Go Back  Offshoreonly.com > Technical > General Q & A
Need help choosing new cams >

Need help choosing new cams

Like Tree0Likes

Need help choosing new cams

Reply

Old 01-25-2003, 11:48 AM
  #1
Registered
Thread Starter
 
X-Rated30's Avatar
 
Join Date: Mar 2001
Location: Monroe, LA
My Boat: 1997/2010 Spectre Catamaran w/ twin 250XS Sports
Posts: 3,882
Default Need help choosing new cams

I am going to change the cams in my 454/425s to try to get a little more top end torque. (Around 4600 rpms, they would max out, even though I had more throttle.) Can anyone suggest a resource or the cams? THX.
X-Rated30 is offline  
Reply With Quote
Old 01-25-2003, 01:18 PM
  #2
Registered
 
formula31's Avatar
 
Join Date: Mar 2001
Location: ohio
My Boat: 1988 Cruisers 2800 Rogue
Posts: 2,558
Default

Oh, this will be a big thread. Ah, I like the edelbrock torker cams because I use gils magnum choice risers which puts the water flow in nearly as soon as stock and I use the torker 2 intake too. I think they are 224,232,.527,.553 at 114 degrees seperation. I run them at 5100 usually.
formula31 is offline  
Reply With Quote
Old 01-25-2003, 01:25 PM
  #3
Dennis Moore
Guest
 
Posts: n/a
Default Tough call!

I have been looking at Mercruisers selection of cams for years now and still haven't figured them out. I really don't know which cam you have in the 425. If it is a 425 HP I believe that you have the 454 with the same camshaft as the 500 HP carb engine and the factory stock dual plane intake manifold. In my opinion you can't do much better than this camshaft. But it could be some other camshaft too! I would remove the camshaft and send it to Comp Cams to have them measure it and make a suggestion on a new camshaft. They do this sort of thing all of the time and the charge is minimal. Give them a call.
Otherwise my suggestion would be a camshaft with 224/230 intake/exhaust duration @ .050 with minimum lift (under .550) a 110 degree lobe separation angle with the intake at 4 degrees advanced (but this may be the cam that is already in your engine!).
Sincerely
Dennis Moore
 
Reply With Quote
Old 01-25-2003, 01:37 PM
  #4
Registered
 
formula31's Avatar
 
Join Date: Mar 2001
Location: ohio
My Boat: 1988 Cruisers 2800 Rogue
Posts: 2,558
Default

Oh yea, i forgot. I run mine 4 degrees advanced too.
formula31 is offline  
Reply With Quote
Old 01-31-2003, 10:41 AM
  #5
Registered
Thread Starter
 
X-Rated30's Avatar
 
Join Date: Mar 2001
Location: Monroe, LA
My Boat: 1997/2010 Spectre Catamaran w/ twin 250XS Sports
Posts: 3,882
Default Re: Tough call!

Originally posted by Dennis Moore
I have been looking at Mercruisers selection of cams for years now and still haven't figured them out. I really don't know which cam you have in the 425. If it is a 425 HP I believe that you have the 454 with the same camshaft as the 500 HP carb engine and the factory stock dual plane intake manifold. In my opinion you can't do much better than this camshaft. But it could be some other camshaft too! I would remove the camshaft and send it to Comp Cams to have them measure it and make a suggestion on a new camshaft. They do this sort of thing all of the time and the charge is minimal. Give them a call.
Otherwise my suggestion would be a camshaft with 224/230 intake/exhaust duration @ .050 with minimum lift (under .550) a 110 degree lobe separation angle with the intake at 4 degrees advanced (but this may be the cam that is already in your engine!).
Sincerely
Dennis Moore
The engines are the Gen VI HO motors. the cams are pt#24502311, 211/230 duration @ .050, ans lift is .510/.540.

BTW -- if you are the same Dennis Moore, I just bought one of your books.
X-Rated30 is offline  
Reply With Quote
Old 01-31-2003, 09:17 PM
  #6
Registered
 
formula31's Avatar
 
Join Date: Mar 2001
Location: ohio
My Boat: 1988 Cruisers 2800 Rogue
Posts: 2,558
Default

Yea, thats him. What exhaust are you running? If stock, I would question the 110 degree seperation he recommended, might be close to reversion. At least it scares me.
formula31 is offline  
Reply With Quote
Old 02-01-2003, 12:10 AM
  #7
Registered
Thread Starter
 
X-Rated30's Avatar
 
Join Date: Mar 2001
Location: Monroe, LA
My Boat: 1997/2010 Spectre Catamaran w/ twin 250XS Sports
Posts: 3,882
Default

EMI Thunders, but I have welded extentions on so that the H2O doesnt mix with the exhaust for another 3-4 inches. (As suggested by EMI.)
X-Rated30 is offline  
Reply With Quote
Old 02-01-2003, 12:25 AM
  #8
Platinum Member
Platinum Member
 
mcollinstn's Avatar
 
Join Date: Sep 2001
Location: tn
My Boat: 1991 F311SR1
Posts: 5,516
Default

Why advance 4 degrees. Do you need to sway your torque curve that far downward? Or is that to prevent reversion?
mcollinstn is offline  
Reply With Quote
Old 02-01-2003, 04:30 PM
  #9
Registered
 
formula31's Avatar
 
Join Date: Mar 2001
Location: ohio
My Boat: 1988 Cruisers 2800 Rogue
Posts: 2,558
Default

Years ago I read that advancing would lower the max power rpm. Since I dont like to spin em much over 5000, I gave it a try many many years ago. I used a removable cover timing cover and a Cloyes Hex-adjust and ran it at 0, then at 2 advanced, then at 4 advanced, then 6. 4 gave me the best speed. I stuck with it. Mercs older Hp engines like the 440's etc. ran with the #1 intake centerline at 105 which on my cam turned out to be 4 degrees advanced. The biggest problem is intake valve to piston clearance when you do this. I run at .085, less than recommended but safe as long as rpm's are limited. I wasnt aware that it would have any affect on reversion. Dont know.
formula31 is offline  
Reply With Quote
Old 02-02-2003, 08:49 AM
  #10
blown1500
Guest
 
Posts: n/a
Default

4* advance on a cam usually gives the best power curve. Many cams now come with the 4* ground in so you don't need to use any means to advance it yourself. Check your cam card. "Straight up" means if you have 114* lobe separation, you should have the intake lobe at 114* ATC. If you look at the cam card and it says the lobe center is something other than 114* on this cam, it is ground with the advance already in. If you advance 4* more, you are advanced whatever they ground in PLUS the 4* you just added. On most near-stock engines, 4* advance on reasonable sized cams does not cause serious valve to piston clearance problems. YOU SHOULD CHECK though!!
 
Reply With Quote

Quick Reply: Need help choosing new cams


OSO Sponsor
OSO Advertiser
OSO Advertiser
OSO Advertiser