Why dose 75 only have 165hp?
Race Director
Joined: Apr 1999
Posts: 15,146
Likes: 477
From: NM
Re: Why dose 75 only have 165hp? (Racer-X)
First year for cat converters. 75 was the leading edge of the power stealing emission equipment. The auto cos had not yet figured out how to deal with the new emission requirements and maintain power.
How to improve? It is still a chevy small block so any standard hot rod mods will work. Intake, cam, heads, exhaust.
tom...
How to improve? It is still a chevy small block so any standard hot rod mods will work. Intake, cam, heads, exhaust.
tom...
Melting Slicks
Joined: Feb 2000
Posts: 3,052
Likes: 0
From: Vancouver BC, Canada
Re: Why dose 75 only have 165hp? (Racer-X)
motors were choked with 'new' smog gear. helpless victims of insurance, politics, and emissions. nevertheless, sales increased every year in the mid70's.
Team Owner
Joined: May 2001
Posts: 29,745
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From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
Re: Why dose 75 only have 165hp? (Racer-X)
They were low powered due to government mandates for cars that consumed less fuel. And in the days before better making power by having more efficient motors (fuel injection, computer controlled, special shape combustion chambers) they got better mileage by making less power.
They usually put in low compression pistons and cylinder heads and a crappy cam.
Best performance upgrades would be in the following order.
Cam/lifter/timing chain/valve spring replacement
Intake and carb. replacement.
Headers and better exhaust
Lower CC cylinder heads and thin head gaskets to up the compression ratio.
A better rear gear ratio will get you off the line faster, but will kill top end speed.
Beyond that you have to pull the motor and build it up again.
They usually put in low compression pistons and cylinder heads and a crappy cam.
Best performance upgrades would be in the following order.
Cam/lifter/timing chain/valve spring replacement
Intake and carb. replacement.
Headers and better exhaust
Lower CC cylinder heads and thin head gaskets to up the compression ratio.
A better rear gear ratio will get you off the line faster, but will kill top end speed.
Beyond that you have to pull the motor and build it up again.
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,482
From: Southbound
Cruise-In II Veteran
Re: Why dose 75 only have 165hp? (Racer-X)
Base engine L48 Corvettes essentially received GM smog engines in order to meet federal emissions standards. Any L48 can be built up to respectable performance with an increased compression ratio (new pistons) and an L-82 camshaft. Cheap mods since the parts are available almost everywhere.
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Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: Why dose 75 only have 165hp? (Racer-X)
The morons in charge at that time thought we were going to run out of gas or
choke ourselves to death on pollution whichever came first.
choke ourselves to death on pollution whichever came first.
Intermediate
Joined: Jun 1999
Posts: 36
Likes: 0
From: Issaquah,Wa,USA
Re: Why dose 75 only have 165hp? (Racer-X)
Two questions:
1. What changes were made to the 76 to give 180 hp?
2. Any one know what hp gains would you get on a 75 or 76 with new high flow cat converter and recurving the distributer?
1. What changes were made to the 76 to give 180 hp?
2. Any one know what hp gains would you get on a 75 or 76 with new high flow cat converter and recurving the distributer?
Intermediate
Joined: Jul 2000
Posts: 33
Likes: 0
From: auburn ga
Re: Why dose 75 only have 165hp? (MotorHead)
I'll take a stab at this one. Since power is torque times angular velocity, and if the L-48 has the same torque as an L-82, then it stands to reason that the L-48 is not able to deliver that torque at the higher RPM's. This is owing to the fact that the L-48 doesn't flow as much air as the L-82. I think the cylinder (pressure times volume) of the L-48 is about the same as the L-82, it's just that the L-48 can't deliver as many power strokes per second as the L-82. It sounds like the L-48 would benefit from better heads, better cam, better exhaust, and higher compression. Well, that would be about everything I guess :jester
I had a 79 Caprice with a 140hp@3200 305 that got 245ft*lbs@1800. Good for moving around a car-boat but it fell flat on its face at anything near 3k rpm.
I had a 79 Caprice with a 140hp@3200 305 that got 245ft*lbs@1800. Good for moving around a car-boat but it fell flat on its face at anything near 3k rpm.
Le Mans Master
Joined: Dec 2000
Posts: 5,245
Likes: 25
From: Blue Ridge Georgia
Re: Why dose 75 only have 165hp? (tiger)
Looking at your questions I'm going to give you the best advice that you'll ever receive. START BUYING CHEVY HIGH PERFORMANCE MAGANIZE. You never be sorry for the information thats in each mag.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Re: Why dose 75 only have 165hp?
Fix exhaust. See:
Why Exhaust is problem for HP on 75-81 http://www.corvetteforum.cc/ubb/Foru...ML/008082.html
Cam (& intake), then heads.
Why Exhaust is problem for HP on 75-81 http://www.corvetteforum.cc/ubb/Foru...ML/008082.html
Cam (& intake), then heads.
