Aftermarket Horsepower?

[73stinger]

Which aftermarket bolt-on increase the horsepower the most in early C3 (68-73)?

 

[92ghost]

Your question is very open ended. If taken literally I'd say a supercharger or twin turbo setup.

 

[92ghost]

OOPS Didn't see the pole until after my reply. For some reason the pole did not show up. Makes me look like a heal.

 

[Copdogcorvettes]

It is still an open ended question. For the HP per $ I have to say a good air cleaner system. Also to get more from headers you still need a good Air Cleaner. So for these reason I voted for The Air Cleaner. It is the basic to start with and makes everything else work better.

IF IT Can't Get Air It Isn't going to GO!!!!!!!!!!

 

[Stallion]

Headers. You should also add true dual as well, and obviously no cats. That isn't just power, but it's sound too.

 

[Flared69]

extractors/headers & intake manifold imo.

 

[mike weyman]

the exhaust has to be adressed first, but then there's nothing like a little port and polish with a side of gasket matching to wake up a tired engine.

 

[Evolution1980]

easy question, hard to answer

As you'll see from the replies above and below, it's not usually worth doing one without doing something else.

It's almost easier to say which is the least effective and work backwards. So I'll put in my 2¢

Least to most: Synth Oil, Ignition, air filter, headers, internal parts
Obviously, I placed my vote for internal parts. But you're talking nickel and dimes versus tens and twenties.

Synth oil: only real explanation is that it lowers internal resistence of moving parts and can reduce overall heat buildup. You'll see zero gain from your "butt dyno".

Ignition: Plain and simple, any engine will run like poop with an ill ignition system. So again, no noticable gain on the butt dyno.

Air filter: Can make a slightly noticable difference on the butt dyno if your old one was really choking the the intake. Though there has been talk on occasion that some paper filters work better than K&N's and the like in some setups.

Now that's the nickel and dime stuff. The remaining two items are considerably more expensive, but will also give corresponding gains in HP.

Headers: Yes, these can make a significant difference if you are replacing the old cast-iron manifolds. However, you didn't say anything about replacing mufflers and what not. But yeah, headers can give you a noticeable boost on the butt dyno.

Which leads us to my vote for Internal Engine Components. I'd say that you replace a cam by itself, and you'll possibly get the most HP boost (depending on proper cam selection). You can also include such items are roller rockers, pistons, lifters, etc. Basically, anything between the crankshaft and the heads! That leaves some good stuff to play with. But again, this can all add up. I would say that a cam swap is cheaper than headers and can probably give you more hp gains as well. (Cheaper if you have the ability to do it yourself. If you are paying someone else to turn the wrench, then headers are likely the cheaper labor cost.)

Again, when all is said and done...you're really not going to do any of the last two without having the air intake and ignition correct. Most people make internal engine mods their last item since headers are an easier job to tackle for shadetree mechanics.

 

[KANE]

Think cam, Vortec heads, intake manifold, and headers-


Assuming your engine is in good shape you'll be set.

 

[bossvette]

As you'll see from the replies above and below, it's not usually worth doing one without doing something else.

It's almost easier to say which is the least effective and work backwards. So I'll put in my 2¢

Least to most: Synth Oil, Ignition, air filter, headers, internal parts
Obviously, I placed my vote for internal parts. But you're talking nickel and dimes versus tens and twenties.

Synth oil: only real explanation is that it lowers internal resistence of moving parts and can reduce overall heat buildup. You'll see zero gain from your "butt dyno".

Ignition: Plain and simple, any engine will run like poop with an ill ignition system. So again, no noticable gain on the butt dyno.

Air filter: Can make a slightly noticable difference on the butt dyno if your old one was really choking the the intake. Though there has been talk on occasion that some paper filters work better than K&N's and the like in some setups.

Now that's the nickel and dime stuff. The remaining two items are considerably more expensive, but will also give corresponding gains in HP.

Headers: Yes, these can make a significant difference if you are replacing the old cast-iron manifolds. However, you didn't say anything about replacing mufflers and what not. But yeah, headers can give you a noticeable boost on the butt dyno.

Which leads us to my vote for Internal Engine Components. I'd say that you replace a cam by itself, and you'll possibly get the most HP boost (depending on proper cam selection). You can also include such items are roller rockers, pistons, lifters, etc. Basically, anything between the crankshaft and the heads! That leaves some good stuff to play with. But again, this can all add up. I would say that a cam swap is cheaper than headers and can probably give you more hp gains as well. (Cheaper if you have the ability to do it yourself. If you are paying someone else to turn the wrench, then headers are likely the cheaper labor cost.)

Again, when all is said and done...you're really not going to do any of the last two without having the air intake and ignition correct. Most people make internal engine mods their last item since headers are an easier job to tackle for shadetree mechanics.

there is no substitute for cubic inches stroke it

 

[Stallion]

What's the rule of thumb (if there even is any, I might just be making this up)? Stroking gets more horsepower (top-end?) and boring gets more torque? Is that right?

 

[bossvette]

What's the rule of thumb (if there even is any, I might just be making this up)? Stroking gets more horsepower (top-end?) and boring gets more torque? Is that right?

generally speaking for a given engine size an over square bore to stroke ratio will yeild more horsepower at a higher rpm for example the Z-28 Dz 302 made gobs of horsepower at high rpms but was lacking in low rpm torque, but boy when it hit 3000, hold on .
on the other hand the 305 which has a smaller bore but longer stroke is more of a torque motor and runs out of breath early (kinda like me):L .
Harleys are an example of a long stroke small bore, they make smooth power from idle to their limit.

 

[Bender]

How much is a super charger for a 350 anyways?

 

[Copdogcorvettes]

One of the 144 street charger like that made by B&M/ Holley will cost around $2000 for a complete kit. You will need to get some extra hood clearence.

Ckeck out JEGS. I saw them list there. For other units the cost goes up. I have seen some for sell on Ebay for less.

Gary

 

[Flared69]

the biggest horsepower increase my car has gone through:

Just replaced the accelerator rod. The old one was bent a little and snapped at the shop today

anyway, now i can put the pedal way back instead of how it was before. Now i get real horsepower

 

[Jack]

I base my choices on MOST bang for the buck.

68-74 C3 came OE with true dual exhaust that flow pretty well.

Most existing 68-73 C3 have small block, most of those have a base motor such as the lower performance L-48.

71 and up C3 have an ignition curve that is optimized to help motor meet emissions standards... is not a performance curve. So, for those my first choice is a simple recurve kit (~$40). For most folks I don't consider a cam a bolt-on part... but it's not too difficult and a decent hydraulic flat tappet cam & lifters can be had for under $100.

For example ... a 73 C3 with base L-48 has an exhaust that flows rather well... so I'd say go with a recurved ignition & another cam. Those parts will cost about same as a set of cheap headers... and will make more giddyup than would a set of headers.
JACK:gap

 

[JohnZ]

Intake, heads, cam, and exhaust, properly matched for how you plan to use the car - an engine is just an air pump, and until you can get more air/fuel mixture through it, nothing else makes much difference.

 

[Buckskin7T7V]

Not Horsepower but performance off the line power, would be the Gear Ratio. Go from a 3.07 to a 3.55 and it seems as if you added a 100 horsepower.

 

[Glensgages]

Not Horsepower but performance off the line power, would be the Gear Ratio. Go from a 3.07 to a 3.55 and it seems as if you added a 100 horsepower.

How true.
My stock '82 ran 15.704 @ 86 MPH w/ OEM 2.87 gears (86 MPH @ 3500 lbs calculates to 151 RWHP);
with 3.73 gears, it ran 15.003 @ 91 MPH (179 RWHP), but I think the car 'nosed-over' before the lights (poor fuel pressure?).
If you can live with poorer MPG, and increased RPM, where else can you find 7-tenths, 5 MPH, and almost 30 HP for the money (I had $550 invested, total), short of N2O ?

 

[Wolverine]

Jack,

You mentioned adding a recurve kit as a cheap way to improve performance. Do you have any suggestions on where one can be ordered? This is something that I am interested in trying.

Thanks.