Tried and True 304 Builds?

"The calculation is woefully wrong for performance use, not bad for mild cruising around."

The calculations are based on engine pumping capacity only. There are other factors, especially in performance use. A smallish carb usually works well on the street and for low speed pulling, but becomes the choke point on a drag strip or any time the engine will be running high rpm (over 4K) often, or should I say is expected to deliver performance at 4K and above. Velocity of the charge is important, especially for low speed work. That's why it's hard to get a good street/strip combo that delivers good gas mileage AND good high speed performance with a carb. Small carb works best for economy, big for performance. Most street driving is done in the 2000-3000 rpm range, with occasional short bursts up to 4000-5000. Most engines built strictly for street (most stock engines) start to fall off power around 4000-5000 rpm, a drag engine hasn't peaked yet!

Greyhounds_AMX wrote: The 268H would give you a lower DCR by about 0.3 points, but about 1% more overall intake flow capacity than the XE256. So with the 268H I'd expect you'd probably have the same power within a few hp, but you'd have a rougher sounding idle, and you'd be able to run 87 octane if you wanted to. Plus the valvetrain would be quieter and last longer (lower hydraulic intensity).

Oooh, good info! Thanks!

Class Guy wrote: I recommend you pay attention to compression ratio when you are assembling parts and building.

Well, if I could really get compression where I want it, I'd have 9.5-10.0:1, but right now I'm gonna have to to do whatever little tricks I can to squeeze out as much CR as possible. (Which will probably barely be measurable. I can't think of anything besides using a really thin gasket, honestly.

Greyhounds_AMX wrote: The 268H would give you a lower DCR by about 0.3 points, but about 1% more overall intake flow capacity than the XE256. So with the 268H I'd expect you'd probably have the same power within a few hp, but you'd have a rougher sounding idle, and you'd be able to run 87 octane if you wanted to. Plus the valvetrain would be quieter and last longer (lower hydraulic intensity).

Are you going by advertised duration , or duration at .050 when you come up with your figures? At .050, the Comp would close intake at 35*ABDC, and the Lunati at 34.5*. The Comp has -(2) degrees overlap at .050. Lunati -(7.5). I agree that the Comp idle should be rougher with more overlap, but with the intake valve close at essentially the same, will the octane requirement be much different?

There is a set of new flat top 290 pistons on ebay.  If your 304 is stock bore, and the bores are in really good condition, you could put the 290 pistons in it (I'm sure someone will confirm this can be done after reading this).  They'll bump up compression over the stock 304 dished pistons.  Put moly rings on them, measure combustion chamber volume, measure deck height and choose a head gasket in the thickness and diameter you need to achieve the comp ratio you want.  Cometic sells a few off the shelf head gaskets for the 304.  I think the thinnest is .027".   Go with a Comp High Energy cam for a quiet valvetrain that stock valve springs should be able to handle, and you'd have a stout bottom end.  Wouldn't hurt to upgrade springs to something slightly stiffer, but, most seem to have no issues on stock springs with the High Energy cams under .500" lift.