stock 4" cast exhaust... how much power?
02-13-2008, 10:41 AM
#11
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Here is the deal... I have this 3" Stainless marine system now, made in 1989, old shool, I do not have 2-5000.00 in the budget this year for a Gil, Imco, or stainless marine system, I need to wait one more year at least, I can get good 4" cast stuff for free, main reason is with this system I have now it is almot impossible to do plugs and work on the front of the engines, if I can change to the 4" stuff for free and not lose power I will do it so I can work on this thing easier.
I mean, ther performance of the systyem I have now cannot be good anyway in my opinion, but back in the day it must have been OK if it was made aftermarket?
Like I said, if the cast stuff will perform the same as what I have I will change it.
I mean, ther performance of the systyem I have now cannot be good anyway in my opinion, but back in the day it must have been OK if it was made aftermarket?
Like I said, if the cast stuff will perform the same as what I have I will change it.
02-13-2008, 11:03 AM
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Aren't thos just regular 420 Mercs in your boat? If so, then that stock exhaust isn't going to hurt it much.
My theory is though. If it ain't broke, don't fix it.
How do you know the free exhaust you are getting doesn't have a problem somewhere? At least yours works properly right now.
My theory is though. If it ain't broke, don't fix it.
How do you know the free exhaust you are getting doesn't have a problem somewhere? At least yours works properly right now.
02-13-2008, 11:41 AM
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Aren't thos just regular 420 Mercs in your boat? If so, then that stock exhaust isn't going to hurt it much.
My theory is though. If it ain't broke, don't fix it.
How do you know the free exhaust you are getting doesn't have a problem somewhere? At least yours works properly right now.
My theory is though. If it ain't broke, don't fix it.
How do you know the free exhaust you are getting doesn't have a problem somewhere? At least yours works properly right now.
02-13-2008, 02:12 PM
#16
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420's had reversion problems with they stock cast, thats one of the reasons merc went to gils way back when. I don't know who makes what you have but it looks like it may mix the water further down stream then the stock 4"
I think reversion is more of a problem then flow in your case. If it works and does not allow water in cylinders I agree Jeffman1000 if it's not broke don't fix it.
I think reversion is more of a problem then flow in your case. If it works and does not allow water in cylinders I agree Jeffman1000 if it's not broke don't fix it.
02-14-2008, 04:40 PM
#17
You can't put enough cam into the engine with stock exhaust. It will revert water. I would say 400-425hp. Also, you're loosing power with the stock exhaust. It might make 420hp with the cast exhaust, when in reality it will make 460hp with good exhaust. Good exhaust is also more important in N/A engines.
02-14-2008, 06:29 PM
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just a side note , if you wanted an inexpensive upgrade to your exhaust , 496 manifolds work in place of the stock manifolds , they flow a little better and as a bonus there a dry joint between the riser and manifold
i was going to buy a set for my motor when i found a sweet deal on a set of true headers , but i got a few responces from people with 496 exhausts selling em between 200 and 400 bucks , not bad for a small upgrade
i was going to buy a set for my motor when i found a sweet deal on a set of true headers , but i got a few responces from people with 496 exhausts selling em between 200 and 400 bucks , not bad for a small upgrade
02-14-2008, 07:00 PM
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just a side note , if you wanted an inexpensive upgrade to your exhaust , 496 manifolds work in place of the stock manifolds , they flow a little better and as a bonus there a dry joint between the riser and manifold
i was going to buy a set for my motor when i found a sweet deal on a set of true headers , but i got a few responces from people with 496 exhausts selling em between 200 and 400 bucks , not bad for a small upgrade
i was going to buy a set for my motor when i found a sweet deal on a set of true headers , but i got a few responces from people with 496 exhausts selling em between 200 and 400 bucks , not bad for a small upgrade
02-14-2008, 07:22 PM
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http://www.offshoreonly.com/forums/s...d.php?t=178721
i just posted in the parts wanted section , couple weeks no replies , then i got 3 in one day , feel free to drop em an IM , as i said , i already got a set of headers and wont be needing em
also , what did you do with your 420 cyl heads when you upgraded?
i just posted in the parts wanted section , couple weeks no replies , then i got 3 in one day , feel free to drop em an IM , as i said , i already got a set of headers and wont be needing em
also , what did you do with your 420 cyl heads when you upgraded?
