Advice on 454

I recently bought a 2000 Advantage 21 Br jet boat. It has a basic 330hp carbed 454.

I am looking for a low budget Hp, wondering if a cam upgrade would get me to 400hp range, and not update the heads, or exhausr.

If I have to update heads or exhaust, the. I will just leave it as is, or jump up to a 450hp carbed 496 build.

Any advice you have would be greatly appreciated.

70 hp is a huge ask from a cam swap. I think 30-40hp is more realistic and perhaps less if the heads suck and the exhaust is a restriction.

Xring01 said:

I recently bought a 2000 Advantage 21 Br jet boat. It has a basic 330hp carbed 454.

I am looking for a low budget Hp, wondering if a cam upgrade would get me to 400hp range, and not update the heads, or exhausr.

If I have to update heads or exhaust, the. I will just leave it as is, or jump up to a 450hp carbed 496 build.

Any advice you have would be greatly appreciated.

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I have a 1998 454 (7.4 MPI) with 330hp. I was told it is a 2 bolt main and not to do any performance upgrades to it. Run it the way it is, or sell it and by something else.

RogerThat99 said:

I have a 1998 454 (7.4 MPI) with 330hp. I was told it is a 2 bolt main and not to do any performance upgrades to it. Run it the way it is, or sell it and by something else.

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The 454 MPI that was in my old boat was 310 horsepower. Was told the same thing sell it and upgrade. It still runs like the day I bought it, friend owns it. Was told 1200 hours no problem with that motor but do not mess with it. It was not the same as the 454 330 HP that was stock power had I went with a jet instead of IO.

Xring01 said:

I recently bought a 2000 Advantage 21 Br jet boat. It has a basic 330hp carbed 454.

I am looking for a low budget Hp, wondering if a cam upgrade would get me to 400hp range, and not update the heads, or exhausr.

If I have to update heads or exhaust, the. I will just leave it as is, or jump up to a 450hp carbed 496 build.

Any advice you have would be greatly appreciated.

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I just wrote a very similar answer on the "other" website.

The performance limiting factors on that engine are, compression, cylinder heads, camshaft, intake and exhaust. In order to realize gains, changing the cam alone is not going to do much for you, you would need to get rid of the "peanut port" heads, cam swap and intake manifold.

There is no issue with making more power with a two bolt block, I have built stroker engines (489, 496, 498) with factory GM two bolt blocks that run fine. One made almost 600 hp on the dyno, for a jet boat.

A single carbureted 496 should be easily around 550 hp with the correct combination of parts.

obnoxious001 said:

I just wrote a very similar answer on the "other" website.

The performance limiting factors on that engine are, compression, cylinder heads, camshaft, intake and exhaust. In order to realize gains, changing the cam alone is not going to do much for you, you would need to get rid of the "peanut port" heads, cam swap and intake manifold.

There is no issue with making more power with a two bolt block, I have built stroker engines (489, 496, 498) with factory GM two bolt blocks that run fine. One made almost 600 hp on the dyno, for a jet boat.

A single carbureted 496 should be easily around 550 hp with the correct combination of parts.

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Agree 100% with this. Except for one thing, changing the exhaust is a must. The stock exhaust is borderline with reversion with a stock camshaft. Any cam with more overlap at all will cause reversion.

Thanks for all of your comments.

Its pretty much what I was expecting.

With regards to reversion, can someone enlighten me on that.. Thats a new term for me?

When I bought the boat, I ran it on the Colorado River.. it did 4700RPMs up river at 47MPH, and 4800RPM's down river at 50MPH on GPS. So I am guessing its a 48MPH Boat in flat calm conditions. Maybe I should just be happy with that.

I have a couple of Engine builders local to me, I might talk to them...

I know one of them has a 496HO with a Charger on it, and one piston let loose... Maybe get it cheap enough.. rebuild it, with a carb, and some mild head work, should be an easy 500hp ish. HUMMM.. Maybe just buy the Long Block with the exhaust??? Would he go for that....he could sell the charger to another customer.

There's a few different exhaust systems that came on the Marine Power and Indmar engines. Some of them will take some camshaft with no problem. Post of pic of your exhaust so we can identify what you have.

Also, anything after 1991 will be a Gen 5 or Gen 6 block which were only made as 4 bolt mains.

Marine Industries West said:

Also, anything after 1991 will be a Gen 5 or Gen 6 block which were only made as 4 bolt mains.

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I was adding the two bolt comments for those others who mentioned them, since they are stronger than most believe.

obnoxious001 said:

I was adding the two bolt comments for those others who mentioned them, since they are stronger than most believe.

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Totally agree

Marine Industries West said:

Also, anything after 1991 will be a Gen 5 or Gen 6 block which were only made as 4 bolt mains.

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obnoxious001 said:

I was adding the two bolt comments for those others who mentioned them, since they are stronger than most believe.

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So mine being a 98 is a 4 bolt?

RogerThat99 said:

So mine being a 98 is a 4 bolt?

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Affirmative

Xring01 said:

Thanks for all of your comments.

With regards to reversion, can someone enlighten me on that.. Thats a new term for me?

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Reversion happens during the time when the intake and exhaust valve are open at the same time while the piston is in the intake stroke. It will pull from the exhaust as well as the intake. If the riser/elbow is short and mixes the exhaust with the water close to the bend above the manifold, it will pull water into the cylinder at idle

BDMar said:

Reversion happens during the time when the intake and exhaust valve are open at the same time while the piston is in the intake stroke. It will pull from the exhaust as well as the intake. If the riser/elbow is short and mixes the exhaust with the water close to the bend above the manifold, it will pull water into the cylinder at idle

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Thank you for the detailed explanation. I can see how that could happen.. Especially at higher RPM's.

Xring01 said:

Thank you for the detailed explanation. I can see how that could happen.. Especially at higher RPM's.

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Like Brian mentioned, generally it happens at idle or very low RPM's. When you're running high RPM's there's enough air pressure coming out of the exhaust to blow out the moisture.

Ok,
Here are the pics of the motor
indmar, with Edelbrock performer intake and a carb that I do not recognize

RogerThat99 said:

So mine being a 98 is a 4 bolt?

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A 1998 engine should be a Gen 6 block. You can confirm that by the casting number on the rear of the block above the bellhousing, checking against the list on Mortec.com. The Gen 6 is a good block, accepts many of the parts that work on the earlier blocks, but take a different crankshaft, pan and timing cover. That engine should have a factory hydraulic roller cam.

Xring01 said:

Ok,
Here are the pics of the motor
indmar, with Edelbrock performer intake and a carb that I do not recognize

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Note that your first photo shows an external water leak where the exhaust riser mounts on the manifold. Plan on getting that apart to check it out and replace gaskets at the very least. If it's leaking externally, likely it's also leaking inside the exhaust manifold, and will end up putting water into the engine when it's not running.

Can't see enough of the carb to know what it is, Holley is making a different type carb now I think, as well as Pro Comp (read that "Chinese")

Those manifolds will let you put a mild cam in with no problem. They actually have a pretty long water separation from the exhaust. The water doesn't get introduced until the end of that riser where the 4" hose attaches. As far as horsepower restrictions from that exhaust, they're actually not bad up to about 500 HP. Indmar used those same manifolds on their 502-502 engines. They will be good manifolds for a mild build up. As Barry mentioned, the riser gaskets look like need some attention. But from a horsepower capacity and a water/exhaust separation, I wouldn't waste money on another set of exhaust with the projected project in the 420 horsepower range.

To note, there are better flowing exhaust systems out there, but for what you're wanting to do, I'd rather see the money spent else where.

The problem you'll run into with a cam change is that your existing valve springs wont be set up for a more aggressive camshaft. The stock seat pressures are usually really low. I don't know what kind of budget you're working with or if you're doing this work yourself. My suggestion to keep this is cheap as possible, would be to look for a set of 781 heads. I would take them into Clay Smith, have them set up the heads with new valves, springs, seals, guides, etc. Use FelPro 1037 gaskets to install the 781 heads on your gen 6 block. Clay Smith can set you up with a nice cam and lifter set. Step up your carb to a Quick Fuel M850. Change your ignition to a MSD 83606 ready to run distributor and MSD 8222 coil. Pro comp makea nice a single plane oval port intake that work well with the 781 heads. With the right camshaft, you'll be able to use your existing exhaust with no problem. Add ARP rocker studs and some decent roller rockers. Those changes will land you in the 425-450 Horsepower range. Here's a rough and I mean rough idea of what you'd be looking at in parts,

Head cores - 200
Head work - 1200
MSD dist and coil - 550.00
Quick Fuel Carb - 650.00
Plug Wires - 80.00
Cam and Lifters (roller) - 650
Roller Rockers - 250
Pushrods - 180
Guideplates and rocker studs - 100
Pro Comp intake - 200
Head Gaskets - 80.00
Intake Gasket - 30.00
Timing Chain - 160.00
Misc, carb line, carb bracket, bigger flame arrestor - 200

To do it right you're in about 4600 in parts.

It adds up quick.

Thanks MIW

I really appreciate your input

$4600 for 100-125hp wow.

I added up the numbers for the heads, work and all the parts, seems to me that it would be better and maybe cheaper to just go with Aluminum heads from Edelbrock or AFR.... that way you have 30-40lbs in weight.

Hell even Procomp heads would be alot cheaper, but i have no experience with them. Heard they are chinese made, which scares me off.

It might be smarter just to seel what I, with 93 hours on it, start from scratch with a 496 build.

Yeah, the Edelbrock heads are pretty inexpensive. The seem to be a great buy for the money. Their products have a great reputation for quality. The Edelbrock heads also have a 110 CC chamber so you'd see a compression bump giving you more HP. Roughly a whole compression point - from 8-1 to 9-1. With those Edelbrock heads and the right cam you'd be knocking at 500 HP.

If you decide to go with pre-assembled after market heads, I would advise that you have them checked out by someone who knows their head setup. Make sure the seat pressures are set up for the cam you choose and the guide clearances are correct. We've seen alot of pre-assembled heads even from reputable companies that come in and need tuning up.

Marine Industries West said:

There's a few different exhaust systems that came on the Marine Power and Indmar engines. Some of them will take some camshaft with no problem. Post of pic of your exhaust so we can identify what you have.

Also, anything after 1991 will be a Gen 5 or Gen 6 block which were only made as 4 bolt mains.

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Gen 5 went 91 to 95 I believe. My gen 5 is a 1995. I run the 781's with low compression and decent results. 278/290 & 590 lift cam and crappy logs G.M. Alum intake. Good thread.

Thanks for your input.

I am still gathering info. Havent made any decisions yet.

Xring01 said:

Thanks for your input.

I am still gathering info. Havent made any decisions yet.

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Don't spend 4k on a few minor upgrades. Spend it on gas, accommodations, fun and retirement.