Tom Monroe's book states C40E-6015B is:

1963-65 260ci block w/ 7" motor mount holes. 3 freeze core plugs per side and "260" is not cast between lifter bores. 5 bolt bell.

Starting w/ 289, "289" is cast between lifter bores.

What are your head casting numbers?

 

He said the heads had 289 cast into them I thought... Doesn't mean it's a 289 block though. 289 heads will fit right into a 260. Pretty darn similar motors unless you start comparing an early 5 bolt bell to a later 6 bolt... My money says its a 260 with 289 heads swapped in there somewhere down the line.

 

Yeah I saw that 289 post.
I was curious what year the heads were.
Would be interesting if they matched car build date.
289 heads were made in 1963 to 1967.

 

yea, sadly im starting to believe its a 260. I was really hoping it was a 289, but its all good. I was planning on changing it to a 4bbl carb. Any thoughts on that?

 

stock OEM 4bbl is my choice.

 

cool, any chance i can get 250-300hp?

 

Im not sure yet. guess ill find out when i overhaul it.

 

BTW...I love near stock 64.5.

I would not over bore 260 block unless required; those things don't grow on trees.

My goal for 260 would be 225-250HP.

Need to port head and install large valves; 1.94/1.60 chevy valves.

Windsor Jr head would be good also.

verify compression ratio.

Check all clearances of course.

non-roller rockers.

stiffer valve springs.

stock cam.

65 GT exhaust manifolds.

dual exhaust.

tune carb.

 

My 260 has 289 stamped on it as well.
As I think they all do.
Well I can only speak of mine, but that is what I have found out.