Go Back  Offshoreonly.com > Technical > General Q & A
Question for the cam guys >

Question for the cam guys

Notices

Question for the cam guys

Old 04-12-2011, 06:33 PM
  #1  
Registered
Gold Member
Thread Starter
 
Join Date: Apr 2010
Location: Daniels, WV
Posts: 895
Likes: 0
Received 10 Likes on 5 Posts
Default Question for the cam guys

I installed this cam kit (see link below) in my new engine and a few folks brought up the possibility of reversion but were not for sure. I would like some more opinions before I sink a ton of money in an exhaust system this year or if I can get by without it this year and upgrade the exhaust next year. It's a SBC with stock Merc manifolds and risers, thru transom exhaust that exits about six inches above water line at the back of the boat while at idle speed. So in another words the tips are always out of the water. Any input or experience with a similar setup would be appreciated!!

http://sdparts.com/details/gm-perfor...parts/12480002
87MagnumII is offline  
Old 04-12-2011, 08:49 PM
  #2  
Registered
 
Join Date: Feb 2011
Location: Birch Run, MI
Posts: 402
Likes: 0
Received 0 Likes on 0 Posts
Default

Thats a borderline cam for water reversion, especially for stock manifolds. Also your manifolds could be corroded making the problem worse. Reversion is not about where the tips exit the boat, its where the water from the exhaust enters the manifold and then the engine sucks water back into cylinders while its running. Some performance manifolds are a lot better at keeping water out with aftermarket cams than the stockers. Your cam has a 112 LSA, while a 114 is usually used as the minimum to be sure no reversion happens. Hopefully someone with more experience on SBCs chimes in as I have played mostly with BBCs

If you can swing a new exhaust I would do it, because you are going to see very little gain from that cam alone. And it wont do you any good to wait until next year for manifolds if all your valves are shot or you hydrolock the engine
rexcramer1 is offline  
Old 04-12-2011, 08:53 PM
  #3  
Registered
iTrader: (4)
 
Join Date: May 2009
Location: Chicago, IL; Onekama, MI
Posts: 3,887
Received 121 Likes on 66 Posts
Default

Originally Posted by rexcramer1
Thats a borderline cam for water reversion, especially for stock manifolds. Also your manifolds could be corroded making the problem worse. Reversion is not about where the tips exit the boat, its where the water from the exhaust enters the manifold and then the engine sucks water back into cylinders while its running. Some performance manifolds are a lot better at keeping water out with aftermarket cams than the stockers. Your cam has a 112 LSA, while a 114 is usually used as the minimum to be sure no reversion happens. Hopefully someone with more experience on SBCs chimes in as I have played mostly with BBCs

If you can swing a new exhaust I would do it, because you are going to see very little gain from that cam alone. And it wont do you any good to wait until next year for manifolds if all your valves are shot or you hydrolock the engine
+1 to the above... Look at stainless marine, they make a nice set up for small blocks...Also do a seach in the swap section, there was a set of stainless manifolds for a good price.
endeavour32 is offline  
Old 04-12-2011, 10:18 PM
  #4  
Registered
 
Join Date: Oct 2005
Location: Millstadt, IL
Posts: 1,888
Received 18 Likes on 9 Posts
Default

Originally Posted by rexcramer1
Thats a borderline cam for water reversion, especially for stock manifolds. Also your manifolds could be corroded making the problem worse. Reversion is not about where the tips exit the boat, its where the water from the exhaust enters the manifold and then the engine sucks water back into cylinders while its running. Some performance manifolds are a lot better at keeping water out with aftermarket cams than the stockers. Your cam has a 112 LSA, while a 114 is usually used as the minimum to be sure no reversion happens. Hopefully someone with more experience on SBCs chimes in as I have played mostly with BBCs

If you can swing a new exhaust I would do it, because you are going to see very little gain from that cam alone. And it wont do you any good to wait until next year for manifolds if all your valves are shot or you hydrolock the engine
I'll give it a +2, well said
jeffswav is offline  
Old 04-12-2011, 10:39 PM
  #5  
Registered
Gold Member
Thread Starter
 
Join Date: Apr 2010
Location: Daniels, WV
Posts: 895
Likes: 0
Received 10 Likes on 5 Posts
Default

Tried to find the post in the swap shop but no luck. Is there any specific type of riser that I need? Can I put aftermarket risers on stock manis to get by for a season or is the manifold itself the issue? I understand that the water mixes with exhaust but how far back does the mix need to be? I'm kinda lost here, sorry guys. I appreciate your help I really do
87MagnumII is offline  
Old 04-12-2011, 11:14 PM
  #6  
Registered
Platinum Member
 
Join Date: Mar 2008
Location: Vancouver BC
Posts: 1,181
Likes: 0
Received 0 Likes on 0 Posts
Default

There are so many things that contribute to reversion other then just lobe sep. I would have no fear of running that cam with the stock manifolds. Let it idle for a bit and pull a riser off right away before it cools down and condensation starts. You'll be able to tell if you have an issue.
If you can afford better manifolds now your engine will be able to take better advantage of the new bump stick. Also, a lot of engine failures are due to water leaking at the wet joint on factory manifolds.
HaxbySpeed is offline  
Old 04-12-2011, 11:58 PM
  #7  
Registered
Gold Member
Thread Starter
 
Join Date: Apr 2010
Location: Daniels, WV
Posts: 895
Likes: 0
Received 10 Likes on 5 Posts
Default

Originally Posted by HaxbySpeed
There are so many things that contribute to reversion other then just lobe sep. I would have no fear of running that cam with the stock manifolds. Let it idle for a bit and pull a riser off right away before it cools down and condensation starts. You'll be able to tell if you have an issue.
If you can afford better manifolds now your engine will be able to take better advantage of the new bump stick. Also, a lot of engine failures are due to water leaking at the wet joint on factory manifolds.
When you say wet joint are you talking about where the riser bolts down on the manifold? And when I pull the riser where am I looking for water? Down inside the manifold?
87MagnumII is offline  
Old 04-13-2011, 07:22 AM
  #8  
Registered
iTrader: (1)
 
Join Date: Feb 2011
Posts: 2,640
Likes: 0
Received 4 Likes on 3 Posts
Default

87Magnum, FWIW, I was running a comp cams 226*/236* @ .050 .540/.547 on a 112* LSA in my 454 with stock exhaust and silent choice with no reversion issues. Of course, big block and small block are two different animals, so I don't know if that would make a small block less or more prone to reversion. I have read that larger cubic inch engines "see" a given cam as milder than smaller engines, but conversely, I have also read that the larger piston/bore/stroke "pulls" harder on the exhaust stroke overlap. I personally feel like you will be OK with the short duration on that cam. A lot more can be read into it with the actual valve open/close events rather than duration and LSA numbers.
Budman II is offline  
Old 04-13-2011, 07:30 AM
  #9  
Registered
Gold Member
Thread Starter
 
Join Date: Apr 2010
Location: Daniels, WV
Posts: 895
Likes: 0
Received 10 Likes on 5 Posts
Default

Originally Posted by Budman II
87Magnum, FWIW, I was running a comp cams 226*/236* @ .050 .540/.547 on a 112* LSA in my 454 with stock exhaust and silent choice with no reversion issues. Of course, big block and small block are two different animals, so I don't know if that would make a small block less or more prone to reversion. I have read that larger cubic inch engines "see" a given cam as milder than smaller engines, but conversely, I have also read that the larger piston/bore/stroke "pulls" harder on the exhaust stroke overlap. I personally feel like you will be OK with the short duration on that cam. A lot more can be read into it with the actual valve open/close events rather than duration and LSA numbers.
I will see if I can dig up the cam card as it has all of the other info you mentioned and see if that helps
87MagnumII is offline  
Old 04-13-2011, 06:03 PM
  #10  
Registered
 
Join Date: Oct 2005
Location: Millstadt, IL
Posts: 1,888
Received 18 Likes on 9 Posts
Default

Originally Posted by Budman II
87Magnum, FWIW, I was running a comp cams 226*/236* @ .050 .540/.547 on a 112* LSA in my 454 with stock exhaust and silent choice with no reversion issues. Of course, big block and small block are two different animals, so I don't know if that would make a small block less or more prone to reversion. I have read that larger cubic inch engines "see" a given cam as milder than smaller engines, but conversely, I have also read that the larger piston/bore/stroke "pulls" harder on the exhaust stroke overlap. I personally feel like you will be OK with the short duration on that cam. A lot more can be read into it with the actual valve open/close events rather than duration and LSA numbers.
Duration numbers are usually smaller on SBC. They cannot be compaired to BBC specs.
jeffswav is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.