Quote:
Originally Posted by tmhutch
Not that many people are interested in reading several pages of information...
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let alone understand it
Quote:
Originally Posted by tmhutch
Also important to note is that one of the most benneficial component of advancing the ICL is the elevated dynamic compression ratio resulting from the earlier intake valve closing point. Raising the DCR from 8.0:1 to 9.0:1 is just like raising the static compression ratio because they both have a direct affect on cylinder pressure. However, unlike static compression the benefits of advancing the intake centerline and increased dyanamic compression diminish as RPM increases.
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Advancing the cams a few degrees does increase DCR but only very little, the power gain comes mostly from the intake valve being open much further early in the intake stroke.
As far as 106400 cammed engines only making 370 rwhp, the biggest culprit is poor intake manifolding. Intake centerlines may be worth 10 - 20 hp but the proper intake manifold on a 106400 combo can easily pick up 50 horsepower as long as their are no other RPM constraints. Advancing the intake centerline works especially well on a stock intake manifold engine because it brings the camshafts powerband more in line with that of the restrictive intake. It's probably safe to say there is about 50 -70 horsepower sitting on the table for 90% of the modular engine builds out there.[/QUOTE]
I agree. The 106400s are not a good match for the stock intake or even a short runner (10"). We've gotten 370rwhp with 18 degrees less duration, stock heads and a ported intake and the mid range was much greater than what the 106400s provide. The 106400s need shorter runners (FR500, Sullivan) but in a 281ci engine they would make peak around 7800.
Advancing the cams works exceptionally well with the FR500 and Sullivan also, not just the stock intake. The reason is that a wide LSA cam set with a short runner (5-6") results in horrible mid range power. Going with a 106-108LC gets the flow going the right direction sooner.
One more thing, the higher the compression, the later you can open/close the intake valve.