After spending many hours searching and reviewing threads on hp gains, I thought I'd ask the question out loud. What is going to be the best bang(s) for my buck??
I would like to keep the bottom ends together as they are fresh (50 hrs) but since the motors are out of the boat for some minor oil drips I just can't help myself, I'd like to move up to spinning a 25 pitch prop from a 23 plus. This is what I'm starting with;
2 461 ci 4 bolt steel crank, dimple rods,

freshened G.M HiPo iron, rect. port heads 2.25 intake, 1.88 inconnel exhaust

cam is ultradyne 288-296-114 hydraulic flat tappet

weind team'G' intake , 850 holley double pumper, t-bolt ign,

Imco power flow exhaust

This combo is making 485 hp at 5300, and 486 ft/lbs at 4500

I'd like to see top end around 5000-5100 rpm, this is pushing a 40' 12,000+ lb boat.
I was thinking about the bore notching, hyd. roller cam change, head work/change. I am looking to spend about $2000 total--so changing the heads is a stretch. I was thinking about whipples-- after much debate I think i'll make do with this for one more year.

Anyone have any ideas or see something that i missed

Hello, del sol,
You didn't say if your heads are GM or aftermarket. The best head I have used in this type application is Merlin OVAL PORT. They are not that expensive and your valves and hardware will work in them. Just pocket port them and check port match. You will be better off with a oval port intake as well, but the square port will work.
The hydraulic roller is a super idea and would be my first change. Be sure you have the correct valve springs and consult with a MARINE camshaft expert at the cam grinder of your choice-don't just talk to the guy who answers the phone!!
I have built several engines similar to yours and used Merlin heads with single plane intakes and hydraulic roller cams. No one ever changed the heads to ANY other type-square port, iron or aluminum of any brand on these and made as much power.
A lot of people seem to think you must have aluminum BIG ports to run, but the right size is what works best.
We run the Crane 139741 a lot-great in a motor like this!!
PM me if I can help!




11

blown1500
Thanx for the reply, I changed the head descr. as for the merlin oval ports, are the alum. or iron? and can you get them in bare heads? The other thing i've noticed is that it seems that i'm running pretty large numbers on my intake/exhaust compared to alot of people lift int. 550, exh. 575. It does give it a great sound out of those straight pipes at an idle and at throttle though

With only $2k to spend (total) on two engines. Hmm, the only thing I would be able to suggest is head porting and concentrate on the exhaust side.
Add a competition 3 angle valve job and there's $2k easily.

I agree with 1500 that the oval ports are a better selection for your cubes. If you're able to find a couple sets of ovals that are less than 300 cc's intake runners, that in my opinion, would be the way to go. Especially if you found a set with around 110cc combustion chambers. That would increase your comp ratio to around 9.5 assuming you have the stock 8.75 compression now.

By doing the above your hp wont jump by a huge amount but your torque will.

DAVE

del, with a boat weighing in at 12,000lbs you're going to need as much torque to get that 12,000 pound mass moving! First, with all due respect I would use some DUAL PLANE aluminum hi-rise intake manifolds....not an open plane intake as you already have. My cousin's 461's were bore notched, has hydraulic flat tappet 218*/226* camshafts on 110* lobe seps with a lift of only about .520", with 8.6 comp ratio, some poor and very CRUDE GM casting oval port semi open chambered heads that he had pocket ported and had 2.19"/1.85" stainless steel valves installed, 800cfm Holley carbs and DUAL PLANE aluminum hi-rise intake manifolds on it and on the dyno it made 461hp @5100rpm and 510 foot pounds of torque from 3400rpm to 4900rpm---VERY FLAT which is excellent! These were done with tubular dyno headers but he is using GIL exhausts with bone dry tailpipes. He will probably lose about 20hp or so going from the dyno headers to the GILS. This combination is STILL extremely respectable for the kind of parts he has in it!

What kind of exhaust manifolds are you running? The oval port Merlins would be a good way to go as blown1500 and Dave F have suggested OR you could send your current rectangle port heads to JimV and have him install wedges within the intake runners and really see a healthy gain. You'll have to weigh the cost differences from the Merlin oval ports with some bowl porting to the wedge mods and decide from there. I also think a hyd roller cam would be a good move as the others have suggested. Hydraulic roller cams, lifters and new springs are going to use up half of the $2000 you're willing to spend though, another $500 for the dual plane intakes. Also, you might consider a bore notch job that is worth the cheapest 30 horsepower/torque increase you'll ever see. Anyway, you won't have much $$$ left over to buy Merlin oval port heads with bowl porting and valves and springs installed or even have wedges insatalled. If you are doing some mods for next year then you're going to have to decide what mods to do this time around that will be cost effective-------believe me, it can be a very tough spot to be in when you're trying to spend your money as wisely as you can. However, there is sometimes just no way around it though. But for sure, I would switch from single plane intakes to a dual plane and do a bore notch job and if you're going to be upgrading to a supercharger in the future, you might consider having the hydraulic roller cam (the one you're going to get this time) be compatible with the super charger set-up as well. Usually this will involve keeping the cam on a 114* lobe seperation. That way when and if you do go to a super charger in the future (as you were thinking about) then you won't have to spend more $$$ money for a pair of new cams that will cost you $600. One thing I am quite sure of though is that with a 12,000 pound boat---you NEED TORQUE mon!!!

Save your money, $1000 per engine is not going to get you any noticable performance on the water with over your current setup IMO, try some 25 labbed props probably make a bigger dif altho 12000 lb maybe to much of a compromise on the mid range perf

Ursus,

Those are pretty much what my thoughts are. With a 12,000 pound boat I'm quite sure he spends most of his time cruising and he will need and benefit from a ample amount of torque in the mid RPM range. Plus, if he decides to hammer it he will see much better throttle response from the torque as well.

Del sol, dual plane intake, hyd roller cams, bore notch= TORQUE!
With these mods you'll be able to stay right around the $2000 range of your budget.

My thinking is he is already making 485 hp and has decent exhaust,intake manifold cam package,heads, the gains to be had spending only 1k will be small on the dyno and non existant on the water, $2k is what you spend on exhaust system, intake manifold, bigger valves etc getting from 415 to 475 hp and he is already there

ursus, I am talking more about Torque than I am horsepower, but he will gain Horsepower as well. Would he not especially benefit by at least installing dual plane intakes and a hydraulic roller cam? Wouldn't it shift his torque curve down to a lower, more usable RPM/cruising range? With a boat that weight (12,000lbs), I would say he probably has to cruise at about (rough guess here) 3500-4000rpm minimum to keep the boat on top of the water and from acting too sluggish (it's just a guess). Again, what I am talking about is Torque and Throttle Response---although he would see some Horsepower gains from these mods as well.

BTW, I am not trying to upstage anyone here. I also, don't want to make myself look like I don't know what I am talking about here either. It also comes down to what the guy wants to do as well, but if I am wrong (I certainly have been before) then would some of you other experienced comrad boat and engine fellers and dudes step in and tell me where I am at fault or where my theory is wrong on this please? Or is ol' ursus and I trying to split hars, or what? Thanks

Mark/KAAMA

I am not trying to upstage, trample toes or split hairs and was not questioning whether the mods you suggested would do what you said they would, they would. My thinking is out on the water it will only make a hair of difference and in a blind driving test (well maybe not blind ) you would be hard pressed to see the difference. It depends what you want I guess, my opinion was from where he is, which is 485 hp and he already has aftermkt upgraded exhaust,intake,carb and cam he was better off putting the $2k in the whipple account but thats just my opinion.