need help figuring out what this block is

[74_schiada_flat]

I have done alot of research and keep coming up with 2 answers...
1966 396 2blt. and 1966 427 2blt. i'm sure it can only be one of them! :cry: :confused: :cry: :confused: lol
(3855961) is the casting number. with a "P" next to it facing from the bottom
(D 18 8) or (D 18 6) is the casting date "pass side of block"
theres also a "K" and a "24" close together under where i found the casting number
as well as "high perfromance" and "pass"
and the heads casting numbers are "3964291"
and say high performance as well.
is it a 396 a 427

[Jordy]

mic the bore and see what you come up with. Did it have a crank? Figure out the stroke on that. ;)

[74_schiada_flat]

mic the bore and see what you come up with. Did it have a crank? Figure out the stroke on that. ;)
its fully assembled, and running.

[76BARRON]

yes it can be 396,427 at the same time...you add 396+427 then devide by two and you get 411.5 ci and that is a very rare motor indeed! :D :D

[Jordy]

its fully assembled, and running.
Run it until it breaks and then figure it out. ;)

[EXTREMEBOATS]

What you have is a 427 according to Mor-tec.com :D

[74_schiada_flat]

What you have is a 427 according to Mor-tec.com :D
what is the link where you are getting that info?
when i check mortec they give me this....
3855961....396.......65-66...2 or 4 bolt
3855961....427.......66......2-bolt
how do i tell which of the two it is?

[EXTREMEBOATS]

Check out Roadsters.com. I see your point. This site says 396. It also has a different number for the 427. Do ya feel lucky? :idea:

[Squeezing Spectra]

Is there any numbers stamped on the deck pad still ? you can tell exactally what it is from that.

[74_schiada_flat]

well i was told it was a 427 when i bought it so i'll just have to asume so for the time being.
I am going to sell it and i'd like to be able to tell people what it is.
it's a killer motor, seems tight as hell. full crane roller everything.

[Squeezing Spectra]

How much do you want for it ?

[74_schiada_flat]

$3,000 - pan and tunnel ram.
the crane roller, cam lifters, and rockers are brand new.
cam card says...
PART # 11-770-8
GRIND # CB XR274 R-10

[MR.ED Hydro]

Your gonna have to take the heads off I think... Check the bore and it will be finalized between the 396 and the 427 since they have the same size crank.
The heads you have are the same that I ran on my 396 last year, and are pretty good for old GM stuff. They are rec port closed chamber heads, and they have the largest "as cast" rectangular port runner volumes for factory installed heads according to the NHRA (lists as having a max. of 327cc). This makes them ideal for normally aspirated setups.