Thread: Making A Small Block 350 As Fast As It Can Be

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How much HP is enough for you?

Note that: HP = Torque(ft. lb.) x (rpm/5252)

HP is only equal to Torque at 5252 rpm and usually you have to go to higher rpm to raise the HP over the torque and at low rpm Torque is greater than HP. If you stroke a 350 to 383 the compression ratio will automatically increase since you are now squeezing more displacement into the same combustion chamber in the heads. Domed pistons will raise the compression ratio also so if you do both change to domed pistons AND stroke the crank you may get a compression ratio that will ping badly. With the gas of today maybe you should not go over 10:1 and maybe 9:1 is a reasonable goal. You can go a little higher if you buy expensive aluminum heads, but about 9.5:1 should be the goal with today's gas and iron heads (aluminum heads dissapate heat better and run coolrer, along with possible corrosion problems)

With a 383 you will definetely get more torque (grunt) in the low rpm range, BUT unless you are geared just right the longer throw of the crank may reduce your upper rpm range. For the street a 383 is probably a major improvement, but then you need to consider other things. I stayed with a 0.030" overbored 350 because I only have an 8" rear and I don't want to trash my 700R4 even though I had it beefed up. The added torque of a 383 will put stress on the rest of the drive line. Then you can compare NO, turbos and positive displacement blowers. There are several options which all put added stress on the lower end of the block. Turbos are supposed to be gentler but take time to rev up. Positive displacement blowers are "sudden" but severe. The use of NO is intermittent at your choice but if you overdo that you may destroy your engine. The option I kind of like and think about whenever I think I might be able to afford a positive displacement blower, is where you set up an air conditioning compresser clutch to the front pulley of the blower and then you can turn the blower on and off as the situation or whim requires. Also note that with a blower, the mpg drops drastically to maybe as low as 10 mpg or lower. I have read that E85 has higher octane ratings, but then it takes more E85 for the same energy as a given amount of gasoline. Then there is more heat from more fuel! For that reason you could change the pistons for forged units (which can be noisy before they warm up.) It is relatively easy to melt a cast piston with more fuel or NO. I recall driving a 1300 cc VW with a Judson positive displacement blower on it and looking in the mirror asking where is all the smoke coming from, after burning a dime-sized hole in the top of a cast piston! Then what about the rage over "Biodiesel" maybe we should all be rebuilding the old Oldsmobile 350 Diesel and in 10 years pure gas will be rare? Overall, you should try to find a book store with one of the books by David Vizard on building the SBC; he has a lot of dyno-tested ideas.

Don Shillady
Retired Scientist/teen rodder