How to upgrade 420HP 454cui
07-22-2009, 02:08 PM
#11
Registered
Assuming a 10 percent increase in volumetric eficiency, you will still need to spin the engine to 6000 rpm to see 530 hp. The most Merc ever got out of a 454 was 450 hp and that engine had a hyd roller, 800 Holley and a single plane intake. 550 is pretty easy with a small blower and it won't be nearly as bad tempered.
07-22-2009, 04:12 PM
#12
Registered
Thread Starter
Join Date: Oct 2006
Posts: 104
Likes: 0
Received 0 Likes
on
0 Posts
Assuming a 10 percent increase in volumetric eficiency, you will still need to spin the engine to 6000 rpm to see 530 hp. The most Merc ever got out of a 454 was 450 hp and that engine had a hyd roller, 800 Holley and a single plane intake. 550 is pretty easy with a small blower and it won't be nearly as bad tempered.
07-23-2009, 07:58 AM
#13
Registered
I was thinking along the lines of a Wieand 256 blower with a single carb running 5-6 lbs of boost. It would be safe on a stock engine without an inter cooler on 93 octane and make 550 hp easy. You could find a used 525sc blower for less money but they really should use an intercooler if you're going to try for 550 hp. Sure there are things you should do to ensure long life. Larger oil lines and fittings and a larger oil cooler are at the top of the list. The engine should be in good shape to begin with, good compression and not too many hrs. on the valvetrain. The stock cam in a 420 is the same cam as the 525sc. It's a pretty good sc cam although it's mild and a flat tappet hyd. If the engine is in good shape, it's mostly a bolt on.
07-27-2009, 02:03 AM
#14
Just an FYI, Dave Wessledye just rebuilt an old pair of real simple 454cid engines for a guy....8.8cr, 750 Hollys, GM rectangle port heads...bone stock no port work or anything, GM DUAL PLANE intake manifolds, and some of RMBUILDER's easy going hydraulic roller cams.....dyno'd at 481hp @5300rpm and somewhere around 500 lbs of torque----dyno'd with water cooled marine tubular headers, alternators, all belts & pullies, etc. Jetted a little rich too!
I'd say not too shaby (I thought maybe 450-460hp at the most) for bone stock heads and dual plane intakes with an easy does it roller cam. Engines were some really old Merc Cyclone 400hp engines.
I'd say not too shaby (I thought maybe 450-460hp at the most) for bone stock heads and dual plane intakes with an easy does it roller cam. Engines were some really old Merc Cyclone 400hp engines.
09-08-2009, 10:39 AM
#15
Registered
Thread Starter
Join Date: Oct 2006
Posts: 104
Likes: 0
Received 0 Likes
on
0 Posts
Leave it 454 CI. Use the square pot heads. Edelbrock 454-R single plane intake. Incerease comp around 9.5:1+-. Call bob for cam.
You don't need a bigger carb than 750 +-. I have tried biger ones on the dyno and they don't help with the HP as the engine can only use as much carb as it needs.
The shorter crank will let you rev that engine higher. If you don;t mind ocasionally spinning it over 5000, then you should have no problems getting the piower you want. The sroker kit is not worth the extra cazh IMO?
You don't need a bigger carb than 750 +-. I have tried biger ones on the dyno and they don't help with the HP as the engine can only use as much carb as it needs.
The shorter crank will let you rev that engine higher. If you don;t mind ocasionally spinning it over 5000, then you should have no problems getting the piower you want. The sroker kit is not worth the extra cazh IMO?
http://www.summitracing.com/parts/HRS-CL120405/
http://www.summitracing.com/parts/HRS-CL120255/
09-08-2009, 11:26 AM
#17
Registered
Platinum Member
Just an FYI, Dave Wessledye just rebuilt an old pair of real simple 454cid engines for a guy....8.8cr, 750 Hollys, GM rectangle port heads...bone stock no port work or anything, GM DUAL PLANE intake manifolds, and some of RMBUILDER's easy going hydraulic roller cams.....dyno'd at 481hp @5300rpm and somewhere around 500 lbs of torque----dyno'd with water cooled marine tubular headers, alternators, all belts & pullies, etc. Jetted a little rich too!
I'd say not too shaby (I thought maybe 450-460hp at the most) for bone stock heads and dual plane intakes with an easy does it roller cam. Engines were some really old Merc Cyclone 400hp engines.
I'd say not too shaby (I thought maybe 450-460hp at the most) for bone stock heads and dual plane intakes with an easy does it roller cam. Engines were some really old Merc Cyclone 400hp engines.
09-08-2009, 12:03 PM
#18
Registered
iTrader: (2)
Join Date: Aug 2005
Location: Between A Womans Leggs in IL
Posts: 6,306
Likes: 0
Received 1 Like
on
1 Post
mrfixxall
Dont let the looks of the engines fool you they are new with app 80 hrs on them..
http://www.offshoreonly.com/classifi...o30340-en.html
Last edited by FIXX; 09-08-2009 at 03:30 PM.
09-08-2009, 01:48 PM
#19
Platinum Member
Platinum Member
The stock Merc 420 or Merc/Gil replacement exhaust on a Merc 420 HP with GM heads will not likely make 550 HP NA. If the exhaust is still wet, not likely even 500 HP. As others have said, on a 454-470 CI block with GM heads your best bet is a small blower. Besides the heads, the exhaust is also a big HP hurdle.
Merc made a 525 SC, would it make sense to copy this format? The 525 SC should also be the low cost upgrade.
Merc made a 525 SC, would it make sense to copy this format? The 525 SC should also be the low cost upgrade.
09-08-2009, 04:27 PM
#20
Just an FYI, Dave Wessledye just rebuilt an old pair of real simple 454cid engines for a guy....8.8cr, 750 Hollys, GM rectangle port heads...bone stock no port work or anything, GM DUAL PLANE intake manifolds, and some of RMBUILDER's easy going hydraulic roller cams.....dyno'd at 481hp @5300rpm and somewhere around 500 lbs of torque----dyno'd with water cooled marine tubular headers, alternators, all belts & pullies, etc. Jetted a little rich too!
I'd say not too shaby (I thought maybe 450-460hp at the most) for bone stock heads and dual plane intakes with an easy does it roller cam. Engines were some really old Merc Cyclone 400hp engines.
I'd say not too shaby (I thought maybe 450-460hp at the most) for bone stock heads and dual plane intakes with an easy does it roller cam. Engines were some really old Merc Cyclone 400hp engines.
