Symptom of leaky header
 

If header is leaking would a misfire be a common symptom?

At idle mostly. If it's in a spot that can leak towards the motor it will fill the cylinder to the point the starter won't turn it over like I had and your oil will be a milkshake. I could definitely hear it at idle though

Yeah mine is starting to mis at idle. It's a new motor that I just built and was running on engine stand I bought used CMI headers that were "certified pressure tested" so I suspect this may be the problem. When I first fired it off all was good and I was holding it at about 1800 rpm for several minutes. Then I let it idle for a few minutes. After about 5 mins idling I noticed it started missing. Everything else is new. Ignition,carb heads are fresh from machine shop etc. I know there are several other variables it could be but bottom line I should have pressure tested the damn things before I bolted them on instead of taking someone's word. Fortunately it's still on the stand and not in the boat yet. Gonna pull them and test them if for nothing more piece of mind. If there not leaking I will troubleshoot elsewhere.

Yes

hope u drained it down don't wait

About to go do it. Not 100% sure it's leaking but have to go see. Been sitting abouy 48 hours in climate controlled building so hopefully not enogh time to hurt anything if it did leak

What distributor? My MSD had a short in the pick up. The dyno operator heard it right away didn't know what it was but found it and replaced the pickup. It went away. He said it was the first time he had ever seen it.

DUI distributor

Well pulled headers and water poured out of 7 of 8 primarys. These are absolute garbage and just further teaching me you cant atke anybodys word for ****!! Shame on me for not pressure testing myself and putting them om my brand new motor!! Spun the motor over to get moisture out of cylinders. Pumped oil in the spark plug holes and spun it over some more. Hopefully didnt hurt anything. No signs of water in oil so thats good I guess

We are very close. Your headers and blocked needed to be drained. We had 16 degrees a couple of times now and a couple days not above 32 in a row. I have seen 2 engines hurt already from not winterizing. Just saying. Good that you pulled spark plugs out and turn the motor over, then fog the heck out of each cylinder. I never store any exhaust manifolds / risers or headers especially CMI's for long periods with water in the jackets even in warm climates. Good luck John

Make sure to check your tail pipes as well. I had the same problems but it was the tails not the headers

Running on engine stand only so far. No tails on yet but thanks for info

Running the headers with gaskets?leaky exhaust gaskets will help revert water.

I do have gaskets

Can you typically hear a header gasket leaking in a boat? I had to wrestle the hell out of my starboard header to get it on, and when running it I sometimes think I can hear a little bit of a "chirp" coming from that side of the engine. I do know from experience with cars what a bad header leak sounds like, and I know that they also can have a bit of a "ringing" sound to them. Don't really want to deal with pulling it off to check if not necessary, because it is so hard to get back on. Any other ways to check for header gasket leaks?

Look closely for carbon tracks .

Run your hand around the flange while its idling. You'll feel it.

Dump fogging oil down the carb with the engines running @ rpms of 1200 to 1500 and you will see the smoke pour out at your leaks. If it is a EFI / MPI engine use a small outboard gas tank with fresh gas in it and mix in 2 stroke motor oil about 15 to 1 or a tad less - then hook the portable fuel tank / fuel line to your inlet fuel barb and the run the engine, keep the engine running till you find the smoke coming out the leaks if you have any. Been doing this for 30 years finding header and manifold leaks also inspecting the gaskets for blown across areas.

I'll start with looking for carbon tracks as it has been winterized at this point, but when we get a run of warm weather I might start it up and check for leaks as described. Thanks for the hints.

Not to be contrary, but I'm trying to wrap my mind around how the header leak can promote reversion. It would seem that any leak in this area would simply try to pull exhaust / air back into the port through the path of least resistance when the valve is open and the piston starts moving downward. If that path happens to be a bad seal in the header gasket, in my mind it would be logical for it to actually lessen the pull of exhaust back through the exhaust primary itself. Now if I do have a leak I am definitely going to fix it, but I'm just having trouble trying to picture how this would affect reversion in an exhaust system. Has anyone been able to document this happening? Does it have something to do with exhaust scavenging?

KR252, please accept my apology for hijacking your post.:hijack:

No prob. Back to my problem I have contacted the guy I bought headers from and says he will refund money upon proof of pressure test as his ad stated "pressure tested". I'm gonna do that this afternoon. I'm sure it's the headers. Has to be unless I really did something wrong and blew both head gaskets in less than 10 minutes on a new motor with decked block resurfaced fresh heads and Fel pro marine head gaskets with ARP head bolts torqued in proper sequence proper torque??? Anything is possible I guess but will know for sure later when I pressure test these headers

Stand up guy, pretty rare if you get your money back, good luck

KR, any chance it is reversion? What cam are you running? I had a lot of issues with reversion while idling on a stand with my 489. I would see about a teaspoonful of water sitting in each primary when I pulled the headers. Oil never got milky, but I was definitely getting reversion when it idled - you could shine a flashlight up the collector and see that it was wet as hell all the way back to where the primaries connected. Interestingly, when I installed a set of mufflers on the collectors that had salisbury flappers it almost eliminated the reversion. I did extend the inner pipes in the collectors just in case, but I was surprised how much of a difference a set of tips made. The flappers acted like a backflow preventer. This engine was running some pretty mild cam specs too, so I was quite surprised to see any reversion at all, but sometimes you get a "perfect storm" of factors coming together to bring it on.

It would be nice if you had a set of known good headers or manifolds to run on it real quick. It is good that you have the avenue of returning the pipes if they fail the pressure test.

Good luck with it.

Cam pretty mild. 228/236 @50. 590's lift on 114. I do have a set of Gills with tails I can put on to test as well

I also had about 1/4-1/3 of a cup in each primary too lol

My cam had milder specs than that (on paper), but slightly higher lift. However, you have to keep in mind that the specs at .050 lift can be deceiving when it comes to reversion, especially with roller profiles. Rollers usually get the valve off the seat much quicker, so the actual overlap can be longer than with a flat tappet that has similar specs. Also, in my case I had a set of AFR heads that have a much more efficient exhaust port, which allows exhaust to flow into the cylinder as easily as it flows out. Add to that the fact that it has a stroker crank that pulls the piston down the hole with greater velocity, and you can see that "perfect storm" developing that I was referring to.

Another thing to consider is the angle that the engine is sitting when it is on the stand. You might need to block the front of the stand to give it similar "pitch" to what it would have in the boat. Things like that can make a huge difference.

Thanks for info. Pressure testing this afternoon and will go from there

Headers are fine. Problem is the guy had custom 15 degree flanges welded on the ends where the tails would attach. Also in these angled extension has a 90 degree elbow with a corkscrew looking water sprayer. This is all so the headers can be run without tails and you can just use 4 inch rubber hose between header and tips. Anyway they never tested them by actually flowing water from rail all the way through to the sprayers inside the collector. Anyway with the headers off the boat I hose clamped a water hose to feed on rail and put the connector in line to run water all the way through the sprayer. Well the sprayers were installed too close to end of collector and diverts some water straight back into the exhaust tube almost immediately filling the rear primary with water I know everyone reading this will be like water sprayers in the collector?? What the hell are you talking about haha. I've never seen it either. It was all done by a shop called Stainless Works in Arlington Washington custom stuff but wasn't planned out well or tested for that matter. Anyway I've got some experimenting to do with them to fix the problem but it's doable Take the sprayers out of the equation and pressure test headers 100% fine

:worthless_without_p

Sorry, you made me do it! ;)

My Lightnings had a weird design for the way the water was introduced into the exhaust stream - they just had about four 3/8" holes in the top of the collector spraying a curtain of water straight down. Damned thing looked like Niagara Falls. And on the bottom they had another 3/8 hole to drain the water out of the collector when not running - this also sprayed straight up. The result was two large streams of water converging and splashing everywhere. I had an exhaust shop add a stainless steel inner pipe to direct the whole mess towards the transom.

Here is a link to my epic thread with some pictures of what I had to do. Maybe it will help. (scroll to page 11 to see what I'm talking about)

http://www.offshoreonly.com/forums/g...-mild-cam.html