Kind of a newb to "car motors" .... my forte is small engines, powersports, motorcycles and jetskis... my big boy toy is somewhat alien to me, but i have some older generation guidance assisting me, but not marine performance mentors... so i'm hoping you guys can help me. I recently acquired a boat this past summer and with some "minor" issues since then i used this winter to learn the boat inside and out and remedy some of the things that weren't copacetic. So what started out as a re-rig with new wiring and dash panel and gauges and GPS, then turned into leaky steering rams, which also made me want to repaint the engine compartment all pretty which had me taking the engine out and seeing some rusty plugs and exhaust valves and a nasty pair of exhaust ports in the head and exhaust manifold, which made me take the head off to clean the head and lap the rust off the valves, which made me find a aluminum holley intake manifold leaking water into the motor, which made me pull the other head off for chits and giggles, strip the heads, clean and relap both heads, leaking crossover tube gaskets... i could keep going.

So these are the pictures of the engine that was sold to me with the boat. I will tell you what i was told is in it.... and then hopefully this can be either confirmed or denied, and i'm needing help on pinpointing the best gaskets for my application because i'm all cleaned and lapped and everything has been through the parts washer and air compressed clean and oils and bagged.

Told to be "basically a HP500" dynoed at 540HP... with JE flat top pistons, forged GM crank, some other beefier rods, chevy bow tie short deck block, mild porting on heads, crane cam.... that's all the information i was given verbally.

my heads are 14096188 HI-PERF
the valves look huge, they valves practically kiss when seated, are they modified oversized?
my bores measured roughly 4.6"
i can't read the block casting number well, can you? there is a bow tie logo on side. L0051107 ? can you read my picture differently?

when i first took the motor apart, it was carboned up big time! i cleaned all the pistons and heads and combustion chambers... i don't know anything about the carb.

the motor supposedly now has roughly 60 hours i would say with my useage towards the end of the summer. It ran good and smooth and pushed my boat to 70mph GPS at 5100rpm or so.

i still need to pressure check my imco powerflow manifold for leaking to see if that was my water and rust on the starboard side head middle two cylinders.

I hope and think i'm at the point of reassembling the motor... just want to ask expert opinions here if anything is screaming out to you, and if you can tell me what gasket kit and head gaskets i need. Also, i think i need to replace my alum intake manifold. what intake manifold should i get?

Thank you in advance!!
STEVE

It is not an HP500. It is an engine put together to look like an HP500.
It has some HP500 cosmetic parts.
The HP500's had roller cams.
I highly doubt it makes 540hp, more like 450-460hp.

It looks like you have a Mark IV engine block and heads with standard 2.19(maybe 2.25)/1.88 valves
You need the exact bore to get the correct head gaskets. Use Felpro Marine or Cometic head gaskets.
I have generally used Felpro gaskets for most stuff. You will need to order based on what engine parts you have.

4.6 bore?

The block oil drain mods and epoxy in the valley scream of bulldog origins .non original pistons say to me its prob pushing 550 cubic inches of displacement

As griff said its not an hp500, it does have some decent parts though.
Bowtie block
Mk4 rect port heads
Intake, rockers etc.
If the budget allows, a good Hyd roller cam could really wake it up.

And the 4 or so roller rockers with the corners ground off are clearances to fit the blue aluminum mercruiser valve covers ,have to put those back in the same spot

There are two rockers, one on each head where the corners are ground off to clear the valve cover. The valve covers originally had two layers of cork gasket plus the O-ring built into the covers. Without the two layers of cork gasket, the valve cover hits the rocker studs

I will get calipers and precisely measure my valve sizes and bore sizes in a little while and report back.

What type of cam do I currently have, and you tell me if the budget allows a hydraulic roller cam will really wake it up… How much are we talking, I am open to it. For some reason those lifters and the crane gold rockers made me think I had a hydraulic cam.

Is there anything else that I can check or take apart or identify that will better help you guys assist me? I really do thank you so much in advance for the assistance. I'm just at a crossroads of slapping it back together or getting this thing to make some horsepower and make my boat fly. My labor is free, and 5k to drop it off at a engine builder wasn't really in the cards.

Retrofit roller cam and a set of decent hydraulic roller lifters will run around 900. Maybe slightly less.

Also, you do have hydraulic lifters, just not roller ones.

If it was a 4.600 bore, with a 502 HP500 4'' crank, it would be about 532CI.

I would be taking a hard look at those old iron GM castings. They have been known to rot and leak water in the engine. I'd have them pressure checked at a machine shop at minimum before reinstalling. Looks like you got a decent amount of water in there.

Maybe its just me, but the set screw in your rocker arms, appears to be down quite a bit. How much thread did you have engaging on the rocker stud?