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600 HP 468 build recipe for 18' jet.

Nikwho

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Hey guys,

I'm in the beginning stages of my 468 engine build. I've set a goal of 600-650 HP, as I believe that is a realistic and relatively safe goal (reliability-wise), given my general budget. I want to run on premium pump gas. I don't have a hard budget for the build, but it is not going to be a no expense spared deal. Im fine commiting another $3,000-$5,000 into this ordeal, from where I am at now, sitting on most of the parts, with most machine work done. I want to find a happy medium between dollars, reliability and horsepower. So, setting a goal of having an HONEST 600+ HP BBC, I am looking for some guidance.

What I have:
I've got a freshly machined '72 Mk. IV BBC block. Two bolt mains, studded with ARP main studs. Forged 4" stroke crank, 4.310" bore, Speed Pro forged pistons(L-2465F 60) with 27.1cc dome. 049 heads. Heads also machined. New guides, valve surface machined, but don't have valves or valvetrain components selected as of yet. I also have not purchased rods. Im looking at running these Eagle H-beam forged rods:

So, I have my short block, less a set of rods (6.135", to run the pistons that I have) and balancing. I already have the machined 049 heads. I have not measured to see what size valves the heads were cut for. If I need to go oversize to meet my goals, I'll pass that on to machinist, come time to have the heads built. Without knowing the exact deck height of this setup, or the exact cc's of the combustion chambers, I believe that I am looking at roughly 10.14:1 static compression.

So, with the collection of parts that I have, and my general goal of 600-650 real world HP, where does this put me? I want to run thru transom exhaust/headers. Want to steer away from OTT headers.

So, this leaves me to cylinder heads (valve sizes and other valvetrain component selection), camshaft type/grind selection, intake selection and carb selection. I should be able to meet my HP goal with a single 850 cfm carb, though I have two matching Quick Fuel 650's and two matching Edelbrock 1405 600 cfm carbs, so those are an option that would save money in a dual carb configuration.

Camshaft choice? Assuming that a hydraulic flat tappet is less likely to get me to my goal. I'd be fine running a solid flat tappet cam, if it will allow me to meet my goal, with a fair degree of reliability. Im okay with frequent valve adjustments. Solid or hydraulic rollers are a more expensive option, but can add some reliability and less frequent valve lash adjustment, if hydraulic. Assuming that a high quality roller setup is going to run $1,500+, I'm okay with a flat tappet cam, if it will meet my goals.

I had been looking at this Howard's cam, but I'm not sure that it would produce the 600+HP that I am reaching for:

Intake:
I had thought that with my 468" deal, and 600-650 HP goal, I'd need to reach this at a slightly higher RPM? Tunnel ram, dual 650cfm carb setup? Perhaps a Victor and single 850cfm carb?

I'm still in my initial planning stages. Looking for guidance to steer me in the general right direction. Don't want to overbuild, nor spend money twice, by replacing the wrong components.

Any help from you far more experienced guys would be so greatly appreciated!

I'm assuming at this point that I'll end up running this in my 1974 18' Tahiti. It has a 12JC pump and hydraulic Place Diverter. Willing to change impeller as needed to optimize performance.

I would like to be able to pull a tube or skier/wake board. Looking for a reliable family hot rod to run primarily on the Colorado river. Mostly Laughlin to Havasu, and the Parker strip. Also will see various lakes occasionally.

Thanks in advance for any help!

Nik
 

78Southwind

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I think you will need a lot of work to those 049 heads to push the horse power into the 600 range. I am not sure if you are going to build the engine yourself or if you are looking to have it built. James at Bostick Racing Engines has a nice engine he builds that he calls The 650 (he uses 990 heads though). He also builds a nice 580 HP engine with the 049 heads. The following is his posts on his facebook page.


"The 650" 461 Chevrolet, 10.3:1 pump gas friendly, Gm iron 990 heads "marine spec" worked by BRE (bronze guides, stainless Ferrea 2.19 & 1.88 valves, hardened exhaust seats, Stg 3 port & polish) Dart single plane intake, GM 4 bolt block completely machined by BRE (line honed, index surfaced, bored & torque plate honed), Scat 6.385 h beam rods, SRP 10:1 small dome pistons, GM std 4" stroke steel crank, Crower 1.7 rockers, Crower std solid roller lifters, Crower pushrods, BRE "home made" oil pan (built from a pickup oil pan and modified to control windage and add a few quarts), Schneider custom solid roller camshaft, Holley 1050 dominator, and a 175hp plate system for those times you need a passing gear. The idea behind this engine, besides being the test mule for the shop, was a budget oriented, all gm iron, pump gas friendly, RELIABLE, river hotrod engine that a regular working man can afford to have built and use. In a very heavy gullwing, turning a worked Berk B impeller and new style inducer, it turns 6100-6200 (depending on air) and 6800ish on the 175 shot... which is 96mph on motor and 106mph on bottle in the gullwing. Thus far... we have 3 entire seasons and dozens of nitrous bottles through it and no wrenches have touched it other than to change the oil and check the valve adjustment a couple times per season.

468: 10.25 SRP pistons, stk 7/16 bolt rods, gm steel crank, 4.320 bore 4 bolt gm block fully machined by BRE (line honed, square decked, bored & honed w/plates), 049 oval port gm heads ported, bronze guids, hardened exhaust seats, fitted with Ferrea stainless 2.19 & 1.88 valves and double springs, Crane gold 1.7 rockers, Schneider custom solid flat tappet cam just over .600 lift, Edelbrock Victor intake with a Holley 850 dp on top. Pump gas ski boat engine capable of a 200-250 shot of nitrous (for pulling girthy skiers up... And passing wake board boats) going into a 18' Southwind jet. Made 582@5900 hp and nice flat power/torque curve perfect for a multi purpose jet.
 

obnoxious001

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As mentioned, the 049 heads are going to be the limiting factor unless you spend the money to have them ported.

Personally, particularly since you don't have valves for them yet, I would consider using a pair of the Brodix Race Rite oval port heads. Aluminum heads would allow additional margin of safety against detonation with pump gas, and by the time you have your 049's ported and completed with new valves and hardware, you may be approaching the same money.

Some years ago I built a 468 with ported iron 990 heads, with only 9.6-1 compression, single 850 and roller cam that was for a jet boat and above 600 rpm on dyno. I have one now waiting to go to dyno soon that is similar, but more compression planning to run AV gas in a jet boat, and the 990 heads don't have much port work done to them.

The tunnel ram definitely should add some horsepower, maybe 35-50. There are various dyno tests you can find on Youtube that document that.
 

Nikwho

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So, let's say I set a $2,500 budget for heads... I'm willing to buy some decent heads, if they're going to hold me back. "I'm a peacock, ya gotta let me fly!" 😁
 

Nikwho

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So, I'd like to build the engine to otherwise make big power, pending a head upgrade, then swap heads once I get them. Am I in pretty good shape to do that with my 27.1cc dome Speed Pro forged pistons and running the aforementioned Eagle H-beam rods? I was planning on 600-650 HP because the block is a 2 bolt main. Perhaps I should look into cross splayed 4 bolt caps, and taking the block back to the machinist for their install and align honing of mains? My crank has already been turned and polished. Just awaiting a set of rods and getting the rotating assembly balanced.

To answer the first question, I was planning on building (assembly) myself, but been kinda on the fence. This would be my 6th engine build, but also the highest horsepower build. I want it to be right, so I may have this one built by a professional. Any super reputable engine builders in Phoenix area? I live up in Flagstaff, but have found that most high end work, in general, needs to be outsourced out of our small town.

Nik
 

Nikwho

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I'm not married to the pistons that I mentioned above. But, they are brand new, in the box with rings, and They came with the engine. I didn't like that they were press fit only, but not a huge deal. Im not worried about not running any parts that I have, as they'll just be put on the shelf for another BBC build. But, I'd prefer to use anything that I have, for the sake of saving money.
 

obnoxious001

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Couple of ideas for you, if saving some money is a thought. Eagle makes a newer line of I beam rods that they rate to 850 hp,, around $350 for a set.

If you couple your two bolt block with the 049 heads, proper camshaft and tunnel ram, you may get close to your goal. I didn't take time to calculate compression, some of the 049 heads are 122cc chambers, so sort of need to CC the heads to get a more accurate idea of static compression ratio. If you did change to aluminum heads later, the chambers are more likely to be around 119cc, so a slight boost in compression.

Another point of interest, aluminum in itself does not make more power than iron heads, it's the engineering of the runners that makes a difference.

Converting a two bolt block may cost nearly as much as finding a used 4 bolt block in my experience. I have had several done in my years of building, I want to say the last one I had done 6 years ago may have cost $350, and I may have supplied my own main caps.

I usually use full float pistons, but a press pin can have the benefit of not having to re-bush the rods on a rebuilt. Boat engines usually don't get used as much as a car before needing to be rebuilt, so normally I don't give that much consideration. I also usually get pistons made with custom dome sizes to put compression where I want it. In your case, using aluminum vs iron I normally consider about a half point more compression with aluminum over iron, since the aluminum sheds heat more efficiently. Your older design Speed Pro pistons will use a 5/64" top and 2nd ring, where newer design pistons will run either 1/16" or even narrower metric rings that provide less drag and give a slight power increase.

Based on the sum total of all your statements, including "saving money",,, go ahead and build it yourself, run the 2 bolt mains, 049 heads, with tunnel ram. Buy decent quality valves, I suggest severe duty stainless. I normally choose Ferrea, but any good quailty, since breaking a valve can be pretty disastrous!

I can help you select and buy a cam when it's time (after you nail down the rest of the combination is the correct time to select cam), and quote you on building it if you wanted to bring it to Parker. PM if you want my phone number to discuss that.
 

wzuber

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Engine pro makes an nice economical, inconel exhaust valve you may want to consider. Also, Trick Flow heads has a 280 power oval alum head that is pretty nice. You might give those a look too if your considering an alum head upgrade.
Www.trickflow.com
TFS#4131B001
 

Nikwho

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Thanks guys! Still in the planning and parts selection stage, but definitely still building the engine. So, I parted with the 049 heads, since they were going to limit me some. Also ditched the 2 bolt main block and found a nice factory bore 4 bolt main block. Currently shopping for an aftermarket set of aluminum heads. Also considering a new rotating assembly. I'm not going to try to plan a build around a set of pistons. So, still a Mk. IV block.

Thoughts on this Eagle rotating assembly?


And a pair of these Brodix heads:


Looking at this Edlebrock 7115 tunnel ram. Not "married" to a tunnel ram, or dual carbs.

If I can stick with a +0.030" overbore, I don't want to bore this block out 60 over. The 4.25" crank would make it a 489" displacement. Just ballparking some figures, if I had a 0.010" deck height, -23cc dome pistons, the 119cc chamber Brodix heads, an 0.039" compressed head gasket with a 4.310" bore (guessing here, not looking at a specific head gasket), I'd be sitting around 10.3:1 static compression ratio. This is with a 6.385" rod. I have two Quick Fuel 650's that I'd likely run. Also have another brand new Quick Fuel 750 that I could buy a twin to, but I have a strong suspicion that the two 650's will be plenty of carb for what I'm trying to do.

Nik
 

Mcchevy69ss

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Thanks guys! Still in the planning and parts selection stage, but definitely still building the engine. So, I parted with the 049 heads, since they were going to limit me some. Also ditched the 2 bolt main block and found a nice factory bore 4 bolt main block. Currently shopping for an aftermarket set of aluminum heads. Also considering a new rotating assembly. I'm not going to try to plan a build around a set of pistons. So, still a Mk. IV block.

Thoughts on this Eagle rotating assembly?


And a pair of these Brodix heads:


Looking at this Edlebrock 7115 tunnel ram. Not "married" to a tunnel ram, or dual carbs.

If I can stick with a +0.030" overbore, I don't want to bore this block out 60 over. The 4.25" crank would make it a 489" displacement. Just ballparking some figures, if I had a 0.010" deck height, -23cc dome pistons, the 119cc chamber Brodix heads, an 0.039" compressed head gasket with a 4.310" bore (guessing here, not looking at a specific head gasket), I'd be sitting around 10.3:1 static compression ratio. This is with a 6.385" rod. I have two Quick Fuel 650's that I'd likely run. Also have another brand new Quick Fuel 750 that I could buy a twin to, but I have a strong suspicion that the two 650's will be plenty of carb for what I'm trying to do.

Nik
You are now on the right track, I would definitely do a stroker kit if you are buying a new rotating assembly. The Brodix heads mentioned above or AFR 305 heads with a weiand hi ram tunnel ram will definitely surpass your goal. You are going to be somewhat limited on a cam size due to your header choice with water reversion. I would stick with a cam that has no larger duration than 240@ .050 or 245 @ .050 max... I would try to pick a cam with the highest lift within that duration.
 

Blackmagic94

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650 Bhp on a 468 which is really 467 is 1.3918hp per cube


I dont see this happening without some real heads and a solid roller cam spinning to 7200 plus rpm, which means shaft mount rockers like Jesel and a bunch of other Jesel parts, this is going to be an expensive build



You would be way way way better off to go as big of cubes as you can to get to the power level


498 stroker at .100 gets you 505 cubes now you are talking about a 1.28:1 hp motor and that is way easier to make then what you are asking for


No oval ports




What you need


498-505 cubes
big head big cc alum race heads, like AFR or Brodix
Tunnel Ram with dual 650cc carbs
10.5:1 min compression ratio
Solid roller camshaft with .600 plus lift and 110 LSA
Jesel shaft mount rockers
Jesel Solid roller lifter
MSD billet dizzy with Digital 6 box and coil
Over the trans headers as big of primaries as you can run, under the transom is gonna cost a lot of power







or just run the cheap shit you already bought and install a 8-71 lol
 
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SBMech

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650 Bhp on a 468 which is really 467 is 1.3918hp per cube


I dont see this happening without some real heads and a solid roller cam spinning to 7200 plus rpm, which means shaft mount rockers like Jesel and a bunch of other Jesel parts, this is going to be an expensive build



You would be way way way better off to go as big of cubes as you can to get to the power level


498 stroker at .100 gets you 505 cubes now you are talking about a 1.28:1 hp motor and that is way easier to make then what you are asking for


No oval ports




What you need


498-505 cubes
big head big cc alum race heads, like AFR or Brodix
Tunnel Ram with dual 650cc carbs
10.5:1 min compression ratio
Solid roller camshaft with .600 plus lift and 110 LSA
Jesel shaft mount rockers
Jesel Solid roller lifter
MSD billet dizzy with Digital 6 box and coil
Over the trans headers as big of primaries as you can run, under the transom is gonna cost a lot of power







or just run the cheap shit you already bought and install a 8-71 lol

This.

You are not going to make 600+ hp without some cubic inches, unless your pockets get much deeper.
 

Nikwho

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650 Bhp on a 468 which is really 467 is 1.3918hp per cube


I dont see this happening without some real heads and a solid roller cam spinning to 7200 plus rpm, which means shaft mount rockers like Jesel and a bunch of other Jesel parts, this is going to be an expensive build



You would be way way way better off to go as big of cubes as you can to get to the power level


498 stroker at .100 gets you 505 cubes now you are talking about a 1.28:1 hp motor and that is way easier to make then what you are asking for


No oval ports




What you need


498-505 cubes
big head big cc alum race heads, like AFR or Brodix
Tunnel Ram with dual 650cc carbs
10.5:1 min compression ratio
Solid roller camshaft with .600 plus lift and 110 LSA
Jesel shaft mount rockers
Jesel Solid roller lifter
MSD billet dizzy with Digital 6 box and coil
Over the trans headers as big of primaries as you can run, under the transom is gonna cost a lot of power







or just run the cheap shit you already bought and install a 8-71 lol

Hey, I've been considering the blower route!

BUT, I've decided to not limit myself with the 2 bolt block, 049 heads and Speed Pro pistons. I'm running a 4 bolt GM block, likely the Brodix heads and Eagle 489 stroker kit. I'd like to build a 496 (or bigger), but don't want to punch this standard bore block out +0.060", to leave room for a future rebuild at 4.310". So, planning on 489 cubic inches via a 4.25" stroke and 4.280" bore. Not looking to step up to an aftermarket block with bigger bore, at this point. I work in public safety, so I need to keep it more mellow.

So, sticking to my original goal of building a premium pump gas naturally aspirated 650 HP big block. I think that I'd like to figure this out at or under 6,500 RPM, for reliability sake.
 

Blackmagic94

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Hey, I've been considering the blower route!

BUT, I've decided to not limit myself with the 2 bolt block, 049 heads and Speed Pro pistons. I'm running a 4 bolt GM block, likely the Brodix heads and Eagle 489 stroker kit. I'd like to build a 496 (or bigger), but don't want to punch this standard bore block out +0.060", to leave room for a future rebuild at 4.310". So, planning on 489 cubic inches via a 4.25" stroke and 4.280" bore. Not looking to step up to an aftermarket block with bigger bore, at this point. I work in public safety, so I need to keep it more mellow.

So, sticking to my original goal of building a premium pump gas naturally aspirated 650 HP big block. I think that I'd like to figure this out at or under 6,500 RPM, for reliability sake.
Not gonna happen without a solid roller and rpm with low compression for pump gas. 550 hp is where your gonna be lucky to get to with this combo
 

Nikwho

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Seems like plenty of guys are doing it!? I am not opposed to a solid roller. In fact I fully anticipated it!

You're saying that a 496/489 can't make 650 HP with a solid roller cam, Brodix heads and premium pump gas?
 

Nikwho

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Seems more than doable. What am I missing? 550 HO is easy with a 468 with 049 heads. Why is 650 HP unobtainable on pump gas, Brodix heads and another 1/4" of stroke?
 

Nikwho

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Here's a link to a thread over at performance boats. Look at post #9. GN7 posts his dyno results of a "single 4 barrel oval port pump gas 496" that exceeded my goals by a lot! 709HP @ 6,200 RPM. Seems like a well thought out build with quality parts is more than capable of making 650 HP under 6,500 RPM, even on pump gas.
 

Blackmagic94

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Seems like plenty of guys are doing it!? I am not opposed to a solid roller. In fact I fully anticipated it!

You're saying that a 496/489 can't make 650 HP with a solid roller cam, Brodix heads and premium pump gas?

What compression and rpm? And you were first talking about shitty heads and stoke stroke. Yeah big heads and cubes will help.

And solid roller is not a family cruiser setup. It requires valve adjustments
 
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Nikwho

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In fact, my cousin just built a 496 that exceeded 650 HP on pump gas, even at 6,000 RPM and with a Performer RPM intake. Then, when swapped to a Victor Jr, the same engine produced 668.8 HP at 6,500 RPM. And that was with 93 octane pump gas. Would have likely picked up 30-35 HP with a tunnel ram, I would think, albeit above 6,500 RPM, but probably not by much. So, it seems like my goal is VERY attainable.
 
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Blackmagic94

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In fact, my cousin just built a 496 that exceeded 650 HP on pump gas, even at 6,000 RPM and with a Performer RPM intake. Then, when swapped to a tunnel ram, the same engine produced 668.8 HP at 6,500 RPM. Would have likely picked up 30-35 HP with a tunnel ram. So, it seems like my goal is VERY attainable.
Am I missing that you said 049 heads and 468 to make 650. Now it’s big cubes and heads. Hmmm yeah that’s more realistic.
 

Nikwho

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Am I missing that you said 049 heads and 468 to make 650. Now it’s big cubes and heads. Hmmm yeah that’s more realistic.
Ahhhh, YESSIR! Makes way more sense now! Initially, in my original post I had 049 heads, 2 bolt block and a set of Speed Pro pistons. I realized that I wasn't going to get to my goal with that combo, and didn't want to have those parts dictate my build.

So, in a later post, I indicated that I found a standard bore 4 bolt Mk. IV block, and I'm looking to run a forged 489 Eagle rotating assembly and Brodix heads. 😁 Sorry for the confusion.
 

probablecause

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Like Blackmagic94 said, stroke it! I would personally do a 555 with 121cc heads and keep compression around 10.5
 

Nikwho

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Like Blackmagic94 said, stroke it! I would personally do a 555 with 121cc heads and keep compression around 10.5
I can't build a 555 out of a stock Mk. IV block. Buying a Manley 555" rotating assembly and a Dart Big M block adds like $4,000 on top of building a 496, for which I already have a block. If it weren't my money, I'd suggest that, too. But, that seems pretty overkill for a 650HP goal, albeit nice! Just not what I am doing here. I'm building a 650HP 489/496" engine with a GM block. 😁
 

probablecause

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Get the die grinder out and let's go ape shit. However, 496 is a great option too. Don't forget about a little squirt squirt with a 100 hp NOS shot. But the two-bolt main would concern me a little there. Heads and cam are where you want Torque monster on the 049 or 781 heads will require some work. Good luck and keep us posted.
 

Nikwho

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Get the die grinder out and let's go ape shit. However, 496 is a great option too. Don't forget about a little squirt squirt with a 100 hp NOS shot. But the two-bolt main would concern me a little there. Heads and cam are where you want Torque monster on the 049 or 781 heads will require some work. Good luck and keep us posted.

Yeah, the last few times I've tried to buy NOS, I haven't been able to find it. For reliability purposes, though, I don't think that I'm going to put any spray to this engine. Would be fun, though! Then again, so would a 555" stroker! Sadly, though, I have to balance my baller tastes with my public safety budget! LOL

It's super easy to clearance a factory block for the 4.25" stroke crank, but it's impossible to go that big on the bore. Those 555" kits have some crazy bore, like 4.560"! That's not obtainable on any GM 454 blocks. That's more than a quarter inch overbore, when we struggle with bores greater than sixty thousandths at times. BBC's don't have that much wall thickness, PLUS, from the reading that I have done, the cylinder walls become unstable when going much further than 4.310", particularly when faced with high performance demands.

As blasphemous as this sounds to Chevy guys, if I were going to try to go with that much displacement, I'd probably build a BBF at that point. I had a Kona with a 521" BBF that ripped! I'm sticking with a 489, possibly a 496" BBC. My particular goals should be pretty easily attainable with that displacement. Even if that means a solid roller cam.
 

Nikwho

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On a good note, a discussion on this topic led a friend to inform me that he has a 4.280" bore 4 bolt main block that needs a bore.

Looking at ordering this rotating assembly:


With these rod bolts:

And these heads:

This kit indicates that it is good for 1,500HP, with the rod bolt upgrade. I figure that the room to grow is worth the extra $170. This kit is 4.310 bore x 4.25" stroke (496") and has -18cc domed pistons. The Brodix heads have 115cc combustion chambers, 312cc intake chambers, #240/#550 seat pressures, 2.25"/1.88" valves and Titanium retainers.

With a head gasket that is compressed to 0.039", with a bore of 4.310, my static compression ratio would be right around 10.5:1, with a zero deck. That should be pump gas friendly. I could move to heads with larger chambers, if I ever wanted to go to forced induction.

I'll need to figure out my camshaft and impeller still, but I have some time before I need to worry about any of that. I will plan on a pump rebuild and upgrade to appropriate parts (hardened shaft, plus bronze or stainless A or AA impeler) but I think that this will allow to pretty easily meet my goal, with plenty of room to grow in the future, and should provide good reliability. Gonna get these parts ordered and my block to the machine shop. Looking at running this combo with tunnel ram and dual 650 Quick Fuel carbs, and MSD Digital 6 ignition box.

Thoughts?

Nik
 

obnoxious001

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On a good note, a discussion on this topic led a friend to inform me that he has a 4.280" bore 4 bolt main block that needs a bore.

Looking at ordering this rotating assembly:


With these rod bolts:

And these heads:

This kit indicates that it is good for 1,500HP, with the rod bolt upgrade. I figure that the room to grow is worth the extra $170. This kit is 4.310 bore x 4.25" stroke (496") and has -18cc domed pistons. The Brodix heads have 115cc combustion chambers, 312cc intake chambers, #240/#550 seat pressures, 2.25"/1.88" valves and Titanium retainers.

With a head gasket that is compressed to 0.039", with a bore of 4.310, my static compression ratio would be right around 10.5:1, with a zero deck. That should be pump gas friendly. I could move to heads with larger chambers, if I ever wanted to go to forced induction.

I'll need to figure out my camshaft and impeller still, but I have some time before I need to worry about any of that. I will plan on a pump rebuild and upgrade to appropriate parts (hardened shaft, plus bronze or stainless A or AA impeler) but I think that this will allow to pretty easily meet my goal, with plenty of room to grow in the future, and should provide good reliability. Gonna get these parts ordered and my block to the machine shop. Looking at running this combo with tunnel ram and dual 650 Quick Fuel carbs, and MSD Digital 6 ignition box.

Thoughts?

Nik
#1 You will not drop enough compression with heads to change to forced induction, unless you had 10.5 with closed chamber heads, so get that thought out of your mind.

I have done a couple of jet boat engines that made over 600 honest dyno horsepower.

The first I did some years ago, 9.6-1 compression, 990 heads with unknown porting job, solid roller cam, single 850 carb, 617 hp at 6300 RPM.

The latest one I did ran at Westech a few months ago. 460 cubic inches, probably a fuzz over what you are considering for compression, 990 heads with no porting, solid roller with as stud girdle, single plane intake, 750 carb on a spacer. It made 608 hp at 6500. Tunnel ram would probably give you about 30 more horsepower. I didn't build that engine for nitrous, but customer added a plate system, "200 shot" made 892 hp at 6400 rpm.
 

Blackmagic94

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#1 You will not drop enough compression with heads to change to forced induction, unless you had 10.5 with closed chamber heads, so get that thought out of your mind.

I have done a couple of jet boat engines that made over 600 honest dyno horsepower.

The first I did some years ago, 9.6-1 compression, 990 heads with unknown porting job, solid roller cam, single 850 carb, 617 hp at 6300 RPM.

The latest one I did ran at Westech a few months ago. 460 cubic inches, probably a fuzz over what you are considering for compression, 990 heads with no porting, solid roller with as stud girdle, single plane intake, 750 carb on a spacer. It made 608 hp at 6500. Tunnel ram would probably give you about 30 more horsepower. I didn't build that engine for nitrous, but customer added a plate system, "200 shot" made 892 hp at 6400 rpm.


how reliable is a solid roller for a jet boat. I mean you could have 10 minutes of continuous idle time going through a no wake zone like the channel at Havaus. Is that gonna cause problems or premature failure of lifters starving for oil splash windage.
 

obnoxious001

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how reliable is a solid roller for a jet boat. I mean you could have 10 minutes of continuous idle time going through a no wake zone like the channel at Havaus. Is that gonna cause problems or premature failure of lifters starving for oil splash windage.
I like the Crower lifters with the forced pin oiling. I have on occasion run the Comp Endure X (I think that's their name), also with forced pin oiling.
 

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how reliable is a solid roller for a jet boat. I mean you could have 10 minutes of continuous idle time going through a no wake zone like the channel at Havaus. Is that gonna cause problems or premature failure of lifters starving for oil splash windage.

You think that I should be less enthusiastic regarding HP goals, and run a hydraulic roller? I have built enough engines to generally have a solid understanding about some different aspects. However, regarding camshaft selection, I honestly don't know shit... I want to build a boat that will go fast, but also want a reliable engine. Valve adjustments, I don't mind. Ugh...
 

Blackmagic94

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You think that I should be less enthusiastic regarding HP goals, and run a hydraulic roller? I have built enough engines to generally have a solid understanding about some different aspects. However, regarding camshaft selection, I honestly don't know shit... I want to build a boat that will go fast, but also want a reliable engine. Valve adjustments, I don't mind. Ugh...


Yes I would rather run a hydro roller look for power via other routes like more cubes or compression
 

obnoxious001

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You think that I should be less enthusiastic regarding HP goals, and run a hydraulic roller? I have built enough engines to generally have a solid understanding about some different aspects. However, regarding camshaft selection, I honestly don't know shit... I want to build a boat that will go fast, but also want a reliable engine. Valve adjustments, I don't mind. Ugh...
Solid roller setups are reliable if set up correctly, with proper cam design, good lifters, and proper spring pressure. You need someone to help you select a cam that makes good power but is easy on valve train.
 

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Geometry is everything with valvetrain setup. Make sure you are not binding or over the specified amount of spring pressure etc.

I'd spend money there and on the headwork (port matching and flow work) if I was assembling something reaching the end of N/A limits for an engine you want to run a few hundred hours without fucking with weekly, it's not a race motor that you go over after each weekend. Money well spent IMO.
 
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Speedmaster makes an entire top end kit with a 320cc intake runner, open plenum manifold, roller rockers and gaskets for like $1200


The only thing you'd really need to check is the available lift on the stems. But that little Comp cam is only .575 lift.

Throw a Comp XM308HR hydraulic roller in it and at 10.25:1 with a good intake manifold and exhaust, it'll be 600-625hp. That Speed master manifold aint great, but it's cheap enough to throw away and put an Edelbrock Victor on there and be done with it.

I've built Super Stock engines that are 590hp using a flat tappet cam, the OEM dual plane and a spec piston with heads that arent as good as those Speedmasters.
 

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Okay, a little update to my engine build situation.

I just bought a complete 502 Longblock (I'm SUPER stoked!)! I have also purchased a set of Brodix "Big Brodie" aluminum heads (119cc combustion chambers) and a Weiand square port tunnel ram (part #1921).

The 502 has forged pistons, rods and crank, and has 4 bolt mains, as I believe that all 502's do. I need to figure out the compression ratio yet, but the engine also came with complete 502 cylinder heads. I'm assuming that I'll still want to run the Brodix heads that I have, but also have the options of the 502 heads, some 049 castings and a set of 820 castings, though, if I run an iron head, it would be the heads on the 502.

Looking at running a couple of Quick Fuel 650cfm carbs on the tunnel ram.

I need to figure out my compression ratio first, and foremost, but I am thinking that I finally have a group of parts that will allow me to pretty easily meet my goals!

Also, considering running the boat on 100 octane, which with aluminum heads should allow me to run up as far as 12-12.5:1. I don't want to go more exotic than that, as far as fuel goes. Once I nail down my static compression ratio, I would sure love some help with selecting a camshaft!

I know that this thread has gone full circle now. I started off wanting to build a pump gas friendly, iron headed 468" deal! Now, that has turned into a 502, with the Brodix "Big Brodie" aluminum heads, etc. You guys have been great and I really appreciate all of the help so far! I'll report back when I get my compression ratio figured out.
 
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It's a Gen V or VI 502 from a boat. I believe I was told that it is the Mercruiser 525 HP engine. I didn't write down the casting number and I just left my friends shop. I'm picking everything up tomorrow at noon, so will have more information then. It's all forged (pistons/rods and crank), with roller cam shaft. Has Erson roller rockers on it. Kind of a neat deal, my friend that sold it to me has a second twin to itm. He is going to build that engine as a 540" stroker, for his Chevelle. He told me that I could take the camshaft, rods and pistons out of the other engine, too. So, why not!?

I'd like to put a 4.25" stroke crank and new rotating assembly in it, but being factory bore, low hours, good cylinder walls, and an all forged rotating assembly, I feel like a rotating assembly swap at this point would be money poorly spent. Perhaps a 540 rotating assembly in the future, though!
 

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Hoping that the heads will be a good fit for the engine. Will need to figure out what camshaft to run, too. I would not like to fall short of 650 HP, and would love to get to 750 HP! Shouldn't be too difficult to meet my goals with the 502 and Big Brodie heads, I would think. I'll update with additional information tomorrow, as I would like to get this deal going. It's the perfect time of year to get this thing built. I think that I can take my time, do everything right, and have the boat turn key again by April! I'll have to have the pump gone through, too! That's why I was trying to steer away from buying a new rotating assembly. To be safe, I'll likely tear it apart tomorrow and get it to the machine shop to get vatted, magnafluxed, etc. I'll have the machine shop measure the deck height, too, and see if we'll want to deck the block while it's there.
 

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Those big brodie heads are some huge heads for a 502. Are you going to bore and stroke the engine? Here is an interesting build by @cyclone here on the boards for his old Roger's he had back in the day. https://www.motortrend.com/how-to/0410or-build-740hp-block-chevy/

Just curious what 502 block is it?
Funny, I think that I may have owned that Roger's hull, a few owners after Mike owned it. I bought it off of a now deceased WWE wrestler. That's a whole other story, though. I was thinking that these heads would be perfect for this 502 build. Was going to build a 496 with them initially. I think that eventually the engine will go to a 565" deal (4.600"x4.25") but having the factory bore and all forged rotating assembly in tip top condition makes it hard to cough up another $3,000 for another forged rotating assembly.
 

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