Originally Posted by
jaywischmann
Went to the pick your part today and found a 1965 t-bird with a 390. Pulled the heads, rocker shaft assembly, pushrods, and intake manifold to install on my 360.
My current heads are C8AE-H
My current intake is stock 2v
New parts are:
Heads: C4AE 6090G
Intake: C5AE 9425C
The intake is a 4v which will get a Holley 650 double Pumper.
The 6090G heads have larger ports and bigger combustion Chamber volume. Will there be any problem with this swap? Will I get any increase in HP, torque? Any down side to this swap? Thanks.
Jay
Hold on!
The intake will work ok, but check it for port mismatch. Probably OK.
The carb: Double pumper is not what you want, see previous posts, or search Holley or other fine brand web sites for "how to pick a carb" or similar.
The heads: You say they have larger combustion chambers than your current heads? Have your measured them? IF they are bigger, you are looking at even lower compression than your current pathetic 8.2, and a reduction in torque and probably horsepower. (You might be able to rev it higher, regaining some HP, but this would be a big unknown)
The 360 suffers a sunken piston, and no head change will fix that. Larger CC's will just make this worse, and not in a good way....
Now, the '65 T-bird motor is going to be a 10.1 CR if stock. Cam wise, it may be a bit better than the 360, but stock it's pretty much all done before 5000 rpms, with peak power at 4500. This is mainly due to the exhaust manifolds.
Serving suggestion:
--get a vacuum secondary 600 or 650 4bbl
--install that with your new manifold
--forget the heads
--install a set of headers.
Until you fix the compression--which requires a piston change* if not a change to the 390 car rotating assembly--and cam it up, those heads are going to hurt, not help.
*.060 or so 352 pistons will work, if you can find them and if your 360's bore will take them at only .010 over