[dre1984]

I have a bbc 402 casting 3999290 year 71 to 72 it has been bored 1.25 over to a standard 4.250 427 and now I am wondering what's is the biggest stroke it can take or better left with the stock 3.76 crank not a daily driver just a weekend racer any ideas and thanks

[techinspector1]

Since it's not a street driver, have you put any hard block in the water jackets? Have you sonic tested the cylinder wall thickness? Just curious.

As far as stroke, I have never owned a 3999290 block, but I would think that you would be able to stroke it just like any other BBC short deck (9.800") block. 4.250" X 4.500" would make a 510 if you could find pistons with the right compression height.

[cobalt327]

Originally Posted by dre1984

I have a bbc 402 casting 3999290 year 71 to 72 it has been bored 1.25 over to a standard 4.250 427 and now I am wondering what's is the biggest stroke it can take or better left with the stock 3.76 crank not a daily driver just a weekend racer any ideas and thanks

Unless it's a 4-bolt, I wouldn't take the stroke (in a racing engine) beyond 4" unless you put caps on it. YMMV.

[techinspector1]

Originally Posted by cobalt327

Unless it's a 4-bolt, I wouldn't take the stroke (in a racing engine) beyond 4" unless you put caps on it. YMMV.

Sounds reasonable to me.