Need input on 496 stroker buildup.......
 

I have been a lurker on the board here many years and have a 26 ft cruiser. I just got a Donzi 26ZX with no engine and have a 1995 454 mag carb engine for repowering...........

Engine has no top end but all accessories. 4 bolt block with Forged crank, dimple rods with 7 1/16 bolts and forged pistons as well. All stock and original and the crank looks perfect. Motor has been sitting many years and had a few pistons with light rust around the rings but some PB blaster and light tapping freed them up easily. I am thinking about getting a scat 4.250 crank assembly and the block should easily clean up with a .030 overbore for a 489 stroker. Motor has a real big oil/pwr steering cooler at least a foot long. I am leaning towards getting larger oil lines and nice, high flow connectors as well with a HV oil pump as well.

I would like to see about 550-600HP and over 70MPH.....

I am planning on getting some Aluminum heads around 300/310 Intake port volume and also getting a closed cooling kit as well as there is a ton of room for it. I am on Tampa Bay so this is a salt water deal all the time. Motor is a flat tappet cam so how big can i go without problems with reversion? Thinking about .550 lift range with about 240 duration @ .050 max? Retrofit roller conversion is pricey.... Single or dual plane intake? I am thinking RPM airgap running about 5,200 max? What is a good carb to use? Around 800CFM sound right? Qhick fuel? Holley marine carbs? I do have an LM-1 and will get a jetting kit as well so tuning will be spot on!

I like the EMI exhaust as well to connect to the thru hull pipes...... I am new to performance boating but have many years hotrodding cars .......

I am not going to try and re-invent the wheel here so I want to get info on what are good, proven, and reliable combos for a 600HP carbed 496 stroker..... I want to do this right! Thanks in advance!!!!! TBF

I would love to see what the experts have to say on this thread, I might be in these stage in soon...

8-71 blower to get 600 hp out of a 454....

Well, maybe 600HP is a little wishful thinking but this will be a 496 motor with good heads that I will probably do a bit of grinding on. With a decent cam and a good exhaust as well should at least be good for 1 HP per cubic inch and then some! It would be great to hear some different combos with single plane vs. dual plane intakes? I have questions about finding an economical or somewhat economical cruising speed where you can cruise on just the primaries only? what RPM and speed? If I could cruise at 50MPH at less than 20GPH that would be awesome.... I want to see if anybody has a closed cooling system as well if i go with aluminum heads I don't want to run sea water through them.....

Laz @ Mesa Balancing offer me to turn my 330's into reliable 496 strokers with reliable solid 600 hp's .
Wishful thinking?

Sorry i cant comment on this trend even tho i have built many 496 stroker engines that put out over 600 hp..Some people on here take it as me bashing their trend but realistically its only me making truthful comments..
Good luck on your build..

P.S. all i will say is make sure the coolent passaged in the block are not all coroaded and fust is not flaking off the coolent passages..4.250 crank and rod combo is just a little hard on the cylinder walls and need as much iron as possible..

I agree completely! Many 500" big block mopars making 600HP plus easily... takes good heads and good parts combo....... I am sure there are a few guys here that can chime in with their combos..... lets see em!! Anybody have any preference for the eagle over the scat rotating assemblies? I used a set of the scat H-beam rods on my 7.4 build in my wellcraft and they were plenty beefy looking..... How much compression can I use with Aluminum heads and be reliable and detonation free? 10-1 about the max????

Thanks... It seems that the slightly longer rod 6.385 tends to reduce the sideloading compared to the standard length 6.135 rod? As far as rust and scaling... yes there is some issues with the block I have. I plan on getting this block sonic tested just to be on the safe side.... My last 7.4 engine I built had the same issues and it checked out good... it is only around 400HP but it is holding up great. These marine 454 blocks are thick!

lets say a 315 afr cylinder head and a 10.1 compression,,with the heads being alunimum it like having a 9.0 compression engine..because the alunimum heads disapate the heat so fast you can get away with it at lower coolent temps..

Thanks Mr.Fixx... Obviously you have some experience here so please feel free to chime in anytime!!! Do you have good luck with single plane intakes or dual planes? I have no idea what kind of rpm I will end up with and I did not get the prop pitch, but it is a stock 502 bravo 1.... 3 blade.... I am thinking I will not spend a lot of time over 5,000 rpm and the dual plane might be a better choice for me........ C'mon guys.... Let's see those combos.....

fixx
 

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...

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

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

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

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.

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)

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

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

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.

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

Project moving forward as a 502 now as the original 454 block was no good..... Still using probe 10.2-1 pistons with 6.385 rods.
Going to get a dyno tune as well and tune for part throttle with the primaries open all the way before secondaries open..... I want to get an economical cruise speed on just the primaries only..... Did I just say economical?

Check out the following dyno tests of various big block combos...... Looks like a 600HP engine is not that hard to build? These use headers of course but I am shooting for 550-575HP...... Also look at the 496 with the air gap intake and the bigger motor with the single plane...... Looks like the air gap is the one to use for an NA 500 cube or less motor.....Smaller motor made more power but used the good AFR heads...... I will definitely post my results and maybe a video if I can figure it out.




http://www.chevyhiperformance.com/te...k/viewall.html




TBF

Ok, a month later and I got stalled a bit on the project but moving forward now...... Everything back from the maching shop and putting it all together hs week. 502 Marne block bored .030 over so it's a 509. Probe forged mid dome pistons 10.25-1 compression wit aluminum heads. Pro-comp heads needed work but they look like they will make power. They say 320cc but they look bigger.... Some say 335.... I gasket matched the piss out of them pretty deep so they have to be bigger than 320, I did not want to go larger but had to as I Mach the big fel -pro gasket to the heads and air gap intake. Cleaned up the short side with a nice radius and blow blended all ports. Minor porting and I did not touch the guide bosses as I have heard the horror stories about the springs crushing the top of the ports so I left as much meat as possible to keep the strength. These heads are very light and I would not use them for a real high horsepower application and think I am on the edge with these....... Cam is from marine Kinetics and .610/.595 lift 228. @ .050 duration.... 4/7 and 2/3 cam lobe swap same as GM LS motors....... Supposed to even out the firing pulses and put less stress on the crank and main bearings and mainweb area..... Comp cams roller rockers and morel roller lifters........ Trend custom length pushrods....Exhaust is ceramic coated in and out aluminum merc 496 HO with stainless risers to Corsa 4" captain call exhaust to 4" pipes with no mufflers........ Carb is 850 mighty demon wt a 1" open plenum spacer for a little more volume. I think I have done my homework and have a well thought out combo for this 26ZX..... Thanks to all who have helped by posting their info to help people like me not have to re-invent the wheel....... I am going to. Use a 26P 4 blade PBravo prop initially to see where I stand and get a drive shower as well...... any more comments and suggestions please keep them coming!! TBF

I'm in the processes of building a 496 as we speak to. And mild thunder ha helped me out a ton. He put together a pretty good build sheet.

fixx
 

oh boy now 2 granades..let me know when to duck....:party-smiley-004:

"Fixx" are u saying that these builds are a ticking time bomb can u give me some incite then. Please

I think not!!!! I got a huge oil cooler and HV oil pump with big lines! Mild duration cam with forged pistons/crank and H-beam rods...... Nobody pulling the pin on a grenade here!!! TBF

Many people on this website are very tight lipped about their engine build combos and I dont understand it? Big secret? This is not rocket science by any means..... To be critical and not offer any specifics to back up and support the supposed argument kind of weakens the credibility of certain people...... I started this thread asking for help in building an engine combo..... If you don't care to add to the discussion in a constructive way then just don't....... OK? If I want some extra drama in my life I will call my ex-wife.... WTF over?

I'm not trying to start any drama, I'm just wanting to learn as much as I can that's why I asked.

I think we are on the same page here Boss..... My comment was not directed at you..... TBF

I hope to have this engine on the dyno by the beginning of July..... Going to use my wet exhaust for as close to actual conditions to try and get the tune accurate...... Stay tuned!! TBF

I am still working on my project.....got stalled a bit as I was in Miami almost all of July getting some training. I am an out of work Airline Pilot and between getting another type rating and job fairs and moving, I have been busy to say the least. I should have the engine at the dyno by the end of the week....... TBF

Looking forward to hearing the outcome! Don't listen to the few TURDS here that always chime in from the peanut gallery..... Consider the source and carry on. Congrats on your build BTW!

The weak link in the combo that I see is the Procomp heads. I would be very leary about them. I have heard horror stories about seats dropping out of them.

I am building a 489 myself now. Scat crank 22cc dome pistons h beam rods alum heads 118cc with 330 runners. 500 efi induction system should see 580 plus hp

My 2 cents I have run pro comp heads and made good power my only issue was stripping the exhaust bolt hole threads and for the same money get a set of pro header heads bare have all the good stuff put in and run it hard better castings

Next engine will get AFR heads and headers for sure!! Motor is getting Installed this week. Got my reversion issues fixed with the 496 manifolds. The pro-comp heads needed quite a bit of work to correct some issues but it sounds beefy!

Somewhere in this thread it was recommended that you email or call Bob Madara with Marine Kinetics with your proposed setup, 585-654-8583
IMHO he is a priceless resource that is available here on OSO

Good luck with your project

I have seen a few guys try pro-comp heads because the price is just too tempting. Every one of them had some sort of issue with them. Stripped bolt holes is a common problem but I have also seen bolt holes out of location, valve guides not properly installed and even one combustion chamber 1/4 inch out of location. Seems like they have serious quality control issues if they even have such a thing.

What kind of power/ torque are you getting, also what reversion issues did you have with the 496 manifolds. Thanks in advance, Randy

not to drum up from the dead, but what wound up happening? Did you get any numbers?