Performance Upgrade L-48
Thread Starter
Racer
Joined: Aug 2005
Posts: 377
Likes: 3
From: Northville MI
Performance Upgrade L-48
I've been reseaching my performance upgrade for the 1975 L-48; I have a quick question, would it be worth it to upgrade the cam without a head and Carb change? If so what Cam would best suit my application? I have the original L-48 head and Q-Jet. I also plan on True Duals from Mid America and tuning the car using Lar's peck performance article. Any idea of new HP ratings? Any suggestions are welcomed! Thanks
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
You need to match your cam to your tranny and rear gear to get the most out of it, if you put too large a cam in it you will have a dog off the line that will take all the pleasure out of driving it.
What is your budget? If you can spend about $1500 you can get a top end kit that will have alum heads, alum intake and cam giving you a nice power upgrade.
What is your budget? If you can spend about $1500 you can get a top end kit that will have alum heads, alum intake and cam giving you a nice power upgrade.
Melting Slicks
Joined: Jul 2002
Posts: 3,128
Likes: 3
From: Deltona (son of Deland and DAYTONA) FL
Originally Posted by 1975Stingray
I've been reseaching my performance upgrade for the 1975 L-48; I have a quick question, would it be worth it to upgrade the cam without a head and Carb change? If so what Cam would best suit my application? I have the original L-48 head and Q-Jet. I also plan on True Duals from Mid America and tuning the car using Lar's peck performance article. Any idea of new HP ratings? Any suggestions are welcomed! Thanks
This year I borrowed the Holley HP750 carb off my 383. This got me down to 14.8. I replaced the HEI becuase my original one had a seized mecahnical advance. That got me down to 14.6. Not bad for a car with 3.36 gears, a tight converter and a factory rating of 15.9
All this on the original smog heads. I could get the car in the 13's easily with 3.70's and a higher stall converter. Low 13's if I throw in some decent heads, but I have my AR 383 waiting on the stand.
Melting Slicks
Joined: Jul 2002
Posts: 3,128
Likes: 3
From: Deltona (son of Deland and DAYTONA) FL
Originally Posted by 1975Stingray
When you say Trans, what do you mean? I have an Auto, not sure of the final Rear end ratio. I would need to change the rear end?
) that rear end ratio can give you the most bang for the buck in the acceleration department. If you have a 3.08 or 3.36 now, jumping up to a 3.70 will give you a nice seat of the pants feel, as long as you don't do a lot of highway driving without an OD tranny.
Thread Starter
Racer
Joined: Aug 2005
Posts: 377
Likes: 3
From: Northville MI
Originally Posted by Fevre
You need to match your cam to your tranny and rear gear to get the most out of it, if you put too large a cam in it you will have a dog off the line that will take all the pleasure out of driving it.
What is your budget? If you can spend about $1500 you can get a top end kit that will have alum heads, alum intake and cam giving you a nice power upgrade.
What is your budget? If you can spend about $1500 you can get a top end kit that will have alum heads, alum intake and cam giving you a nice power upgrade.
Thread Starter
Racer
Joined: Aug 2005
Posts: 377
Likes: 3
From: Northville MI
Originally Posted by isosceles
Last year I added dynomax ceramic coated headers, MAD chambered dual 2.5 " exhaust and a Comp Magnum 270H cam. I used all this with the stock HEI and Qjet. The best improvement I saw was from 15.2 to 15.0 in the 1/4.
This year I borrowed the Holley HP750 carb off my 383. This got me down to 14.8. I replaced the HEI becuase my original one had a seized mecahnical advance. That got me down to 14.6. Not bad for a car with 3.36 gears, a tight converter and a factory rating of 15.9
All this on the original smog heads. I could get the car in the 13's easily with 3.70's and a higher stall converter. Low 13's if I throw in some decent heads, but I have my AR 383 waiting on the stand.
This year I borrowed the Holley HP750 carb off my 383. This got me down to 14.8. I replaced the HEI becuase my original one had a seized mecahnical advance. That got me down to 14.6. Not bad for a car with 3.36 gears, a tight converter and a factory rating of 15.9
All this on the original smog heads. I could get the car in the 13's easily with 3.70's and a higher stall converter. Low 13's if I throw in some decent heads, but I have my AR 383 waiting on the stand.
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Thread Starter
Racer
Joined: Aug 2005
Posts: 377
Likes: 3
From: Northville MI
Originally Posted by isosceles
I learned the hard way (guys on the forum tried to warn me, but I'm hard headed ) that rear end ratio can give you the most bang for the buck in the acceleration department. If you have a 3.08 or 3.36 now, jumping up to a 3.70 will give you a nice seat of the pants feel, as long as you don't do a lot of highway driving without an OD tranny.
) that rear end ratio can give you the most bang for the buck in the acceleration department. If you have a 3.08 or 3.36 now, jumping up to a 3.70 will give you a nice seat of the pants feel, as long as you don't do a lot of highway driving without an OD tranny.
Drifting
Joined: Nov 2002
Posts: 1,665
Likes: 1
From: Ontario
My 1977 L48 was originally 180hp at the flywheel. After I made these mods I dyno'd 240hp at the rear wheels (maybe 270hp at the flywheel)
- Comp Cams H268
- Hooker Comp headers
- Dual 2.5" exhaust, high flow cats, Magnaflow mufflers
- Weiand 8004 intake manifold
- Recurved stock distributor using Lars papers
- Retuned stock QJet using Lars papers
When I can afford it a set of heads should get me another 30rwhp or so. If you don't have all the money right now you can slowly upgrade your engine. For example do exhaust one year, intake & cam the next year, do heads a ways down the road, etc.
Good post you may want to read:
http://forums.corvetteforum.com/sho...d.php?t=1165420
- Comp Cams H268
- Hooker Comp headers
- Dual 2.5" exhaust, high flow cats, Magnaflow mufflers
- Weiand 8004 intake manifold
- Recurved stock distributor using Lars papers
- Retuned stock QJet using Lars papers
When I can afford it a set of heads should get me another 30rwhp or so. If you don't have all the money right now you can slowly upgrade your engine. For example do exhaust one year, intake & cam the next year, do heads a ways down the road, etc.
Good post you may want to read:
http://forums.corvetteforum.com/sho...d.php?t=1165420
Thread Starter
Racer
Joined: Aug 2005
Posts: 377
Likes: 3
From: Northville MI
Originally Posted by Boofers
My 1977 L48 was originally 180hp at the flywheel. After I made these mods I dyno'd 240hp at the rear wheels (maybe 270hp at the flywheel)
- Comp Cams H268
- Hooker Comp headers
- Dual 2.5" exhaust, high flow cats, Magnaflow mufflers
- Weiand 8004 intake manifold
- Recurved stock distributor using Lars papers
- Retuned stock QJet using Lars papers
When I can afford it a set of heads should get me another 30rwhp or so. If you don't have all the money right now you can slowly upgrade your engine. For example do exhaust one year, intake & cam the next year, do heads a ways down the road, etc.
Good post you may want to read:
http://forums.corvetteforum.com/sho...d.php?t=1165420
- Comp Cams H268
- Hooker Comp headers
- Dual 2.5" exhaust, high flow cats, Magnaflow mufflers
- Weiand 8004 intake manifold
- Recurved stock distributor using Lars papers
- Retuned stock QJet using Lars papers
When I can afford it a set of heads should get me another 30rwhp or so. If you don't have all the money right now you can slowly upgrade your engine. For example do exhaust one year, intake & cam the next year, do heads a ways down the road, etc.
Good post you may want to read:
http://forums.corvetteforum.com/sho...d.php?t=1165420
Thanks!
Le Mans Master
Joined: Apr 2000
Posts: 5,981
Likes: 0
From: Houston,Tx. USA
For a grand only I would also stick with the rear gear swap; IMO, a cam change without head work, and exhaust upgrade won't do a whole lot..might even give you less performance. Think of the engine like a huge set of lungs (air in, and air out).
I have an L-48 and myson-in-law has an L-82 and I run stronger because I have a 3.70 gear and he has 3.08, or 3.36.
I have an L-48 and myson-in-law has an L-82 and I run stronger because I have a 3.70 gear and he has 3.08, or 3.36.
Race Director
Joined: Dec 2000
Posts: 10,896
Likes: 2
From: CO
I changed my 75 L-48 rear gears and it made a big difference (3.70). At sea level I estimate I would run a low 15 or could squeak out a very high 14.
Up here at 5k feet ASL I ran a 15.8 at 90something, they say 1 sec drop at sea level is about normal. Thats the only performance mod at this time is just the gear swap.
Up here at 5k feet ASL I ran a 15.8 at 90something, they say 1 sec drop at sea level is about normal. Thats the only performance mod at this time is just the gear swap.
Melting Slicks
Joined: Jul 2002
Posts: 3,128
Likes: 3
From: Deltona (son of Deland and DAYTONA) FL
Originally Posted by 1975Stingray
I understand, I can be the same way; I just want to do the best bang but not hurt the overall drivablity of the car. What's a good street gear for both street and highway driving?
Now I'm going to trailer the car to the track and I don't even need the OD tranny!
