Reversion

[enkeivette]

Theres talks on the interwebs that cams with more than 230 degrees of duration can have 'reversion' issues and theres danger of sucking in water. (Boat apps) This sounds like a load of bs to me, what do you guys think?

First of all, duration AND lobe sep angle come in the play with overlap. So a cam with a 110 lsa and 232 degrees of duration would have about as much overlap as a 114 lsa 236 degree cam. So a static rule like that is retarded.

Secondly, for the exhaust to suck in water, that tiny little bit of overlap is going to have to overpower the other 3 cylinders in order to actually suck air in all the way from the collector. Sound theoretical at best and realistically impossible to me.

Thoughts?

[94cobra69ss396]

My dad was running a Comp 292 which has 244 at .050 and a 110 lsa and never had an issue.

[enkeivette]

My dad was running a Comp 292 which has 244 at .050 and a 110 lsa and never had an issue.

And he had wet exhaust?

[94cobra69ss396]

Yep. He was using the Gleenwood exhaust logs pictured below.

https://post.craigslist.org/imagepreview/m/5N95K65M43k83K83H2c6606826052d2641eda.jpg

[Shaolin Crane]

Theres talks on the interwebs that cams with more than 230 degrees of duration can have 'reversion' issues and theres danger of sucking in water. (Boat apps) This sounds like a load of bs to me, what do you guys think?

First of all, duration AND lobe sep angle come in the play with overlap. So a cam with a 110 lsa and 232 degrees of duration would have about as much overlap as a 114 lsa 236 degree cam. So a static rule like that is retarded.

Secondly, for the exhaust to suck in water, that tiny little bit of overlap is going to have to overpower the other 3 cylinders in order to actually suck air in all the way from the collector. Sound theoretical at best and realistically impossible to me.

Thoughts?

The lavey craft race boat driver confirmed they were having "sucking" problems with large duration cams. The talk came up when my neighbor asked him about which cam to run with his new motor in his lavey craft. It definitely varies by application and the entire cam needs to be viewed when installing in a boat with water logged exhaust. I'd call Isky, or clay smith for input as they both make the most boat application cams from what i can remember. Though from personal experience our boat motors have always been boosted so overlap was very low if any. He also mentioned different types of wet exhausts but i cant remember what he said.

[enkeivette]

Cool, thanks guys, if Rons dad can get away with a 244 110lsa, I should be good with a 242 110lsa.

And if youve heard of race motors squeaking by Ron Im not terribly worried. Im not interested in asking comp, they either wont know or theyll tend to cover their ass. Warranty of fitness for a particular purpose kinda deal, know what Im sayin son?

[enkeivette]

Prob be a good idea to move water outlet past any u bends in the exhaust too.

[Shaolin Crane]

Cool, thanks guys, if Rons dad can get away with a 244 110lsa, I should be good with a 242 110lsa.

And if youve heard of race motors squeaking by Ron Im not terribly worried. Im not interested in asking comp, they either wont know or theyll tend to cover their ass. Warranty of fitness for a particular purpose kinda deal, know what Im sayin son?

That's why I didnt mention comp, they have not been the greatest guiding light when i've called about cams. Isky and clay smith have been around the longest and are both local. The owner of clay smith's son lives here in covina. You can also call ACC (american custom cams) and he can do any grind for $75 as long as you have a core for him. He ground the cam in the blue car.

[enkeivette]

Oops, meant to say, "squeaking by Guy."

[Vettezuki]

. . . You can also call ACC (american custom cams) and he can do any grind for $75 as long as you have a core for him. . .

I vaguely remember hearing of this company. Apparently they can really dial in an application. Do they have blanks on the shelf?

[Shaolin Crane]

I vaguely remember hearing of this company. Apparently they can really dial in an application. Do they have blanks on the shelf?

Probably, i usually keep a stock cam on my shelf just in case.

[Shaolin Crane]

Oops, meant to say, "squeaking by Guy."

Actually they werent squeeking by, water doesnt like to be compressed so, boom. They actually run a very mild chevy in their race boat. Its gotta last

[enkeivette]

Actually they werent squeeking by, water doesnt like to be compressed so, boom. They actually run a very mild chevy in their race boat. Its gotta last

So they destroyed their motor, then rather than just run dry exhaust they ran a more mild engine in a RACE boat??

[Shaolin Crane]

They wanted a motor that could go the distance. My dads boat, the one I pictured actuallyraped that thing in the straight line. That was also the day my dad popped his motor trying to beat it, the difference is in the boat and controls. They want a boat that isnt going to sacrifice reliablity when alot of times the off shore races depend on driver and water conditions, not the power of the engine.