455 Cam

« **on:** December 20, 2013, 09:24:20 AM »

I need a new cam for my 455 olds. As far as I know, the engine internals are stock. The cranking compression is around 150 lbs. I assume it is an 8.5 to 1 engine since there is no oil cooler. I am running an A impeller in a Berkeley pump. I may switch to an AA at some point. It has an Edelbrock 750 carb, O4B intake, Ka heads and Berkeley logs. Comp cams recommended the XE268H cam. Mondello recommended either the 18-20 or the 20-22 for a little extra. I would like to avoid changing rockers and pushrods, possibly springs. I am also looking at the XE262H as a possibility. It seems like it would be good with an AA impeller. Does anyone have experience with these cams?

The boat is a 19 foot Fiberform Malibu.

Thanks, Mark

« **Reply #1 on:** December 20, 2013, 12:25:56 PM »

The AA impeller is going to require more hp across the rpm range vs the A imp.
The AA will probably drop your rpm by about 300 over the A, and maybe more if your pump is 'loose'.
I'd keep the .050" duration around 240* or less for the logs and snails.
Looks like springs are going to be req'd for most cams, and push rod geometry should be addressed too.
Find out what is in it now before you commit to a cam.

Dan'l

« **Reply #2 on:** December 20, 2013, 02:27:25 PM »

Is there numbers/letters on the stock cam that would identify it? I believe it is the original 1973 Berkeley Packajet cam, but am not positive. I have yet to pull it out yet. I just know that a couple of lifters are not moving as they should and causing a tick. It may just be the lifters, but I figured I would replace the lifters, cam and springs so they could all break in together.

I contacted Berkeley, but they did not have stock cam information available. They said one of the extreme marine comp cams (268 or 280) are what most guys install. It is interesting that Comp did not recommend one of their marine cams

My thought on the AA is to provide good hole shot and cruising performance. It would also keep the 455 from running dry. In my perfect world, turning a AA at 4600-4800 rpm would be ideal.

Thanks for the help.

« **Reply #3 on:** December 20, 2013, 05:13:40 PM »

I would call comp cams and tell them what engine u got and have the power band in at 48 to 5000 rpms. Not 6 to 6500 rpms its a boat not a car.

« **Reply #4 on:** December 20, 2013, 06:33:12 PM »

Renegade -

The XE268h is what Comp cams recommended for my setup with a max rpm in the 4800 range and an idle of 800 rpm. I noticed that the cam says it is good up to 5800 rpm on the website, but the camquest software shows this cam peaking at around 4500 rpm in a 455 similar to mine. The heads must be killing it.

« **Reply #5 on:** December 26, 2013, 01:26:41 PM »

Running into the same issue, debating between the xtreme marine cam or the 268... My lifters were doing the same thing, now that the motors apart, over half were either frozen or had minimal movement.

« **Reply #6 on:** December 26, 2013, 03:17:58 PM »

"I assume it is an 8.5 to 1 engine"

IMHO: Might be worth pulling the heads to cc the pistons/heads to calculate your static compression ratio. If you over-cam an 8.5:1 engine it'll be a dog.

FYI: My old 10.25:1 Olds with the Mondello 22-25 cam (or any maufacturer's equivalent) would spin an AA impeller to 4700-4800 through the logs, with a Quadrajet on a Torker manifold. I believe that this was pretty typical performance.

Good luck!

« **Reply #7 on:** December 26, 2013, 08:43:24 PM »

There are a few more things to consider.

How the camshaft is installed and rocker ratios have to be taken into consideration, not just the grind.

IMHO, I like the XM268H installed 2.5 degrees advanced over recommended. Also use good roller tipped rockers with a stock ratio of 1.6:1

If you want it to be really snappy but don't want to spend a ton of money on the rest of the valve train, get the XM280H cam and run small block Chevy 1.5:1 ratio rockers.... Less lift, more duration and it will idle like it's pissed off...

You really can't miss with the XM268H, but use the recommended Comp springs and upgrade the retainers and rotators...

Also be sure to check for coil bind and maybe even convert over to screw in studs. It really is a cheap upgrade when you do the math.

Don't forget the break in process is crucial on these flat tappet deals....

GT

mstrader77

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