Cujo336

Hi folks. I'm new here but have been reading a lot of your posts. I'd like some opinions and advise I have a Formula 336 with built Gen VI 502's. I was told they were built to 500 hp each. Can't prove it but the boat will or did run 70-72 at 5000 - 5200rpm and 25 pitch props.
I've got about 440 hours on one motor and the other one has had some problems. Over heat two years ago but it ran alright last season. But I'm sure it did some damage. Last weekend an oil line touched my exhaust manifold and melted a hole in it. All the oil shot out. I fixed the line and it idled fine. Sounded great until I bumped it up to 2300 rpm. Heard something rapping in it. Figuring a busted rod or something. I won't know till I break it down next week. Needless to say it's time for a rebuild. So I'm doing them both. I'm looking to upgrade to 650-700 hp. We all want to go faster. Lol. My question to you all is how would you do it. Rebuild it as a 502 and add pro chargers or a roots type blower at about 5 lbs or make them 540's? I am also considering just making the 509's. I'm running bravo1s. I'm not looking at upgrading the drives now but will later.
I can do most of the work myself, except for the machining.
Are there any spec sheets out there on how to make it a 540? Any good instruction manuals?
What would it take to do it?

Sonic24

I was faced with a similar decision on my Formula 223. After I priced out the rebuild parts needed to do it correctly, I found I could buy a complete engine cheaper, transfer my marine accessories then sell my current engine as a re-buildable core. I get good, reliable, dyno tested, power with a warrantee. I could have done the work myself, but better to get it done by an expert that stands by his work. I highly recommend you do the math up front before you jump in with both feet. Tim Mangus (585.671.0082) built the engines in my Formula 272, and he is building the engine for my Formula 223. Not only do I recommend him, he is who I am doing business with.

Just my two cents.

F-2 Speedy

iTrader: (6)

I think what most do to build a 540, is 4.500 bore, 6.385 rod and a 4.25 crank, this is what I did with my gen 6 502's..........you can offset some of the cost by selling your rotating assembly's.............

Budman II

iTrader: (1)

There are a ton of threads on this forum answering your questions if you want to do a few searches. Might get you more info rather than waiting for replies from folks who have already replied to this question in the past. Helpful hint - set up a budget, then plan on doubling it! You may find the need to upgrade things like exhaust, oil coolers, fuel system, coupler, and drives when you jump up to power levels like you described.

Budman II

iTrader: (1)

Also - do a similar search on the "Technical - General Q&A" forum - it gets a lot more traffic for questions like this.

endeavour32

iTrader: (4)

My engines are supposed to be 650 hp here is what I have, FYI they are 509's but that isn't going to make any difference.

10:1 Cr
Crane 741 Cam
Dart intake
Holley HP 950 Carb
Dart Pro 1 Heads ported by JimV

It would be cheaper to just but the AFR 315 heads as they flow similar to the ported Pro 1's. Pro 1's will still out flow them, but the AFR's will be close.

If you can hit the compression ratio with your current pistons that will save you some money. You will need to also replace your lifters so all in plus any machine work I'd say you are going to be around $6000 per engine. Then depending on what you are using for exhaust that may need to be changed. If you wanted to use this combo in a 540 you would most likely see another 40 hp.

getrdunn

iTrader: (7)

Look into Ohio crankshaft also to get some ideas on rotating assemblies (strokes kits). Their one of several however have heard some pretty decent results from them. I believe they come balanced however I'd have a shop balance anyway or at the very least make sure they are within tolerance. Not sure what intakes you have however along with fresh bore and stroke as mentioned above heads will be a must in order to achieve anything close to your goals. Recent thread on 548 build with 305 cnc AFR's, 454r intake, 1050 Dom, hyd roller, 10.5 CR = 700 hp.

Not an inexpensive recipe but certainly worthy. You could always do the rotating assemble for now and freshen up your existing heads and run it and do the other good guy parts later. Just depends on you budget if you have one.

Cujo336

Thanks guys. I am willing to drop some coin on them. But I'm looking to do comparisons cost wise. My intakes are Victor Jr. Pretty sure I'm going with the AFR heads. I've got Gil exhaust now and probably switching to headers. I'll look into Ohio crank too.

monster12valve

If you sell the Gil... Let me know!

Cujo336

I'll let you know monster.