403 LS2 / AFR 205’s lays down 550+ RWHP!!

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10-24-2007, 11:51 AM

#21

Tony Mamo @ AFR

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Quote:

Originally Posted by ScreaminRedZ

Hey Tony, I'm looking to get a set of heads within the next year. I want something that keeps stock compression ratio so that I could go with a blower if I chose, but I also want a head that will work decentlyl if I decided to stroke the motor instead. I know that some work will be needed on out of the box heads for that, but minor work isn't a big deal, I just don't want to have to buy new heads if I decided to stroke it down the road.

Will these heads work for these goals? From the post above it seems like it.

Thanks!

For the benefit of ScreaminRedZ and others discussing the same, obviously these results prove that a well thought out stroker even with 205's can still make some big power and in some respects is really a better choice for a customer who is more concerned with usable torque and throttle response on the street. I bet this combo feels stronger at part throttle than a typical 427 build (with larger ports) due to the 205 heads. I would estimate an out of the box 205 may have been 20-25 RWHP weaker here so keep that in mind, and would also require a cam with more exhaust duration to be more optimized. Still....even in the 520-530 range, that is still more than respectable for everything essentially being bolt on "out of the box" components and the throttle response and low RPM grunt would still have been strong due to the smaller cross section of the intake ports.

Also, for those reading this, you must keep in mind that the rest of the combination was condusive to the end results as well....that is important to realize. If you hit a chassis dyno with the exact same combo (ported heads and all) but was running a heavy LS7 clutch, 4.10 gears, and heavy 12" aftermarket rims and tires you may only have seen 520 RWHP out of the exact same set-up. No EWP....now your at 514.....you get my point. I usually run my "air dyno" on the conservative side and I went into this expecting between 520-540 RWHP (and 500 TQ), thinking the end results would fall somewhere in the middle. I was really surprised how well the TQ curve carried which is the obvious reason the big HP numbers arrived as a function of pure mathmatics. Note however the peak is a little early (a good thing for most applications) so the smaller port does come into play here but essentially does exactly what I wanted it to do....bring alot of power and torque to the table early where a guy that spends most of his time on the street can really appreciate it. The fact it still managed to match or exceed what weve seen typically from larger head and cam (slightly more aggressive) combinations just made those other parameters we nailed that much sweeter.

If I had more time available to me I would have been curious to see what my current 83' solid roller engine would have done with the ported 205's. My hunch is it may have made the same or more power in my set-up and added a bunch to the SOTP feeling driving around town, especially considering its more displacement challenged than its 402/403 larger brother and would have benefited from the smaller port even more.

Ironically, I'm actually currently working on just the opposite type of cylinder head project, putting the finishing touches on a larger 15 degree "bolt-on" style 235 cc cathedral port offering. I will debut this head design in a few months on a 447 CID build that will be flogged on the engine dyno and installed in my C5 shortly thereafter.

Look for more updates and results on that project towards the end of the year.

Cheers,
Tony

Last edited by Tony Mamo @ AFR; 10-24-2007 at 12:10 PM.