quote Originally posted by Pappy: You sure about this? Might wanna research that a little bit more

While GM says it is a direct decendant of the SBC they simply call it a GM V8.
http://www.gmpowertrain.com...1_LS3%20Gen%20IV.doc

quote Originally posted by Xyster: Proofread much?

Differences in heads meaning air flow. If DOHC were less fuel efficient, why would GM be moving all their V6s to DOHC, and already have all their 4cyl engines on DOHC? My point was there is a lot more to the engines, which you are simply ignoring, and simplifying the argument to DOHC vs pushrod, when it's not that simple. And there are other differences in the heads than simply the DOHC vs pushrod one. Like, how much air they flow, how the air/fuel package swirls and tumbles through the ports, etc… And the LS4 intake is pretty restrictive as well, while the N* intake is much more open.

And I'm not sure how your friends are "testing" their AFM cars for MPG differences, but I suspect they're doing it wrong.

The biggest advantage to 4 valve heads is the dramatic increse in flow at the onset of the valve opening. Cylinder fill/evacuation is much more rapid (efficient) and less valve lift is needed (lower spring pressures, less dramatic ramp angles) to achieve good performance.

I was going to use BMEP to support your arguement:
BMEP constant tq cid
149.87 150.8 323 325 LS4
156.70 150.8 292 281 N*
193.19 150.8 278 217 LLT

But, I see you are using ricer HP/Liter so I've lost interest.

quote Originally posted by dobey: But I suppose why bother with the N*, when they're pushing 325 HP out of a 3.6L V6.

[This message has been edited by Xyster (edited 06-14-2011).]

quote Originally posted by Xyster: I was going to use BMEP to support your arguement: BMEP constant tq cid 149.87 150.8 323 325 LS4 156.70 150.8 292 281 N* 193.19 150.8 278 217 LLT But, I see you are using ricer HP/Liter so I've lost interest.

Uh, ricer? No. HP/CID has been a useful comparison for years. GM spent several years/dollars trying to get 1 HP/CID out of the Gen1 SBC in the 60s. And now, they have to meet CAFE standards to put cars on the market. The best way to do that for them is to start reducing standard displacement, and increasing HP/CID. And the target customers for the cars that came with N* don't care about having a big V8 in it. They need to be able to drive it reasonably affordably. The N* is one of the last bigger money pits on the GM books, and replacing it with the same engine they're putting in everything else is going to help them financially. The only numbers that matter for GM are the ones with $ next to them. If they bring back the N* in the future as a High Feature platform V8 instead, that would be awesome, but right now, they need to drop it like a bad girlfriend and start recovering from all the bad decisions made over the past 20 years that put them where they are now.

GM had 1hp/inch in 1957. The fuel injected 283ci/283hp. I remember one of my classmates had a 57 chevy with that engine.

Yup.