496 Flame Arrestor
 

Guys,

So my tuner is telling me the stock 496 FA, that has been refitted to the intake on my ProCharger, is probably robbing me of HP or RPM, or both. So I’m looking at it…..

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Truthfully, I seriously doubt the FA is doing anything toward its purpose. I can’t imagine a flame front is ever going to reach that far, in the event of a backfire, given the intake tract the ProCharger kit has, and I’d say the intercooler would probably serve the FA purpose just as well (it might well get wrecked in the process, but that’s gonna happen anyway). I’m tempted to make an open bellmouth, like the drag guys use, but I would kinda like the idea of at least a birdcatcher kinda thing, and there’s always the USCG regulation thing. So….

It looks like there’s at least three layers of screen, if not four. I’m thinking I could remove all but one, retain the cosmetic appearance of a FA, still prevent a solid object ingestion, and allow for WAY more flow. Thoughts? Has anybody taken one of these apart?

Thanks. Brad.

Any chance of getting it on a dyno and make a pass with, and without the FA? No guessing involved.

There is an old thread in here somewhere where Smitty articfriends pulled a 502MPI one apart and dyno'd the difference. I don't remember the results and it's for a different app so may not be relevant but may give you some type of insight.

Xlint,

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Little late for that. Besides…. Without a dyno specifically set up for closed cooling (consumed water), it’s nearly impossible to do a dyno pull. We could potentially just do a with/without empirical test. But, I can tell you, without a doubt, without some sort of bellmouth, the “without” flow will be worse than with the FA.

Thanks. Brad.

Dave,

I’ll give Smitty a shout.

Thanks. Brad.

on most carb FA's the finer screens get removed and they only use the single outer screen on performance builds. I dont know the difference in flame arresting or performance but just that most of the builds I have run across many had the screens removed and just kept the one for looks and to keep big stuff out.

Comped,

That’s kinda what I had in mind. Just gotta get it apart without wrecking it.

Thanks. Brad.

This ! ^^^
He found a bellmouth that added good power. Do a search, if can’t find, contact him. He’s a good dude !

Guys,

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Letting the silicone set up.

Pretty much nothing but a bird catcher now. Should flow a LOT better.

Thanks. Brad.

I was just going to suggest "thinning" out the mesh. It's been talked about on here before.

I was never a fan of the clamp on style, but that looks pretty thin, seems like the wrong corner to cut when the worst case scenario is igniting your engine bay

Lots of better flowing aftermarket parts for $100-200 without introducing additional risk

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I use K&N and they work well, and it’s your lucky day as I have a brand new extra one you can have for $65

either way the engine room looks freaking amazing

CheckmatScarab,

That's an OEM Merc 496 FA.

As I stated in the starting post, I have serious doubts a flame front is going to be able to travel that far, plus through the intercooler and the ProCharger.

Thanks. Brad.

BoatNT,

I've been told the K&N flows worse than the OEM 496 breather. Or, at least, they offered one at one point in time that did. Do you have any data on that one?

Thanks. Brad.

Brad, in that same thread I referenced, the 502MPI version of that K&N filter killed HP compared to the OEM flame arrestor. Again, different app but I bet you are correct also.

I guess different people have different experience, back when I replaced my stock flame arresters on my fountain with twin 502’s and added it KN I noticed the difference in a positive way, that was just me

no, I don’t have any data. I don’t get that consumed with a filter, you can remove that filter and drive your boat and I guarantee you’re not gonna see any difference so a filter is not going to help you, all I can tell you is the stock 496 flame arrestor is not providing any filtration, all the belt dust goes right through that stock filter and into your engine, I like the K&N because simply it filters better it sounds better and does not affect in a negative way and no more belt dust in my throttle body

and I will tell you one more thing, and I know a lot of people are gonna disagree with me because I am full of crap, and I don’t know what I’m talking about, but in the unlikely event you ever have any kind of fire in your boat and it ends up being from a backfire and there is an investigation by the insurance or anybody else and see the flame arrestor has been modified you’re gonna have explaining to do,
let’s think about this if mercruiser could get more performance out of those engines and did not have to add the mash to their flame arrestor why would they?

Not impossible, but unlikely for a fuel injected motor to backfire. I'm pretty safety conscious, and I'd do it.
I don't think it's really "cleaning" any air. It's typically not dusty out on the water, nor in a boat bilge.

Run the boat in the water with and without the arrestor. Lig the runs on the Holley. Did it make more boost without the arrestor? Did the computer add more fuel? That will tell you which way is making more power.

BoatNT,

I can tell you the FA was, in fact, collecting belt dust, as I had to clean it off every year. Part of that was how the engine was initially set up when we bought the boat, with the crankcase vent hose just kinda dangling in front of it, so I'm sure a lot of that was a combination of belt dust and oil vapor. I made an adapter that goes between the ProCharger and the FA where I connect that crank vent that, at least, keeps the oil vapor off the breather. I also now have a catch can that that vent hose goes through, so there should be little to no oil vapor getting to the intake tract; the crankcase vent hose simply acts as a vacuum source now.

I certainly get the insurance thing, and the safety thing, in general. But the reality is the intake tract is dry to the valve runner, is about four feet long, and a flame front would have to make it through the intercooler and the ProCharger to get to the FA. Add to that the fact that I've literally never had a backfire.

There very well may be little to no effect from a FA in an NA scenario, but I have to think there would be in a boost application. Anything that reduces restriction is going to increase flow. Physics. Will it make a difference in my application, given the stock heads and exhaust? Maybe, maybe not. Gonna see.

As for Merc and their pursuit of HP.... I've given up on that mindset. They could have easily gotten 500+HP out of the 496, with nothing more than slightly heavier valve springs, a better cam and a proper tune. All they'd have had to do was sell what GM was selling as the HP3. But they didn't. They went after GM legally for it instead. These engines are so incredibly neutered for the sake of longevity and reliability (I get it) it's not funny. In the case of the FA, they simply complied with USCG requirements and went with it. There was probably literally zero lab time involved.

At the end of the day, I can buy a good used OEM FA on eBay for $100, or maybe your K&N for $65. Time will tell.

Thanks. Brad.

UnderPSI,

I would have to build a bellmouth, or this test would be an exercise in failure. In our model boating world, there were a couple guys that did exhaustive testing of carb intake opening shape, and found that a straight tube, with no funneling geometry at all, was the absolute worst-case scenario, short of an inverted funnel. What I would likely do, if I were interested (I am curious), now that I've gutted mine, is to get a non-molested FA and try them back-to-back. But we know a bellmouth is beneficial, because we see the drag guys use them almost exclusively. It is interesting to note that the OEM 496 FA does, in fact, have a bellmouth feature, even if minimal, behind all that restriction.

As it is, we have no way of knowing if this modification actually has any effect, as we've changed several things over the winter that can't not have an effect of its own; smaller ProCharger wheel (from Ø4.25" to Ø4") and a significantly larger cam). We were seeing ~4lbs of boost at WOT (5K RPM) last year, and we expect to see 6 or so in our current configuration. I've made a spanner wrench and added holes in the blower wheel hub so that, in the event MAT is too high, I can go back to the Ø4.25" wheel on the water.

Thanks. Brad.

This thread and post reminded me of when I bought this jet boat with a 468 years back. When I brought it home I noticed it had a PAPER air filter/cleaner on it! Could there BE a worse option to put on a boat?! :D :D
Backfire: blow up boat
Splash air filter: blow up motor

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Dave,

Ah, yes. The old garden hose. I remember dad blowing these off the water in our blower motor V-drive without even getting into the secondaries. Good times. :cool:

Thanks. Brad.

Oh absolutely! There is very little chance but still, anything is possible! Just not a place I would gamble

I was having an engine dyno'ed and for fun decided to remove the arrestor, no difference in numbers on the screen, it was actually 2hp lower but chalked that to variance. Point being there wasnt any reason not to run one in my case

I'll have to swap mine out with some kindling, let's see how she breathes after that :D

CheckmateScarab,

If you just pulled the FA off, leaving the TB neck bare, THAT was your loss of HP. Had you put a bellmouth on it, you'd have seen a significant increase.

Thanks. Brad.

$478, what are they made of... gold?

Padraig

Padraig,

Totally agree. It's a performance part. Wadaya 'spect? :picard1:

That was just the first link I came across.

Thanks. Brad.

Brad, I know arcticfriend did actual dyno testing on 502 maybe he has info on the 8.1 also. Great guy any time I talked to him.
Isn’t Raylar the 8.1 performance expert? Maybe he has some info for you.
Engine looks good!

Liberator,

Yup. I’ve read the entire thread. And I’ve spoken to him and texted back and forth many times. I’ve reached out to him on this. Waiting to hear back. Patience is a virtue, they say.

I’ve also spoken with Larry at Raylar on numerous occasions. We haven’t spoken on this specifically, but I’m sure he’d agree, at least on the performance aspect.

Thanks. Brad.

The factory FA you showed does NOT really look restrictive, especially after gutting it. The replacement KN clamp ons they sell for 454/502 mags for most part are hp killers, my dyno testing showed it was the retarded adapter that took it from a rectangle to a circle that was the biggest restriction, hp killer on those, Smitty