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.

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.