Originally Posted by rube'68'03
F-Bird: As muh as i would like to get the old thing supercharged, its currently not in my budget. I will be taking your advice and getting the heads porter and the 1.94x 1.50 valves. The cam though, what kind of lifters/rockers should i look into?
if you have to pay someone to port these heads, its not really worth it.
Its a DIY thing on these and most stock factory SBC heads.
Porting labour costs money. it's labour-time intensive.
Port them yourself, first, then get and pay for the machining done. (new valve job etc) Don;t be shy with the porting. They need a good work over.
Use stock type long slot rockers. A hyd flat tappet cam and lifters is fine. stock diameter springs are fine EG lunati 73943.
When the machinist machines for aftermaket valve seals, get him to shorten the guide boss for high lift and the seals.
shorten the boss by .200" with the .530" -.550" aftermarket valve seal cutter.
Keep the cam under .500`lift. .440" to .480" lift is fine. Shim the springs to equal height 1.70" to 1.73"
Pick the cam duration based on intended engine rpm range. When you cam these motors up, they want to rev.
The whole point of using the 305 heads is to keep the total cost down. Don;t spnd /pay for stuff that you don;t need.
( professional head porting,screwin studs,,,, roller cams,r roller rockers etc etc. KISS
pay attention to the finished size of the chambers and the engine compression ratio.
Ya it matters. Whne you get the heads off your 307 measure the deck height at TDC. (dished piston.... flat top??)
the 416's can be flat milled to 51cc if nessessary.
here is a nice moderate cam for your 307 w ported 305 heads, RPM intake, headers and 650-750carb.
Comp cams Dual energy 265DEH 12-208-2 9.5 to 10:1 cr.
needs a stall and gears for best. perf. in a 307. Anything with similar duration will work well.
cam selection is very criticial on small CID motors. this one will buzz well past 5500 rpm in a 307 w ported heads.
A "3500 stall" 10" and 4.10's is not too much.