First off hello everyone Im Nick and im new to this forum. Im from Western PA and i play with old parts to see what i can get out of them.(yes because im cheap)I have a bunch of stuff laying around the garage i want to put together and drop in my jet boat. Boat is a 72 16' sidewinder currently powered by a 355ci chevy. Fastest ive gotten out of it is 60.3mph. I have a low hour Mercruiser 454 that has stock peanut port heads and stock flat tap hyd. cam. It is a 1 piece rear main motor not sure of year).I have indmar aluminum manifolds into thru hull exhaust. I plan on using 781 heads i have already. Stock flat top pistons( should be a whopping 8:1 static comp ratio). The question is can i use the roller cam setup out of my 502 in the 454 for any valuable gain. Has anybody done this with good results or should i just leave the flat tappet cam in the motor. Thanks in advance

The cam and head swap combined should give decent gains.

I hope. Its a significantly bigger cam from the specs that i found on the internet. (.480 vs .580 with a 1.7 rocker). I couldnt find a journal size for both cams tho and i didnt want to tear into that 502 that far if the cam journals were a differant size and i couldnt use it. I have to have the heads decked to clean the gasket faces up but i dont think thats going to make a huge compression gain at .020". Ill cc the heads when they come back and hopefully this combo runs good. Then again the boat weighs around 600lbs bare so how bad could it run with a 454 in it👍🏻

are these both gen 5 or gen 6 ???
or 454 mark4????

1 pc rear main so I would assume 5/6.

So it’s not a stock 502 mag camshaft?

Honestly im not sure about the 502 cam. That motor is mid 90s. Single piece rear. I know its a roller because ive physically seen the lifters but as far as stock im not sure. I will check it with a dial indicator before i use it to verify but i wanted to make sure it would even work before i dig it out of the corner to rip it apart. Everything else in that boat was bone stock. It came out of a 34' baja boss. I will eventually build it but it needs a sleeve. The 454 is a reman merc motor. Was labeled 330 hp. I think gen 5.

I also have the rectangle port heads off that 502 i could use but i didnt rip it that far apart to see what casting they are. If i use the roller cam i will maybe try to use the springs at least out of the 502 heads if not the whole heads.

Why not just use the complete 502????
The stock 502 mag mpi roller cam is, I think, .483 lift. The stock 502 carb flat tappet cam is .510 lift

The 502 needs a sleeve in the block and gone thru. I have a 496 for my VIP and eventually i wanted to build that 502 with a blower on it. The 454 i have laying around. Just want to put it together with the best parts combo i have.