Turn 348 into 409

[Catmandu60]

How easy would it be to turn a 348 into a 409, or can it even been done?

 

[models916]

it's just a number

409 crank (cheap) fits the 348 block, 30 over on pistons and you get about 385 cubes. 60 over is bigger yet. 427/396 crank (more money) (3.75 stroke) and 30 over is in the 413 neighborhood. The only hang up is they require a custom piston (much more money). Not hard to get but expensive. Show-Cars and other have complete assemblies that go as big as 4 inch stroke. Your block and around $2,000 gets you started. Check my old posts for pics, I have a 30 over 348 with 409 crank in my 62 belair.

 

[threeimpalas]

Using .030 oversized pistons and a 3.76 (396/427) crankshaft will net you a 408.

 

[crossy]

so you would turn down the BBC crank .200 on the mains ?
the Rod journal is the same. Which rods/pistons get used for that 408?

 

[models916]

more to it than that

counterweights need to be trimmed, snout needs to be resized also. BBC rods and custom pistons and it's done.

 

[Catmandu60]

Ok guy's, another question. I was told that these 2 motors share the same block but not the same heads, but the 409 heads are will bolt right on the 348. With that in mind, couldn't I do this by boring and stroking the block and changing the heads to 409 heads

 

[models916]

bore-ing

Few 348 blocks will bore to 409 spec. All the heads interchange as long as the intake pattern matches the heads. Check Show Cars on Ebay for stroker kits. You can make any size you want. My 348 block has a 409 crank and 333 truck heads with offenhauser 2x4 intake. Sonic test the thickness of the casting to determine the safe bore on the 348 block and go from there.

 

[RCE1962]

Models

I was always under the impression that the 409 heads would have a clearance problem with the valves VS 348 bore / cylinders. I know nothing about this at all ....but this possibliity for interchangability is intriguing.

Ron

 

[Tom Kochtanek]

Maybe the later truck 348s?

Models mentions: "Few 348 blocks will bore to 409 spec."

I'm no genius, but I'm guessing that those later 348 truck engines, the one's cast towards the mid 60s, might be very similar (before final bore) to the 409 castings of that era. Those particular blocks might be able to take a greater overbore that those late 50s-early 60s passenger car 348 blocks. It just makes sense that the General wouldn't go through the hassle of having multiple castings by around 1964, just making one that can be bored either as a 348 (to go into a truck) or as a truck 409. Maybe just the truck engines with the cutout reliefs would have been cast this way?.

I don't want to start any rumors, this is just a hunch. Is it possible to verify this? How would that be done, sonic testing?

If it were the case, and you were able to locate one of these later blocks, you might be able to open her up a bit more if you decide to go that route.

I'd just take a 348 and stroke it with a 409 crank, but then you've got some expenses associated with new pistons...

My 2 cents, probably worth less than that .

Best,
TomK

 

[oldskydog]

Can't verify it but I remember reading somewhere that the 655 cast truck 348 blocks had thicker cores and could (or might) be bored out to 409 spec, as TomK mentioned. Sonic testing would verify that.