Reversion what is the impact?
 

As I understand it reversion in general terms is the sucking of 'sea' water into the exhaust pipe outlets due to certain cam design parameters. That is not the question.

What are the actual proplems that reversion causes?
1.) Corrosion only?
2.) Hydraulic lock of pistons?
3.) Other????????

Re: Reversion what is the impact?
 

Corrosion for sure, if bad enough it can hydrolock the engine. It can make the exhaust valves brittle enough to snap off. Water can get into the oil wiping out the engine. The list goes on..

Re: Reversion what is the impact?
 

Worst case scenario-the water hydro locks the piston,bends or breaks the connecting rod destroying the motor,more likely though,water quenching the exhaust valve makes it brittle then head breaks off stem then destroys the motor. Mild reversion-milkshake oil,rust and pitting in affected cylinders,Smitty

Re: Reversion what is the impact?
 

check,you beat me while i was typing,Smitty :D

Re: Reversion what is the impact?
 

i lost 2 engines last year to it :mad: :mad:

Re: Reversion what is the impact?
 

vrooom vroom bang! got the picture...with reversion the engine will be very short lived. run dry exhaust and forgedaboutit

Re: Reversion what is the impact?
 

Son of a gun! Almost sorry I asked.

Does the hydraulic lock happen in a middle of a run lets say or upon start up after turning the engine off and restart?

What's the best/easiest way to find out if you have a reversion issue?

Re: Reversion what is the impact?
 

What exhaust are you running and what cam.I was told by my exhaust manifold company to run the motor at idle for ten to fifteen minutes with my quit system in the closed position.Then shut off engine and remove riser and see if the manifold is wet inside.If it is then you have trouble.

Nordic95

Re: Reversion what is the impact?
 

Sorry Bill :(
I had to warn you though....
It's well worth checking for peace of mind.

Re: Reversion what is the impact?
 

Please do not appologize. This is need to know stuff.

Since my o2 wide band sensor survived a 12 min. run with a lot of idling I am hopefull BUT will still conduct tests suggested.

The cam timing @0.050 is....
- intake opens 6.0 BTDC
- intake closes 44.0 ATDC
- intake duration 230
- exhaust opens 57.0 BBDC
- exhaust closes (1.0) BTDC
- exhaust duration 236

The exhaust is stock Merc 496HO with turbulators removed.

Re: Reversion what is the impact?
 

What is a "quit system"?

Re: Reversion what is the impact?
 

everytime mine has happened, it was when I was slowing down from a high RPM run, I have 11k worth of new headers that should fix my problem. :(

Re: Reversion what is the impact?
 

Was it hydraulic lock or broken exhaust valve?

Re: Reversion what is the impact?
 

hydraulic lock leads to broken exhast valve wich leads to broken piston wich leads to broken block wich leads to broken heart wich leads to broken wallet wich leads to broken family.... :( :( :D

Re: Reversion what is the impact?
 

add bent connecting rods to the what can happen list. The biggest impact... Broken Wallet.

Re: Reversion what is the impact?
 

dayum a wanna cry after reading that post...

Re: Reversion what is the impact?
 

The highest rate of reversion occurs at or close to idle. Reversion will cause corrosion of intake and exhaust valves. Depending on the cam grind you will get a great amount of cross talk between intake and exhaust at low engine speeds (idle).

The biggest problem with reversion is that water ends up in your oil. Most people mistake the water in the oil for a blown head gasket or leaking intake manifold gasket. Since water doesn't like being compressed when it enters the combustion chamber it squeezes past the piston rings and milks out the oil. If this goes unchecked your oil will break down rapidly.

Best way to check for reversion is to warm the engine up the run at or close to idle. Shut down and immediately remove an exhaust manifold/header and check for water. If it's wet you have reversion.

Re: Reversion what is the impact?
 

:evilb: :evilb: :evilb: its sad but true............ :drink: :drink:

Re: Reversion what is the impact?
 

10K :rolleyes:

Re: Reversion what is the impact?
 

What is the "QUIT SYSTEM" of which you speak?

Re: Reversion what is the impact?
 

Silent Choice, it reverts the exhaust through the bottom of the gimble vs the tailpipes

Re: Reversion what is the impact?
 

Rage:

Your 496HO engine is an efi motor and if you got a fairly correct cam in there the LSA of the cam is the most important number. On a 496 efi that number should be between 115 to 119 degrees. If its not you could develop a serious reversion problem. If your motor idles smoothly down at 650 rpms in gear I suspect you have a correct LSA and reversion should not be a problem for you.

Ray @ Raylar

Re: Reversion what is the impact?
 

Nordic 95?

Re: Reversion what is the impact?
 

Sorry. Disregard "Nordic 95?"

Re: Reversion what is the impact?
 

Is reversion more prevalent in a blower motor with a blower cam?

Re: Reversion what is the impact?
 

Is a higher LSA number or a lower LSA more of a reversion problem?

What would be the reversion potential of LSA114 degrees in your opinion?

Bill

Re: Reversion what is the impact?
 

Rage
They are talking about quick & quiet or silent choice exhaust, where your exhaust can be switched between a full thru the prop exhaust and out the transom tailpipes. These systems can back exhaust exit water back up in the sytem and lead to some serious reversion. with the cam spec you've listed on your 496 with a probable 116 to 119 lsa on that fuel injected cam, reversion won't be a big issue, but valve and seat corrosion can be. The stock GM iron heads come with iron head material machined in head seats and cheap steel valves that can rust when subjected to cool down moisture in the system especially on the valves that are left hanging open, This is why we use high quality stainless steel valves that are QPQ nitrited in our aluminum heads. No corrosion period!

Ray @ Raylar

Re: Reversion what is the impact?
 

Thanks as always for the information Ray.

Just to make sure I understand you, the LSA on my cam is 114. I thought that a given physical cam can have only one LSA. I am unclear about your meaning when you said "with the cam spec you've listed on your 496 with a probable 116 to 119 lsa".

Does reversion increase when the LSA is a (1.) larger numerical value i.e. greater than LSA119 or (2.) a smaller numerical value i.e. less than LSA115 or (3.) both when the LSA is a larger numerical value i.e. greater than LSA119 or a smaller numerical value i.e. less than LSA115.

Thanks,

Bill

Re: Reversion what is the impact?
 

All it takes is a mist of water to spray onto a red hot exhaust valve and kaboom....

Re: Reversion what is the impact?
 

Ray?

Re: Reversion what is the impact?
 

i've noticed a lite bit of surface rust in the ports, but the valves and combustion chambers were free of any signs of water,i am running stainless marine exhaust with comp cams extreme marine cams,xm 272, in a carbed 454 w/ performer intakes, is this anything to be worried about??? wouldn't raising the idle speed slightlt higher help alleviate the problem?? comp cams swears that these cams will not cause reversion, also, what affect(if any) does ignition timing play??

Re: Reversion what is the impact?
 

Check the gaskets between your manifold and exhaust pipes. Also pressure test the exhaust manifold and tail pipes. If you have a leak you will get reversion.

If you have rust signs on the ports it's probably in places you can't see it.

What timing are you running? In the past I've run run 34-36* in my NA motors.

What are the specs of the cam?

Re: Reversion what is the impact?
 

"If you have a [exhaust] leak you will get reversion". Really? Why is that?

Re: Reversion what is the impact?
 

The exhaust escapes thru the leaky gasket creating a vacuum.

Re: Reversion what is the impact?
 

The threads of both of my o2 sensor bungs one inch above the exhaust manifold flange on the 496HO exhaust risers do not make an air tight seal such that a water drop will occasionally wick out from the threads at idle. When I place my hand over the o2 sensor bungs I do not feel any exhaust flow at all when engine running.

Is that enough exhaust leak to cause reversion by itself?

Re: Reversion what is the impact?
 

Bill,
If your sensors are not sealing they will leak water even though this is not a clear case for reversion. This is a very common phenomina that occurs with CMI Etop joints as well. The water will find any path to the outside if it is there. I have seen this on numerous CMI setups and when removed for inspection there is no sign of water anywhere. Some have even welded this joint to eliminate this.
Use some high temp RTV on the threads and this should help from frying your sensors.
Dave

Re: Reversion what is the impact?
 

Dave,

HaMon are you sitting on some beach with a laptop and satelite feed reading OSO posts?

1.) "that occurs with CMI Etop joints" are these the joints where two of the exhaust tube sections are welded to make a continous tube and they missed a spot?

2.) "that occurs with CMI Etop joints" if the water is not from reversion then from what/where?

Actually I have not seen the sensor(which comes with a metal gasket) leak as yet. It is the bung plugs that leak the water by the threads on both risers. However I have been trying to protect the sensor by using the bungs until the engine is warm and in open water by running with the bung plugs to get there and then switching to the sensor just for test start. When I remove the bung plugs the water is puddled in the female threads. When I pop the risers there is only moisture visable above the flange except for the ceiling of the (long) front and rear exhaust manifold runners. The two short runners and everything else in the exhaust manifold is black and dry.

Any other thoughts besides sealing the threads of bungs and sensor?

Re: Reversion what is the impact?
 

If a previous post is correct and the following are the cam specs for.......
Merc HP525EFI 236 int,246 exh, 114 sep, .06++ lift
Merc HP500EFI 230 int,236 exh, 114 sep, lift int .598 exh .610

.....then for my cam : 230 int,236 exh, 114 sep, lift int .598 exh .610 to have reversion what could be the contributiong factors (in addition / other than an exhaust leak)?

Re: Reversion what is the impact?
 

Rage:

The LSA is the difference in degrees between the centerlines of the lobes between the intake cam lobe and the exhaust cam lobe. This LSA when smaller generally creates more overlap or the period where the intake and exhaust valve are open at the same time depending on the valve event timing of the cam.
Generally on fuel injected engines this LSA is kept wider or larger to provide a lower manifold pressure (vacuum signal) at idle on a bigger cam to keep the MAP signal smoother to the ECM.
You will have to be careful with your motor at that duration and valve timing with a 114LSA. Reversion at idle and on decel could be an issue for your application. Who recommended your cam specs to you? On the specs you listed I believe you mean your intake closes at 44degrees after bottom dead center, not After top dead center as you listed it. This means by the numbers you listed that the intake and exhaust valves will be open at the same time for almost 100 degrees of overlap. That seems high so check your cam specs again. I am just not sure of your cam specs here and what the real situation may be on your motor.

Ray @ Raylar

Re: Reversion what is the impact?
 

The cam is a Crane #OEM0988 and the intake does close at 44 degrees ABDC.