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Engine Guys Need Quick 454-420 Recipie

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Old 08-17-2006, 08:11 AM
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Default Engine Guys Need Quick 454-420 Recipie

I just need to know what could hop up the HP in this 454-420 motor with a quick and simple change(cam and heads?) Turns out I had detonation in engine. ended up with tulipe valve and melted electrode, and 1 or 2 damaged piston. So while it's all opened, any recommendation on what to change to give a 30 to 80 HP more ? I need to know fast cause I'd like it to be back together ready for the fun run on lake champlain september 2nd ! If possible give what parts number to use and roughly how much more HP I should get with your recipie.

Thanks for your fast help!
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Old 08-17-2006, 10:37 AM
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Default Re: Engine Guys Need Quick 454-420 Recipie

Your engine already has a lot of good parts in it. All forged internals and big port heads. If you already have the single plane intake and Holley 800 carb, I would rebuild to stock except for a hyd. roller cam like the Crane 139011. It has 226 int./234 ex. duration @ .050. .587 int./ .610 ex. lift . And I would send your heads to Jim Valako, Jim V here on the board for his wedges and port work. While they are there he can do a valve job and set up the springs correctly. Real tube headers would be better than the stock exhaust also. I bet that would make over 500 hp and still be drivable.
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Old 08-17-2006, 05:03 PM
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Default Re: Engine Guys Need Quick 454-420 Recipie

Man... I tore them down today. 3 holes in valve, 1 melted piston, little water in the other engine... So I brought all that (heads intake exaust) to my engine builder. First look at it, he said the heads were 454-365... Then asked me if the pistons had a little dome on them, slightly angled on the piston, and if they were domed piston, it really was a 365... Well, they're domed. So what I had was exhaust and air filter from 420's. Got screwed... weak 365 instead of healthy 420...makes a difference.
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Old 08-17-2006, 08:37 PM
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Default Re: Engine Guys Need Quick 454-420 Recipie

Jeff, I don't know about the pistons. but the rest of the bottom end is the same. Sounds like you have to replace the pistons anyway. I think the 365 and the 420 use the same heads. The 420 is full roller valve train though. So go with Patriyachts advice and you'll still end up where you want to be.
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Old 08-17-2006, 08:57 PM
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Default Re: Engine Guys Need Quick 454-420 Recipie

I'm I better off rebuilding these as 365 hp I sell them back, and buy HP500 for 7-8 k? I would think so if I think quick. Have to figure it out though.
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Old 08-17-2006, 09:21 PM
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Default Re: Engine Guys Need Quick 454-420 Recipie

contact JC performance... Jeff will give you some help.
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Old 08-17-2006, 09:25 PM
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Default Re: Engine Guys Need Quick 454-420 Recipie

Payton is right. The only internal difference between the Merc 365hp and the 420hp is the 420hp has Crane Gold roller rocker arms, and a larger cam. All rotating parts are FORGED in both engines.....so, the 365's are actually a very good baseline engine to do mods to. But in order to give the engines a little more kick I would add a hydraulic roller cam like Patriyacht has suggested sounds pretty good/close, then do a little pocket porting on the heads. Also, an aftermarket exhaust manifold system like a Stainless Marine, GIL or something comparable will DEFINATELY help with any mods you're doing. Try not to be in too much of a hurry....that's when things go sour! Hope it goes well for you.
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Old 08-17-2006, 11:24 PM
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Default Re: Engine Guys Need Quick 454-420 Recipie

GM sells a crate motor, 454, Gen 6, 502 heads, JE Pistons, 420 hp, all balanced, MARINE warranty, $5200 or so.

1800runsnew.com has them.......

this will be much less money and headach that what you are considering....
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Old 08-18-2006, 07:35 AM
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Default Re: Engine Guys Need Quick 454-420 Recipie

What I suggested will still work except you more than likely don't have the correct intake and carb. The internal parts are the same on the 420 and 365. Forged crank, dimpled 7/16 bolt conn. rods, 4 bolt mains. The cam , carb and intake are the major differences. Take what I said above and add the carb and intake from a hp 500. 800 Holley and a Dart single plane intake. You will need the entire valvetrain from Crane as none of the pieces from the 365 will be up to the job.
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Old 08-18-2006, 10:44 AM
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Default Re: Engine Guys Need Quick 454-420 Recipie

thanks everybody to help me out to try to get out of this sh.t as smooth as possible.
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