How to tell if there was reversion/or leak with headers?
 

I have lightning headers.
I ripped apart the motor and one cylinder had some light rust streaks in cylinder. If reversion, I would imagine it would be more then one cylinder. engine builder said might be header leak.
Would the header show a discolor where the water would sit in it if it had a leak? None discolored.
Or if it just could have been from sitting outside for a few days. After I pulled the heads water ran down into the cylinders(Forgot to drain block). I did not look it over real close the day I ripped it apart.
Thanks

the merc 525s with cmi headers have an issue with reversion and water in the nu 8 cylinder.
go to dry exaust to get rid of the issue, that is what my friend is doing in the spring

Pressure test the headers off the engine to verify if they are OK or leaking.

Best Regards,
Ray @ Raylar

Does the 496 suffer the same problem with CMI headers?
And what's the best way to pressure test them?
Thanks!

Ray is correct, pressure test them off the motor. If you send them back to Lightning Jan will test them for you I'm sure, he has a nice jig for it. Reversion usually causes some heavy corrosion in the exhaust ports if you've been running it in that condition.

Just curious why it is necessary to test them off the engine? Will a leak not show up, or is it just easier to spot a leak?

They usually test them by pressurizing with air and submerging in a water tank and look for bubbles just like you would with a radiator or tire. It's allot easier to do this off the engines. :D

Remember, the leaks that you're after are inside the header not on the outer jacket.

Thanks for the reply, I tested mine yesterday using water hose and pressure gauge attached to the inlet and outlet of the water passages in the headers. Pressured them up and made sure it held for several minutes. Just wanted to make sure I was not missing something.

Just to check if I got it right:
1) attach a water hose (with a closing valve, I suppose) to the inlet which leads to each cylinder exhaust;
2) attach a pressure gauge to the outlet on top of the header;
3) open water and pressurize (30 psi, or what? The gauge doesn't go above 25 in normal usage);
4) close the valve on the water hose;
5) check for pressure losses after several (how many?) minutes.
Is the above correct, or am I missing something?

I understand it would be better to test them off the block, but I'd rather not remove them for nothing...

Besides, any recommendations specific to CMI sport tubes on 496 HO?

Thanks in advance!

[QUOTE=mapism;2995597]Just to check if I got it right:
1) attach a water hose (with a closing valve, I suppose) to the inlet which leads to each cylinder exhaust;
2) attach a pressure gauge to the outlet on top of the header;
3) open water and pressurize (30 psi, or what? The gauge doesn't go above 25 in normal usage);
4) close the valve on the water hose;
5) check for pressure losses after several (how many?) minutes.
Is the above correct, or am I missing something?

I understand it would be better to test them off the block, but I'd rather not remove them for nothing...

Besides, any recommendations specific to CMI sport tubes on 496 HO?


That is the way I did it. My hose water pressure was approx. 40 psi, which should replicate or exceed conditions seen on the water. I watched each one for maybe 5 minutes and no change in pressure was noted. I figured if there was a leak it would have been obvious fairly quickly. Good luck and I don't have any additional insight into 496's.

Many thanks.
By 'each one' you mean each header, surely?
I couldn't figure out how to check each cylinder separately.
Besides, it would be pointless: if there's any leak, the header has to be removed anyway, I suppose.

Yes, approximately 5 minutes per header. A leak would need to be dealt with by removing the header and replacing or repairing.

who can repair leaking headers?

Any good welder.... but.... most headers are heat treated and welding puts stresses into the stainless that can generate new cracks. Once you start welding on them you usually end up chasing cracks for ever. The other problem is the inside jacket may be coroded and is thinner in spots, likewhere it cracked. Welding can blow though and make holes, big mess!

I've had many headers welded in the past to get through a weekend or to finnish a season but a crack is a good sign it's time to replace. I just through out 2 sets for this reason. Leaking headers can cause some big $$$ in engine damage and I don't think it's worth the risk.

just my .02

Just to complicate things for you:

Leak checking doesn't always reveal a leak. When running the inner jacket is hot and the water jacket is cool. The differential heating will open up cracks that don't show up on a pressure check.

Mapism:

The CMI 496 sportubes are really good at getting water in the back two cylinders of even stock 496's with stock camshafts. They have very little or no downturn in the lower two cylinder tubes that enter the collecter area of the header and with some boats with captain's call or silent choice switchable exhaust or low fall to the transom exhaust outlets they can get a lot of water vapor and actual water in the header that will run downhill into those last two cylinders on the engine at idle.
We've seen this and damage on a lot of 496's with Sportubes on even stock engines!

I always reccomend welding some 1/4" high 45 degree slanted anti-reversion rings in the tips a few inches back towards the engine from the water injection point inside the tips. These will prevent a lot of water and water vapor from migrating back up the header which occurs along the inside diameter of the tube in what we call the 1/8" dead air boundry layer. Ya, thats right! air does not flow in this inside 1/8" thick boundry layer and in some cases it even moves backwards from standard exhaust pulsing without actual reversion. We see this damage on 496's even when the headers are not leaking from cracks in CMI's.

Best Regards,
Ray @ Raylar

Geez Ray, now you got my attention! :eek:
I surely would like to get more than the current 200 or so hours out of my engine, possibly with a kit of yours on it!...
Let me see if I understood correctly what you mean, with the help of a pic of my engine compartment.
I added a blue line to show (approximately) the hull waterline.

First of all, by "the back two cylinders", do you mean the last one of each header (hence two in the engine overall), or the last two of each header (whose tubes enter the collector below the other two)? I guess you mean just the last one of each header, because I can clearly see that it has much less downturn than the others?

Secondly, isn't there already some sort of anti-reversion jacket inside these diverters, where the water injection rubber hose is connected?
Mind, the header was already installed when I bought the boat, and I never removed it, so I've never seen it inside.
But I guessed that there should be some protection, considering how near the water injection point is to the 4 tubes collector.

Another thing which should help is that the boat (Fever 27) sits pretty low in the water astern, so when the engine is idling the downward angle of the diverter and exhaust tip is even higher than it appears in the pic.

Anyhow, after 20 hours or so during this season, the engine seems to be running just fine - fingers crossed!...

Considering these premises, if you think that it's worth making the anti-reversion protection that you suggest, could you please describe it in more details? I mean, how should those rings be shaped, and where exactly should they be welded? I don't get it when you say "in the tips a few inches back towards the engine from the water injection point inside the tips".
...it might well be just a problem due to my poor english, please be patient... :drink:

Many, many thanks in advance!

http://i23.photobucket.com/albums/b3.../HL/Header.jpg

Verses the stock 8.1 exhaust, the CMI system in the photo has a much longer water separation lenght, downward angle, and more effective anti reversion system, for a switchable (sound choice) tail. Although many customers are using the same system on modified 8.1s, a longer nonswitchable tail pipewould be recommended on a modified engine.
You may want to investigate the water system for proper flow and volume. The incomplete fill of the header causing the discoloration is more of a cause for concern.

When it goes boom is always a solid indication.... :drink:

Everybody Likes to Blame "Reversion"!
 

Mapism & JRZ:

Pictures can be a bit decieving and distorting with respect to angles and dimensions, but what I am talking about there is the lower two tubes on each header on each side. If you get into the engine compartment and look straight over at the header you will see that where these two tubes enter the collector with the other two tubes, the lower two tubes have almost no real downturn or angle on them, maybe a 1/4" or so, couple this with the fact that when you install CMI's captain's call switchable system as you have Mapism, the distance now from the water exit in the tip to this low point for the two lower tubes (back cylinders) has been shortened by over 4" on one side and slightly more on the other. This is putting the water into the header so close to the low tubes and the collector thats its almost impossible to keep water and heavy water vapor (steam) out of the engine and especially the back cylinders.
This is one of the reasons I also don't like switchable or captain's call type switchable exhausts on Performance engines . these systems were a stopgap measure at best many years ago on smaller engines with less power.
When you are idling the engine the water mixed with exhaust gas is hitting at an almost right angle(obstruction) on the blade of the switchable exhaust, it causes exhaust gas mixed heavily with water to strike the plate with some velocity and bounce back into the exhaust stream with the pulses of a 4 cycle engine and with this location so close to those lower tubes with almost no real downturn or angle, you have a reciepe for slow damage and ultimate disaster!
This problem does not show up with all CMI headers or manifold systems, but this problem is amplified with this any header system where with your boat like a lot of other 23-28 foot boats the Bravo dimensions put the collector of the header so close to the switchable blade. You most likely have and I would suspect on a closer inspection or teardown you will find water and moisture damage in your rear cylinders. If I am wrong, then I will eat the CROW!
Hate to scare the hell out of everyone with 496 Sporttube systems, but there have been just to many 496 engines , even stock ones suffering from rear cylinder water damage.
I suspect most are the ones with the switchable systems described here.

Best Regards,
Ray @ Raylar

JRZ , thanks for pointing out the discoloration, but I think what you're talking about is just the reflection of the shelter roof where the boat is stored. I'm attaching another pic below: as you can see there's also a reflection, but different from the first one, due to the different angle.
By memory, the steel as such has no discoloration, or at least I never noticed any. The water pressure ranges from 5+ at idle, to 15 or so around 3000 rpm, up to 25+ at WOT.

Ray, I see what you mean. I will definitely consider, as also JRZ says, a non switchable tail, if I will upgrade the engine.
But time being, the engine still seems to run nice and strong, after 60 hours or so with the CMI headers (the last 20 on freshwater, and previously saltwater). Shouldn't any cylinder damage be reflected also on the performance by now, to some extent?

Besides, is there anything I can do in the meantime to reduce the risk of major damages? For instance:
1) if as you say water and exhaust gas bounce back after hitting the switchable blade, I guess that keeping the straight exhausts always open should cure at least that part of the problem, or am I missing something?
2) since the effect we're discussing is only relevant when idling, would it help keeping the engine slightly accelerated (say 900-1000 rpm), rather than idle, whenever possible?

Any other suggestion is also welcome, of course. Many thanks in advance!

PS: Ray, I'm still missing how exactly the rings you mentioned should be shaped, and where they should be welded.
http://i23.photobucket.com/albums/b3.../HL/Intake.jpg

Mapism:

My suggestion is the following:

1. Take a compression test of the rear two cylinders on both sides of the engine and compare them to the front cylinders as a cross check and a leak down test comparison would also point out any water (rust) damage to the valves, valve seats, cylinder bores or rings. If all is ok, you're still good!

2. You can slo use a bore-scope to look into the spark plug hole to view any valve rusting or bore rust or damage, if one is available for your use.

3. With your system, Eliminate long or low rpm idle periods with the Captain's Call system switched closed and do not run the engine above 1200-1500 rpms with the system closed also!

If you are water damage free now, you would appear to be in good shape and maybe just lucky. Hope you are damage free and you can enjoy your boat without the problem showing up.

Best Regards.
Ray @ Raylar

That's fine Ray, I'll try to arrange that before hitting the water again next season.