Have you ever heard of brake specific fuel consumption? It's not constant for all engines.

And there are times where factors that allow additional horsepower at wide open throttle that do not reduce part throttle fuel economy.

What about examples such as electric fans and pumps, crank scrapers, combustion chamber designs that promote swirl or allow higher compression without detonation, gas ported pistons, thermal coatings, headers, etc.?

Sure toss on a single plane intake, larger cam, heads with large volume runners and part throttle economy will degrade at the expense of full throttle horsepower. Maybe economy drops at full throttle, but whose caring much about economy at that point?

Maybe not entirely free at highest rpm, but if you think of quicker throttle response, for instance, and part throttle torque, also.

I usually drive my Firebird (6.3 Liters v8-500-520HP+) and at average it drives 5.5-6 Kilometers per Liter.

Sometimes I drive my '2000 Nissan Pathfinder (3.3 Liters v6 -around 230-250HP), and it drives 5-6.5 Kilometers per Liter.

Keep in mind that both are automatics, and at 60 mph. they are both around 2000 rpm's.

That's fuel effiency. -Free horsepower

So even if the 2000 Nissan has EFI,- the lack of headers, the bad exhaust system (y type), the presence of CAT, and possibly bad head/combustion chamber flow, -it has very poor effiency.

I don't agree with the "ruin" part at all. It's an improvement on a non #'s plain car, especially when it's kept all Pontiac Iron. Aluminum heads are ok, but I just don't see the appeal on a street car.
Now, more fast Birds out there I agree with regardless of how you do it.

Clarifying my last calculations:

Actually that figure is when 'mixed' driving
-both highway and city.

Actual highway figures is

-Pontiac 6.3 v8 ,-63-65 mph (just around 100 kph) 9-9.5 kilometers per liter. (22-23 mpg)

-but in the 3.3 v6 Nissan, it's 7.5-8 kilometers per liter

-The only place where the smaller engine actually is better, is in the city (proberbly because of the EFI vs. mechanical fuelpump)

If your worried about the fuel cost. Don't do it and park your MUSCLE car. If your not worried. Brush your teeth. You'll get more smiles per hour. DO IT

Had a train wreck on my last post. Started over.

Yes, Mike, have heard of BSFC, use it all the time. Just make sure that you guys are not giving the wrong impression when you talk about it.

Claus, I'll bet that if you put the Nissan engine in your Firebird - not that you would - that you would get better than what you're getting now. Compare the vehicles and hp needed to push them before comparing the mpg and cruise efficiency. Although 22 US mpg is pretty good already especially with 500 hp! And yes, I'll admit that it would certainly feel like a free lunch!

I have parked my '69 for the last while in preparation for the next engine combo that will make around 450 hp and get over 25 US mpg at 70-75 mph. I want to be able to afford to drive it as much as I feel like.

I wish I could loosen up a bit, but new baby on the way has me puckering a bit.
We will see after the baby comes along.
Until then I will just have to heem and haw about it.

Ya, ruin was the wrong word.
Should of said "new and improved".

That's what you said about the 1st one.
I understand.
Had to wait 18 years before i could get back to mine.
Just like bust'n your bal**
Make sure you get yours involved while thier young.
Use the bird for short family drives whenever possible.
I never had that chance cause i got rid of everything except the torn down 67.
Didnt have time or $. Regret it now.

if ya need help on the bird joe, dont hesitate to ask! would be nice to work on someone else's while they pay for the parts...lol. if i HAD THE CASH FOR MINE, I'D BE IN THE GARAGE RIGHT NOW!

If you like doing body work, i can keep you busy till next spring

If you like doing body work, i can keep you busy till next spring [/quote]

whats the pay and is the garage heated? if the price is right, i'm game!

Come to think of it, also have 2 engines.
1 needs assembled, the other completely gone thru.
Or how about doing a set of heads...or changing out a set of rear gears.
No problem finding something for you to do here

No charge, you to do it for FREE!

I'm going the 2 engine route. My original 400 shortblock is sitting on an engine dolly for prosperity while a 455 block I acquired is in the shop getting built up for fun.