L-48
Thread Starter
Drifting
Joined: May 2004
Posts: 1,258
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From: Huntsville Alabama
L-48
What are some ways to get more horsepower out of a 75 L-48. The motor already has true dual exhuast, a eldlebrock intake, and a 650 holly carb on it. But I want a little more horsepower so what are some Ideas. Thanks
Melting Slicks
Joined: May 2002
Posts: 2,508
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From: Wisconsin
The biggest problem is the heads. Get some small chamber heads to bump the compression back up and a cam to match and you'll be happy. It'll be fun, not too fast, but more like it should be. Which heads specifically? No idea. Someone else can chime in there.
Pro
Joined: Oct 2003
Posts: 565
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From: I'm bleeding, making me the victor!
Horsepower is usually in direct relation to dollar amount. How much are you willing (or able in my case!)to spend? Intake manifold, cam and headers are usually the first add ons. Heads are probably the best way to add power but usually are expensive. Keep in mind, there are cases where rebuilding and or modifying used heads can cost as much as buying brand new ones. For the money, GM Vortec heads will work well with your stock cam and exhaust manifolds but require a different intake. Of couse there are many good cylinder heads out there, I hear Edelbrock aluminum heads are first rate. I am partial to factory performance heads because of their quality, fit ,and reliability. Do some research on the web and pick up some Hot Rod or Car Craft type magazines. There is a wealth of information out there on how to do just want you want. But like I said up front, how much you gonna spend????????? 
Melting Slicks
Joined: Aug 2004
Posts: 2,165
Likes: 950
From: Keizer Oregon
A set of edelbrock rpm aluminum heads with a smaller chamber and a nice cam will help you out alot. you won't have to change your intake for the rpm heads, the smaller chambers will increase your compression ( L48=8.5:1 CR 
) also aluminum heads allow more compression than iron heads for a given fuel quality------you might still be able to run 89 octane. And you will lose weight off of your car if you ditch the iron heads. there are many choices for cams out there, but you could always just make it easy and get the matching rpm cam (although I have never used one personally) But the rpm heads on my stroker 383 make bunches of power..........good luck
) also aluminum heads allow more compression than iron heads for a given fuel quality------you might still be able to run 89 octane. And you will lose weight off of your car if you ditch the iron heads. there are many choices for cams out there, but you could always just make it easy and get the matching rpm cam (although I have never used one personally) But the rpm heads on my stroker 383 make bunches of power..........good luck
Safety Car
Joined: Feb 1999
Posts: 3,631
Likes: 14
From: Fountain Hills AZ
Originally Posted by Silver00V6Camaro
What are some ways to get more horsepower out of a 75 L-48. The motor already has true dual exhuast, a eldlebrock intake, and a 650 holly carb on it. But I want a little more horsepower so what are some Ideas. Thanks
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Pro
Joined: Oct 2000
Posts: 629
Likes: 1
My idea, would be to have the distriibutor recurved (LARS) and then set the timing correctly (LARS timing paper). Most times, best things are also the most basic. I did the lowest cost things 1st. I found a used aluminum intake (Edelbrock Performer) for $25, then added the matching Performer Cam. Also added a nice set of headers. By the way, if you can find the orginal carb, the stock quadrajets actually flowed 750 cfm and once LARS works his magic on one of those puppies you'll be flying. Stock times on my L-48 equipped 1979 was around 15.9's and I've gone 13.96 at 98 mph with the stock 3:55 gears. But then BIG BLOCK fevor hit me.
Indy
Indy
Last edited by Indynut; Sep 25, 2004 at 08:23 PM.
Advanced
Joined: Sep 2004
Posts: 70
Likes: 0
From: Ontario
I agree with the above comments, you can also
switch to an electric fan and a set of underdrive pulleys to free up some horses. And also put on some roller rocker arms.
switch to an electric fan and a set of underdrive pulleys to free up some horses. And also put on some roller rocker arms.
Last edited by trotter73; Sep 25, 2004 at 10:03 PM.
Advanced
Joined: Sep 2004
Posts: 70
Likes: 0
From: Ontario
Originally Posted by Silver00V6Camaro
Also would like some specs on this motor thanks
L48 Engine
Item Description
Engine Chevrolet OHV V-8
Bore x Stroke 4.00 x 3.48
Displacement 350.00
Compression Ratio 8.5:1
Carburetion Four barrel carburetor
Horsepower 165@3800
Torque 255@2400
Distributor High Energy Ignition (HEI)
Melting Slicks
Joined: Oct 2001
Posts: 3,025
Likes: 12
From: Pleasant Grove AL
My L48 has the following mods and it will keep up with, or maybe out run my 67 L79:
Bored +.030
2.5" ramshorn manifolds and 2.5" exhaust, true dual-no cats
9.8:1 compression
cam change, not sure of specs, but almost anything would represent an improvement. Described as "street performance" cam
Edlebrock manifold and carb.
DUI distributor- not sure this is really necessary change, but it came on the engine.
Any and all pollution controls removed, ie air pump, etc.
Bored +.030
2.5" ramshorn manifolds and 2.5" exhaust, true dual-no cats
9.8:1 compression
cam change, not sure of specs, but almost anything would represent an improvement. Described as "street performance" cam
Edlebrock manifold and carb.
DUI distributor- not sure this is really necessary change, but it came on the engine.
Any and all pollution controls removed, ie air pump, etc.
Burning Brakes
Joined: Apr 2000
Posts: 1,076
Likes: 0
From: Dixie TN
Team Owner
Joined: Sep 2003
Posts: 88,393
Likes: 2
From: eville in
Originally Posted by 62fuelie
My L48 has the following mods and it will keep up with, or maybe out run my 67 L79:
Bored +.030
2.5" ramshorn manifolds and 2.5" exhaust, true dual-no cats
9.8:1 compression
cam change, not sure of specs, but almost anything would represent an improvement. Described as "street performance" cam
Edlebrock manifold and carb.
DUI distributor- not sure this is really necessary change, but it came on the engine.
Any and all pollution controls removed, ie air pump, etc.
Bored +.030
2.5" ramshorn manifolds and 2.5" exhaust, true dual-no cats
9.8:1 compression
cam change, not sure of specs, but almost anything would represent an improvement. Described as "street performance" cam
Edlebrock manifold and carb.
DUI distributor- not sure this is really necessary change, but it came on the engine.
Any and all pollution controls removed, ie air pump, etc.
Melting Slicks
Joined: Sep 2002
Posts: 2,783
Likes: 2
From: Engineers do it better.
Start with a good tune up. Rebuild carb and distributor according to Lars paper.
Add headers and exhaust.
Change Intake and cam.
If you can afford, change heads (and the right cam for new heads).
What kind of power do you have in mind?
Add headers and exhaust.
Change Intake and cam.
If you can afford, change heads (and the right cam for new heads).
What kind of power do you have in mind?
Melting Slicks
Joined: Sep 2002
Posts: 2,783
Likes: 2
From: Engineers do it better.
Originally Posted by A78Corvette
http://www.73-87.com/chp/gm350.htm
This might help.
This might help.
A must read.Read all the stages of mods and make notes of all hp/tq numbers with each mod. Then decide where you want to be. Very good article.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Exhaust: http://www.corvettefaq.com/c3/ganeyexhaust.htm
Besides exhaust, actually what it really needs is more cam! Vetterodder is right.
When you rebuild is a good time for heads.
You need to give trans. & rear gears for cam.
Besides exhaust, actually what it really needs is more cam! Vetterodder is right.
When you rebuild is a good time for heads.
You need to give trans. & rear gears for cam.
Melting Slicks
Joined: Oct 2001
Posts: 3,025
Likes: 12
From: Pleasant Grove AL
Originally Posted by comp
how much stronger is it Now???
Like I said, it is at least as strong as the 67 with the 327/350. This is in a 75 vert that is equipped with a 3.36 rear end. The 67 has a 3.70.
Drifting
Joined: Nov 2002
Posts: 1,665
Likes: 1
From: Ontario
FYI - my engine is a stock L48, 100 000 miles and these mods:
-Comp Cams H268
-Weiand 8004 intake
-Hooker Competition headers
-2.5" dual exhaust with cats
-Magnaflow mufflers
-Recurved distributor mechancial advance as per Lars paper
-Richened the stock QJet with primary metering rods 4 sizes thinner & slightly thinner secondary rods
Dyno results - 237 rear wheel horsepower.
I estimate around 280hp at the flywheel, stock was 180hp.
Can't wait to get some decent heads onto her!!!
-Comp Cams H268
-Weiand 8004 intake
-Hooker Competition headers
-2.5" dual exhaust with cats
-Magnaflow mufflers
-Recurved distributor mechancial advance as per Lars paper
-Richened the stock QJet with primary metering rods 4 sizes thinner & slightly thinner secondary rods
Dyno results - 237 rear wheel horsepower.
I estimate around 280hp at the flywheel, stock was 180hp.
Can't wait to get some decent heads onto her!!!