454 Cam selection down sizing?
 

I have a fresh short block 454 with 10.1 compression. Which I am selling to my buddy to help him get back on the water asap. We are trying to put together I a motor using parts we currently have. Going to be using GM 088 Heads. We are trying to decide what Cam to use. I have a Mercruiser 454 Mag cam and a Comp marine 11-306-4. Can I get away with a moderate cam like one of these? Not looking for the extra power, Just want it to run good. Also want to be able to use stock exhaust and stock rocker arms.

how did you achieve 10-1 compression on that motor. You need to run a little larger cam with that compression

That's a whole lot of want.......

Does it make 10:1 with those heads ? I'd measure everything that effects compression and see what it really will have.

if the pistons have a little dome,,it will.

The comp cam has a 110 Lob sep and will not work with stock exhaust. It will revert water.

Use thick head gaskets to reduce compression as much a possible and the stock 454mag cam.

Any good Thick Marine Head gaskets out there?

The pistons are SRP 212135
(118cc @ 9.9-1)

Was planning on using Fel-Pro Head gaskets FEL-17042
Which according to my calculations puts it at 9.8 to 1

If you go with an extra thick head gasket, then your quench numbers go out the window, which in itself could promote detonation. 10:1 on an iron-headed marine engine is asking for trouble, unless you plan to run racing fuel in it. Better break out the Valdez Platinum Card for that one with a boat. I tried to compromise on my 454 years ago - had a set of domed pistons that would have produced similar CR numbers. Jumped through hoops to make them work - had the domes milled down, thicker head gasket, etc. In the end, the engine eventually succumbed to detonation and busted the ringlands off two pistons right near the valve reliefs. IMO trying to throw together a motor for a boat with "parts laying around" is a gamble at best. You can get away with it on a car, but with a boat you might as well belly up to the roulette table. A marine engine needs to be thought out with carefully selected parts that work together within the rigid parameters that a marine environment dictates. Sorry I don't have more help than that, but I wish you the best of luck.

Everyone thanks For all the very helpful information!

I didn’t mean it so much as piecing it together. It turns out my buddy wiped out the short block on his 454 Mag. And I have a 454 10-1 short block. That I have no use for, and would like to use if possible. Anything that can/needs to be done to make this work?

I just wanted to get some feedback on possible use of what I already have before spending the extra money on another short block.

Thanks

the only thing you MAYBE could do id get a custom cam but I still think youre going to have detonation problems

What's your guys thoughts on using comp marine 11-306-4 cam and upgrading the exhaust?

Here are the cam specs

Lift .525
Duration @ .050 In=222 Ex=226
Lobe Separation 110

The high compression is the real issue. Better off to spend the money on new pistons than exhaust to try and make something work.
The quench with using a thicker head gasket is an issue. It prob could be managed, but is still just a band aid. Cometic makes thicker head gaskets.

It sounds like Budman has been through the exact same thing. I think you are better off to do the build right the first time than to try and put some mismatched parts together.

instead of bying aftermarket exhaust think about bying a set of aluminum heads.afr makes some pretty affordable heads that would cost about the same as a good aftermarket set of manifolds.

Not sure where you are at but a friend has a running take out BBC complete with bravo bell housing and exhaust on powerboat swap shop for $1200... if your buddy is trying to salvage the rest of the summer that might be your best bet.

I am in New Jersey- any more information would be great. I looked on swap shop and didn't see anything

Already sold, I'm sure you could find similar more local to you. Good luck.

110 degree LS is what we run in our drag engines.

I have run those pistons 212135's and 37's for about 8yrs. 4 of those years with steel Merlin heads. I have used 17042 and 17048 gaskets 91-93 octane. Don't forget to bore notch the cylinders while you're in there.

I've had nothing but good luck with these piston with iron heads(many motors later). My concern wasn’t so much the Iron Heads vs. Compression ratio. It was more so the higher compression matched with the Comp cam.(I've always ran a larger cam)

But thanks everyone for the help, as I will defiantly be using aluminum heads on a future build, since I heard nothing but good results!