Chevy Corvette Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
10,181 Posts
Discussion Starter · #1 ·
When I bought my '71 with its 87 octane friendly 385 hp 454" marine engine I was impressed with its stump pulling 500 ft/lbs of torque. But as I just can't leave things alone I decided to pump it up by increasing its compression ratio, giving it more camshaft duration, and a higher flowing aluminum intake manifold.

The 385 hp marine cams have a 220/220 duration and .500" lift like the L-82's have and they provide mild lopes (those pleasing to the ear sounds). I chose a flat tappet 286H Competition Cams 236/236 duration with a .556" lift which operates at a higher 2200 to 6200 rpm; substantially hotter than the marine cam.

The 385 hp marine engines have a flat iron intake manifold with small cross section runners and use a 750 cfm QuadraJet carburetor. As such they produce a lot of low end torque but I wanted higher mid range torque so I chose an Edelbrock RPM Air Gap intake manifold with larger cross section runners to flow more air and a 770 cfm Holley.

The 385 hp marine engines have 87 octane friendly flat top pistons so I installed .100" domed pistons that produce a (with my mid 60's 396"/427" heads) 9.95 to 1 compression ratio which requires 91 octane gasoline.

I pocket ported then port matched my heads to my Air Gap intake and then I installed the larger high performance valves for increased breathing. Those modifications alone probably netted another 25 to 30 hp.

After the addition of higher performance parts I would estimate my 454" produces around 500 hp with a small reduction in torque. The question now being how much power is too much power? As my '71 accelerates like a rocket I would say anything that accelerates faster has too much power.
 

·
Registered
Joined
·
4 Posts
When I bought my '71 with its 87 octane friendly 385 hp 454" marine engine I was impressed with its stump pulling 500 ft/lbs of torque. But as I just can't leave things alone I decided to pump it up by increasing its compression ratio, giving it more camshaft duration, and a higher flowing aluminum intake manifold.

The 385 hp marine cams have a 220/220 duration and .500" lift like the L-82's have and they provide mild lopes (those pleasing to the ear sounds). I chose a flat tappet 286H Competition Cams 236/236 duration with a .556" lift which operates at a higher 2200 to 6200 rpm; substantially hotter than the marine cam.

The 385 hp marine engines have a flat iron intake manifold with small cross section runners and use a 750 cfm QuadraJet carburetor. As such they produce a lot of low end torque but I wanted higher mid range torque so I chose an Edelbrock RPM Air Gap intake manifold with larger cross section runners to flow more air and a 770 cfm Holley.

The 385 hp marine engines have 87 octane friendly flat top pistons so I installed .100" domed pistons that produce a (with my mid 60's 396"/427" heads) 9.95 to 1 compression ratio which requires 91 octane gasoline.

I pocket ported then port matched my heads to my Air Gap intake and then I installed the larger high performance valves for increased breathing. Those modifications alone probably netted another 25 to 30 hp.

After the addition of higher performance parts I would estimate my 454" produces around 500 hp with a small reduction in torque. The question now being how much power is too much power? As my '71 accelerates like a rocket I would say anything that accelerates faster has too much power.
It's a valid question, but I think it depends on the driver. I have a 2018 ZO6 (claimed 650HP/650LB/Ft, rear wheel HP is closer to 550 if you look at dozens of stock cars on dyno's). I came from a 1999 C5 1LT 6 Speed manual. It was fun, and I thought it was fast. the first few times I tested the acceleration of my ZO6 I wondered if it had too much power, but I got used to it. If you can keep the thing on the road and between the lines, I think there is no limit. Heck, look at YouTube and you'll find street cars with 1000,2000,3000 HP and more. I'm not sure I need that, but a cool 850 sounds about right to me now. I have raced many cars, and you know there are plenty out there that could beat me, but I haven't lost yet, even with over revving occasionally and catching the rev limiter. It's doggone fast, but I know I can handle more.
 

·
Registered
Joined
·
10,181 Posts
Discussion Starter · #3 ·
It's a valid question, but I think it depends on the driver. I have a 2018 ZO6 (claimed 650HP/650LB/Ft, rear wheel HP is closer to 550 if you look at dozens of stock cars on dyno's). I came from a 1999 C5 1LT 6 Speed manual. It was fun, and I thought it was fast. the first few times I tested the acceleration of my ZO6 I wondered if it had too much power, but I got used to it. If you can keep the thing on the road and between the lines, I think there is no limit. Heck, look at YouTube and you'll find street cars with 1000,2000,3000 HP and more. I'm not sure I need that, but a cool 850 sounds about right to me now. I have raced many cars, and you know there are plenty out there that could beat me, but I haven't lost yet, even with over revving occasionally and catching the rev limiter. It's doggone fast, but I know I can handle more.
Even though I live in the middle of nowhere I find there are very few roads that are wide enough, straight enough, or empty enough to safely open mine up and feel its brute torque for more than a few seconds so all of its power goes unused. I do however love it's pleasing rumpety rumpety rumpety sound as I idle through parking lots in 2nd at about 1200 rpm.

The bad thing about having a quick revving high horsepower engine is its ability to go way too fast way too quick. I am a very cautious driver and never do stupid things like I used to do when I was younger. I have a TH700R4 and 3.70's and constantly remind myself a sudden full throttle in stop-and-go city traffic will force a 2nd to 1st downshift which will break the tires loose and send it out of control.
 

·
Registered
Joined
·
4 Posts
Even though I live in the middle of nowhere I find there are very few roads that are wide enough, straight enough, or empty enough to safely open mine up and feel its brute torque for more than a few seconds so all of its power goes unused. I do however love it's pleasing rumpety rumpety rumpety sound as I idle through parking lots in 2nd at about 1200 rpm.

The bad thing about having a quick revving high horsepower engine is its ability to go way too fast way too quick. I am a very cautious driver and never do stupid things like I used to do when I was younger. I have a TH700R4 and 3.70's and constantly remind myself a sudden full throttle in stop-and-go city traffic will force a 2nd to 1st downshift which will break the tires loose and send it out of control.
Boy that’s the truth though. When I had slower “fast cars” I would race people at traffic lights. Now I leave that to the Subaru crowd. There’s just not enough space, and when you hit 60 in less than 3 seconds it’s just far too fast for city streets. Around here there are a few stretches of Mexico racing if you get my drift.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
10,181 Posts
Discussion Starter · #5 ·
Boy that’s the truth though. When I had slower “fast cars” I would race people at traffic lights. Now I leave that to the Subaru crowd. There’s just not enough space, and when you hit 60 in less than 3 seconds it’s just far too fast for city streets. Around here there are a few stretches of Mexico racing if you get my drift.


Sent from my iPhone using Tapatalk
We have a few roads that are wide and straight but there's always the chance of a coyote suddenly darting across the road. A 120 mph collision with a coyote would certainly kill the coyote but it would also seriously damage a C3. I have driven around 100,000 miles with my L-88 style hood and I've never encountered anyone wanting to race me.

When I make a modification with the hope it'll add power I see how much time it takes to go from 60 mph to 100 mph. No burning tires, no drive train shocks, no shifting gears, just brute torque.
 

·
Registered
Joined
·
10,181 Posts
Discussion Starter · #6 ·
Boy that’s the truth though. When I had slower “fast cars” I would race people at traffic lights. Now I leave that to the Subaru crowd. There’s just not enough space, and when you hit 60 in less than 3 seconds it’s just far too fast for city streets. Around here there are a few stretches of Mexico racing if you get my drift.


Sent from my iPhone using Tapatalk
Once you reach around 450 hp it's pointless to add more power unless you are track racing your C3.
 
1 - 6 of 6 Posts
Top