I'm in the process of rebuilding a set of 454 Mags to either the 420 specs or the 440 HP specs. I'm curious if anyone has experience with both of these engines and if there is a reason why I shouldn't use the 440 cam which as far as I can tell is the Lunati 00026 cam.

Yes I know roller is better, and if I could swing it I would have Bob build me custom roller cams, but I don't have the coin on this build for roller cams, custom push rods, roller lifters, ect. Flat tappet is what it is.

The cam used in the Merc 440hp engine was a hydraulic flat tappet made by Ultradyne...something like 231*/239* @.050 .550" lift Intk and .558" lift on the exhaust with 110* lobe seps.

I always thought the cam used in the Merc 440hp was a bit too much cam for a 454cid marine engine. It had a slightly rough idle, but not too much that you couldn't stand it---but I thought the idle sounded really good with headers. It would probably idle slightly better if ground on a 112* lobe seps.

I believe I still have one of Merc 440hp cams NEW in the box from Ultradyne if you're interested.

Your correct it was an Ultradyne cam, but I'm pretty sure Lunati is now making that cam.

Here are the specs on the Lunati cam
•Advertised Duration (Int/Exh): 293/310
•Duration @ .050 (Int/Exh): 232/239
•Gross Valve Lift (Int/Exh): .549/.558
•LSA/ICL: 110/104


What I'm curious about is dock manners as well as characteristics at cruising 3000-3500 RPMs. I'm running Gil's Dry to the tip so I'm good on reversion, I think. If you had two cams I would be interested as I'm building two engines.

Use the big oval port heads instead of the big squares. It will have better mid range and idle manners. Use a 650 carb as well. 750 is overkill for that sixe engine, and the smaller throttle body will allow for higher velocity which will increase the signal and help with idle.

Just some general info. I always had good luck with flat tappets. Just break them in right and get on with it.

Since you have that dry exhaust, I have a bad ass set of flat tappets I will sell you cheap. THey will make close to 500 on a 420 merc with dry exhaust and oval port heads.

Just get this Crane cam and call it good. Budget priced for a cam/lifter kit. It pulls strong to 5400-5500rpms.
http://www.summitracing.com/parts/CRN-134242/