Other upgrades to a 502.
12-07-2019, 02:38 PM
#11
Platinum Member
Platinum Member
Biggest question is "What's your goal"? How much HP are you wanting? How much does your boat weigh? What drive/transmission is on it? How long do you plan to run wide open at a time (15 second bursts? 45 seconds? 5 solid minutes?).
Next question is "What 502 do you have, what hours are on it"?
If you have a 390 to 420hp 502, then you can run 5 lbs of boost on a stock configuration with an intercooled M3 and expect 500-530hp.
Above 5 psi, you need stiffer valvesprings than stock, but you should already be buying new springs anyhow.
Above 5 psi and 4500 rpm you need to at least put aftermarket rod bolts into your factory rods and have them reconditioned (any time you remove/reinstall rod bolts, the big end has to be cut and resized). Staying below 4500, the factory rods are sufficient, but if you have a lot of hours on them, you may be needing to have the big ends done anyhow. Bolts are a no brainer then.
Stock exhaust valve (HD Stainless) is adequate up to 5 psi. If you go above that and plan to run hard for longer than a burst, you need to upgrade to SuperAlloy or Inconel, and your guy who does the valve job needs to leave a little bit thicker exhaust seat width to help keep the valve cool.
Since you are already planning on freshening the motor, definitely ZERO DECK the block (pistons flush with the deck surface), so you will have "squish turbulence" to help snuff out detonation spikes.
But if you want to really rock and roll, Smitty's recipe is perfect.
Next question is "What 502 do you have, what hours are on it"?
If you have a 390 to 420hp 502, then you can run 5 lbs of boost on a stock configuration with an intercooled M3 and expect 500-530hp.
Above 5 psi, you need stiffer valvesprings than stock, but you should already be buying new springs anyhow.
Above 5 psi and 4500 rpm you need to at least put aftermarket rod bolts into your factory rods and have them reconditioned (any time you remove/reinstall rod bolts, the big end has to be cut and resized). Staying below 4500, the factory rods are sufficient, but if you have a lot of hours on them, you may be needing to have the big ends done anyhow. Bolts are a no brainer then.
Stock exhaust valve (HD Stainless) is adequate up to 5 psi. If you go above that and plan to run hard for longer than a burst, you need to upgrade to SuperAlloy or Inconel, and your guy who does the valve job needs to leave a little bit thicker exhaust seat width to help keep the valve cool.
Since you are already planning on freshening the motor, definitely ZERO DECK the block (pistons flush with the deck surface), so you will have "squish turbulence" to help snuff out detonation spikes.
But if you want to really rock and roll, Smitty's recipe is perfect.
