348 and 409 cu.in. small blocks---

Greg Reimer

Well Known Member
#1
Alright, we all love 348's and 409's, finding them can be an issue. If you are willing to settle for a more conventional motor, get a standard bore 400 small block bare block. Buy a 327 large journal crank, and some space saver main bearings to take the 400 main bearing size down to the 327 size. Get a good set of H beam rods and the best bolts you can find.Get a nice light set of 327 + .125 over pistons, balance and assemble this thing, get the best cam,lifters, valve train parts, and the trickest cylinder heads and intake out there. This engine properly displaces 348 cu.inches. About 40 years ago, a resident mad scientist had a '69 Camaro with a Dana rear end, a Doug Nash 5 speed and one of these engines with some kind of tunnel ram, and the result was a wheel standing 9.60 140 MPH car that he ran at the defunct Orange County International Raceway. Outrageous giggle car.
Now, for the 409. Get a 400 small block, bore it to a final siize of 4.170. The original 400 was 4.125, so that's not as outrageous as it sounds. A Dart block would be a good place to start-they are very thick.Get a steel 3.750 stroke crank, use a 5.850 length rod, then get a set of nice light trick flat top pistons made for the final bore size and pin height. If you can fit a 6 inch rod in it, that would be even better.The .045" overbore makes the 400 a 409.71 cu.in. power plant
I know those are conventional appearing small blocks, but it's whats on the inside that makes it what it is.
 

Greg Reimer

Well Known Member
#2
Now, a 409 inch big block can be made from a 396. Bore it to 4.165.The reason for the smaller bore size than the small block is because the 396 has an.010" longer stroke at 3.760". The piston would be a readily available unit at that size since it is a 402 plus .040". Final displacement would be 409.82 cu.in.There's all kinds of BBC race parts for any level of power output you could want.
 

Greg Reimer

Well Known Member
#3
A far simpler way to build the 348 inch small block is to get a used bow tie or dart block, with the conventional large journal 327 or 350 main size, and bore it to the 4.125" bore size. Those blocks are outrageously thick and can go out that far like its nothing. Then,the large journal 327 crank will drop right in easily. Also, the Dart blocks are available either 4.000 bore or 4.125" bore with either the 350 main bearing diameter or the 400. Not a problem here.
 

SSpev

Well Known Member
Supporting Member 3
#4
actually a 40 over 400 is closer, 408.7 cu in, to a 408.9. my current build.:brow no need for a custom over size piston. built a 30 402 years ago. ran good. and the stroke is 3.766. that last 6 tho is there AND needs to be accounted for.:irk DON"T ask how I know:grumble
 

425/409ER

Well Known Member
#6
Still just winds up being another SBC that looks like every other boring one out there. :dunno Why bother with such wonky (and expensive) combination to get some otherwise meaningless displacement number?
Oh I don't know sometimes odd stuff goes pretty good. Look at the old 3 9/16 stroker engines they made great power, just an off set grind on the crankshaft.
 
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