The HP450 used a hydraulic roller cam.

GM V8 454 cid (7.4L) Gen V.
Sterndrive Models (LH rotation), 4 bolt mains, flat lifters.
7.4L XW 1992-1996, 1XW, start Gen V, no mechanical
fuel pump pad on cylinder block, GM
4-bbl intake.
14 (356)
7.4LX MPI UC 1996, MerCruiser MPI intake. 14 (356)
7.4L PT Bravo 3 UW 1993, cast pistons, start GM hi-rise intake. 14 (356)
7.4L PT Bravo 3 UB 1993-1994, start forged pistons. 14 (356)
7.4L PT Bravo 3 XX 1994-1996, start new design cast pistons. 14 (356)
454 Mag XA 1992-1996, 2XA, start Gen V, no mechanical
fuel pump pad on cylinder block, GM
hi-rise intake.
14 (356)
454 Mag XAA 1995, GM hi-rise intake. 14 (356)
454 Mag MPI UA 1994-1996, MerCruiser MPI intake. 14 (356)
Ski Models (LH rotation), 4 bolt mains, flat lifters.
454 Mag MPI UA 1994-1996, no mechanical fuel pump pad
on cylinder block, MerCruiser MPI intake.
14 (356)
Inboard Models (LH rotation), 4 bolt mains, flat lifters.
7.4L XY 1992, 2XY, start Gen V, no mechanical
fuel pump pad on cylinder block, GM hirise
intake.
14 (356)
7.4L MPI UD 1995-1996, MerCruiser MPI intake. 14 (356)
Mercury Racing built Sterndrive Models (LH rotation).
HP425 UA 1993. GM hi-rise intake, 4 bolt mains. 14 (356)
HP450 UA 1995. 14 (356)
HP525 SC UA 1993-1996, supercharged. 14 (356)

Don't remember any pics on motor/bilge

See this thread...

http://www.offshoreonly.com/forums/g...454-450hp.html

Ok fellers. I have the cam specs for you.
It is a custom grind cam that the engine builder has made in oregon. He says is similar to a 1970 chevelle 454 450hp factory cam.

Intake duration 224
Exhaust duration 232

Lift intake 527
Lift exhaust 553

Center line 110
Exhaust 118

He said he has built hundreds of engines using this cam shaft. They pull great around 5k-5500

His recommended timing is 34-36 all in.

Hunter, what kind of exhaust is on the engine, and specifically, how far away does the water enter the exhaust?

The cam you have is more than likely a Speed-Pro piece. Running the numbers on it, overlap comes in at 75 degrees which is a lot. I'll bet it's sucking in water at idle. Try kicking up the idle to about 900 RPM and see how it acts.

It has imco thumper power aluminum manifolds and risers. I will adjust idle up and see how she does. Thanks for the tip tom.

Hunter, that exhaust is really meant as a replacement for Merc's heavy, iron system (the riser is similar to the ones made by Marine Power). Your cam has more overlap than a Mercuiser HP420 (an engine famous for sucking water). The HP420 was eventually equipped with a Gil system that used a long riser to mix water farther downstream. Bumping the idle might help it, but you have to keep the idle acceptable so that the drive shifts properly.

Play with the idle speed to see how she does.

Ten4. Thank you for the info! Itll be a few days before I can do anything. It's cold and raining here now.