I bought a Mark VI 502 to replace my 92 454, looking to build it up to around 600HP. This is my first build so please bare with me on my inexperience. Would like to keep it dependable and fast, best of both worlds! Still trying to figure out stock head cc on 088 rectangle port, what cam to go with and how to figure out cam lift and duration for a motor build. planning on having head work done just don’t know what to have done yet🤔. Looking for a build sheet to work off of and any suggestions or criticism. Will be purchasing new cam, pistons and possibly new heads. Have about 5K to work off of. 509 sounds good but no diffident direction yet. Thanks

Thanks Griff looking at Arizona speed and marine intake if I keep the EFI system and either Dana or Lightning headers my budget wasn’t including headers Will be closer to 8-10 by the time I’m done. Plus still need to upgrade to dual steering stabilizers. It’s only money !

Any recommendations on witch heads to go with, CC, valving and anything else I’m not thinking of. would like to stay away from anything China made. USA ����

502. Comp cam. EQ heads basically box stock. 8.7:1 compression. Merlin x intake. Quick fuel 850. 565@5800. This was through etops in full marine trim on the dyno. Had I used dyno headers like most it would easily be over 600. Also having sweepers or eickerts would have jumped power by 30+. Very happy with the builds and the boat runs phenomenal. Any questions let me know.

Mike

What are sweepers and eickerts, stock cam? and what CC is stock head on 502. Thanks again for all the help everyone was a rookie a some point ��

https://www.jegs.com/i/Brodix/158/2321011/10002/-1

https://www.profilerperformance.com/...ree-heads.html

lol I was thinking the same thing. I thought the forum was off his dick.

If you want to hear someone wax poetic about “cylinder filling” he’s your guy. What you’re actually going to get: afr heads and a crane 741 cam with more aggressive ramps. (Doesn’t seem wise for valvetrain life to me?)

Thanks for all the help guys ! Going to purchase the Brodix heads and calling Bob at Kinetic. Any suggestions on questions I should be asking with bob.

I would spend the money on a 540 rotating assembly.After that your 600 hp goal will be easy without port work or a time bomb camshaft. Cubes simplify everything.

Tell him you would like both cams to match each other.

Anyone have any thoughts on Arizona Speeds EFI manifolds. Would like to stick with EFI but I know they are seriously restricted in HP gains. Carbs vs EFI ?

Do you think the heads that have the hard anodized are better set up for marine use?

Thanks for all the help, talked with Bob at kinetics going 509 with AFR 305 heads, carb and Victor jr intake with his cam. Anyone have headers they need gone. Thanks again will updated as I start building

These are a chunk of change but a solid seller.

https://www.offshoreonly.com/forums/...e-headers.html

good luck. Have a good head guy go through the heads before install. Ask what the valve seat material is. Also watch the cam specs. Many of those cams have been high lift low duration which are known to beat the valvetrain up.

I thought AFR was a good quality head and Bob Madara was highly recommend thru this site for his cams. What kind of material should I be looking for on valve seats

Thanks MT that was a very good thread to learn off of. Going to talk with Bob about valve train and lift. Should’ve gotten 2 cups of coffee !!����

You won’t make 600+ NA in full marine trim without sweeper style headers. Manifolds and etops just don’t have long enough runners. Even the 525 has sweeper headers to help with its power. Eickert manifolds would be the only manifold capable but they have long runners also. Don’t know which “builders” you’re referring too but talk to mark rinda at Mer performance or eddie young at young performance. Those are 2 quality guys who will lead you in the right direction to make the best power within budget. Remember budget is the most important. Cheap, fast, reliable. Pick 2

Lots of good recipes for 509's. Endeavour32 purchased a couple of used ones from tinkerer a few years back that made well over 600 hp. I might be wrong but seems like they made just under 650. (Doubt marine dressed and likely dyno headers). Tinkerer would be able to tell you more than likely. Pretty simple builds with dart pro one 310 heads with Dart intakes worked over and set up by Valako. Holley hp 950 carbs and 741 cams. Boat ran very well. After a season I believe endeavour32 swapped out intakes to Brodix hv2000's and quick fuel 1000 carbs and made some very worthy gains on the water. Reliable builds and made great power. Only thing I may have missed was the 1.8's on the intakes.

I'm not certain what they CC'd out at after the heads were ported however I'd imagine around 325. Like I said there are many ways you can achieve your goals but just thought I'd share.

Very important to be sure and have your heads set up properly for marine use what ever route you choose to go.

Only over achievers to people who don’t understand how exhaust runners affect NA power and expect more from a Gil, SM or Etop style short runner.

Thanks for catching my mistake on the intake and carb combo. For some reason I thought you stayed 4150. You did forget to mention your custom made hatch air ports. That boat starved for air after your engine swaps. Makes ya wonder if most consider after almost doubling NA power. When in doubt crack the hatch. lol :faint2:

the beauty of side opening hatches. Easy to crack for lots of air.