help with re-build motor specs
 

I have twin 454's one is getting water in the oil so I am thinking Ill re-build both of them. If I am going to do it, I want to do it right. I mean, seven hundred, plus or minus, horse power. I have a great mechanic to help me, but he has never built a boat motor. I would like any advice on how to build the motor, what to put in it and what to look out for so I don't have problems down the road.

If your mechanic friend has never built a boat motor before, I suggest that you do alot of research before you make any decisions. 700 h.p. out of a naturally aspirated 454 ( you didn't mention blowers) is attainable. The problem you will have is getting that much power while trying to keep the compression down to a reasonable number. It all depends on what your intentions are. If you want the motors to be able to run on 93 octane fuel, you will have to keep the compression down to say max 9.7 - 1 With that in mind, you will need a great flowing intake and heads to get your number. That also means real good valve train ( inconel valves), cam shaft, and of course either Gil or Imco manifolds or better yet a set of headers. If you want that much naturally apsirated power, you may be better off building a big cubic inch stroker motor. Remember, there is no replacement for displacement....:D

robbie,
did you mean 700hp each or combined?

700 hp out of a 454 is not going to be reliable with a blower or without.

Im not saying it cant be done but if its not blown the compression will have to be sky high which means racing fuel and the motor will have to spin 6500 rpm or more to make the number. Sustained running of a 454 at 6500 rpm plus will break parts like you have never seen. This high reving motor may not even have enough low end to get the boat on plane with a prop big enough to go fast on top.

With a blower to get 700 hp you will have to run lots of boost which means a lower compression ratio (7/1) a huge blower and intercooler. One fuel mistake (jets) or fuel delivery failure at full blow and the motor is toast. On either setup the engine would have to be torn down frequently to replace bearings rings and valvetrain parts.

Turn key reliability ends somewhere between 500 and 600 hp on a 454. Even at these levels the engine will have a shorter life than the 300 hp stocker.

Dont trust a drag race engine builder to build a boat motor. He can get 700 hp out of a 454 at 8000 rpm for a few seconds between shifts but this will do you no good in a boat. With a boat you need to build power at a sustainable rpm and you only have one gear to work with. You need a wide flat torque curve that wont yeild a high hp number.

Ron

If you are going to start with base 330 Hp engines then you basically have a blocks to start with. The other components are not made to build HP.

If you have 454 mags they use the 502 heads, Manley extreme duty valves, a good forged crank, and good connecting rods. Depending on the year they may have roller cam. This produces 385 HP and can be upgraded 100-150 Hp depending on what you do. Good exhaust is a good place to start to determine your cam profile.

I personally did the blower route and expanded from there.

700 Hp is not attainable with a 454 at under 10:1 and under 6000 rpm unless you have some heads that aren't on the market yet that I havn't heard about. I got 638 Hp out of a 454 but I was running 10 : 1 compression and a very big solid roller cam. The heads were HEAVILY WORKED and the motor would not hold up.

itsa far cry from 700hp but it will be nice and reliable. I am running a small blower B&M 174 and no intercooler. If you went wiath a big whipple or a mega blower and an intercooler you could make more power.

You can see the dyno sheet in the thread i linked to

http://www.offshoreonly.com/forum/sh...numbers+are+in

Robbie,

Tell us what MerCruiser 454 engine packages you have so we know what baseline parts you have (such as what heads you have) to start out with and how much you're willing to spend. I take it these are stock engines the way they sit as of now. In the past I have done a lot of research when building a 454 for hi-performance.

Truthfully, you can probably get a reliable 475-500hp out of a 454. If you have to have 700hp, I would say you're going to have lay down A LOT of SMACK----if you've got that kind of $$$ I would say you won't have any problems then. But if you you're on a budget then 475-500hp is not hard to obtain reliably.

Let us know what you have to start with and we'll go from there if you want our help. I hope it all works out for you.

just leave it stock and have fun.

700HP out of a 454 ? Not too easy .
I did make 625hp out of a 8.5:1 CR 502 , but I had a big solid roller and I had to spin it 5800.

Once you get into cams like that (solid roller) your headache factor will increase, I've definitley learned that one.


Like Audacity say's ... keep it stock and enjoy it.