502 carb 550hp - Blower vs NA
 

I know there have been plenty of "NA vs Blower" threads and I have searched them. But, I would like to hear opinions from the gearheads on here about this specifically.

If you had a 502 Mag (carb version) and you wanted 550hp, would you replace the cam, lifters, pushrods, rockers, springs, intake, carb and exhaust or look at putting a small blower (420 or similar) blower on top with upgraded head bolts/studs, head gaskets and valves?

Which is more cost effective and reliable at this moderate hp level?

I don't think you could make 550HP with a 420 on a 502. Lol
Also, I believe 550HP NA vs Blown are 2 different power levels in a boat.

502 at 550 with typicall bolt ons will likely be peaky and wet exhaust un friendly
502 at 550 with a roots will not , but it will cost you space front and top

This kind of mirrors my thinking, decent cam, above average heads, what can a guy expect?
edit in ; I have zero room to get taller than the current stock setup.

550 hp is obtainable with either, but I agree the delivery will be different. I was looking at getting there NA, and the costs add up quick. Which got me thinking, would it be cheaper and easier to pick up a used blower and go that route.

No right or wrong, just looking for opinions.

If you can make it fit heck yea .

i think what rookie is saying is if you go with a 420 blower you will be way over 550 hp.i am a blower guy but only you can decide what is best for you.the n/a build will not make the torque a blown deal will make but that will extend your drive,s life.what ever direction you choose to go you will need to upgrade to a good exhaust system,change cam&components,either replace the heads or at least have your heads worked,buy a carb or two,etc.if i wanted only 550 hp i would go n/a.

The blower deal will probably make a little more EGT and thus be a little harder on your exhaust valve seats / valves, and etc.

Maybe better to change to a better (thicker head if cast iron) and new aftmkt head with attention to detail from a cyl head guy with thicker seat margins and etc.

Anyway, a cast iron RHS, Engine Quest, Dart head with with a mild cam will put you at that.

A stock head with '731 cam will put you just under that.

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550 HP doesn't sound like much in todays world. But that's in comparison.

But, reality says it is still 550HP...which is, well, a lot.

Yes, that is exactly what I was saying.

Aaaaaand the next expense...what drive are you running?

I missed the sarcasm. :) I know a 420 is way more than needed, but from what I have read it's much safer to turn a big blower slower than a small blower faster.

That's always an issue with Bravos!

Lol, no problem. For the minimal power you are looking for a 250 would be perfect, (Save a Bravo) and I might know where one is coming up for sale soon.

And NO Mild I'm not going to be selling my pair. They will eventually go on the Panther.

Here's my argument in the blower size. Small blowers highly overdriven, make excellent torque down low. Lets say the 250 vs the 420 blower at full throttle, at 3500RPM, both making 6lbs of boost. The 250 will more than likely make more torque there. You probably wont start seeing gains in power, until about 5000RPM. Then, the big blower will walk away from the small blower. Especially when you run hard for long periods of time like, in a boat.

So, if drives staying together was a concern, thats a tough call.

To get back to the original question, its easy. The 600sc merc engine, was nothing more than basically a 502 mag, with a different cam, which was a flat tappet, dished pistons for 7.5:1, and the 420 blower, with twin 700 carbs. It was a very reliable engine, and many added chillers, and cranked up the boost. I know of one guy, who installed chillers, cranked the boost to 10psi, and ran that setup for 10 years!!

I'm a fan of blowers, but like mike tkach says, for only 550hp, no reason to add them. I'd rebuild the setup with some better components to get to 550HP, with 9:1 or a hair less compression. Run that for a while. Then, if you wanna get silly, toss a blower on there, like the 420, or 871, and enjoy 700-750hp as well. :)

How many hours on the mill?

UD

550hp N/A makes more sense to me even though I am also a fan of forced induction. It will be nice to freshen the engine anyways and then you KNOW what you have.

Plus adding a blower....properly....is more work then one might think.

I personally would select parts that are the best value. Sometimes we all go overboard and there are plenty of good choices that will produce very similar results for less money. For example, a 550hp build with some good flowing, less expensive, iron heads over aluminum.

Keep us updated! Enjoy!

This was a hypothetical question. Looking at a boat with a low hour(about 50) 502 Mag carb. I know you can get 550hp with cam, lifter, springs, etc. I understand that is the route most taken.

But, with all the used blowers out there it got me thinking that may be a better option. Bigger blower spinning slower = less heat and more reliability than a smaller blower and less valve train wear.

Wheels were spinning so I was looking for opinions.