What are the differences between a marine bb and car bb - Lateral-g Forums

**glassman** · #1 07-22-2016, 08:54 PM

The time has come to rebuild/replace the engine in my 74 Keaton. Its currently a 455 Olds with 10.25 and a 442 camshaft, its a "Pack-a-jet" sold in the 70's which included a jet.

So, i'm probably going to convert it to a bbc or maybe an ls. Want the torque and ease of a bbc, parts are easier to find. But, i dont know the differences between a marine engine and a car engine. I know the externals are different for Coast Guard/fire & safety.

Any ideas on the long block part?

Vegas69 · #2 07-22-2016, 09:01 PM

I think it's the seasoning of the block to avoid excessive corrosion. I'm not 100% on that.

DB Z28 · #3 07-22-2016, 09:07 PM

Nothing really . When I worked at Mercury racing the block only change was took out the steel freeze plugs and put in brass one .different cam, intake with a cast in bronze water jacket ,marine carb, and marine starter and dist which was vent bowel tubes were different sealed starter and dist that met specs of USCG approved and that was it.

**glassman** · #4 07-22-2016, 09:13 PM

Good to know, thanx for the info. I'm trying to find a 454 maybe a crate, looks like they may not be available anymore....just started looking though

Todd, i had heard that too, may be for the newer alum blocks (LS) ones in the higher dollar tournament boats.

SSLance · #5 07-23-2016, 04:41 AM

I believe the exhaust valves in the heads are different in a marine application as well. Inconnell exhaust valves are sometimes used in marine heads to handle the heat better. Marine engines run at a steady high torque RPM for long periods of time which can overheat standard auto type exhaust valves.

68Cuda · #6 07-23-2016, 07:38 AM

What about 10.2" deck vs 9.8"? Are tall deck engines more prevalent in the marine world? If you are looking to just do a crate engine, nothing crazy high horse or big cube then the tall deck has little advantage. For big hp or big cube then the longer rod you run with the tall deck will help.

Che70velle · #7 07-23-2016, 08:20 AM

I worked in an race engine shop in the 90's that built quite a few off shore racing engines. They were big block chevy's, and as mentioned above by db z28, virtually no differences. If I were doing it for myself, I'd go aluminum heads for the weight savings. Cam choice is crucial in a marine app, as you are looking for torque. A lot of high end boats today have LS2's or LS3's in them.

**Flash68** · #8 07-23-2016, 01:34 PM

I'd consider replacing that window AC unit first....

DB Z28 · #9 07-23-2016, 02:17 PM

the more the Hp engines the more we changed out parts .We also replaced the valves with Manley stainless valves. recheck all the torque spec on the engine. All the old parts like valve springs , valves ,cams intakes all got sold to Competition Products out of Oshkosh WI.

**glassman** · #10 07-23-2016, 04:28 PM

Quote:

Originally Posted by Flash68

I'd consider replacing that window AC unit first....

Did u see the sticker on the boat genius? I've screwed up the backyard even more, think 14 junkyard (collectibles) all piled on the lawn next to the pool, lady Pamela was cool with it.....