What Runner cc for stock cubed ls1
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From: FORT WALTON BEACH
What Runner cc for stock cubed ls1 I have always said you want the smallest runner volume with the highest flow. That is how I have always judged cylinder heads. If you go too big you loose velocity and loose power. Maybe not Peak but you loose power. In another post there is a guy with 236cc runner volume on a stock cubed 346. His cam duration is in the high 230s on intake and exhaust. And his headers are 1 7/8. He dynoed low at 410rwhp. I believe his setup is mismatched. AFR does not recommend their 225s on stock cubes. Due to not enough velocity in the heads at regular rpm, giving a bad cylinder fill. They do recommend them on big bore strokers. The bigger cylinders can make use of the bigger ports by pulling more air through the heads in turn raising the velocity. What are your opinions on this.....
Our CNC ported heads that we install on stock shortblocks are in the 225-232cc range, we have tested some smaller ports, but they did not make as much power for us. The key is the combination of parts. For example, our CNC ported LS6 heads have outpowered the AFR 205 heads by 20 RWHP when used with a LS6 intake and Kooks headers. The AFR 205 seems to work very well when used with a Fast 90/90 intake/TB and very long primary length headers, such as the LG's. We just had a set of our Stg 1 5.7 heads make 451 RWHP, so it is all in the combination of parts.
The size port in cc is an old school way of lookin at things. Although it works in most apps, the cc size of an LS1 engine is already "large" to begin with at 200cc. The question is are the heads in question effecient at that size. The LS1 loves airflow, but it has to be through a port that isnt "lazy" down low. The ports could be 240cc and still make good power on a 346 as long as the combo of parts are well selected(as Brian said) and the cylinder head in question is effecient.
Since u both are talking heads can u suggest a head for my COMP 214-222 559-566 115+4 running threw shorties/x-pipe and stock exhuast...I have the PTB and Pulley too and this is a GTO A4 with a 3200 stall....
Originally Posted by Brian Tooley
For example, our CNC ported LS6 heads have outpowered the AFR 205 heads by 20 RWHP when used with a LS6 intake and Kooks headers. The AFR 205 seems to work very well when used with a Fast 90/90 intake/TB and very long primary length headers, such as the LG's.
Interesting information. I have AFR 205's w/ a mild cam (comp cam) duration @ .050" = 216/220, valve lift w/1.5 rockers = .525/.532, & 114 LSA. Weiand intake (similar flow rates to ls6), & a ported TB rated @ 1,050 CFM (am assuming that's @ 28 in. of water pressure drop). Very long primary length headers (custom made). Primaries run all the way to horizontal w/ the ground @ the collector. Always thought that maybe this was restrictive, but, from your testing looks like maybe they are ideal.
What would you anticipate my RWHP numbers to be & would there be a greater benefit from the 90/90 intake & 90mm TB? We run up to 6,200 RPM max..
Thanks in advance for your comments.
Last edited by LS1-450; Sep 12, 2005 at 07:42 AM.
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From: FORT WALTON BEACH
That weiand intake is gonna cost you due to heat soak. They do flow like ls6 intakes but being made of metal allows them to get hot faster and stay hot longer. Also what is up with the 1.5 rockers? 1.7 is stock on a ls1 ls6. If that was a misprint I would guess 410 give or take 10
