Gmc 454

[Crazcnuk]

Funny part is, with a 'normal' rear end gear and an OD tranny, I estimate I should get around 20mpg, at least.

The 454, over the last 40years, is just about the least efficient engine chevy made. Not because it had to be, but because GM decided that, while we like the big cubes, we don't really need the power.

The design engineer that designed the small block, for GM, in 1954 stated that " All internal combustion gasoline engines should produce 1hp/cuin."

My 502 produces 502hp. It is NOT a racing motor. It has a very mild cam.

For all you 454ers, there is no reason that your engines can't produce 450hp, allowing you to regear and get FAR better fuel mileage than you currently get.

One guy, in Edmonton, Alberta, had a 454 powered Firebird, dynoed at 423hp, and routinely got 28mpg highway...

[HobbyMan]

I agree. They screwed around with the timing a lot. They tried to stick my dad with the low gear ratio differential but he made sure that he got good highway gears.

[Crazcnuk]

It isn't really the timing. It's the camshaft. You can change just the cam and lifters and totally change the engine.

If you really want to do it right, you rebuild the engine using 9.5" -10.5:1 pistons, better heads and a cam, preferably roller.

The XS1100 puts out approximately 1.5hp/cu in. I don't think the 1hp/cuin deal is really that great these days.

Crane has a cam that puts my 502 to 640hp, w/o changing anything else on the engine. The 502 has big valve aluminum heads and 9.5:1 compression, with a carb, rather than FI.

[HobbyMan]

Advancing and retarding valve timing should make some difference depending on what RPM you run at mostly and how advanced or retarted it is. Spark timing will make a minute effect. Yeah, the stock cam wasn't exactly made for power.

[mrutah12]

exhaust leak

hey hobby will check on a price on manifold for you and get back with you i work at a parts house will let you know

[HobbyMan]

I already got a right manifold. I was going to get a left but they were more expensive than I thought.