads. It should out do the 350hp rating from the old days..

79 vette

I have my original block L48-Trick flow twisted wedge heads,comp cam 268,rpm air gap intake,1.6 roller rockers,msd ignition,Holley avenger 670 ,dynoma headers,2 1/2 in dual exhaust with x pipe.Dont know the hp but it runs good

Stewart's74

Good thread guys.
My issue is that I still am using stock heads.
Stewart

Techno

To get hp you compromise low end hp. This compromise is mostly done with the cam. Low/mid/high. Where do you want it? Low/mid or mid/high. You can't have all three. Sometimes not even 2.
Better breathing is done with intake and exhaust- it improves the cam selected.
I doubt you can get this level of hp without drasticly compromising low/mid performance. It can be done but now your talking about a single purpose drag motor with a power spike and little else. So maybe you can get 350 hp at 7300-7600 and almost nothing everywhere else.

This could be done with 1 additional componant. A blower or nitrous. Both de-compromise intake/exhaust/cam compromises made.

Unless they made great improvements on that desktop dyno I don't think its worth anything. Change different stuff on it and it makes rediculous claims.
Compare those numbers to a BB and it did it with a radical cam and high compression. Roller cam maybe but isn't the duration low for a SB? I don't know.
I played with it for a while and found it to be weird.

bams12

Alot of these ideas I have looked into for a performance improvement on my 1980. My problems seem to come from the fact that I do not want to alter the stock hood on my car. I know that I looked into alot of different combinations but always came up with hood clearance problems. I really like the look of the stock hood and will not modify it . Brent

Budman68

It's alot harder than people think. I'm not calling anybody out, but when most people dyno their combo 400 hp turns into 250 hp. I would try one of those package deals and add highier compression pistons. Compression = HP

stingr69

Maybe you could BUT it will be the hard way. Lets assume you can't afford heads but you could pay for some pistons. If you keep the stock crappy heads and rework them, drop in some domed pistons, get a wicked cam, some real good rod bolts and balance the assy I know you could get there with a lot of RPM. Thousands of stock cars do it every weekend on tracks all over the country. Not the best way to get there, but it can be done. People running on the street have a different rule book ($$$) so they build them with better heads and milder cams but the same principles apply. All you need is more compression and flow.

-Mark.

GOSFAST

Fairly easy, with slightly higher C.R., about 9.5/9.75 will do it. Finished a '69 Camaro original 350/300HP and had to use ALL external components. The factory cores including heads, intake, and original cast iron exhaust manifolds. We used Ross L/W pistons and the factory L-82 cam. We tested it with 2 different carbs just for comparison purposes. First test was with 650 Holley with stock alloy intake (for Holley, not for car), then with customer's own intake and Q-jet. HP and torque numbers were almost identical. We made 355+ HP @5800 and 385 Ft.Lbs. @ 4100. This was through his stock exhaust manifolds. We got a call from the resto shop when they road-tested the car and they had told us it actually was better (felt more powerful) than any LT-1 that they had restored up to that point. Thanks, Gary in N.Y.
P.S. We weren't specifically chasing HP on this engine, we built it totally for longevity. It did have all top-notch internals however. A slightly different cam grind could have produced more power, but the cam in this engine was strictly a customer choice.

KenSny

As you can see by the above posts:

HP=$$

AND you won't get there with the stock smog heads.

BigBlockk

A blow through turbocharger.

BigBlockk

Later.....

Yellow73SB

Flat tops with 64cc chambers arent gonna be 10:1. my car with 355, flowed heads(spent a grand on them even after i ported them my self), performer rpm,the carb in my avatar(650cfm) , .550 lift 236* at .50 lift, the heads are 58cc's probally around 10:1 10.25:1 . i dont even think it will get 350 hp because nothing is really that big on it i just wanted a pretty relible motor to start racing with so i can learn to take corners .it wont even do a burn out with slicks on although i do have a victor on it and it doesnt start pulling untill like 3500 thats why im putting in a performer so i can make power the whole range since its a hydrolic roller.. wait till you see my big block im building next.

Yellow73SB

I want a procharger. they dont have turbo lag. the guy a few shops down has one and his car is so fast and thats with the biggest pully on when he puts a smaller one it will have even more.

cardo0

That L82 was designed with the stock ram exh manifolds in mind. For a 1st time engine rebuild or just cam swap that is really my 1st choice as it would be hard to go wrong using it. That cam should work well with almost all c.r. and exh sys. And i see that is the same cam now used in the 290hp Goodwrench 350 crate mtr. Same exact mtr except for L82 cam (#3896962) and makes 40hp more than before in the "929" cam/ 250hp combo - just by cam alone.
IMHO 1hp per c.i. is very easy to do for the least amount of dollars. Even with stock wheezer heads some simple pocket porting and thinner hd gasket for little more c.r. and a lot better quench should get u there still using just stock junk pistons. Other little tricks help too like if u can't install screw-in studs then at least pin in the rocker studs. While heads are off why not elongate the slots for 1.6 rockers too? 3 angle vlv job is cheap while heads off and why not 4 or 5 angle if u can find the right shop?
Ok i'll shut up but just my 2 cents here. cardo0

glen242

Gonna have to mill a lot more than 0.001 to get any worthwile compression increase. Just happened to look at some specs for my TF heads. Flat milling 0.006 will give 1 cc less. My guess is that you are running 76 cc heads. Milling your heads down to 64cc, using a 6 cc for the pistons, 0.039 gasket, and stock +/- 0.025 in the hole, you get 9.6 CR. You do the math. Don't forget quench.

mandm1200

Yes it is possible to get 10:1 with flat tops. The above example with 64cc heads and the normal thick head gasket comes out to be 9.6:1. Change to thinner head gasket of aout .020 and the compression is now at 10:1. Not only will the thinner haed gasket increase the compression, it will allow for a tighter quench. With an appropriate cam, the engine should be able to make 350hp. How much above that will depend on the cam and heads. As others have mentioned, getting a package from a company such as Edelbrook isn't a bad idea. A 350 SBC is a common item and they should have tons of experience with them.