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Upgrading Engine Ideas

Old 08-10-2008, 06:57 AM
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We currently have a 2000 Checkmate 259 Convincor. We purchased the boat new in 2002. The engine (454MAG MPI) and drive (B1) have 275 hours. The boat had an engine upgrade kit installed at about 215 hours.(cam, exhaust, valvetrain upgrade). The engine was dynoed after upgrade at 461HP (5100RPM) and 514lbs/tq (3800RPM). Recently the engine lost power and a compression test was performed. Here are the numbers by cylinder: 1-150,2-150, 3-130, 4-100, 5-110, 6-85, 7-170, 8-85. Any thoughts on what could be wrong? Anyway I am using this problem as an opportunity to upgrade our power. I would like to stay NA and go to a carb motor. Should we try and salvage the motor we have or go to a larger displacment motor? 600HP is the goal number. The boat has full hydraulic steering and HP tabs. The engine must be user friendly as this is a family boat. Wife needs to be able to drive it. The boat will be used for cruising, some water sports and an occasional WOT run. The project budget is 15K.
Thanks in advance,
Rob
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Old 08-10-2008, 07:08 AM
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I would say your headgaskets are toast. Sounds like you did the exaust and cam already. I would pull the heads and see what you have then get them to Jim Velako for a port job. Upgrade your head gaskets to atleast felpros.

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Old 08-10-2008, 08:19 AM
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Before you take anything apart, run a leakdown test. That will help identify where your problem really lies. Then put a dial indicator on all the rockers and see if you may have lost a cam lobe or two.

600 horse is going to be next to impossible to get out of a NA 454 that will still run on 93 octane- and it still won't be terribly wife-friendly. 600 out of a 502 is still fairly warm and the cam you'll need to do it is going to necessitate new exhaust that will be resistant to reversion.

Keep in mind, your standard Bravo isn't going to like 600 hp. Not at all.
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Old 08-10-2008, 08:38 AM
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Originally Posted by Chris Sunkin
Before you take anything apart, run a leakdown test. That will help identify where your problem really lies. Then put a dial indicator on all the rockers and see if you may have lost a cam lobe or two.

600 horse is going to be next to impossible to get out of a NA 454 that will still run on 93 octane- and it still won't be terribly wife-friendly. 600 out of a 502 is still fairly warm and the cam you'll need to do it is going to necessitate new exhaust that will be resistant to reversion.

Keep in mind, your standard Bravo isn't going to like 600 hp. Not at all.
Well put.. To avoid reversion and that wild cam you should just go w/ a 502 block and then stroke it to a 540. I just seen a couple 540 make well over 600 n/a.
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Old 08-10-2008, 09:05 AM
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We are building a 502 complete with aluminum heads,hydraulic roller cam,world intake,holley hp carb,mostly new parts,will have it on dyno soon should be around 600 hp,motor will be ready to bolt in ,complete with sm exhaust.Much better than working with your 454 and well within your budget,if interested dave 410-956-5381
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Old 08-10-2008, 10:03 AM
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The lowest # being #6 makes me think your motor had a lean spot somewhere and I would suspect your valves got hot and tulliped or pistons burn't/head gaskets burn't. Being it lasted 60 hours before doing it I would suspect maybe your fuel pressure was a little low recently or you got some gas that had a ton of alchohol in it or less octane then what it was advertised to have had. I like 502's and 540's but you could put a stroker crank in your 454 and build a 496 that would make 550-575 hp fairly easy. The real thing is weather you get aftermarket heads or not,wags 382 built some carbed 502's w/afr heads that made in the 575 range if I remember correctly and still had fairly small cams with excellent idle and tq,Smitty
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Old 08-10-2008, 10:14 AM
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just had mine done over the winter, same boat except 502 mpi. world steel heads ,cam, stainless marine exhaust, cool fuel system, ecm remap. retained the stock injection and dynoed out at 552 hp w/ 620 fp of torque. boat gained about 10 mph on top with nice accel and mid. can run about 74-76 mph top. next move is external steering and some k planes. your hull is only designed to go so fast, so keep that in mind.
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Old 08-10-2008, 10:30 AM
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To get 600 out of a 502, you'll need a good set of aluminum heads and a cam right around the Crane 741 spec. Plus compression pushing close to 10:1. Tube headers wouldn't be necessary but the only manifolds that will support that power would be the Eickerts or the SM's.
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Old 08-10-2008, 11:21 AM
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Originally Posted by JRider
I would pull the heads and see what you have then get them to Jim Valako for a port job. Upgrade your head gaskets to atleast felpros.
As others have stated getting 600HP out of a naturally aspirated 454 is going to be tough. I just redid my 454's and I got 590HP with solid roller cams, Jim Valako ported steel Merlin heads, 9.6:1 compression, Holley 750 carbs, Jim V ported my Wieand Stealth dual plane intakes and on 93 octane.

With your budget of $15K I would stroke to a 496, and Call Jim V about what heads and cam combo you want with how much power. He can order the heads and port them for you and send them to you. I know he has a recipe for a mild 496 that is in the 600+hp range.
JimV (616) 889-0928 you will be well under your budget of 15K
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Old 08-10-2008, 12:58 PM
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Originally Posted by RJBBC
The engine (454MAG MPI) and drive (B1) have 275 hours. The boat had an engine upgrade kit installed at about 215 hours.(cam, exhaust, valvetrain upgrade). The engine was dynoed after upgrade at 461HP (5100RPM) and 514lbs/tq (3800RPM). Rob
Those are about the exact same dyno numbers as my cousin's 461cid engines modified from the Merc 330's----461hp @5100rpm and 510lbs of torque @3600-3800rpm. Flat tappet hydraulic cams, 8.6 cr, oval port GM old (semi-open chamber) truck heads with larger valves installed and bowl/pocket ported by JimV with dual plane intakes and Holley 800carb. Jim also did a "bore notch" job on the cylinders which is supposed to be good for about 30hp/tq or so.

I am curious as to what kind/brand of exhaust system you now have on your engine...???

I once owned a pair of 468cid engines in my boat that back in 1994 supposedly made about 620hp @5500-5700rpm with tubular dyno headers on someone's dyno in Chicago....Merlin oval port heads, 2.30" intake valves, bowl/pocket ported, mechanical/solid roller cams 248*/254* @.050" lift on 110* lobes, 9.5cr, Dart single plane intakes, Holley 850cfm carbs. I honestly don't know if those HP figures from the dyno are with all belts, water pumps and pullies, etc or not---but I kinda doubt it.

Those were some pretty respectable numbers back in 1994, but the guy who owned my boat before me with those engines was ALWAYS changing out new valves springs, and lifters about evey 50 hours or so, but it was a maintenance nightmare. So, 600hp out of a naturally aspirated 454 can be done, but it isn't going to be user friendly. You'd get there a whole lot easier if you added a superchager to your engine. Just make sure the rest of your engine (cam profile, comp ratio, etc,) is compatible with the use of a supercharger....and you'd still be way under $15k!

FYI, I know of a friend who had just built a pair of really mild 509's with B&M 420 Mega blowers, hydraulic FLAT TAPPET cams, bowl/pocket ported GM rectangle port cast iron heads that made about 665hp @5600-5700rpm with 4-4.5lbs of boost on Wesseldyk's dyno with all belts, pullies, pumps, assesories, etc.
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