I just figured out that the motor in my '73 is an L48 . Its obvious to me now that I should had done more motor-related research before buying the car. I was more concerned at the time in low mileage, getting a sound frame a solid body and ensuring that it was all original. I was hoping to bump up the performance/compression but now I'm wondering if the motor can take it. Does anyone know if the L48 has 4-bolt main bearings? Also, has anyone tried juicing up an L48? I'm not looking to make it a rocket but I'd like to get the HP up to at least high 200s. 300HP would really make me happy. I'd prefer to at least keep the block original.

Thanks

 

I did my L48 top-end with comp cams 262H cam, Dart ss 165 heads (used), shorty headers, recurve distributor and edelbrock performer. I kept my Qjet. Spent about $1000 and am very happy with the output. It pulls hard to 5500 rpm. Thanks to forum members for the support!

 

Chevy did some weird things back in the early 70's... Your L48 could be a 4 bolt mains, but that chances of it are pretty slim... They usually cam with 2 bolt mains, nodular crank(cast), and I believe cast pistons and rods.. It might sound bad but for a driver its not too bad...

With its lower end, I think if you are producing or 400 HP or so you wouldn't be stressing it out too bad... However, you would probably want to keep you Redline around 6000 and no more than 6500!

If you don't like the lower end at all, don't go running to buy a GM small block crate engine. IMHO - they aren't much better than an L48... Yeah, the 4 Bolt mains and forged steel crank sound nice... But the Powdered Metal rods are pretty much a cast rod. The hypereutectic pistons are the same way... pretty much a cast piston with a higher silicon content.

What I would do If where you?
I would take the block to a machine shop... Have him check the cylinder walls for wear, if necessary bore it out to the minimum. Also I'd have install 4 bolt splayed caps which are suppose to be stonger than the regular 4 bolt mains. Then I'd probably buy a rotating assembly from Eagle or Scat with 4340 forged crank and rods with forged pistons for a 350 or 383 depending on what you want... I believe a good complete rotating assembly from Summit would cost some where around $2000.. Don't ever go cheap when buying your lower end parts!

As for the heads, you would probably be better of buying some AFRs or edelbrocks... I don't know what AFR has now for a SB but the 2.02/1.6 valves are hard to beat.

As for the intake, the Edelbrock Performer RPM Air-Gap is hard to beat.. On their web site they will tell you that it wont fit under a stock hood which is a bunch of BS. If ya buy the factory style drop base it would easily fit with a 3" and could fit with a 4" if you beat the wings of the wing nut with a hammer- haha

As for a carb if you going with a mild set up I'd look into a holley 650... If you go with beefy cam maybe the 750..

As for cams... I wont go into that because everyone has their preferences some like the hyd. rollers, and others like the hyd. flat tappet.. I would just stay hyd. unless you want to pop off the valve covers and adjust the valves every so often!!

Hope this gives ya a general idea!

John

 

You can handle 400hp easily with a 2 bolt main. Just use quality fasteners (ARP).

People forget that a Corvette is just a Chevrolet. It is a lot easier to buy a solid frame and hop up the motor than fix a rotten frame attached to a good motor.

 

I still have the original 2 bolt block in my car. I don't know how much power it produces but its way more than stock. (Original rods too, resized the big ends and installed ARP bolts)

 

This is the basics. Free up the exhaust too. keep the good stuff and change out the stuff that is holding you back. The first steps if you want the most bang for the buck.

If you want to take it to the next level, look and see what BK Broiler is running. He is laying down some very good track numbers with a few more mods other than just engine. It's going to take some money and some effort but thats what it takes to go faster.

-Mark.

 

IMO, othere than heads and exhaust needing get rid of the heat riser mess on pass side, change the intake manifold for something lighter weight and less restrictive....You may want to put on a set of #113 '88-91 vette heads, and if you have the wiring talent, put on an old TPI system with speed density computer like '91 vette, and you will have a damn decent performing engine doing about 300 hp or so with no sweat...bet you can get it all done for like 1500 bux....you spend wisely...a set of aluminum aftermarket heads will cost 1200 bux alone, so I don't think they bring enough bang for the buck compared to a freshened up set of 113s for 500 bux total.....194/150 valves are enough, the 202 valves are for bragging rights, and top end performance tweeks....drag racing all out...

 

The L48 is just another Chevy engine.
If it was in a Nova you wouldn't have ask at all if it could handle it, but already added carb, intake, cam, heads and headers and floored it out the driveway!

 

If you are only looking for 290-300hp out of the engine, you don't need much. A cam swap, dual exhaust, aluminum intake manifold, and a good tune-up will get you there. If you are looking at new heads, you can get 350-375 and still keep it very streetable.

 

Camshaft and exhaust will do wonders for an L48!

 

I had my L48 Beefed up to 400hp. New Heads, Cam, Intake, Carb, Headers and Electronic Ignition. Runs smooth with a little Lumpy sound to it but it runs on 91 octane. Don't worry about only having a two bolt main. Good Luck

 

Geesh is this true?
I could swap my cam / ntake remove my cats and be in pretty good shape?
THat souds like the way to go.. I think that 300 hp would make me happy....
Could I use the same carb?

 

no shet.

 

well said

My stock bottom end L48 makes 270 rwhp with the 'bolt-ons' in my sig.

 

What cam specs do you recomend?

 

Any Coments on this statement?

 

Dunno the laws in your state, and year of your car, but if no one is looking at it all the time, sure, why not?? i'ts not LEGAL, but done all the time....

when you get rid of things like EGR, especially, it changes the calibration of the carb a bit/lot....and so you need it rebuilt by Lars or someone who knows just what to do, not as easy as we think....

putting true duals on with no cats, crossover pipe, and stock say '72 mufflers at 2.5 inch diameter pipes is about good as you can do and stay relatively stock looking....want attention?? put on a loud muff....your choice....

allways a good idea to cam up a bit, but most guys wind up over camming and killing bottom end torque, making the car a PIA to drive on the street....don't go overzealous there...too mild is allways better than too WILD....

 

No reason you can't reuse the q-jet. Definitely rebuild it though. You can probably get up to 300 with a cam and intake, but bumping up your compression with some good flowing heads would help quite a bit.

 

Check out this link for a series on beefing up what is equivalent to the L48. The link is part 2 of the series, after adding headers, Edelbrock intake and an aftermarket cam. It put out 336 hp with some pocket porting of the heads. Even without the pocket porting, you would be over 300 hp. For the rest of the series, search the site for Goodwrench Quest.

http://www.chevyhiperformance.com/te..._ii/index.html

 

Everyone likes to bash the L-48 but it actually is a pretty good foundation. Most were 2 bolt ( Mine is) but a few were 4 bolt mains. Headers, true duals, different heads and you'd have a good ride for little bucks. ( OK, maybe not little bucks, dollar amounts are relative)