Go Back  Offshoreonly.com > Technical > General Q & A
454 Mag build.  yes another post on this! >

454 Mag build. yes another post on this!

Notices

454 Mag build. yes another post on this!

Old 10-26-2011, 08:23 PM
  #1  
Registered
Thread Starter
iTrader: (4)
 
Join Date: May 2009
Location: Chicago, IL; Onekama, MI
Posts: 3,887
Received 121 Likes on 66 Posts
Default 454 Mag build. yes another post on this!

OK I'm in the planning stages of building a set of 454 mags for my Formula 292. The engines have around 300 hours on them so I would like to use as many of the parts as I can. Here is what I have

Dart Single Plane Intakes
Stock 454 Mag intakes
Gil Exhaust with thru transom dry to tip tails

I've been reading many of the posts on this subject but there isn't really any concrete info in them. Some guys say the dart is to big for a 454. Others say it isn't. Some say the stock manifold can make good power with a 1" spacer. As for the heads I'm thinking about having Jim V install wedges, depending on the price. I have an other option as well.

I have another engine that I build last year that has AFR 260 ovals with a weiand stealth intake. I could take the top end off that engine and put it on these and buy another set of heads and intake. But I would rather not!

Now all I'm after is around 470-500 hp. I don't think I need the AFR's for that amount of HP but I'm not ruling that option out. I know that tons of OSO members have done what I'm thinking about what are your opinions on this and what worked for you?

Last edited by endeavour32; 10-26-2011 at 08:47 PM.
endeavour32 is offline  
Old 12-10-2011, 04:52 AM
  #2  
Registered
Gold Member
iTrader: (1)
 
KAAMA's Avatar
 
Join Date: Oct 2000
Location: Western Michigan
Posts: 4,457
Received 72 Likes on 44 Posts
Default

IF you have the Merc 454 Mags----I'm thinking those are the 365hp engines that have 4-bolt mains, and have all the good, forged rotating internals and big rectangle port heads....just need to replace the stock GM stamped steel rocker arms with a good aftermarket ROLLER rocker arm system.

To obtain 475-500 HP.....looks like you already have a better breathing aftermarket exhaust system (GIL), then you will most likely need to do a cam upgrade....a hydraulic roller cam that will make power up to about the 5500rpm level or so.

Along with the above mentioned components, you can use the stock GM Rectangle port heads, you already have---just have JimV do a slight clean up short side radius on the INTAKE side and then do a bowl port/short side radius job on the EXHAUST side.

I would also add bronze wall valve guides. An open plane intake manifold such as the Dart would provide good torque and power for this application.

Back in the mid 80's, I had a friend who had a 302 Formula and he used the stock GM rectangle port heads, upgraded hyd cams (flat tappet), open/single plane Team G intake manifolds, GIL exhaust system and a Holley 800cfm carb and the boat had great throttle response from the midrange to the top.

You could use the oval port AFR's, but I don't think it would be necessary for 475-500 HP.

I would consult Bob Madara/RMBuilder of Marine Kinetics for the cam upgrade. Have fun.

Last edited by KAAMA; 12-10-2011 at 04:57 AM.
KAAMA is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.