Reply With QuoteI personally ran a 252/258@.050 .680/.708" 114 C/L. Solid roller, Gil exhaust with no reversion problems on a 502 mag.
What is the biggest cam you've seen successfully used with a thru-hull wet exhaust? I'm interested in the durations @ 0.050 and lobe separation specs so I can calculate overlap.
I personally ran a 252/258@.050 .680/.708" 114 C/L. Solid roller, Gil exhaust with no reversion problems on a 502 mag.
I personally ran a 252/258@.050 .680/.708" 114 C/L. Solid roller, Gil exhaust with no reversion problems on a 502 mag.
27° overlap compared to 4° for stock mercruiser cam (Crane p/n 132561)
Anyone else?
Wet exhaust is a very "loose" way to compare exhaust systems. I had "wet" CMI e-tops on my Baja and ran some very large cams with no reversion. The exhaust actually exited below the water line at idle and the water mixed with the exhaust at the end of the tailpipe inside the boat. The motor was a Dart Pro1 aluminum headed 496" stroker. With 12:1 compression I ran an Erson solid roller with 278/284 duration @ .050" on a 112+4 installation. This cam had .680" lift. Then with 13.25:1 compression I ran a Comp solid roller with 272/280 duration @ .050" on a 112+4 installation. This cam had .714" lift. The 13.25:1 combo was by far better than the 12:1 combo. I got carried away with too much duration and not enough compression! Typical enthusiast learning the hard way. With stock "wet" manifolds please don't run much more than 228/235 duration @ .050" or else you will suck water!!
If memory serves me well, which it doesn't any more.
272/272 @.050
.642/.642
110 lobe sep
Lighting water jacketed exhaust
500 BBC w/871
13% over
11#'s boost
BIG lopey idle
no reversion
Wet exhaust is a very "loose" way to compare exhaust systems. I had "wet" CMI e-tops on my Baja and ran some very large cams with no reversion. The exhaust actually exited below the water line at idle and the water mixed with the exhaust at the end of the tailpipe inside the boat.
That definition of "wet" is pretty much what I'm talking about. Stock Mercury exhaust manfolds and a thru hull exhaust which sits right at the waterline when the boat is not moving.
Putting the biggest cam in a boat engine to make it go faster is not a good idea if this is what you are up to. A well thought out combo is your best bet.
Chris
Another thing to consider is that if it is a Bravo boat, it needs a decent idle, anyway.
Putting the biggest cam in a boat engine to make it go faster is not a good idea if this is what you are up to. A well thought out combo is your best bet.
Chris
This is a paper exercise. I've read tons about reversion concerns but as my technically minded friend told me simply looking at the lobe separation is not enough. I'm just wanting to gather some practical experience of what works and what doesn't to know where that limit is at.
No parts changes planned with this question. Just wanting to understand where the "line" is at.
A well thought out combo is your best bet.
Chris
BINGO
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