Quote:
Originally Posted by xb-60
Good point olddog. There's an article I've come across a couple of times 400 HP 302 ci AFR 165 cc(Stock Cam) about obtaining over 400bhp from a SBF 302 while retaining the stock factory hydraulic roller cam, main changes being heads (to AFR165), by using higher ratio roller rockers, and headers/extractors. Main point is that it uses the stock factory cam. Does that mean that it would retain some manners at the bottom end while delivering at the top end (with the power graph still steep at 6200rpm)?
OK, I've said that my preference is to stay with CI heads for authenticity, but this seems to me to indicate that I could easily stay with a 302
Cheers,
Glen |
One note of caution, magazines dyno numbers have often seemed too good to be true. After all they are marketing magazines, with advertisers paying the bills. The advertisers usually supply the parts.
If you will note on their chart the Hp is still climbing quite steep at the 6200 rpm when they stopped. The Hp had not peaked, so why did they top? Valve control issues? Were they afraid the bottom end would let loose? We they weary the stock block might split in two (in a few dyno sweeps, probably not)?
Now you are wanting to make power to 8000 rpm. I assume that means a peak at around 7500 or a little less. As good as the 165cc AFR heads are, they will not flow enough to do that. You would need at least the 185cc AFR heads. This mean low port velocity at lower rpms and less torque down low.
To keep the engine from wanting to buck cruising at 1500 rpm, you will have to keep the valve overlap very low, similar to a factory stock cam. You will need higher lift to get the flow at top end, and you are going to have to lengthen the duration out to make power up top. The trick is going to be, how do I do this without killing the bottom end? My theory, which is counter to what most experts will tell you, is to keep the duration under 230 and go with better flowing heads. I feel that will give you a long flat torque curve. You will still end up with low torque at low rpm because of the port velocity, but the milder cam will not want to buck and hop off idle. To still flow enough air to peak the Hp at 7500 rpm is going to require very good heads, that most experts will tell you are way too big for a 302. Now remember this is my theory that is untested. I could be very wrong, and probably am wrong. However, the article you provided tends to support my theory.