402 with 427 internals

[deception05]

I was wondering if you could get a SLP 402 or any other 402 and just put in a 427 rotating assembly or would more work be involved? Is this possible if so what would I need to make a block a complete motor?

[Mr. Luos]

You need more bore to get to that 427. Stroke can't do it all.

LS1/LS6 block sleeved.

[Rhino21149]

I was wondering if you could get a SLP 402 or any other 402 and just put in a 427 rotating assembly or would more work be involved? Is this possible if so what would I need to make a block a complete motor?


Bascially, that's what the SLP 402 has already. To get 427 cubic inches you have to have 4 1/8 bore and a full 4" strock. the only way to get that is to buy a C5R block which is built that way, or wait and get a new LS7 block which is also built that way -- both are aluminum with 4.125 inch bore sleeves.
Aluminum LS1s and LS6s had a 3.9+fractions bore and if you stroked them to 4 inchs you got 383 cubic inchs.

the Silverado and Escalade and Tahoo use the same casting as the LS2 blcok but in iron. Weighs more, but you can bore it. So:

Cast iron 6 liters, and the LS2 aluminum blocks, have a 4 inch bore, and so:
-if you keep the stock 4.00" bore and put a 4 inch stroker crankshaft in, you get 402
if you bore a cast iron one 30 thousands over and use a 4" stroke, you get 408 ((In my mind this is the best bargain out there)
if you bore a cast iron one 60 over and use a 4" stroke, you get 414, but you are also taking a chance that the cylinder walls are too thin.
if you get the C5R block you have 4.125" with a 4" bore and 427.6 cubic inches.

There are 4 1/8 inch stroker crankshafts. These require machined the block and you have a really poor stroke/rod ratio, and there is not much room on the piston for good ring spacing, but they give you 427 with a cast iron 60 over engine.

And people have gone more extreme to 4.25 inch stroke. Not a high RPM or long lived engine I'd think. That gives 427 cubic inches with a normal 4 inch bore, and 455 with a C5R block's 4.125 inch bore -- which is how MTI builds its 455 GTO.

Frankly, the best pargain is to go with the 408 cast iron. Its close to bullet proof and fairly cheap (good short blcok is less than 4500.

[Liquifire]

How much can you get the C5R block for (w/ 427 set up) if forged internals?

[Rhino21149]

How much can you get the C5R block for (w/ 427 set up) if forged internals?

I had mine built: The block alone is list price of about $7-$8K from GM, but I got mine for $5K by shopping around (it was new and in the crate, I just found it at a discount). Crowler forged internals, plus custom pistons (my engine builder wanted to use piston-centered rods and designed the pistons himself and had CP make them) cost about $4,500, and I paid $7,000 for finish machining and assembly (but that includes testing, finishing and putting together and mounting the heads), to a really good shop (Charlie Hempfield Racing - they do a lot of Nascar stuff and built a Daytona 500 winner within the last decade).

You can buy short blocks with all forged internals for if you look around: MTI, T Byrne, and Katech are three places I'd look. I remember it being about $12-$15K for the short block. Long blocks with good heads were about $17K and complete engines, ready to go (essentially a crate engine 427 C5R) were about $23-$26 from Lingenfelter, MTI, or Katech. Lingenfelter will be the most streetable, MTI produce the most power for the street but be extreme, and, of course Katech builds the GM race engines.