Cig35Mistress

Hello all, I've enjoyed reading the posts in the forums for a while and now I am looking for some advice regarding a set of motors I am building for my 1978 35' Cigarette Mistress. I removed a pair of merCruiser 454/400's that were already .030 over with rectangular port 990 heads and Holley carbs and Strip Dominator intakes, virtually stock. Here is what I am thinking about doing, and was advised to do by the machine shop, but I am interested in what you guys think.

Re-bore the blocks .060 over with new Scat 4340 Forged 4.250" stroker cranks to make 496CI, new Scat 4340 H-Beam connecting rods, Clevite HP rod and main bearings, Dura-Bond cam bearings, JE forged 14cc dome pistons, either at 9.5:1 or 10.25:1 compression, (I would like to retain the ability to run on 89 octane available at most marinas) Total Seal Classic Race rings, Melling HV oil pumps, Comp Cams Xtreme Marine cam kits, including cams, lifters, springs, retainers, locks, timing chains and gears, 254 @ .050 intake duration and 264 @ .050 exhaust duration with .575 intake lift and .578 exhaust lift, Manley Severe Duty 2.190” intake valves and 1.900” exhaust valves, Manley Chrome Moly Pro Series pushrods and Crane Gold wide body 1.7 ratio roller rockers, put together with ARP stainless bolts and Fel-Pro gaskets. As far as bolt-on items, I’d like to use Magnaflow cam-driven water pumps, Stainless Marine crossovers and thermostat housings, the original Strip Dominator intakes and Holley carbs, new wiring harnesses, one-wire alternators, high torque starters, all new heavy duty oil coolers and Russell hoses and fittings. For exhaust within my budget I am debating between Stainless Marine, Revolution Marine or maybe used true “tube” headers.

I’m still planning on running TRS outdrives with Speedmaster lowers, coupled to Borg Warner 72C transmissions. I plan to rebuild the transom assemblies, gimbals, drives and trannys as well because I don’t want to exceed my budget and move up to the Konrad’s just yet.

Let me know what you think of my proposed “build sheet,” I am open to all opinions as I am relatively new to this and these are the first set of engines I am building. According to the machine shop doing the work, with the above setup I should see about 600HP at 9.5:1 compression and 650+ at 10.25:1. Who knows though, only time will tell.

Thanks in advance for all of your help!

Harry
1978 Cigarette 35’ Mistress - “The Cigarette”
Palm City, Florida

rmbuilder

The cam is excessively big for your application as is the 10:25 compression on 89 oct pump gas. That cam will literally be impossible to live with in your set up. Is the engine builder experienced in marine applications? Following is the cam outline and spec card. (82* overlap)
HYDRAULIC- Jet w/ B impeller, 10:1 Hyd. Hyd. 3200 to 6800 11-252-4 XM298H 298 316 254 264 .575 .578 112ş
compression, river drags, Bracket Racing.
http://www.compcams.com/Technical/Se...umber=11-252-4
Bob

Bad to the bone

Great looking boat i have a 77 35 a went thru i will email you some pics.
Great boat, solid ride, need good power to 70. If you are running 89 i would
suggest keeping compression in low 9's. I have 10-1 aluminum heads 502
and have to run premium. Good luck.

phughes69

Nice boat Harry. I too have a speedmaster II on my boat and wanted to know what size props you have on it?

Thanks
Pat

CMS Racing

I would agree with to old step up and put a bettr roating assy. like a calies or crowler, lunati. the cam is a bit to big need around 236. int and 242. exh at .050with .580 to .600 lift on .112 food for thought

Cig35Mistress

Thanks for the advice guys, keep it coming as I am all ears! Anyone have any ideas for a cam kit that would work better? I haven't had a chance yet to look on Comp's website . . . this machine shop has built many marine motors and that was the cam kit he recommended, and he also said that the 10.25:1 compression wouldn't be too high because I was pushing the boat with two motors. Like I said, I am novice at all of this, and I want to do it right!

Thanks for the comments on the boat, it has been my lifelong goal to restore an original Aronow built Mistress and I finally got my chance. The hull was sprayed Memorial day with super jet black Awlgrip and an Awlgrip vivid red bootstripe. I'll be painting the bottom white and adding all of the graphics as on Aronow's original 32' "The Cigarette." I think it will give the boat a nice, classy, retro profile!

Hope to hear from all of you in the future!

Har

cuda

I wouldn't run so high of compression. It won't run long on 89 with 10.25. Remember, a boat is always running uphill.

PatriYacht

If you're using GM iron heads, keep the comp. down to about 9.25. Flat top pistons should put you there. The biggest cam I would even think of running would be a Crane 741. On a 496 it would put your power peak up in the high 5000 rpm range. 575-600 hp is possible. If you want 650, you'll need some good ported heads.

MESABALANCING

I completely agree with RMBUILDER it seems marine engine experience may not be present We tried years ago running that piston with 10.5:1 in the old 400s when I worked at Custom Engine Service and I can tell you everyone we did with iron heads came back with burned pistons because they will not run on 89 oct for any extended period of time specially with those cams he's proposing.If you'd like I can give you some specs of 496 combos I've built and are currently running with 150 hrs that the customer has changed the oil 5 times and has not touched a single bolt on the engine apart from that. These engines made 650 hp and 620 ft lbs of torque. Please fell free to call any time and I'll give you some specs Sincerely Laz Mesa

deboatmon

Nice boat. Been there, done that. I think the best bang for the buck is to find a 502EFI pullout from a performance shop and just drop it in. Add decent exhaust, maybe roller rockers, Inconel valves and you will have substantially more torque for your older, heavier boat. The added torque and cubes will offer lower cruising RPM and the EFI's have proven reliability. You also have a great platform to upgrade with. And, you'll most likely save money over what you're contemplating. Even left stock, it's a great package.

Good luck.