340 head clearance?

-
b5cuda

b5cuda

Well-Known Member
Joined
Jun 30, 2007
Messages
224
Reaction score
33
Hey gang,
Putting together a 340 this winter and thinking about head selections. Block has been bored .060, will use speedpro forged pistons (LF2316F). Machine work done and balanced. Have not decided on cam. Going in a street cruiser '69 cuda. 4-speed OD, 3.55 gears. Was thinking of using a set of 273 adjustable rockers. My questions are what compression ratio is desirable (I think RHS heads or magnums would give me a 10.5 or better ratio) and what heads will fit without valve clearance issues? Thoughts appreciated. Thanks!
Bill
 
rhs and magnum heads are close chamber heads...you need to see how far the pistons still out above the deck of the block...with that knowledge you can pick a head gasket that is going to give you clearance.....probably going to need about .053 gasket...

the L2316F pistons will handle the 2.02 valves with no problems...
 
Thanks Tony - guess I need to do assembly before I know for sure on piston height. Appreciate the tips!
 
I see you've already had it balanced. If you hadn't I was going to suggest having the piston tops machined off to give you a zero deck motor. Then you could run any of the closed chamber heads with no issues and Felpro 1008 gasket which is 0.039 thick.
 
Don't assume that you will have enough valve to piston clearance!
That piston # looks vary familiar and i think it is the same piston i have in my 340.
I did NOT have enough Valve to Piston Clearance do to a ski jump at the end of the valve releaf were it meets the flat top of the piston.
Removed the bump and had tons of clearance. and that was with a MP .474/280 Hyd cam.
 
Another question I'm chewing on is valve size... if I go with an old set of 360 heads (instead of newer closed chamber type), does it matter whether I go with big or small valves? I'm guessing the small valves would be a little better than big valves on economy and response at the low end. Does it make much difference?
 
I thing the 1.88 would be the best choice in a stock head, But the 2.02 would not be a deal breaker by any means.

La heads 360/340 heads will give you around 9.4X with a .028" head gasket.

If you have a nice set of LA head go for it. if not, and they are going to cost a lot of work aka guides seat and valves, the RHS head would be better performer and less money in the long run, w/ more compression potential. but piston to head clearance will have to be figured out aka head gasket thickness.
 
remember went you are checking valve to piston clearance you check it during the overlap period of the camshaft...went the valve is at max lift the piston is way down in the bore...
 
You must log in or register to reply here.
-

Back
Top