Then you certainly need to watch camshaft size. You will easily over cam that engine. In fact, I'd say the factory 340 cam would be to big. Those heads are going to be a real cork with 318 size intake valves. You now are displacing 390 cubes. That was a Ford big block. Get it? You need more cylinder head.
Is the OP capable of a good port job, does he have a flow bench ? Why does everyone assume that everyone can port a set of heads and get great results.
Two things. 200CFM will piss 390 cubes off. Secondly, camshafts don't "bleed off" cylinder pressure. That's not how it works. A camshaft with a later intake valve closing event simply closes later than a "smaller" counterpart, so it does not fill the cylinder as completely. SO the pressure is not there to begin with. You cannot "bleed off" what isn't there. Our good good friend Jim Laroy corrected me on that years ago and he's dead right.
for an off the shelf cam, that's what's up.
Basic RPM Range:
1500 to 5000
Valve Lift Intake:
.450
Valve Lift Exhaust:
.465
Duration Intake:
267
Duration Exhaust:
277
Duration at 050 Intake:
213
Duration at 050 Exhaust:
223
Lobe Separation:
112
I run one also.. but haven't run many others so not fair for me to say it's better
but dealing with them was nice...
Yeah we get that. We're trying to give you good advice. You need to listen. It's not a 318 anymore. 318 heads are not going to be conducive to making decent street power.
To give you a better comparison. Chrysler introduced the slant 6 in 1959 at 170 cubic inches, quickly followed by the 225. That's 55 that's FIFTY FIVE more cubic inches, yet Chrysler used the 170 head design and port configuration all the way through to the end of the run for the slant 6 on ALL THREE engine sizes.....and guess what? The cylinder head is THE NUMBER ONE limiting factor for a performance slant 6 because of that. YOUR engine is 72 that's SEVENTY TWO cubic inches bigger than a 318. I don't care what these guys say......and I mean no disrespect, but there is no way the 318 heads will be adequate. It's not about making the most power. It's about something performing decently for the amount of time, trouble and money. You will be disappointed with 318 heads. But by all means, use them if you want. It's your project, it's your money time and trouble. Good luck if you do!
It's up to you, but were not talking max power either, 318 heads are barely adequate for a mild 318 (5,000 rpm) nevermind a 390, most would be lucky if they make more than high 200's hp (250-300 hp) with stock 318 heads. A 390 may squeeze a little more than a 318 will out of them but I wouldn't expect great 2500-5000+ rpm power number, power will be down across the board, torque takes airflow too.
A set of speeemasters probably your best bet, or second hand Eddies.
Barely. He wasn't running any vacuum advance and timing limited to 32 degrees total mechanical advance with a long curve for best results when towing. Really too much vehicle and not enough gearing. 4.56's would have been good, but 4.88s would have been better. There was a lot of room for improvement in the carburetion department as far as tuning went. I think it would have gotten by on 89 octane if the carb tuning hadn't been so idle and intermediate rich. I wasn't able to convince him to get into the fuel restrictors to straighten the tune out.You get by with 93 in it? I kinda wanna build mine to use worse gas.. an extra $2 a gallon adds up over years... funny how gas was supposed to be cheaper now...
Those 596 heads with some 2.02 intakes, matching the bowls to 89% of valve size, and porting the wing divider out in the roof and contouring the guide would be a step in the right direction.Not sure where you are in CO, but this is in Denver:
Mopar 360 la parts - auto parts - by owner - vehicle automotive sale - craigslist
FB marketplace is better that CL these days, but I can't access it on my work computer
