454 modifications
 

I have a 96 Powerquest SX220 with a 454 (I beleive it is 300 or 310 hp). I am thinking about doing some modifications to the motor and was wondering if this is still good advice:

http://www.offshoreonly.com/forums/s...ight=454+roids

I am running 63 mph right now, would like to run a solid 70. I want the motor to be reliable, and am looking for advice as to what the best course of action is.

All that info is great. Do some more searches and you will come up with enough information about diff combos to keep you reading for the next few days.

Many people have done modifications from minor to ridiculous with their 454's. If you have questions ask them as some people (i know i do ) enjoy learning new things that work with diff combos.

i have worked over 454's now 468's ( bored 60 over). tuff call for you. i have alot into mine . full roller motor merlin rectangle port heads, custom cams, gil dry pipes and so on. about $8000 each , maybe more. 450-500 hp. very reliable. i thought about 502 crate motors ($6000 or so) but this way i know what i have and my engine shop is very fussy. it will take you about 100 hp to get the speed you want i think. just remember nothing comes cheap & you get what you pay for...

I have to put my two cents .... if your intent is to freshen the motor, then now is the time to go ahead on with the mods. Here is what I'd recommend (I am no expert, just a HP junkie): a good Eagle rotating assembly with 4.250 stroke with a forged assembly and flat-tops, this will make a 496ci with a .030 bore of your stock 454.

If you are not going to put boost to the motor, shoot for right around 10:1 compression. If you might add boost later, stick with around 9:1 or 9.25:1.

Get a decent size hydraulic roller something about midsized, get a decent set of marine style heads.... spend the money with a good head porter, use a 2.30 SS intake and a 1.88 or 1.90 exhaust (Inconel fo sho) make sure you have excellent mid-lift flow numbers and the most important isnt peak flow, it's average flow from .300-.650 lift. Go with a good intake, something like an RPM or torquer and say a 800cfm carb. And to make it even less expensive, re-use the heads you got, just have bigger valves and DEFINITELY have the port work done to the stock heads. Now with the ported stock heads, you'll lose probably 50hp or so.... maybe a tad more, who knows, but it would definitely be cheaper.

That should be good for an easy 450-500hp on pump gas with the good heads, without turning it stupid high rpm. Hell it might make more!!

If you just want more power.... buy a blower and be done. That is the cheapest and easiest HP in the world. And reliable as all get out.

Just my opinion.... take it for what it's worth... it's free.

i'm just not sure what kind of $$$ Gaiter want's to spend. i do know from experiance that 500-550hp can be done but to do it and get long life out of it is two differant thing's. i got 7 year's out of these engine's til last summer, i think that's pretty good so i went back to my builder to do it again. my builder said add a blower and cut engine life in half.

Scarabfun.... getting that kind of power out of a 468 reliably is not a problem. Getting 650hp reliably.... now that is tougher, but could be done.

I'm not sure what kind of money he wants to spend either, but as you stated, HP is not cheap.

I am a little confused about boat power.... I have built numerous street motors for my different hotrods throughout the years. One of which was a 406 23 degree headed small block on pump gas that made 575hp. And I drove that motor for almost 2 years and I never lift and am always stomping the gas. I dont see the big problem with making a big rat make decent power on pump gas that will live.... the only thing I could see needing to do is change valve springs each season.

If you had a 468 and it only made 1.2hp/ci that it would make 561hp. My small block made 1.41 hp/ci!!!

Not trying to get in a pissing contest here.... just making a statement and in a way asking a question.

Are boat motors THAT much different than street motors?

i know, i'm not trying to pick a fight. running a marine engine is best described as driveing up-hill all the time, the engine is alway's under load. even drag motors get to coast.

The edelbrock RPM marine heads are very cheap and come with inconel exhaust valves. I did the top end on a stock 330 horse 454 with the RPM oval port marine heads, air gap intake, 750 carb, Comp xm270h hydraulic flat and didn't touch the bottom end. It made 485hp and had a nice flat torque curve. it has just over 400 hours on it now without a single issue. I built another one with the same top end package, but a better rotating assembly and a slightly bigger hydraulic roller. It made 510hp

Rock on... I hear ya on the always under a load. I think we're on the same page.

Haxbyspeed.... that sounds about right on par with what I'm saying. Were those heads you used box stock?

Love these types of discussions... I could do this all night long. LOL

Right out of the box for both. Just checked the spring pressure and bolted em on..

In the mid 90's Jim Benny of Balt MD area rebuilt my cam wiped 330hp type 454 into 470-480hp for me for cheap. Used stock cast two bolt crank, flat tappet hyd. cam, took stock oval port heads and enlarged the valves, better springs, used set of roller rockers, stock shot peened GM rods and a slightly used set of forged pistons. Used "stainless marine" exhaust manifolds - all you need in that power range. This engine went almost 500 hours before a fire took it.
Took my little 20 ft monza from low 60's to 76MPH with a volvo drive and 28" pitch prop, and then it took my 24 excalibur to 80mph. No expensive parts needed in that power range.

1. Rebuilding my Longblock = $3,500
2. exhaust= $1,500
3. terrorizing passengers with the wind distorting my face for 4+ years = priceless

mine will be dynoed soon so i'm realy looking forward to see my number's. we're estamating on my number's now so i'm hoping for 500+hp with 550ftlbs tq. also my merlin head's are iron and i know alum. would make more power.

Not always, iron or aluminum doesn't really matter. Other then heat shedding and weight savings aluminum doesnt give you a performance advantage over similair flowing iron heads.

Hell Yeah HangTime27.... thats exactly what I'm talking about.

We should start another thread titled... "what engine combos and power made ". LOL

Good example for just wise parts selection and careful assembly that will net big gains.

Haxby.... sounds great man. Now throw a great port job on them things and I'd be a 30-40hp increase... and that would put the 454 (461 @ .030) at 540-550hp with good reliabilty.

Thanks guys.... this is fun.

The only way the aluminum would give a power increase is by allowing a little more compression without the detonation that would occur with iron heads.

Yup, and bump up the compression. The 510hp package was only 9:1.. I'll be dynoing a freshened up 525SC with lightly worked edel. heads and a smaller cam next week. Can't wait to see if we can make 600hp for cheap..

"heat shedding" :cool-smiley-011:
still a somewhat disputed topic

I am not sure what I want to spend, I am just trying to figure out if it is worth working the 454 or getting my hands on a 502. I understand engines and how they work, done a fair amount of work on them as well, but mostly maintenance stuff - the deepest I have ever got is head gaskets. I am a snowmobiler too, so lots of work on two strokes. Modifying engines for more power is new to me though, outside of strapping a set of headers on an old camaro.

I guess I am just looking for some ideas, and opinions on whether or not this 454 is worth working on. Again, reliability is very important to me, and I don't want to be reworking it every year. I would prefer to stay out of the bottom end of the motor. Almost every post here does include head replacement, is this because of the "peanut ports"? Would the motor really take a supercharger "as is"?

I agree with others. 500hp out of a 468 is not hard to do. And at 500hp you don't have to have a 4 bolt block, or forged crank. Just be sure to use top quality ARP fasteners. The key to the HP will be in the heads and cam. Try racejunk.com for some good, clean used ARF heads and talk to a cam builder for the right set up. Years ago I did just this in my Scarab. Went from 454 to 468's, had a very good machine shop do the machining, and I assymbled the motors myself. The KEY, is to have the proper clearances for a marine engine. There are plenty of experts on here that will share some info with ya for your project. BTW the whole project was not very expensive and the boat was completely transformed, without breaking the bank.


Darrell.

Haxby,

Just curious.....what would a job like that cost. My peanut-port 454/330's have about 500 hours on them. Thinking maybe in a season or two of making some minor changes like that. So what would a ballpark cost be? And would the Bravo 1's stand up to it long-term? Another question....can you rebuild one motor at a time instead of both at once or does that mess with things? Man I'd LOVE someone to teach me how to rebuild a motor!

www.high-performance-engines.com check this site out talk to scott miller

If your short block is in decent shape, you pick your parts right and run a decent tune up there are absolutely no reliability issues. Your peanut port heads are going to take some power off the top end, but depending on what RPM you spend the most time at it might not be an issue. A good marine cam like a comp xm262 and a performer 2.O with a 750carb will get you in the 420hp / 485ftlbs range and awesome throttle response, even with the p-nuts

You can stick a blower on there but unless you've been through it before plan on spending twice as much as you think it will cost :D

I should add.. Better exhaust is also going to help huge. Those power numbers are on the dyno with good aftermarket exhaust