aussiesteve

many simply use a 350 block and go the 3.8 stroke.

i am talking to enging guys advising to get

1 cylinder size
2 piston speed

to generate power
i understand i think they mention GM Bowtie sportsman block and short rods to build a hot 383.

rather than the simple 350 block +030.

the block i see is a GM bowtie 4.117 inch to 4.155 inch cnc machined block

or a dart 4.125 block from dart.

is this correct

Orr89RocZ

iTrader: (20)

Thats been very popular. 350 stroke in a 400 bore aka 377". Long rod not short to give high rpm higher piston speeds. But if not limited by class rules or whatever or for a street build, might as well take the cubes and go 406" off the bat. More power every where

86LG4Bird

iTrader: (1)

^^THIS^^

AlkyIROC

Thing is if you already have a good 400 block, why would you want to destroke it in the first place? The only time you would have to is if you were in a racing class that limits displacement. If you have a 350 block, then it's more cost effective to just make a 383. Any aftermarket block has better castings than any production block and will allow for greater bores and strokes.

Bore makes HP. Stroke makes torque.

As for bore size and stroke, my BBC has a 4.625" bore and 4.375" stroke and +0.250" rods. I spin the engine to 7400 rpm on the dragstrip and the bob weight on my crank is far greater than what a SBC is going to make. I use a Dart Big M block. Even with the huge overbore, the cylinder walls are still a minimum of 0.300 thick. Boring out a production 502 block that comes with roughly a 4.500" bore to that size makes very thin cylinder walls.

The longer the rod you use means the wrist pin needs to be higher in the piston (special pistons). This can push the wrist pin up into the oil control rings. Although this isn't a problem, it does start to affect other things like how far down the compression rings can be placed in the piston etc.

Old school 383 was to use a 400 crank and rods with 350 pistons but with available aftermarket parts now, you can use a 400 crank with the longer 350 rods and special pistons to work with them.

Long rods give more dwell time at TDC. A few extra degrees of crank rotation with the piston still at TDC can make more power.

aussiesteve

my 400(408) is tired its stock bottome end and has a corroded cylinder 10 years now,,,,yes we use cast rings to stop ring damage but its been a good motor and i will not sell it..put ut on a trolley and leave it under the bench for another project.

this engine guy i spoke to has real fast cars and an 8 second 1300 kg car..john kuiper sydney australia..he mentioned the +30 over 350 blocks but also said i can go the other way and get cylinder volume AND piston speed by using a 400 block or a bowtie block that will alliw a 383 setup that will have no problems crossing the line at 6500rpm....its early days and i was going a crate motor but not now..i will get a local build..steve

Orr89RocZ

iTrader: (20)

All depends on how much power you need to make. Bore size and piston speed arent really concerns if power desired is low and within a reasonable rpm range. I mean a well thought out 355 sbc can make 500 hp by 6500-7000 rpm no problem. If you wanted more than that but didnt want to rev over 7000 then going stroker 383 might allow you to get 500-540 hp by same 6500-7000 rpm range. Or build a 406 and make 500 by 6000-6500.

If you wanted 600 you would really have to move some air and a 350 would have to turn very high. A 383 still turn close to 7000 rpm maybe even 7500. A 406 maybe 6500-7000 depending on build.

More power you want to make on a sbc, the bigger the valve size needs to be which means bigger bore to utilize it. Big valve usually is big ports which is big rpm or you need big cubes to tame it down into the street rpm range of 0-7000.

aussiesteve

The 500 540 area is where i would like to be with out spending $11500 on a crate motor that got border line mechanicals mostly made in china and made to a price. My goal is to get over that line at 6000rpm and not with high stall converters or crazy gears that are useless on the highway,,,,the engine builder i will use has lots of combinations and the more i ask the more i learn.


The engine guy is a currant C/Gas record holder down here and been at it 50+ years and is a pretty humble guy. John Kuiper Sydney Australia.
i like the bowtie sportsman steel block and a Manley or Callies bottom end Crower is too expensive


https://www.andra.com.au/latest-news...nationals.html

aussiesteve

Thats more or less what my engine man said,,a workin 383 bustin its back side at 6500/7000 or a 400+ getting it at 6000/6500 ,,BUT STILL CROSSING THAT LINE AT MAX RPM is where i think we need to be and thanks for the solid info.