Question: Without going into the engine, can you increase HorsePower by...

[Mitch]

A Stock 1978 with 185 HP: Without going into the engine, can you increase that HorsePower by doing any/all of the following? If so, how much??

1. Change spark plugs to Racing Plugs and Best Plug Wires

2. Install Headers

3. Eliminate the Catalytic Converter

4. Install True Duals with a top-of-the-line Muffler System

5. Replace the Stock Breather with an Aftermarket One

6. Replace Stock Tires to a particular size

7. Higher quality Oil

8. Higher Octane Gas

9. Replace Stock Carb

10. Anything Else

Would any of the above help with Torque?

 

[minifridge1138]

1. No
2. Yes.
3. Yes.
4. Yes.
5. Possibly.
6. No.
7. Yes.
8. No.
9. Possibly.

You could probably do everything on the list (even the useless ones) and get so little horsepower you'd need a dynometer and a computer to tell the difference.

Although I have heard that the stock headers being made in St. Louis had some quality control issues and some were installed that were more restrictive than others.

Out of everything on the list, the headers would be your most noticeable difference.

Let the flame war begin.

 

[Hib Halverson]

First, let me say that some of the mods inquired about may increase performance, but the size of the performance increase might be small. For the purposes of this discussion, I'm going to answer the questions without respect to the size of the increase.

1) Plugs and wires...maybe. It depends on what plugs/wires are on the engine now and their condition, compared to the plugs/wires to which you will change.
2) Yes.
3) Yes
4) Yes
5) No
6) Maybe. Depends on a) if you mean power at the rear wheels or at the motor and b) what size you might use.
7) Maybe. Depends on what oil is in the engine now and what oil you might use.
8) Maybe. Depends on whether or not the spark curve and fuel calibration you have now are compromised due to problems with knock.
9) Maybe. Depends on what carb you have now and how the engine performs now, compared to what you might use.

 

[JohnZ]

In simple terms, an engine is a fixed-displacement air pump; anything you can do to flow more air through it (assuming it's done right with components properly matched and tuned) will generally result in a performance improvement, as will a displacement increase. Anything you do otherwise isn't going to gain you anything you can feel. It's really as simple as that.

 

[USA-1]

the starting place would be the exhaust system. to get more air in, you have to get more out. properly prepared, your Q-Jet will probably have ample flow. tweaking the jets and metering rods will increase the performance. with the small primaries drivability will be retained but the large secondaries are there for WOT. an aftermarket dual plane intake manifold should be on the list. something else that should be considered is a camshaft. carb, intake, cam,and headers will make a marked improvement in horsepower. it all has to do with flowing air. this is fun stuff

 

[L48]

relevance: cat, headers, duals. Carb maybe.

No one has mentioned ignition. A 78 still has mechanical advance, so you can get lighter weight springs to get it to dome in sooner. Also timing - bump it up four more degrees before TDC. I am not certain this increases horsepower, but it brings it in at a better time.

How about underdrive pulleys? That will increase rear wheel HP.

I would think headers, no cat and duals should get you at least 20 HP on that engine.

 

[Rodney Gold]

You will gain a much more seat of the pants feel of more horsepower by simply shortening your diff ratio to a 3.5:1 or so and installing a 1800-2000 stall (if its auto)
If you don't do the heads and cam , all the other mods you wanna do are not at all cost effective in terms of hp gains as the stock heads and cam will be a bottleneck.

 

[GT6Steve@aol.com]

an aftermarket dual plane intake manifold should be on the list. something else that should be considered is a camshaft. carb, intake, cam,and headers will make a marked improvement in horsepower. it all has to do with flowing air. this is fun stuff

Which manifold would be an improvement without compromising the Smog check? My old Jag beats the pants off my 81 and that's just not right. How much can I do and still pass Smog reliably?

 

[Hib Halverson]

Actually, unless you change the hood, there are few aftermarket intakes which fit C3s.

I know Nevada has a smog check but I'm not familar with the specifics. Your 81 is a computer controlled car so I'm going to guess to still pass smog you have to maintain all OE emissions controls.

If it were me, I'd do the following
1) headers and an aftermarket low restriction cat
2) Edebrock Performer manifold and camshaft package
3) Recalibrate the secondary side of the electronic Quadrajet for best performance.
4) Heads with hi-po street port/polish and multi-angle valve seats and faces.
5) Find a tuner who still makes a chip for the ECM which alters the spark curve to go with the mods.

 

[Scottsredvette]

Which manifold would be an improvement without compromising the Smog check? My old Jag beats the pants off my 81 and that's just not right. How much can I do and still pass Smog reliably?

Depends on what kind of Jag you have. I've got a stock 1975 XJ12C, V12,
326 cu in, 285 hp that will still embarrass quite a few cars.

 

[Hib Halverson]

I passed an XJ12 the other day in my V6 Camaro.

Ok...I squeezed the nitrous to do it.

 

[Jack]

Without going into the engine, can you increase HorsePower by...
A Stock 1978 with 185 HP: Without going into the engine, can you increase that HorsePower by doing any/all of the following? If so, how much??

1. Change spark plugs to Racing Plugs and Best Plug Wires

2. Install Headers

3. Eliminate the Catalytic Converter

4. Install True Duals with a top-of-the-line Muffler System

5. Replace the Stock Breather with an Aftermarket One

6. Replace Stock Tires to a particular size

7. Higher quality Oil

8. Higher Octane Gas

9. Replace Stock Carb

10. Anything Else

Would any of the above help with Torque?

I'm all but in Florence.
If you were to pull your 78 motor out & put it on an engine dyno ... assuming it's it pretty good shape & in pretty good tune ... it'll probably make about 250 hp. Compare that to hp figures you see publicized for GM crate motors. Yes, true duals & no cat will help a lot ... headers a bit more .. and yes you can sure get away with all that here in PeeDee. Keep your 78 air cleaner & carb (have good tune though). Hi$ oil ain't gonna do much here. A good refurb, tune & curve on your distributor will help too. Good wires are always needed ... not race wires just good wires.

 

[Mitch]

I'm all but in Florence.
If you were to pull your 78 motor out & put it on an engine dyno ... assuming it's it pretty good shape & in pretty good tune ... it'll probably make about 250 hp. Compare that to hp figures you see publicized for GM crate motors. Yes, true duals & no cat will help a lot ... headers a bit more .. and yes you can sure get away with all that here in PeeDee. Keep your 78 air cleaner & carb (have good tune though). Hi$ oil ain't gonna do much here. A good refurb, tune & curve on your distributor will help too. Good wires are always needed ... not race wires just good wires.

Hello, Jack...
I already have headers, true duals, new muffler system, new p255/60r15s. The car when stock was rated @ 185, but sure feels like more than that now--particularly on top end. Do you know someone around Florence/Timmonsville area that I can trust to (has the knowledge) to take a look at my Vette and maybe adjust my carb and distr? Thanks!
http://i4.photobucket.com/albums/y122/waswink/MY1978CORVETTE/zzzzMYengineOTHERside.jpg

 

[Jack]

Mitch you have a PM ... just email me

 

[Vette79]

I'm all but in Florence.
If you were to pull your 78 motor out & put it on an engine dyno ... assuming it's it pretty good shape & in pretty good tune ... it'll probably make about 250 hp.

250hp??? Stock?

 

[Evolution1980]

One thing I want to interject into this conversation is the use of the term "true dual" exhaust.

To me, that means one set of exhaust on the left side, one on the right, and at no point does the exhaust gas from one side touch the other.

FWIW, they serve a purpose, but it doesn't necessarily mean 'increased power' unless you are comparing it to the OEM stock exhaust.
Almost any aftermarket exhaust ("headers") will be better than the restrictive OEM setup of the cast iron manifolds. The rest of the system actually isn't that bad, IMHO.

Does anyone here consider the use of an X-pipe or H-pipe to mean the system is no longer "true dual"?
And as far as those go, an X-pipe will have a different effect on the power curves than an H-pipe. It depends on your intent for power. Trying to increase torque or HP?

 

[Jack]

I guess "true duals" has more than one meaning???

To me ... it differentiates between a system having (A) a single exhaust pipe run from V8 to either 1 or 2 mufflers and 2 tailpipes/tips OR (B) like a pre-cat C3 system having 2 exhaust pipes run to 2 mufflers & 2 tailpipes/tips. To me ... true duals with an added X, H or balance pipe remains true duals. Just my take on it. Again, to me ... true duals means it doesn't only have 2 exhaust tips but it also has 2 exhaust pipes and 2 mufflers.

 

[Jimdvette]

Back when they first introduced these "smog" cars with the "unleaded only" gas. The State Inspections really didn't enforce the equipment verifications . The quick fix to the 75-79's were to put in a 74 exhaust system eliminating the cat and making it a true dual exhaust enabling the engine to breathe a little better. Tweaking timing and the carb is something you would do during a tune up enhancing your performance. In some cases we used to install the 69 side exhaust . They made it look good and sound nice. Less restriction equals better breathing.

 

[KANE]

1. Change spark plugs to Racing Plugs and Best Plug Wires
2. Install Headers
3. Eliminate the Catalytic Converter
4. Install True Duals with a top-of-the-line Muffler System
5. Replace the Stock Breather with an Aftermarket One
6. Replace Stock Tires to a particular size
7. Higher quality Oil
8. Higher Octane Gas
9. Replace Stock Carb
10. Anything Else

FWIW- All of the above generates 100hp on on Honda... according to the import crowd!

 

[Jack]

one-time CAC forum member "Mitch" passed away 28 FEB 2012

A Stock 1978 with 185 HP: Without going into the engine, can you increase that HorsePower by doing any/all of the following? If so, how much??

1. Change spark plugs to Racing Plugs and Best Plug Wires

2. Install Headers

3. Eliminate the Catalytic Converter

4. Install True Duals with a top-of-the-line Muffler System

5. Replace the Stock Breather with an Aftermarket One

6. Replace Stock Tires to a particular size

7. Higher quality Oil

8. Higher Octane Gas

9. Replace Stock Carb

10. Anything Else

Would any of the above help with Torque?

today is Friday, March 02, 2012 and yes I realize this is an old thread.
regarding the Original Poster "Mitch"
from his obituary

FLORENCE, SC
Talmage Mitchell Rhames, 58, passed away Tuesday, February 28, 2012 at a local hospital after an illness.

Although he resided in same locale as I and we shared an interest in C3 vette, he and I met only a time or two; I had not seen or communicated with him in about 3 years. He had a very nice black 1978 vette but I think he may've sold it a year or so ago. I open today's local newspaper and am saddened to learn of his passing earlier this week. Stoudenmire-Dowling Funeral Home is assisting the family.

May the Lord bless and keep him.