Water reversion camshaft question
05-15-2013, 03:19 PM
#1
Registered
Thread Starter
Join Date: Jul 2011
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
Water reversion camshaft question
Another cam question
I'm having second thoughts about adding the captains call exhaust to my boat. Previous I had no water reversion problems with 2 years on the boat. Will adding captains call increase the possibility of getting water reversion while running the exhaust out of the prop? Or would it be more likely that info had no reversion problems before I will not have them now?
Details on the boat
.40 over 502
Ross 8.8:1 pistons
GM performance aluminum heads
Procharger
Gil/Hardin Marine headers and risers
Custom Hydraulic roller cam. .230 intake .242 exhaust @.50 114 lobe separation installed at 113 degrees
4 inch corsa captains call exhaust
I will never run the captains call above 2500 Rpms and will very rarely run it at idle.
I'm having second thoughts about adding the captains call exhaust to my boat. Previous I had no water reversion problems with 2 years on the boat. Will adding captains call increase the possibility of getting water reversion while running the exhaust out of the prop? Or would it be more likely that info had no reversion problems before I will not have them now?
Details on the boat
.40 over 502
Ross 8.8:1 pistons
GM performance aluminum heads
Procharger
Gil/Hardin Marine headers and risers
Custom Hydraulic roller cam. .230 intake .242 exhaust @.50 114 lobe separation installed at 113 degrees
4 inch corsa captains call exhaust
I will never run the captains call above 2500 Rpms and will very rarely run it at idle.
05-15-2013, 05:21 PM
#3
Registered
Thread Starter
Join Date: Jul 2011
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
My boat idles high anyways. So anything between 1000-2500 should be safe?
05-17-2013, 08:29 AM
#4
Only the Best Will Do!
Join Date: Nov 2004
Location: Palm Coast, FL
Posts: 548
Likes: 0
Received 0 Likes
on
0 Posts
Another cam question
I'm having second thoughts about adding the captains call exhaust to my boat. Previous I had no water reversion problems with 2 years on the boat. Will adding captains call increase the possibility of getting water reversion while running the exhaust out of the prop? Or would it be more likely that info had no reversion problems before I will not have them now?
Details on the boat
.40 over 502
Ross 8.8:1 pistons
GM performance aluminum heads
Procharger
Gil/Hardin Marine headers and risers
Custom Hydraulic roller cam. .230 intake .242 exhaust @.50 114 lobe separation installed at 113 degrees
4 inch corsa captains call exhaust
I will never run the captains call above 2500 Rpms and will very rarely run it at idle.
I'm having second thoughts about adding the captains call exhaust to my boat. Previous I had no water reversion problems with 2 years on the boat. Will adding captains call increase the possibility of getting water reversion while running the exhaust out of the prop? Or would it be more likely that info had no reversion problems before I will not have them now?
Details on the boat
.40 over 502
Ross 8.8:1 pistons
GM performance aluminum heads
Procharger
Gil/Hardin Marine headers and risers
Custom Hydraulic roller cam. .230 intake .242 exhaust @.50 114 lobe separation installed at 113 degrees
4 inch corsa captains call exhaust
I will never run the captains call above 2500 Rpms and will very rarely run it at idle.
Best regards
05-17-2013, 09:24 AM
#5
Registered
Thread Starter
Join Date: Jul 2011
Posts: 61
Likes: 0
Received 0 Likes
on
0 Posts
Ok if I never use it at idle and only use it in the 1500-2500 range cruising across the lake I should be ok? What's the highest rpm everyone recommends using it? Would I be safe to 3000?
05-17-2013, 09:50 AM
#6
My understanding of reversion is that it is more of an issue at idle, particularly low speed idle. Basically, the intake charge and exhaust charge do not have enough velocity and momentum to overcome the piston heading downward. Seems to me as the engine speed increases, airflow velocity will increase and there will be less reversion. This is basically why you will hear the lope disappear as you increase engine speed. Now at some point if you are running the exhaust flow down a Y-pipe to a single exit point back pressure will become an issue and I guess you could once again encounter some exhaust reversion, but it's hard to say where that point will be. I have heard that there is actually a negative pressure venturi effect produced thru the prop when the boat is in motion, but I have no way to verify that.
FWIW, I was running a 454 with a Comp Came Xtreme Marine flat tappet that ran 224* / 236* @ 0.050, 112 LSA with stock Merc manifolds and Silent Choice. I ran it with the exhaust closed at idle, as well as at cruise all the way up to about 3500 RPM with no sign of reversion. However, it is somewhat of an apples to oranges comparison to your setup. You have 50 more cubes, and longer duration, although at a 114* LSA.
Might be a good idea to talk to one of the camshaft pro's, like Bob M. at Marine Kinetics.
FWIW, I was running a 454 with a Comp Came Xtreme Marine flat tappet that ran 224* / 236* @ 0.050, 112 LSA with stock Merc manifolds and Silent Choice. I ran it with the exhaust closed at idle, as well as at cruise all the way up to about 3500 RPM with no sign of reversion. However, it is somewhat of an apples to oranges comparison to your setup. You have 50 more cubes, and longer duration, although at a 114* LSA.
Might be a good idea to talk to one of the camshaft pro's, like Bob M. at Marine Kinetics.
05-17-2013, 10:14 AM
#8
Registered
Join Date: Sep 2012
Location: Denver, CO
Posts: 131
Likes: 0
Received 0 Likes
on
0 Posts
My understanding of reversion is that it is more of an issue at idle, particularly low speed idle. Basically, the intake charge and exhaust charge do not have enough velocity and momentum to overcome the piston heading downward. Seems to me as the engine speed increases, airflow velocity will increase and there will be less reversion. This is basically why you will hear the lope disappear as you increase engine speed. Now at some point if you are running the exhaust flow down a Y-pipe to a single exit point back pressure will become an issue and I guess you could once again encounter some exhaust reversion, but it's hard to say where that point will be. I have heard that there is actually a negative pressure venturi effect produced thru the prop when the boat is in motion, but I have no way to verify that.
FWIW, I was running a 454 with a Comp Came Xtreme Marine flat tappet that ran 224* / 236* @ 0.050, 112 LSA with stock Merc manifolds and Silent Choice. I ran it with the exhaust closed at idle, as well as at cruise all the way up to about 3500 RPM with no sign of reversion. However, it is somewhat of an apples to oranges comparison to your setup. You have 50 more cubes, and longer duration, although at a 114* LSA.
Might be a good idea to talk to one of the camshaft pro's, like Bob M. at Marine Kinetics.
FWIW, I was running a 454 with a Comp Came Xtreme Marine flat tappet that ran 224* / 236* @ 0.050, 112 LSA with stock Merc manifolds and Silent Choice. I ran it with the exhaust closed at idle, as well as at cruise all the way up to about 3500 RPM with no sign of reversion. However, it is somewhat of an apples to oranges comparison to your setup. You have 50 more cubes, and longer duration, although at a 114* LSA.
Might be a good idea to talk to one of the camshaft pro's, like Bob M. at Marine Kinetics.
That cam you mentioned is the same one I was talking about in my post. So, you were able to run it okay? How did you like it?
Sorry for the hi-jack! However, your answer might be beneficial to the OP too.
05-17-2013, 12:08 PM
#9
Seemed to run fine - no reversion at least. Of course, as they say, YMMV. Don't know exactly how much power it made - boat was seeing about 61 MPH on a good day (88 Baja Force 235) with Performer RPM, Q-jet, GM 820 casting oval port heads with bowl porting and 2.19 intake valves, etc. Might have run better with a Holley, but then again, might not have.
