330 Hp to 400 HP
 

I've got a pair of '89 330 hp engines with 195 hours on them and I want to build them to 400 hp limiting the RPMs 5000. I think I'm going to be using Gil's for the exhaust and I would like to be able to run the stock carbs if possible. Are the peanut port heads good for that power? What cam do you guys suggest? This is going to be a low budget build by that I mean flat tapped cam, stock bottom end, ect... I just built an all out BBC for my 242 but this project I'm sticking to the basics!

You're going to need new heads. Get a set of 049s, 781s, or Merlin large ovals. If you want to save cash I would use an out of the box, one step up from the 370 cam from Crane. You could also run a re-grind of the Merc 420HP cam, and be fine with Gil exh. You won't make 420HP with a Merc cam stuffed in your 330's though. The 330s have 8.0 - 1 compression, and it only gets bumped up to around 8.4 with smaller cc heads and a 0.027" Cometic head gasket. You can fly cut the heads and probably get your compression close to the 8.75 that Merc uses if you don't want to swap pistons.

I can help you with head gaskets and probably heads/springs/head work if you need it.

I wouldn't rule out the heads. Heres what a local did with his.

"Mark ran a isky 280 cam 232/565” 9.5cr ported 236 head 454 to 5600rpms 547hp / 580ft lbs"

You'd waste more money porting these garbage heads than you would spend on 049s or 781s. Just get the right castings and be done with it. I have 5 sets of peanut port heads. If anyone wants to turn them into high performance 547hp heads I'll sell them dirt cheap!

I have to call BS on 547 hp with a peanut port heads! My 439 BBC was a max effort build, designed by Bob Mandera and built by Dave @ wesco racing and I'm at about 530 hp with AFR 265 oval heads, custom cam, custom carb and eickert headers.

I'm at a toss up to either do a mid build on my 330's or just sell them complete and find some nice 420's and refresh them.....

I think he was being sarcastic

I know what you are trying to do, I had the same idea several years ago. Do yourself a favor and leave them alone until you can do it right. A stock 330 will run well for years as is. If you try to just change out a couple of parts and make more HP you will blow it up over and over. The only upgrades that can be just bolted on are exhaust and roller rockers.

Thats kind of my take on this as well... I really don't feel like dumping money into the 330's. I'd rather go the 420 route or find a nice set of 502's.

Search Maximum Rat here on the forums or VortecPro on the web. It would be easier as wjb21ndtown suggests to install the bigger heads to get that power but it isn't the only way to get there either.

I've made 400+ hp with peanut ports multiple times. For a small cube engine that you only want to turn 5000rpm they're not a bad option, especially when they're already bolted on.. I agree with everyone else that said just drive it and spend your money on some different mills. If you do upgrade the cam's even to a decent flat tappet then you'll need to do springs too, while you're in there you'll want to replace the seals, then the stock rockers, then the 5/16 pushrods, then the..... It just keeps going. :drink:

Sell your motors and find two good motors all ready built. Trying to rebuild yours will disappointing and to expensive. There's alot of good motors around cheaper than building yours . I've tried rebuilding the 330 for HP and it's more trouble than it's worth.

Jeff, what do you think about adding large ovals, a matching edlebrock performer intake, and a set of roller rockers to a 330hp motor? That's what I was thinking about doing in the next month or so. The 049 and 781 heads have a 5cc smaller combustion chambers. That 5ccs + adding a 0.027 head gasket will raise the compression from 8.0 to 8.4ish.

It seems like an easy way to squeak 30-40 hp out of these motors without really doing anything that would hurt them, and I will get to freshen up some tired parts as well (head gaskets, springs, valve seals, etc.).

I'm pretty sure both the 049 and the 781 castings have at least 119 cc chambers, so you will definitely not increase compression by switching to them. I had a set of 781's cc's by my machinist, and they came in at around 124 cc. The 049's are large chamber as well. You might look for a set of the mid-70's 820 castings - they come in around 112 cc. Another option would be the late model Vortec's, which I think are around 109 cc, but they have the swirl intake ports that can limit flow.

Endeavor, I would definitely try to sell your complete engines. If they only have 195 hours on them, you should have no problem finding a buyer. Put that money into a pair of 502 short blocks, and you will be ahead of the game.

I don't know why everyone says 781s have such large cc chambers. If you look up the casting # on the Motech website it lists them at either 115 or 113. That's what I've found on every set I've ever ccd. I have four sets of 049s right now that all measure either 113 or 115.

I can't stand vortec heads. They have decent sized runners and small combustion chambers, but other than that, IMO they're junk if you want to have any sort of performance other than a stock 300hp ish towing motor.

Look on the Mortec website for the specs. I used the 820's with 113cc stock then milled down to 110cc. That would get you a little more compresion. Without the cam you will see very little gain. If you do a cam you will need exhaust. To get any real power you need to bore and stroke it with forged internals. You see were I am going with this, learn from my mistakes and leave it alone till you can do it right. If you really what to do somthing bolt on some aftermarket exhaust and roller rockers. That will get you about 2MPH. That way on your next project you can do a cam and head upgrade. http://classic-web.archive.org/web/2...ec.com/bbc.htm

781's are larger look at the link I just posted 049's are even bigger

I'm going to leave the engines I have alone and look for at pair of 502's or 454/420's. I know what I had into my engine in my 242 and it was close to $10,000. X2 thats $20,000, I'm not spending that again when some nice take outs will get me to my speed goal of around 70 mph.

Your on the right track.

I see you have 2 boats, that makes sence now.

I have many times built 560 HP 236 headed 467s with 9.6 comp, its not BS, just fact. My 9.2 comp 228 @ 050 flattappet 467s make 530 HP @ 5800 RPM, (29.92 60 degrees, dry air) with 236 heads, performer RPM intake and stamped LS6 rocker arms. As a side note Im allways open to dyno challenges, please feel free.:evilb:

Why would anyone turning a 454 5000 RPM want a bigger runner than what a 236/peanut would provide. Air speed is the key here. Bob care to comment on my post?

781 castings 119-121 cc 049 castings 121-124 cc 236 castings 121 cc.

X 2.

In case people aren't aware, the Summit Racing house brand BBC cast iron heads are from Dart. They are cheaper then the Dart Iron Eagle's, but I don't know if that's because the 'house deal' or they have cheaper parts in them.

Back on topic, if doing anything with heads I'd find some that have a smaller combustion chamber

Whose exhaust system do you prefer on these ?

Do your run a crossover system or standard type Mercruiser ?

What size oil cooler do you install ? Preferred oil pan ? Stock 300hp one ?

If you don't mind sharing, do you have any pics of these installed in boats to see the above parts you use ?

computer got stuck sorry.

tripple post. sorry. Dang computer.

SB, these engines mentioned are are for automotive applications, I couldnt imagine the HP loss with marine exhaust. I test these engines on a SF 901 dyno with 2 inch full length headers into 3 inch exhaust. I know nothing about boats, but was searching forums and found this thread and felt compelled to stand by my dyno numbers, thanks for your interest. But to answer your question, dry 1 7/8 X 36 headers into a top ten shoot out 3 inch center in center out muffler.

Okay, thanks for that info.

Was wondering how you'd make those engines you mention survive. Just couldn't see it happening.

The performance boating I/O world can be and usually is very different. Valvetrain, camshafts, rotating assemblies, oiling, of course exhaust and a lot of times heads, intake, and carbs.

Stock low hp motors, not many differences.

I think my 530 HP peanut port would survive fine if you could keep the water out of it. 112 lobe separation, 18 inches of vacuum.

Many car performance engine builders thought/think the exact same thing when entering the I/O boating world.

How hard could it be...right ? Well.........

Exhaust and water is one thing - and yes it is big! - but there are many other items (as I've mentioned) that will bite you in the butt if kept on the automotive theme.

Steep learning curve - better not done at the customers expense. Or in the case of the DIY that's built 1 or even many performance car motors, homework and experience is advised before jumping head in. These I/O (offshore) forums are chaulk full of people (edit in : engine builders and DIY's) destroying equipment (motors, etc) and being served lots of humble pie from the assumption of "what can be so different."

Anyhow....... that's just the way it is. Hope this helps.

I think if you use the right clearances, head gaskets, exhaust valves, and oil pan, and of couse if the customer keeps the water out of the exhaust you can be sucessful, I have been.

I did a 330hp build last winter and i got robbed somewhere along the line.
I used bob mandara cam w a .6 lift cam, and 781 heads ccd by head shop around 113-115.
The motor is in a 24 pantera which i read do 75mph with na magnums, I went from 58 to 64 mph max after rebuild. Rebuild included forged domed pistons, morel lifters, bobm cam, 781 heads. I alreads had sm exhaust. Im currently in process of installing some oxgen sensors to get jetting a little better bc im on the rich side

I thought i was going to have a radical motor but i couldnt get this motor over 5000 rpms with a 23 pitch prop 3 blade,
makes no sense

I remember your build, did you leave it a 454 or go to a 489/496? The 454 should make about 480HP, stroker motor about 520HP. Don't believe what people tell you about how fast there boat goes. Even when I pass people they tell me they had throttle left LOL

Car engines and marine engines are completely different animals. I'm assuming vortecpro is the same vortecpro from the chevelle site. When I built my last engine i consulted with many people on the build of my 427 (440 CI) marine engine. Of which one was Chris Straub from the Chevelle site. He said there was NO WAY i could build more than 425 hp out of that engine and have it work in a boat. I ended up letting Bob Mandara spec the entire engine. We ended up with right around 525 hp at 6100 RPMS. This pushed my Formula 242 to 68 MPH. That said I find it VERY hard to believe that your going to be able to build 550 hp in a 454 with peanut port heads that will work in a boat, possible I guess but highly unlikely. There are lots and lots of variables that are MUCH different than an automotive application.

My new build engine is 468 with stock bottom end, 088 heads, Isky 270/280 mega, 1.7 roller rockers, Edelbrock intake and 750 marine carb. Made 407hp at 5000rpm and 474ft lbs max torque at 3800rpm on the dyno at Orlandi Performance.

Dry exhaust...108 lobe center? compression?

Wet exhaust, 114LC its not a big cam I didn't want to worry about reversion, 8-1 comp but might be a little higher heads were used and we shaved a little off. Below is the link for the cam specs.

http://www.flatlanderracing.com/iskycamsmarine.html

that motor could tolerate more compression,some horses hiding in there

Yep, I thought it would make more. I'm happy with it for now it was my first engine build. The stock 330 decided to eat the number 7 exhaust valve last year. It's got about 12 hours on it now and I'm trying get the right prop on the boat for it before it goes into storage.