SB.
running 12g wire right from bat thru relay to distrib
I purchased the heads new from Ron Sporl Performance, Manley Inconel ex Manley intake, can't remember the size but next bigger than 2.25 runners ported pockets bored out to bring comp down to 9.5 pistons were down .010 in block
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ignition timing may be holding you back, do you run premium? similar 502s to yours made best hp at 35, 36 dgrees of timing on my dyno with iron heads, a factory 500 mefi runs 35.9 timing on top BUT it does have a knock sensor. If I dyno a 9-1 iron headed engine at 32 vs 34, 35, I will see about a 20 hp drop at 32 sometimes, at 29, im sure its more BUT if your running 87 and since you dont have a knock sensor, I wouldnt get too carried away with total timing. Id also say to install afr bungs in your headers and see what your afr is at wot, Smitty

See post #2. He has bungholios with sensors installed in both.
Hmmm, looks like GM dual plane too.

cams installed to advanced,should be around 109-110icl

polishing chamber is okay,,really need to see that exhaust port,that will tell if your gonna make some hp,,plus,that cam doesn't have near enough spred,its not a street car,8-10° will be the norm w/ good exhaust ports,,merlin probably needs 12-14°.run it for the season then change some parts.

MORE INFO: I am running the stock gm intake manifold dual plane but cut down the center divider about half way. Icon forged pistons, run 93 octane, long rod eng. sniper keeps wot f/a ratio at 11.8 which I can set to whatever I want so that helps against detonation but I do not have knock sensors or electronic timing reduction. I set my timing at 29 to be safe for break in and I just havent had the balls to bump it up to 33/34. I would like to do that w/ an experienced tuner either on water or prop dyno. My overhaul had a lot of Chiefs but no 1 person in charge. I should have just take the boat to a reputable guy and dropped it off and said call me when its perfect. I really did respect what Ron Sporl told me to do regarding the heads and cam selection and timing pos, now weather or not my builder knew what he was doing and actually set it to 104/106 I don't know. I now Stuphen 30 has been on this forum quite a bit and maybe you are right about 109/110. Not sure if this makes sense but I remember Ron saying the pistons I had would give me too much comp so he ground open the pocket and I think he set the cam to lower the running comp to give me about 9.5/1, does that make any sense?
https://cimg1.ibsrv.net/gimg/www.off...ea2d5454ac.jpg
https://cimg1.ibsrv.net/gimg/www.off...24dbd5a731.jpg

Are you driving the boat like worldwide prestige (trim down) buy any chance ? :evilb::bunnydance:

I used to drag race my Action Marine then my STV tunnel v which did 104 on a good day, I'm no stranger to what it takes to go fast but I have always been an outboard guy. I trim up till I feel it start to ventilate then bump down till I feel it catch. At 62 mph the boat is trying to get on the step, the bow oscillates up and down, I need another 5 mph to get her on top and fly. Maybe bumping my timing up will give it to me but now I need to find another prop and debating between a 3 or 4 blade. I don't want to go any slower and I am not having any problems planing or staying there at slow cruise so I am leaning toward 3. The boat weighs about 5200lbs

Well, your timing is very conservative. A/F ratio not too far off from fine.
I have never run any bbc nor sbs with less than 32-34 degrees unless it was getting a shot of funny gas. :) So, I'm not sure how much power you are losing, but I know low and midrange timing being off as little as 4-6 degrees will make an engine accelerate a lot slower than it does with more. Fun vs blah blah. Again, I never have total timing at a lesser value, so can't answer for there. I would assume (uh oh) would make it lethargic there too.

I am going to try to get out in the boat next week. I have a solid hub 21p mirage and will set my timing to 33 and record what I have for a/f ratio at mid and wide open, note speed, rpm and outside air temp, I am at sea level. I am running a 150 thermostat. I am using the stock pointer on the timing chain cover and installed timing tape on the dampner. My piston part # is Icon 808-064