Just use this as an example if you will. But IMO if you are scrambling for a "low budget operational criteria". Then performance boating should not be your criteria. Just don't want you wasting money for having to run better fuel (mill/ higher cr). Or having a non healthy combination of parts. Once you get more flow then other things should be upgraded as well. I'm still running the 781's. And here's my combo.
Stock bore 454 (original) 2- bolt main
781 Bigger valves (2.25/1.88) fully ported/. Bowls blended, milled 10:1
850 Holley
Team G intake port matched to heads
.700" lift solid roller
Stud girdle Etc. etc. Fully Forged short block. ( currently machining for 4-bolt mains during stroker rebuild)
In the end the 781's can make good power but at your level. And mine runs low 70's with this setup. Don't touch em and enjoy your boating season. Other guy that have posted speak the truth. And they have lost more money then I could Imagine trying different things. There's not many on here that don't know what's already been stated. Good luck and curious your final decision on which you choose.

I would change the came, run a 750-800 carb....

I guess no one asked the OP is the motor in need of a fresh top end anyway, or is a performance gain the only reason to take apart the stock 330

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I use lots of 781 and 049 heads for mild street and marine builds. This sheet is a pump gas 496" engine. 4.310" bore.

Here's what I do for our 625hp 625 # TQ package.

1/2" bronze guides core drilled referencing off the original press-in guide.
1.812" alloy exhaust seats.
11/32" stem, stainless intake valve, 2.125" head diameter. (We have this valve custom made, don't go looking in Summit for it).
3/8" exhaust valve, 1.75" diameter, stainless.
4 angle intake seat, cut for larger valve, Intake runner porting, slight matching to std. gasket. It's around a $300 port job.
3 angle radius exhaust seat profiles, slight blending on seat short turn.
Dual or beehive springs, conducive to the cam grind.
spring locators
Seal bosses cut true for positive seal
Resurface head for MLS gasket, 20ra finish.
Heads are pressure tested after machining for seat insert, before installation.
Heads are pressure/heat sealed with Seal-All before final assembly. This is to stop any leaks from porosity and prevent corrosion.


Keep it simple. Don't get carried away with ports that are too big and lazy. Continued cylinder filling ABDC is paramount to good torque and HP. You need a port that can fill when the piston is moving it's fastest, (70-80° ATDC) and will continue to fill ABDC. This is where air speed is critical. Do the simple math on a port size and the engine they will be on at specific rpm points. Use this to determine port size, not advertisements.

We have made over 700 hp with this same head set up on 505" engines. Don't buy into the big intake and exhaust valves on these heads, it's just not required.

Disregard that other sheet, I don't know how to get rid of it.

Ronnie, what are the approximate cam specs on the 625 HP engine?

Yes the top end needs to be freshened otherwise i would not be screwing with it.
Simpley put i am tryimg to maximize my return on the money i need to spend for required repairs.
Thank you for asking.
.

So, this is what you are suggesting for the OP (who is not interested in changing cam or etc) ?

If yes, how much to do it ?

What gains or plus's will he get for the $$$ ?

Unless one of the stock heads are cracked, your best ROI is to fix what you have. Any other heads you will buy will need to be gone through, and if you aren't building an entire package, you aren't going to get any noticeable seat-of-the-pants gains.

.650"/.650" 252°/256° on a 110° or 112° Lobe sep. Hydraulic roller, pro series Morel lifter.

Honestly, a cylinder head set up like this benifet a greatly from higher compression (than stock) and a cam to compliment it. We have used 781 heads, with stock valve sizes and no porting and made 580+ hp with just 10.25:1 pistons and a generic Erson hydraulic flat tappet cam.

Would I put a fully reworked set of heads on a stone stock motor? Probably not worth the expense. Spending the money on pistons and a cam would net bigger results.