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All these articles are in gross/crank engine dyno horsepower. That means nothing to me. Maybe i've been playing with Mustangs too long, but i want to know what its doing in NET HP or RWHP.

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Got it, so why does it have to be in the context of this particular motor and build? Parasitic loss is going to be the same percentage regardless of what motor is in front of it. Get the percentage based loss of the accessories you're looking to run and apply it to your gross number.

I don't know what accessories eat up, but for drive line loss I see 15 and 18 percent tossed around a lot for manual and automatic respectively.

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Now we're getting somewhere. I'd always used 17% loss from gross to net, which was based off no small amount ov math i did on the subject waaaaaaay back. Problem is, for the life ov me i cant remember how i came about those numbers, so i'm hesitant to use that here. I DO remember that in 1971, the Hemi made 425 gross HP and 350 net (about 17%). Thats not where my math came from though, but an interesting tidbit nonetheless. In fact, playing with the gross to net calcs in 1971 (the only year they rated with both methods) it typically comes out around 17%.

To keep things simple here too, i'm always talking about a stick car, with no accessories like power steering, AC, etc. Just the necessary stuff like alt, one pulley, etc.


What i'm doing here, is not so much building a bench engine, more just trying to figure out how these engines rate next to other modern engines. Still trying to figure out which way to go with the powerplant. Hard to compare a 300HP gross engine to a different 300HP net engine, and so on. I understand the 245 rating was a product ov crappy timing and tune, and equally bogus manifolds and exhaust... so for my intentions it just wont do. None ov the engines i'm comparing it to use gross ratings.

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