Stroking a 502
 

Ok need some help from the experts here thank you in advance . I am wanted to rebuild my 502 mpi I would like to build a 540 if that's the best way to go . If so need advise crank kit cam & heads I really would like to keep the efi if possible I have built a few street cars and i know the marine engine is a different animal so thats why I am here .Also I am running emi wet exhaust .Would like to achieve around 700 hp if possible Thanks again for any help

According to builders I talked to, Bob Madera for one, the stock MPI intake and EFI setup runs out of juice in the 515-525hp range. The easiest thing will be to swap to a carb, or an aftermarket self-tuning EFI, just depends on your budget.

Bob, rmbuilder, will set you up with your heads and cam. Give him a call.

Also, budget for a stouter drive setup, you'll need it. Damn, its a big financial jump from 500 to 700hp.

Thanks well starboard motor took a dump so have to do one figured with 700 hrs just do both and bump them up would be fun to run close to triple digits or over the boats 7800 lbs I was told if I was easy on the sticks drives would hold up for a while cross that in the near future I'm sure

Personally I wouldn't bother with 540's if you are keeping the stock 502MPI set-up.

Then again, a performance 502cid should ditch the 502MPI set up too.

Just my dirt floor sweeping/fixing/ and building opinion.

Oh schit, I missed the 700HP tidbit.

That will be stretching it for a 540 that most are willing to live with.

A better and probably cheaper alternative will be rebuild the 502's and get 8-71 Superchargers.

Just a dirt kicking opnion.

700 HP should be easy with 540 cubes. I am at 650 HP with a 509 and it is turn key.

Both my 540 built by riggs made 685 and 690 with ke exhaust.

First make sure the blocks are not cracked by the motor mount bolts on the block..i would sell they as long blocks and take that money and buy some dart big m blocks..stronger foundation..lets face it by the time you gut the blocks thats all you will have left is just the blocks and you will have to get rid of what you have left for pennys on the dollar..to get what you want to go 540's you may as well go tall deck and make them 700 hp 572's pump gas monsters.... just my o2..

Long time lurker here.... I agree with FIXX. Just tested a pair of 598's in a 33 Eliminator yesterday. Single dominators , Big M blocks , Brodix 2 Plus heads , 264/272 .710 net lift . 748hp @ 5400 & 739lbft @ 3900. Very mild builds with 8.5:1 compression for future blowers. They idle like a station wagon around the sandbar all day long , and rip your hands of the helm when you throttle them up. No substitute for cubic inches. Just my opinion.....

My Buddy just did some 540CI N/A engines. 9.25:1, Dart aluminum Pro 1 heads with a little cleanup, Bob Madera solid roller cam, single plane, 1050 Dominator, made around 680HP at 6000rpm. Real nice engines.

Fixx makes a good point though. By the time you get rid of everything from the rotating assemblies, heads, and MPI system, you are basically left with a bare block, an oil pan, and not much more. And youd prob want to upgrade oil pans anyway.

If you sell what you have there, you can start from scratch with a pair of Dart 10.2 tall decks, and build a really nice 572ci, that can make the power you're looking for. I'd start with the 4.5 stroke and 4.5 bore, rather than bore the new blocks to 4.560 right out of the gate. I dont think the .060 overbore is worth the power gain, even though the dart blocks can go pretty large. Its really not much more money to go from a 540 to a 572 based setup when starting from the ground up.

The only part of this dream that scares me, is the bravo's. The 33 powerplay is known to be a great rough water boat. However, big power, rough water= busted drives. To avoid breaking drives, you'll end up avoiding rough water. And at that point you just have a fast vee bottom.

Or as another option, standard rebuilds on your bottom ends. Aftermarket aluminum heads, new intakes, carbs, new cams, aftermarket aluminum exhaust manifolds, and you'll be around 600HP. You'll be adding 350HP+ to the boat, knocking off a couple hundred pounds of iron off the azz end. The GM steel crank, forged rods and pistons will be fine at 600HP level.