rich allen

Can't keep my fingers out of a perfectly running engine, so looking for something to do.
Originally a 330 hp 454, bored .030 , decked .010. The pistons are TRW's, L2465F with .226 dome, and figure about 9.5-9.6 to 1 comp. with orig peanut port heads. Comp cam#11-306-4 with .222 and .226 @ .05 and LS of 110. Intake is a performer rpm, and carb is edelbrock 750 marine. Exhaust is EMI . Pulls damn hard right now, but loses steam above 4500. Would like to stay around 5,000 rpm wot.
Was told good set of Merlins large ovals would help wake this motor up.
Is this the way to go?, or what about a set of 049's or 781's.
Looking for advice on which way to go, and why. Thanks guys.

birdog

I have a fresh set of 188 heads...With 121cc chambers you can stay with pump gas with your domed pistons..Ports cleaned up & Stainless, Inconel valves...These will put you where you want to be

ECeptor

Edelbrock Performer RPM marine aluminum heads are a great option if you have ~$1,800 in the budget.

If you need some thing cheaper then start with 049s or 781, add 2.19/1.88" int/exh valves, and have them ported. They will give you more power below 6,000rpm than the rectangular port heads.

Not sure about the Merlins. From the hp/$$ numbers I've ran I'd either go with rebuilt 049s/781s or I'd step on up to the aluminum Performer RPMs. My logic is if I'm buying new aftermarket heads, then a ~$100-200 get's me into aluminum ones - less weight and can go 0.5-1.0 pts higher on compression.

Here's some reading on rect vs oval ports for your application.

rich allen

Thanks for the replies. Bird, those heads are square ports?
I'm thinking maybe should lean towards ovals for my application , for better midrange? Wont really be much over 5-5200k and feel those heads might not wake up till over 5k range?
Am I right here?? They would keep comp ratio good, though. Not sure if cam I have can feed enough for the 188's at lower rpm ranges. Mind you, always looking for a couple mph, but motor still serves duty for towing kids around behind boat from time to time as well, and hate to lose too much low end torque.

rich allen

Looking at those Edelbrock marine ovals, they have 110 cc chambers. Thinking that will bring my comp up too high for pump gas ?? Already at 9.6 with 119cc peanuts

birdog

Yep-Rect port, Maybe they are not the "Ultimate" set-up,I'm not sure. Way better than what you have now. but Merc used them on 454mags,420s,500s etc. for years...These are set-up ready to run for the cost of one bare head aftermarket.& you need the big chambers with your pistons

KAAMA

iTrader: (1)

rich, unless you can find a set of 049 GM castings that have had all the correct mods done to them, then I would get the Merlin oval port cast iron heads as they already have the hardend valve seats and come with larger valves and I think you can order them with bronze valve guides. Just have a little clean-up porting done in the bowl areas of the Merlins and you'll be good to go. The larger oval port head will do much better than the smaller "peanut port" heads you now have. The larger rectangle ports are kinda on the large side for a 454cid marine engine.....besides, they have a tendency to crack inbetween the valve seats---I have seen this MANY times on marine engines in the past. I have seen guys spend a lot of $$$ porting their GM rectangle port heads only to have them crack between the seats a short time later. The Merlins are a thicker/heavier casting than the GM heads and do not have that problem.

All the other components you have sound pretty good and should work well with the Merlins if you decide to go that route. I just think the 049 and/or the other oval port GM heads would cost too much to get them into decent shape. I'd put my money on the Merlin cast iron oval port heads. Have fun with your project.

fyhr factor

Hey Rich,
Do you still have your PowerPlay boat?
Where do you Run on the Ct. River? In Mass or Ct.? I bought my 1988 Powerplayxlt 185 last year from a guy in lake george, NY and run it around the area, Mitch's Marina,. Ottis res., Glastonbury on the river, It would be nice to see another Powerplay boat around, I feel like a lonely duck!!!!

1BIGJIM

iTrader: (1)

I would go with the Merlin oval port cast iron heads. You can keep the compression ratio the same and a damn good head for the price. I just put together a set of the Edelbrock 110cc but my diciding factor was I wanted to bump my compression ration up to 9.5. Love the heads. You can pick one up with one hand
I have 781 large ovals that are sitting on a shelf.

rich allen

Hello duck..
No you are not alone.. I still have my Powerplay as well, and she is still going strong. I run mostly in the river as well, above the dam, and anywhere along the way from South Hadley, to Hatfield. Usually end up rafting at the shallows.
By the way, I didn't mind being the lonely duck on the river, and was doing just fine without any other ducks
What color is your boat?