Why is the '78 so weak?

[pasvorto1]

A friend of my wife has a '71 Vette. Looking at the specs, I would guess it is the 350ci with 300+ hp. While my '78 with the 350ci has only 185 (175 in some pages). Did I lose 130hp to pollution control and fuel consumption? If so, do you know of anyplace where a guy can find out what would be need to make the '78 engine comparable to the '71 engine?

 

[Bob Chadwick]

The car was detuned for smog rather than performance. Compression, heads and cam are the most likely culprit.

 

[Vettelt193]

I think the net VS gross HP thing is in play too... wasn't '71 the last year of the 'old way' of measuring power?

 

[Fishman]

Did I lose 130hp to pollution control and fuel consumption? If so, do you know of anyplace where a guy can find out what would be need to make the '78 engine comparable to the '71 engine?

My '78 had the 185hp motor when I bought it. I put in a 350hp GM crate engine in 2 years ago.

An easy, but moderately expensive solution.

 

[Tom73]

A friend of my wife has a '71 Vette. Looking at the specs, I would guess it is the 350ci with 300+ hp. While my '78 with the 350ci has only 185 (175 in some pages). Did I lose 130hp to pollution control and fuel consumption?

The 71 is rated at GROSS horsepower while the 78 is rated at NET horsepower. You did loose some to emission tuning but most of the difference is in the power rating system being used.

tom...

 

[pasvorto1]

Interesting.

 

[Glensgages]

Why is the '78 so weak?

Go and drive an '82;
you'll have to 're-define' weak.....
:eyerole ad

 

[78SilvAnniv]

(175hp in some pages)

That was what mine was, a CA emissions car.
We upgraded with a GM crate engine, however I think ours was a 250hp engine. We have replaced the stock exhaust with dual chambered exhaust and this past winter replaced the heads for a pair that breathe better.
We have had to tear into the engine again to rectify a #4 oil ring/piston and slipped manifold gasket problem. We also purchased a new cam after speaking to a tech at Crane.

I'll let you know the seat-of-the-pants-Whoo-Hooo! factor when we're back on the road!
Heidi

 

[Tom73]

Quick note. The GM "crate" engines are rated at GROSS horsepower. The question had come up before so I just emailed GMPP to confirm. They advised that the "crate" engines such as the ZZ4 etc are rated at Gross HP.

tom...

 

[Evolution1980]

Quick note. The GM "crate" engines are rated at GROSS horsepower. The question had come up before so I just emailed GMPP to confirm. They advised that the "crate" engines such as the ZZ4 etc are rated at Gross HP.
tom...

The engines are always rated by GROSS hp/tq, or in other words, their numbers as produced at the flywheel, which I've also seen referred on to occasion as FWHP.
Every engine model they build to spec will put out the same numbers (within minor percentages). But as soon as you start putting on different exhausts, carbs, auto -vs- manual trans, etc...that all changes the NET horsepower, or rear wheel hp (RWHP). They simply can't put out NET numbers because there's no way to know what someone is going to do with the engine once they have it.

As I learned at the engine dyno shop, a manual trans car will lose around 20% or so and an automatic trans car will lose about 25% or so of the engines stated gross power. That's why RWHP/RWTQ numbers are becoming more relavent than gross numbers put out by the engine alone.

 

[Fishman]

I'll still bet that 350 GROSS hp is still faster than 185 NET hp. :L


The ZZ4 rocks!

 

[rpounds]

Yes, between 71 and 78, the method of measuring HP was changed from gross to net. But also, take a look at the engine specs between the two. You'll find that the compression was lowered way down, the cam profile was less aggressive, the carb was leaned out, the heads didn't flow as well, the initial timing was retarded severely, etc. All of this in the name of emission controls. It's not the 'add-ons' that really choked these engines. It was the band aid approach that was used to reduce emissions. Fortunately for us that own these beautiful beasts, there are good solutions to these anemic performance problems and still maintain emissions standards for those that still have to undergo testing.

 

[KANE]

My '78 had the 185hp motor when I bought it. I put in a 350hp GM crate engine in 2 years ago.

The best remedy for a lack of power - the engine swap!!! I put a 300hp crate with TPI in my old 1978. Great power, and when tied to a 700R4- great gas mileage!!!

 

[Fishman]

WOW!!!

If some of you have not been to DarkShark78's site... you gotta see it!

http://geocities.com/chiphihawk/index.html
Nice work!