Reversion Fears- What exhaust hose can be used?
04-13-2006, 11:05 AM
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Reversion Fears- What exhaust hose can be used?
I have 1988 Formula 311. I completely rebuilt the 454 manum engines.
Added a crane roller cam, ( 741 I believe ) and roller rockers. These are Mark IV blocks. I changed out the stock exhaust to revolution marine. I had reversion, just running on a garden hose with muffs. I likely idled the engines too low. I was so frustrated, I am in the process of removing the NEW rectangular port heads and installing freshly ported, re-valved 781 oval port heads. I hope to get the air velocity up. I plan to add "tails" to the exhaust manifold elbows to get the cooling water away from the exhaust outlet. I am led to understand that I will likely burn the rubber exhaust hose since I will be moving the cooling water away. Is there a Hose that can withstand the exhaust temperatures? If not, would adding a length of stainless pipe, in this area, be a viable option? I don't want to have to worry about idle-ing too low.
Thank you for your time in answering.
Added a crane roller cam, ( 741 I believe ) and roller rockers. These are Mark IV blocks. I changed out the stock exhaust to revolution marine. I had reversion, just running on a garden hose with muffs. I likely idled the engines too low. I was so frustrated, I am in the process of removing the NEW rectangular port heads and installing freshly ported, re-valved 781 oval port heads. I hope to get the air velocity up. I plan to add "tails" to the exhaust manifold elbows to get the cooling water away from the exhaust outlet. I am led to understand that I will likely burn the rubber exhaust hose since I will be moving the cooling water away. Is there a Hose that can withstand the exhaust temperatures? If not, would adding a length of stainless pipe, in this area, be a viable option? I don't want to have to worry about idle-ing too low.
Thank you for your time in answering.
04-13-2006, 11:30 AM
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Re: Reversion Fears- What exhaust hose can be used?
The problem with adding an extension to the inside pipe is trying to keep the cooling water on the top of the pipe. We have dams and fences inside the jacketed pipe to keep the water at the top. Even a stainless tube will burn the hell out of your hand, and be a vapor hazard. I'm agin' it!
04-15-2006, 07:36 PM
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Re: Reversion Fears- What exhaust hose can be used?
You can use silicone hose, it's the bright blue stuff you see on aircraft. 4" is going to cost you some real $$$$ so get ready for the price. You can find it at Aircraft Spruce; http://www.aircraftspruce.com/
Have you concidered replacing your exhaust before you go to the expense of replacing your new heads?
Have you concidered replacing your exhaust before you go to the expense of replacing your new heads?
04-16-2006, 04:58 PM
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Re: Reversion Fears- What exhaust hose can be used?
Thanks for the reply guys. I purchased the exhaust 2 yrs ago,new.
I have used the boat two times since. I had to go through engine rebuilds. I am changing the heads cause I did not like the throttle response of the big port heads. Also, I did not like the reversion that that flow characteristics encourage. The heads are Gen VI, on mark IV blocks. They seemed to seal fine, however there is a split opinion as to whether or not they will not leak or be prone to leaks, due to the water passage modifications that exist in the newer style heads. The aforementioned items are what drove me to the change. I again thank you for your replies.
Doug
I have used the boat two times since. I had to go through engine rebuilds. I am changing the heads cause I did not like the throttle response of the big port heads. Also, I did not like the reversion that that flow characteristics encourage. The heads are Gen VI, on mark IV blocks. They seemed to seal fine, however there is a split opinion as to whether or not they will not leak or be prone to leaks, due to the water passage modifications that exist in the newer style heads. The aforementioned items are what drove me to the change. I again thank you for your replies.
Doug
