1999 454 Mag MPI just quits - videos

[PlayDate]

Thanks for the videos. I realize that it might be difficult to hear but I believe something is amiss in the valve train. Given the history of these engines.....what you are experiencing looks like valves not closing/sealing and it looks like more than one on the port engine. It wouldn't necessarily show up in a static compression check. With fuel and spark stabilized unfortunately it is the only thing left that shows up at 3,000+ rpms.

I would see the same thing in race cars if the valve springs were not strong enough the valves would start to float and the engine would fall off at higher rpms and not recover until the rpms were reduced.....then you could replay the story again (over and over).

It also fits the popping. I would swap the ecms but if that fairs no better.....it is probably mechanical.

 

[370Dancer]

That's the experience and expertise I come here for.
I'm still in cheap enough to pick up a long block and parts swap if need be.
Still, I have to wonder why a year ago, I could pull a 13 Nautilus with a 40 Yamaha at cruise all day long, without a peep out of that engine? But before that, it was doing this.
I would think that valves/springs/rods go bad for a reason, and stay bad. Or maybe I've finally fixed everything else.......
ECMs in the morning.

 

[douglee25]

Have you pulled the valve covers? Anything out of the ordinary?

 

[PlayDate]

Have you pulled the valve covers? Anything out of the ordinary?

It is a PIA to pull the valve covers because you have to disconnect the exhaust manifolds to get to the lower bolts and lift the cover. Yes you can slide the exhaust manifolds down longer bolts but you are just prolonging the agony of pulling the heads.

I believe he has done everything humanly possible to avoid pulling the heads. There is nothing left to do that fits the symptoms. If you watch the video....the rpms start falling once he gets to 3000-3500. If fuel pressure is steady and he has already gone through the ignition and fuel system(as well as swapping components between engines) it has to be something else that fits the symptoms the engine is showing.

We were all hoping it was something simple....but given the history of this engine something does not seem to be mechanically right.

 

[scoflaw]

Did I have the correct answer to this solution about a year ago ? The dying horse can only be beat for so long LOL. Hope santa drops one at your door. Headed south soon, what town do you live?

 

[douglee25]

@PlayDate - that's a good point on the interference.

@scoflaw - what did you state a year ago? Valve issue?

 

[techmitch]

That's the experience and expertise I come here for.
I'm still in cheap enough to pick up a long block and parts swap if need be.
Still, I have to wonder why a year ago, I could pull a 13 Nautilus with a 40 Yamaha at cruise all day long, without a peep out of that engine? But before that, it was doing this.
I would think that valves/springs/rods go bad for a reason, and stay bad. Or maybe I've finally fixed everything else.......
ECMs in the morning.

Have you pulled the valve covers? Anything out of the ordinary?

It is a PIA to pull the valve covers because you have to disconnect the exhaust manifolds to get to the lower bolts and lift the cover. Yes you can slide the exhaust manifolds down longer bolts but you are just prolonging the agony of pulling the heads.

I believe he has done everything humanly possible to avoid pulling the heads. There is nothing left to do that fits the symptoms. If you watch the video....the rpms start falling once he gets to 3000-3500. If fuel pressure is steady and he has already gone through the ignition and fuel system(as well as swapping components between engines) it has to be something else that fits the symptoms the engine is showing.

We were all hoping it was something simple....but given the history of this engine something does not seem to be mechanically right.

Did I have the correct answer to this solution about a year ago ? The dying horse can only be beat for so long LOL. Hope santa drops one at your door. Headed south soon, what town do you live?

How about a accurate vacuum gage on both engines and recordings when the shit drops out and then a running compression test when back at the dock? This will give conclusive information as to the mechanical's as best as possible with given latest performance pics/recordings/post.

 

[scoflaw]

Can't remember but something like do a repower.

 

[douglee25]

Vacuum gauge will definitely show a flutter if something isn't dealing correctly.

Have you done a leak down test?

 

[techmitch]

Can't remember but something like do a repower.

I'm with you guys asper what info. we are getting. The internet is tough. But still, proper comprehensive diagnosis is 85% of the job.

Scof, wish I was closer also.

 

[370Dancer]

Did I have the correct answer to this solution about a year ago ? The dying horse can only be beat for so long LOL. Hope santa drops one at your door. Headed south soon, what town do you live?

Yes, you did. I can still run the boat the way it is because I don't have anywhere to go. Everything is within 3-5 miles, so fast is not important. I've been after this as a labor of love, mostly.
Get off at State Road 70, and come to US 41, go South to Bowlee's Creek. What's your brand?

 

[370Dancer]

Vacuum gauge will definitely show a flutter if something isn't dealing correctly.

Have you done a leak down test?

Long time ago, but within a year

 

[370Dancer]

How about a accurate vacuum gage on both engines and recordings when the shit drops out and then a running compression test when back at the dock? This will give conclusive information as to the mechanical's as best as possible with given latest performance pics/recordings/post.

Could do that while testing the ecm swap. I've had the vacuum gauge on it at the dock and it's solid.
I'll need to find another set of eyeballs though. This has been a solo effort.

 

[370Dancer]

It is a PIA to pull the valve covers because you have to disconnect the exhaust manifolds to get to the lower bolts and lift the cover. Yes you can slide the exhaust manifolds down longer bolts but you are just prolonging the agony of pulling the heads.

I believe he has done everything humanly possible to avoid pulling the heads. There is nothing left to do that fits the symptoms. If you watch the video....the rpms start falling once he gets to 3000-3500. If fuel pressure is steady and he has already gone through the ignition and fuel system(as well as swapping components between engines) it has to be something else that fits the symptoms the engine is showing.

We were all hoping it was something simple....but given the history of this engine something does not seem to be mechanically right.

The manifolds are coming off anyways, but not until after the Christmas boat parade. So, I am anticipating keeping on going, and yanking the heads at the same time. Now the age old question....
refurb, or replace. Can I assume I am past the "marine" parts when talking about heads and valves, or is there still cam consideration that would keep me looking at only marine replacement?

 

[scoflaw]

What town?

 

[370Dancer]

What town?

Bradenton. 30-40 miles North of Cape Coral. NE corner of Sarasota Bay

 

[douglee25]

That's near Cleetus McFarland.

 

[370Dancer]

That's near Cleetus McFarland.

He lives in Clearwater. I haven't been to DeSoto since the early 70's

 

[techmitch]

Could do that while testing the ecm swap. I've had the vacuum gauge on it at the dock and it's solid.
I'll need to find another set of eyeballs though. This has been a solo effort.

The "engine running" compression test will help evaluate the valve train (cam, push rods, rockers, valves and springs). This is done with the Schrader valve removed from your compression gauge hose.

 

[PlayDate]

The manifolds are coming off anyways, but not until after the Christmas boat parade. So, I am anticipating keeping on going, and yanking the heads at the same time. Now the age old question....
refurb, or replace. Can I assume I am past the "marine" parts when talking about heads and valves, or is there still cam consideration that would keep me looking at only marine replacement?

Enjoy the boat parade. The engine will run perfectly for that show.

Can't answer your question about refurb or replace until the heads are off. I have used truck heads on freshwater cooled engines and wouldn't think twice about it. If they are raw water cooled...different story.