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Originally Posted by TomZ
(Post 4923957)
The 741 is a little too much in a 454 without head work and increases in compression.
A copy of the 621 500 EFI cam is what I’d go with (or something close to it). It’ll keep the power band about where you’ll need it for that Chris Craft. I think the duration on the cam is almost identical to the 420 cam, too. Whatever you go with, get it on a Gen VI core (Crane 621 is a Gen VI cam). You’ll be able to use a Gen VI timing set with the retainer that it uses to keep the cam from walking versus having to run a cam button and all that. Definitely run as far away as you can from flat tappets. They’re engine killers at this point. |
Originally Posted by Belt69
(Post 4923980)
Is it that easy to jump to a gen 6 setup? Just the cam and timing chain? So I would need to get the cam retainer plate too, and would I need the roller tappet guide if I order the cam kit that comes with lifters? Or would that even work on a Gen 4 block?
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The Merc 420 has a lot of decent parts in it to start out with. It just doesn't have a lot of compression, and the piston to deck clearance is a little wide to just cut the heads to reduce chamber cc.
On a lightweight boat, the 741 will work well with your other components but you'll be leaving power on the table with your low compression. On a heavy hull, the 741 will be a little soft on low rpm torque with a 454. Optimally, if you could snap your fingers, you would zero deck the block (piston to deck height of zero), you would bore notch the cylinders to unshroud the valves, and you would drop in the 741 cam and springs, along with tie bar roller lifters. Your WEIAND Intake is a decent piece, and your carb isnt really holding you back. Ignition is also adequate. A lot of guys pop in a hot cam and expect another 500 rpm on top end due to the added power, but find that they've lost enough bottom end to make it sluggish to plane with a full load. |
Originally Posted by TomZ
(Post 4923957)
The 741 is a little too much in a 454 without head work and increases in compression.
A copy of the 621 500 EFI cam is what I’d go with (or something close to it). It’ll keep the power band about where you’ll need it for that Chris Craft. I think the duration on the cam is almost identical to the 420 cam, too. Whatever you go with, get it on a Gen VI core (Crane 621 is a Gen VI cam). You’ll be able to use a Gen VI timing set with the retainer that it uses to keep the cam from walking versus having to run a cam button and all that. Definitely run as far away as you can from flat tappets. They’re engine killers at this point. |
Originally Posted by F-2 Speedy
(Post 4923921)
Things will add up pretty quick, cams, lifters, push rods, valve springs, rockers........possibly retainers and clips depending on what heads you have......good luck
Gen VI block, is a different story. |
Originally Posted by Tartilla
(Post 4925478)
Gen V blocks can be drilled and tapped to bolt up thre Gen VI cam plat on the fron of the block. Way better solution in my opinion...than a cam button.
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Originally Posted by TomZ
(Post 4925503)
All the blocks I’ve seen already have the bosses drilled. I believe they used them with gear drives in the heavy duty market.
gen5 I took apart yesterday. Came out of my 94 top gun. |
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