502 roller cam in 454. Worth doing if doable?
 

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.

Never heard of a 580 lift cam in any production 502 lV-Vll. If it's the 480/483 lift cam I'd think twice about it. So you mentioned dial indicating is a must. Any idea of hours on lifters. I realize it's a budget build but.... I can't remember if the gen V had lobe for mechanical fuel pump. I didn't think they did but possibly back on the gen Vl. Also not certain timing set/retainer plate come into play or not.

im not sure of the lift numbers those were just something i found on the internet. I opened the motor up last night. I think im gonna just have to bite the bullet and buy a cam. The 502 has the spring retainer plate in it like you said and the 454 does not have the bolt boss for it. I did run the block number its a mkv 454. Plus side is the heads off that 502. They are 088 heads that appear to be in good shape. Im gonna send them to get magged for cracks and run them. Since im buying a cam now anyway may as well just do the dome pistons and valve springs while im into it. I already have a rectangle port intake so that saves me a little. I guess a thousand bucks is still a good budget for a big block. Should make good power to. Anybody have any thoughts on a good cam for a .040 over 454 with 9.5-9.75:1 compression. 2.25intake valves / 1.88 exhaust

Are you going to change the impeller with the upgraded motor?

We ll see how it runs first

They guy i bought the boat off of years ago told me it was an AB impeller but ive never had a reason to take it apart so this may be it if the rpms are to high. I may try a differant inducer plate if its close but well see i guess. Thank you everyone for all the responses. Good to be in good company of knowledgable people.

Crane 168731. 226/236, 288/298, .587"/.610", 112*

Thanks ill check into that

Decent option and may find a good used one if you put in wanted section. Plenty of them around on shelves I’d imagine. Lots of choices just wouldn’t go any more lift and duration for your CI/build. jmo.

One piece rear main seal and a flat tappet cam would make it a gen 5 454. Only way to easily use a roller cam in a non roller block is to use aftermarket lifters with the tie bar.