Hey Guys,
I am looking to start a project on an 87 2 bolt main Mark IV 454 330 to eventually replace the old Merc 260 in my Sea Ray ( I know I will have to swap to a bravo plate and drive). The block is completely dis-assembled and everything needs to be replaced. I'd like to re-use the 049 heads I have but they will need work. I'd like to settle on a direction to go with the project so I can start collecting parts. Obviously money is a concern but I will be doing this over time to help absorb the cost.

The objective is to build an engine with similar or better performance to a Stock Merc 502, that runs on 87 octane and stays in the normal RPM range (under 5k). Reliability is also important. My boat is heavy so torque is key, currently I have to run it to 3500 RPM's to maintain a plane, which gives me 28 - 30 mph on GPS. I'd like to get that down to 2500 -2800 with the same speed. Others have used a BB with those kind of results.

I have been reading this site and have lots of ideas but need to decide on a definitive plan to move forward.

Option 1 is to bore the block and stroke it to a 496 with all forged parts, have the cam done by bob (RMbuilder), have the 2.25 and 1.88 SS valves put into the 049 heads, use an edelbrock performer intake (not the RPM air Gap because of the raised power band of the RPM Range), and a holley or edelbrock 750 cfm marine carb with GIL exhaust thru hull. Questions on this setup are, what are the negative effects of a stroker kit? Will I have rev it higher to see the torque I need? What compression/piston setup should I be looking at for what I want to do?

Option 2 is to go the "330 on roids" setup .30 over with all forged components, maybe a different piston choice compression wise so that it that won't knock on 87 petro, stock stroke, edelbrock performer intake (to lower powerband RPMs), cam by Bob, GIL exhaust thru hull, 2.25 1.88 SS valves in my 049 heads, and holley or edelbrock 750 cfm marine carb. Will this setup give me the low and midrage torque that Im looking for or will the torque curve be on the high end of the RPM range? What pistons would you recommend?

Is there a better option ?

Sorry for the book, I appreciate your help!

Thanks,
Billy

I can appeciate what your going through and I think your on the right track. If you search all the thread and post I'm sure you'll make a good choice. If you plan to keep the compression down then I would look a little more seriously at your option 1. The bigger the cubic inch the more torque you'll have. You can cerainly get good power out of a 454/468 however you will need to get the compression up near the 9.5 - 1. With that said you should always try to run a premium grade.

If you do stroke it be sure and get a good quality rotating assm. You'll more than likely be fine with the 2 bolt mains with the torque and HP your going after 525 - 550 ?

Good luck.

John

Thanks for the reply John. I am pretty sure I am going to go with stroking and boring to a 496. I have been searching the threads here for a couple of months, which is one reason I even have these two options, as I'm a newbee to big engines

From what I can tell the "330 on roids" would be best served with higher RPM's and higher compression and that's not my goal.

The 496 with the Large Oval's seem to be a big torque engine which should fit my needs well. I just need to figure out the compression I should go after to be able to stay with normal gas and if this will be a reliable engine that I can count on for a lot of hours.

Don't really have a HP goal, as I consider it a byproduct of torque. I think my SB is putting out about 350 lb/ft at its peak, which is about 3500-3800 RPM's. If I can get 550 lb/ft peak, with 350 lb/ft around 2500 RPM's then I will be a happy camper. The SB's torque just kicks in way to late on the RPM scale.

Anyone know if this forged rotating assembly is any good? Looks like its made with Wheeler Forged Components. I think the 049's are 119cc, so if I go with flat top pistons the comp ratio will be 8:6:1, or if I decide to go Domed, its 10:1:1 which would require premium grade gas. Choices choices......

http://cgi.ebay.com/ebaymotors/BBC-4...Q5fCarQ5fParts

With what you are trying to obtain I certainly think you going in the right direction. A 496 with 9 to 1 would be my choice and plenty safe with marina gas. Just guessing however you may have to deck your heads .020 or see what felpro offers in a thin head gasket. Having your heads surfaced/decked is a good idea anyway to assure a true surface. Your 496 should be as reliable as other well built engine engine. A while back I searched out several stroker assm. and it was unbelievable as to how many were out there. Just be sure and stick with the 4340 forged. There are some better cranks available from your well known manufactures however there can get pretty pricey. Your heads will work fine with 2.19/1.88. Airgap intake. I am not real familiar with wheeler but it's more than likely the same as the others in that same price range. You can also look at Adperformance.com. A good cam choice would be a crane 731 or call rmbuilder to suit your specific needs as well as being taylored to your components.