Marine Wet Exhaust Question

[ntheogen]

A friend is doing a 427 MR in a boat with a wet exhaust system. He (and I) has a question about the cam possibly scavenging water in the exhaust. It's a Lunati 40510, Int 237/Exh 247 at 050. Does anyone have any experience they could share about it.

Thanks,

Jack
540-664-for four one ate

[Saltshaker]

Yes, wide center line helps
Jon

[blykins]

A friend is doing a 427 MR in a boat with a wet exhaust system. He (and I) has a question about the cam possibly scavenging water in the exhaust. It's a Lunati 40510, Int 237/Exh 247 at 050. Does anyone have any experience they could share about it.

Thanks,

Jack
540-664-for four one ate

Too much overlap on that cam, Jack.  I wouldn’t use it. You need to cut about 20-25 degrees of overlap out of it. 

[My427stang]

I agree with Brent completely, that cam, not counting lash is 85 degrees overlap, too much when you don't need it.

I doubt any water would travel backwards, but overlap is a necessary evil to take advantage of a good exhaust pulse in a specific RPM range.  I would have to assume that the wet exhaust is nowhere near as efficient as a properly sized and designed header.  In other words, you'd give up power down low and likely not gain it back up top

I'd see what RPM he is going to run it the most, get an idea of the exhaust or even a picture of it, as well as the rest of the build and get a custom flat tappet if that's what he wants

[66FAIRLANE]

I ran that cam in my Fairlane for many years. On a 390 it made about 7" of vacuum, had to idle rich & did not come alive until about 4000prpm. Pulled to 7000 though & sounded nasty. It used to be good at doing this.

[ntheogen]

New cam it is then, thanks guys, much appreciated.

Jack

[RustyCrankshaft]

Also depends on how "wet" the exhaust is. For instance, the stock manifolds used on that engine in the 60's put water in the riser right at the turn from vertical. If you use, or build a riser put the water in farther away from the vertical turn it's hard to pull water back in. Or you can go to dry risers which are double wall all the way to the tips (if thru hull). If you are running the exhaust thru a a leg then it changes things a little. I've run some pretty big overlap cams in 351w's and just moved the water discharge farther down the riser.

But you do have to be careful even with changing the water discharge unless you are willing to do to dry exhaust.