1995 454 Mag genV to "525SC" or "HP420"
 

Has anyone considered doing this in their SB? I am debating on either bumping my compression (9.5:1) and going with a HP420 build-up (still winning for the price) or lowering the compression (7.5:1) and doing a 525SC build-up. I am looking to do the work myself and still putting together the parts list. Any suggestion on pistons and other parts?

Does anyone know the rpm range of the 420SC?
If I was to go the 525 SC route, would I be better off running the Weiand 250 instead of the 177? I think it could leave me room to grow, bump the boost.

Please let me know what you think (or know). I would like to find out what problems I could possibly run into.

I hope to start collecting the parts over the next few months.

Re: 1995 454 Mag genV to "525SC" or "HP420"
 

I bumped up my 1997 454mag With 525SC heads, cam, roller rockers, intake, and threw a intercooled M1 ProCharger on with a custom 650 double pumper carb. I ran 7.5#'s boost for 350+ hrs of fun. According to the numbers my boat ran, I was putting out over 700 ponies. Best of 102mph in my 26' cat. :drink:
Alot better numbers than the roots type blower. the 525SC was lucky to hit 500hp.

Re: 1995 454 Mag genV to "525SC" or "HP420"
 

How Do You Get The Hp From The Speed Of The Boat? Every Boat Is Different Along With Every Bottom. Also Good And Bad Props. The Rite Prop Will Give You More Speed But Not More Hp. So Far For Me This Year I Upped The Hp About 20% And The Speed Is Up Only About 10%. I Know Their Has To Be A Formula In Their Some Where ?

Re: 1995 454 Mag genV to "525SC" or "HP420"
 

I think their is a formula on Bam Marines site.
http://www.go-fast.com/boat_speed_predictions.htm
I do not know how accurate it is. If you know your weight and old prop shaft HP, it is worth a try.

Re: 1995 454 Mag genV to "525SC" or "HP420"
 

What compression did you have to run on the engine? How about the cam? 525SC Heads? I thought the heads were the same as the 454mag.

Re: 1995 454 Mag genV to "525SC" or "HP420"
 

Hey Razor,
How fast do you want to go?
I ran 76mph yesterday with my 24' powered by a basically stock 502Mag.
Personally I think 500-550HP and 80-85mph is about the max for these hulls. Anymore is simply a waste and IMO dangerous...

Like we have talked about before, your engine can be rebuilt to produce 500HP with the right roller cam, head work, good flowing exhaust, and carb intake combo.

The difference between a 454mag and 420HP 454 is valve train, Gil exhaust, and the carb intake combo. The short block and head castings are the same.
A 525SC is basically the same base engine as the 420HP with dished pistons.
Again, IMO, you don't need a 700HP blower motor in a 24' Super. Rebuild your 454Mag to make 420 to 500HP or buy a 435 to 500HP 502cube engine.
I think you can build a 500HP longblock from your 454Mag for around $2500 if you do the assembly work yourself.
500HP 502cube longblocks can be purchased for about $5500.

Re: 1995 454 Mag genV to "525SC" or "HP420"
 

Thanks Pat.
That is the route I wan't to go. I would like to turn 5500 rpm, turning a 24" Bravo 1. I turn this prop to 4900 now. Would a copy of the HP420 be the ticket or should I look at different components. I figure a 850 Holly, (Some type of intake), Ignition setup, Crane gold rockers, HP420 cam or ?, just get the heads redon. I will likely pull the enging in the middle of October.

Re: 1995 454 Mag genV to "525SC" or "HP420"
 

Building a 420HP from your 454mag would be the easiest and least expensive upgrade. The 420HP had a Crane flat hydraulic cam and Crane gold roller rockers. I believe it had a 750CFM Holley on top of a single plane intake. The recommended max rpm for the 420 was 5200rpm.
If you want to build a marine 454 that will make power past 5500rpm, I believe you should go with a full roller cam set-up. A lot of people suggest the Crane 731 or 741. Being that you have a Gen V block, you will need the "retrofit" cam and lifters with a thrust button on the timing chain cover.
The roller cam and lifters will cost a bit more, but is the way to go when building a 5500-5600 rpm 500HP engine. The Merc HP500 502 cube had a 800cfm carb so I don't believe that you will need more than that.
Which ever route you take, the stock heads should be at least bowl ported and the exhaust ports being worked some won't hurt .

Re: 1995 454 Mag genV to "525SC" or "HP420"
 

Thanks, Pat.
When you said I could build one with around 500hp for $2500, what kind of parts are we talking about?

Re: 1995 454 Mag genV to "525SC" or "HP420"
 

Razor, the $2500 is for the long block only. I did exclude new exhaust, intake, and carb you will also need for a 500HP.

A roller cam, roller lifters, roller rockers, and valve springs will cost you around $1200.
Rings, bearings, oil pump, and a marine gasket set is about $400.
I spent $600 on the heads from my 502. That included milling 0.010", bowl bend, opening the exhaust ports some, and a valve job.
On my block I spent $300 to have it cleaned, ball honed, and new cam bearings installed.
Your labor is free so that is how I cam up with $2500 for the long block.