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Old 08-25-2012, 08:57 PM   #11 (permalink)
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Originally Posted by ksa8907 View Post
a ported and polished head/combustion chamber is still the best.

a more efficient burn gives more power, win-win.
For power sure, but this is ecomodder.

Originally Posted by Frank Lee View Post
"Swirl" and "Tumble" were all the rage in the engineering circles at that time.
Thats kind of what I was wondering... was it a fad and marketing nonsense, or was it a radical step up vs past solutions? What about now (since everyone is so power hungry and I rarely see mileage improving each year in most vehicles, most 10 year old listings show the exact same figures), did they go for more power or are newer powerful heads just as efficient?

Originally Posted by Old Tele man View Post
Swirl, tumble, etc., are all air movements at the control of their physical & atmospheric environements.

"Injection" however, is under the control (within limits) of the computer, ie: it does a far BETTER job of air/fuel mixing than did the old mechanically derived "head swirl/flow tumble."
Thats kinda what i'm wondering, unless there are diverging opinions...

Is the consensus that the new 4.8/5.3 type engines should produce BETTER efficiency (dont care about power) at the same part throttle load than older swirling everything type heads?

Originally Posted by drmiller100 View Post
They are the greatest thing ever until you see the 5.3/6.0 heads and look at the numbers of what they can do.
Could you expand? I'm not an expert in any of the newer designs, only older small blocks. Again remember i'm mostly caring about mileage, not ultimate power, to include mileage under differing levels of load. (ie moderately higher towing loads but not full throttle is an example)

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Old 08-26-2012, 12:09 AM   #12 (permalink)
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efficiency is improved by the following:
high compression.
fast burning of the air fuel without detonation
consistent burn rates
little heat lost to the cooling jackets.

Horsepower is all of the above, and add to that high air flow rates.

They are not mutually exclusive. The vortec heads do all the above, but the 5.3/6.0 does it even better.
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Old 08-26-2012, 09:16 AM   #13 (permalink)
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GM Fastburn, vortec, LT1 and LT4 were all kind of chasing the same port and combustion chamber design.
But they were limited by 50 year old valve placement, 50 year old cylinder head bolt placement, intake to head mating (well vortec and LTx have their own intake) and a few other things.
GM was chasing the mythical MPG and hosepower unicorn with those designs.
But couldn't nail it.
It wasn't untill the newer 2007+ LS serries came out that GM took every thing they leaned they coldn't do with on the SBC format and finely used it to build the engine they always wanted and only then they were able to catch up to that unicorn and and run him over...
Maybe some one could post a pic of what that might look like.

1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
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