FIXX

iTrader: (2)

single plane dart works the best..yes on the 6.385 rod length,,you also have to internally balance the engine and use a zero balance flywheel and harmonic balancer..a 396 of 427 balancer will work fine,,you not going to the moon with the engine..10 qt oil pan and a 3x 21 oil cooler ..keep a eye out for a -2 inco shorty and keep the 1.50 ratio,,soat will accelerate faster..you need to talk to bob mandara about a cam 585-654-8583...

tpabayflyer

Thanks Mr. Fixx.... I decided to keep the factory forged 454 crank as it looks new and will get some 6.385 rods and matching pistons... 460 cubes vs. 489 is maybe 30 HP so I will save the money on a new crank and get a closed cooling kit...


I see no problem getting a reliable 520HP from this combo and this is 100HP more than the factory 502/415HP so it should run pretty good! It would have been nice to get some input from people on what there combos are? Is everything a big secret? Am I on the wrong forum? There is plenty of info on the net and dyno tests but these are mostly automotive applications.

I will post my results when I get this motor done next month and think i will get it on a dyno to dial it in..... stay tuned! TBF

f_inscreenname

Not saying its 600hp but ....

1987, MIE/340 (7.4) 454 4 bolt main Big Block
Dip it and hone the decks and cylinders cut .060 over
Block was detailed with all casting debris removed
Scat 9000 Crank 4.25, 496 stroker
Scat 26385P - 6.385 in. Connecting Rods - Bushed -I Beam Forged 4340 steel
Howards Cams 120255 - Max Torque Retrofit Hydraulic Roller Camshafts, Hydraulic Roller Tappet, Advertised Duration 288/294, Lift .585/.610, 112 L/S
Howards Matching Valve Springs 98636 - 130# / 330#
Cloyes Gear 9-203 - Cloyes Wear Plate, 031 in. Thick,
Maxspeeding Hydraulic Retrofit Roller Lifters
Probe 496 Dome Top +18.0cc - SRS Piston Set
Clevite 77 Cam Bearings
Federal-Mogal 4400 M20 Main Bearings
King Engine Rod Bearings CR849HP
Cloyes true double roller timing chain
Mahle - Plasma Moly Coated piston rings
Melling 10778C (Anti-Cavitation) oil pump
Melling HV oil pump shaft.
New Harmonic Balancer
Rotating Assembly Fully Balanced
Comp Cams High-Tech pushrods #7954
Completely refreshed Chevy Heads 14096188 / 454 Open / 118cc / 3angle valve
APR head bolt sets
ARP 1.90 rocker studs
Norris S/S 1.7 roller rockers
Seal Power Gasket set
EDELBROCK BBC R2 AIRGAP INTAKE
Pro Comp 2752 Fuel Pump
Pro Comp Ignition
Pro Comp distributor
Super Stock coil
8mm Accel Hi performance wires
New single wire alternator
Mini (gear reduction and fully marine) starter
Edelbrock 800 carburetor
12" aluminum, oval air cleaner (with K&N filter)
Brass freeze plugs
Stainless steel bolt set
4” Stainless steel risers
496 MerCruiser exhaust manifolds with Tall Risers
Sherwood motor mounted raw water pump

tpabayflyer

Thanks a bunch effin! That cam sounds like a perfect match! Is this motor done yet? It would be great to know how much max rpm you run at...... That sounds like a very well thought out combo!!!! TBF

f_inscreenname

The motor has been done for a couple years now. She is a beast but I don't think my numbers with match anything you all have.
19' / 1972 Allmand SuperNova. 496 mark IV roller motor, Volvo 270 (with trim) 1.61 ratio drive, 23P Solas prop. 5100rpm's @ WOT.

tnc110

tpabayflyer...be sure to post up what you end up doing and your results! I have a 25zx w 454 mag and would love to see what you come up w.

BTW...love the Tampa area...especially bradenton/sarasota...been there a couple times w the Donzi...great times...would love to see your boat next time we come down (prob March)

MILD THUNDER

iTrader: (3)

No reason you cant make good power with that build, even if its a 460''. Dart 310 Pro 1 marine heads, 9.5-10:1 compression, healthy hyd roller cam with decent amount of lift, single plane dart or Proffesional Products hurricane intake (cheaper), 950HP carb.

You'll get tons of guys telling you a 750 carb is enough for a 454. Engine masters just did a small block 500HP engine. They tried a 650,750, and 950 carb on it. Each time they upped the carb size, the engine made more power, throughout the power band. That was on a 500HP engine.

I'd do a 950CFM 4150 style. Then when you wanna build the stroker, youre carb will support that too.

http://www.allcarbs.com/tech.php?art=5

tpabayflyer

Making progress on my build and gathering parts..... I decided to stay with the stock stroke 4" crank as my forged original unit checked out perfectly..... Going to go with the probe 2618 pistons and H-beam 6.385 rods.......... Definitely gong wit a hyd rolled cam either the crane 139011 cam or the Howard's cam from effins build above. Looks like the Howard's deal is quite a bit cheaper than crane with the cams being identical for the most part so I am leaning in that direction............

Heads.... I have done a ton of research and know all about the problems but I did get a pair of the pro-comp heads. 454 units wit 320 intakes and 115cc chambers..... I had to get adjustable guide plates to get the rocker alignment good and I had to finish the valve job in the chambers..... All the valve Seats have a sharp edge or ridge protruding right into the chamber that is sure to create a hot spot and also excessive heat buildup.... Definitely a factor in the rash of exhaust seats that have fallen out of these heads. I have blended the sharp point into the seats and I am not using excessive spring pressure so these units should live with my combo. I realize these heads are really not suitable for a more race oriented build and these lightweight castings have had issues with pulling rocker studs out with big cams using stiff springs......

Block is being bored .030 over and .005 deck..... Should give me right at 10-1 compression with the probe 13731 pistons. With aluminum heads, intake,exhaust, I should be ok with that much compression.......
Edelbrock air gap rectangle heads with mighty demon 850 carb.
Looking to prop this combo for max rpm of 5,500..... Hoping to get 70MPH out of this 26 ft Donzi! I am also going to get the engine put on a dyno and tuned.... I think this is crucial and don't want to fool with a wide band and changing jets on the boat.... I don't need to blow myself up! I hope to get this engine done by the end of the month..... TBF

MILD THUNDER

iTrader: (3)

Sounds like fun.

Something to consider about dyno vs boat tuning. Many times a engine has been dynoed, and tuned on the dyno. Then installed in the boat, and engine burned up because of a lean spot at cruise that wasn't found on the dyno pulls. Most dyno shops will warm the engine, and do some full throttle pulls, and give you a piece of paper. The tune can sometimes vary quite a bit from the dyno to the boat.

At 3500RPM on the dyno, the throttle blades were wide open, and so were the powervalve/s. In the boat, at 3000 or 3500RPM, the throttle blades are partially open. Depending on how your propped possibly even just the primarys open.

I guess what Im saying is, once installed in the boat, Id double check the plug readings at different RPM increments. The dyno tune isn't always the end all setup.

tpabayflyer

Thanks for the great advice! I did not think of that but I am sure I will spend most of my time cruising in the 3,500-4000rpm range.... I will have to see if the dyno can simulate a part throttle, cruising scenario?? I am thinking about as much rpm you can use without dipping into the secondaries for some attempt at an economical cruise speed.... I do have a plate with the fitting for a wide band LM-1 but it is for a regular style, wet exhaust... I am going to be using the dry joint style from a 496HO so I wold need to figure out a plan B for using the LM-1..... I am a big fan of tuning and getting everything spot on.......... TBF