mtocrs1

Alright guys need your thoughts on some mods for my 1989 310hp 454. The engine is fresh with forged pistons (stock compression) stock 330hp cam. It has a performer intake with Edlebrock 750 marine carb and K&N flame arrestor. It is in a 23 footer spinning a 3 blade 21 pitch prop.With this setup I run 60mph on GPS. I want to get 65. I have already purchased but have not installed a set of Imco Powerflow headers. I was thinking about going to a holley 800cfm carb. Am I realistic in expecting 5mph from these mods. Any thoughts?

375stinger

800 is overkill, we ran a 750 on our 454s up to 475horses...do you want to only do external mods without going into the engine? how many rpms are you spinning the 21?

375stinger

id start by changing cam, heads, roller rocker arms.

375stinger

ask someone else for specific part #s......i ono that much

dean51267

I am in the final stages of the same project. Here is what I did:

Comp roller cam setup, there is one made to retro the non-roller setup, 1500 to 5200 powerband, "Extreme Marine" set up

Dart heads - cast iron

Elderbrock dual plane, air gap intake, Elderbrock 750 cfm carb with 1" spacers

Lightening headers

MSD ignigtion

I expect to see 410 or so HP, ran into a snag with the cam, they are working that out now, then will have dyno numbers.

This ends up being about $3500/motor, I am not sure what the left over stuff is worth, I am going to try to move it in a week or so. That should offset some cost.

Larger cam can easily get power up higher, but I want the idol and drivability are low RPM's, so I stayed small.

Payton

You are going to need about 100 more hp to get 5 more mph. You are going to have to swap heads and cam to get that. Still don't rev over 5000rpm very often or the bottom end won't hold up, so you may need to move up in Prop pitch to keep your rpms down after the mods.

cstraub

Cam change and depending on the heads port work or replacement of the OEM castings.

Pat McPherson

The 750 cfm carb is good for 5200rpm on a 454 so replacing with an 800 will not help, only hurt low end.
Your new exhaust will help but only 100-200rpm on top.
More cam is needed; the Merc/Crane 420cam is an upgrade a lot recommend.
The peanut port heads need to go unless you have lager valves installed and have them ported.
Did you stay with flat tops when you rebuilt? The CR with flat tops and 118cc heads is only 8:1. More compression (9:1) would help.
With the flat tops and inexpensive head upgrade would be a set of used Gen VI Vortec heads (L-29). They flow better than the peanut port heads and will raise the CR to 9:1.
Another head choice would be a set of Edelbrock large ovals with 110cc chambers.

mtocrs1

Thanks for the help, I am really not interested in tearing into the motor at this point, just bolt-ons. The only thing that gets me is that Teague is telling me to use the 800. They say this carb is what they always use on these engines with great success. They also recommend using a 1' carb spacer any thoughts. Bye the way I am also planning on a ready to run billet MSD distributor. Anyone using this and did you get any real world gains? Also whats everyones thought on a 100hp shot off Nitrous?

Pat McPherson

No need for the 800cfm carb unless the engine is going to breath more with a cam and heads changes.
If the Merc Thunderbolt ignition is working, don't waste your $$ on a new system.
One thing I have heard of doing is to change the 1.7 ratio stamped rockers to 1.8 roller. This will add a little more lift and reduce friction. You may need to install fresh valve springs if you have not already during the rebuild.
I am going to give them a try this coming season...