I think the day's of head porting are almost done.. You could spend a week on factory iron heads and not come close to a good set of CNC'd heads right out of the box. What's it cost to send your heads out to get ported $1000? plus new springs, resurface, valve job, seals, etc.. Before you know it you're at $1500 with some dumpy old iron castings. Or you can get a brand new set of aluminum heads with all new quality parts that'll show up at your door ready to bolt on all for around 2k..

Those are nice:coolcowboy:

I agree. Also, unless they flow test them and flow test each cylinder you can lose flow, or have inconsistent flow throughout the head.

A friend of mine had a big-name guy port his heads. He wanted an aggressive head that started with an Edlebrock Victor Jr. and he had them ported from there. He paid the guy well for his efforts, got the heads back and had them flow tested. They #'s were worse after porting them than prior to porting them. He took them back 2 more times to the guy who was going to "work some magic" on them, and they never got any better.

If I ever pay someone for porting heads I would like to see the #'s before porting and after porting. It doesn't seem worth it to me, especially with the existence of CNC machines. I realize that even a CNC machine can't get in and clean up casting marks and obvious slag left behind, but that's stuff that I would take care of myself.

I agree for the most part with you guys. Going with some brand new CNC marine heads is the way to go. I had a set of square port heads redone with all new valves, inconel valves, new springs, guides, seals etc. Basically full rebuilds, all of my valves were junk. They did a little work on the bowls, and ended up costing me about 900 bucks or so.

A new set of dart CNC marine heads with inconel valves fully assembled are around 2500? So two motors thats 5k.

I was just stating that if he wants to go thru his current heads, they will support the HP he's trying to make with the right cam, and he can save himself a few grand. Of course if he wants to make 650HP out of his 502, then ya, go with some new CNC aluminum heads.

My buddy had a set of 502's, with old iron merlin square port heads(non cnc and no porting), 741 cam, HP500 intake, and 800 holley. made over 600Hp and 600FT lbs on the dyno and ran great.

Assuming all is good with the 502 what would cost be to get 550-600 hp?....and I know the phrase "if you gotta ask you cant afford it".
Lots of boats out there with twins black power, might be cheaper to get the power out of them instead of selling them and looking to buy blue motors.
Sorry for the highjack......
mike.

Call Eddie at YOUNG PERFORMANCE MARINE he would be you guy. He is great to work with and flat out knows his stuff. I've got 750 horses worth of proof as do a bunch of other guys on here. IMO

double post sorry

Can you put closed chamber heads on a factory 502 to get more out of it?

Most guys say they do not work well on boats. Not sure why?

Everyone has given good advice here. You could rebuild the heads you have and spend the money on exhaust and cam. Forget using 87 octain, I set mine up with 8.9 comp so I could use 89. Again like was said call RMbuilder for your cam.