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TomZ 11-11-2016 04:18 PM

Getting reversion and need some advice
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I'm running Stainless Marine exhaust with long risers on my set-up. The manifolds are the first generation style with short runners. The manifolds are definitely good. I'm getting reversion for sure. At first, I thought my misses at the ramp were being caused by high float levels and steep ramp angles which were causing a wet cylinder. I do not believe that to be the case now.

Running on the hose with the engine lightly surging at idle, I noticed that a cylinder dropped off. I revved it hard a couple of times, and she cleared up; just like at the ramp. Following a hunch, I shut the engine down and went to have a look at the exhaust. With a flashlight, I could see that the inner pipes were wet with water rolling down from the anti-reversion baffles. I removed a riser, and sure enough, I had some water in there; not much, but even a little is a lot in my book. This was evident on both sides of the engine so it's not a bad riser or manifold.

I'm going to replace the manifold gaskets just in case they're leaking and causing a vacuum (I've had the manifolds on a off a good amount this past season so maybe they're just toast), but I'm thinking that it may be caused by cam timing. I'm using a 525 EFI camshaft in my 454. I've gotten conflicting information on this: some say that this cam should not revert water with good risers and the supercharger, others have said that I should get it over with and convert to dry tails (I don't really want to make her any louder than she already is).

Pics of my set-up are attached. Any thoughts?



SB 11-11-2016 05:08 PM

A 454 will revert less than a 502 if they have all the same equipment.

What initial timing and idle speed are you using ?

indysupra 11-11-2016 06:35 PM

You sure the risers don't have pin holes at the bends?

dunnitagain 11-11-2016 06:43 PM

Dry Tails , Why waste your time any other way.

TomZ 11-11-2016 08:10 PM

Originally Posted by SB (Post 4499794)
A 454 will revert less than a 502 if they have all the same equipment.

What initial timing and idle speed are you using ?

Timing is locked at 32 degrees. I raised the idle to about 1K RPM. It has a little bit of surge at that RPM fluctuating as high as 1100 and as low 850. The cooler weather recently has changed this some. It was steadier in the summer.

TomZ 11-11-2016 08:12 PM

Originally Posted by indysupra (Post 4499809)
You sure the risers don't have pin holes at the bends?

The risers have tested good.

I'll get pics of the risers after running. They are soaked just inside of the anti-reversion dams. It's sucking water.

TomZ 11-11-2016 08:13 PM

Originally Posted by dunnitagain (Post 4499810)
Dry Tails , Why waste your time any other way.

I'm close!

Baja Rooster 11-11-2016 11:00 PM

The 525 cam has a lsa of 114*, right?

I have 110* lsa ZZ cam with CMI headers dry to their tip about 4" from the transom. When I pulled the heads the valves were fine and the ports a little sooty as they should be. Just doing the basic math I'm surprised that you'd have a problem. I did pull a plug out of the O2 bung hole and was shocked at how much water was shooting back out of it, but when it's left in place and removed it after shut down it was bone dry. It doesn't take much of a leak at all including the manifold/head gaskets.

I also had a Miss at idle but put a wideband on it and it was in the mid 10's, lol. A screwdriver cleaned that up.

TomZ 11-12-2016 09:23 AM

I'm hoping the gaskets will help.

MILD THUNDER 11-12-2016 09:28 AM

A misfire, or plug not firing, can also cause water reversion. Same thing for a valve that is adjusted a bit too tight, or leaking exhaust valve. I have seen those stainless marine risers leak at the welds in the bend, like indysupra said.

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