1999 454 Mag MPI just quits - videos

I have the 6" elbow extensions on it already, and they are just about touching the hatch when closed. It's a well documented problem with Gen VI engines having such an aggressive valve overlap that the exhaust gets to suck in a bit of raw cooling water, especially if you idle around all day. So the idea is to make the exhaust inner tube a bit longer so the water tends to not make it over the drop back to the exhaust port.
I did manage to get all of the front bolt on crap off last night and this morning. About to clean up the area, take a few pics, and then finish taking the rear stuff off and get after the intake manifold. Tomorrow should be heads day. I need a sky hook.....
 
Made some headway. the onion is basically peeled back now.
Need some thoughts here. what's the best approach for getting the intake manifold off after, oh say 21 years?
When I started removing the intake manifold bolts, most of them were barely over finger tight! Funny, though, a vacuum test did not indicate any leakage. I've read about pouring oil in the gap where the gasket is to loosen it. My initial screwdriver pry did not yield any results. May have to get more aggressive.
IMG_3180.jpeg
 
Turned out I just needed a couple of taps on a screwdriver in all 4 corners, and off she came. We're making headway now.
Next is to pull the rockers, push rods and lifters to see if there's any tell-tale issues.
So far, it's just been the intake manifold bolts not torqued down as much as I thought they should be, and some obvious rust in the exhaust manifold #4. surprisingly, not much sludge either (so far). what I can see of the cam looks clean, and no scarring.
Intake off.jpeg
 
370Dancer said:
Turned out I just needed a couple of taps on a screwdriver in all 4 corners, and off she came. We're making headway now.
Next is to pull the rockers, push rods and lifters to see if there's any tell-tale issues.
So far, it's just been the intake manifold bolts not torqued down as much as I thought they should be, and some obvious rust in the exhaust manifold #4. surprisingly, not much sludge either (so far). what I can see of the cam looks clean, and no scarring.
View attachment 115574
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Maybe it's just the cheap monitor I'm on right now, or just an odd pic, but those gaskets don't look right in more than one place.
 
techmitch said:
Maybe it's just the cheap monitor I'm on right now, or just an odd pic, but those gaskets don't look right in more than one place.
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how so? Rectangular ports 454 Magnum MPI Horizon. Bolt pattern was right, but, I don't know the true history of this engine either. As loose as some of the intake bolts were, I'm thinking the top has been off before.
The push rods all looked good to me. The lifters all cleaned up nice and the bearings were spinning as expected. no flat spots, and the cam that I can see looks fine. Unless I find a problem with a cylinder wall or piston, I think I'm just going to replace the heads and button it back up. all new lifters, push rods, and rockers. There doesn't appear to be a formed gasket across the front and rear for the intake manifold. Just black gasket maker. That also makes me think someone has been here before.
rockers and push rods.jpeg
hydraulic lifters.jpeg
enough for one day.jpeg
 
OK, some of the gasket did come off with the intake manifold. I also busted some of it away to get the tray out. I think that's what you are seeing.
 
The heads are off. They are a bitch to get off if you forget about the 4 lowest bolts to the block.......
Those 4 short ones also bolt right into the coolant passage. After I got them to drain down, the heads came right off. The gaskets look in really good shape, furthering my theory that this engine had been broken into before.
I am replacing the heads, valves, springs, push rods, rockers with all new, so I am mostly concerned with the condition of the cylinders and piston heads in relation to what the heads looked like.
Here are pics of the 8 cylinders, and the valve heads in the cylinder heads. #4 was the only one showing obvious rust in the exhaust manifold. clearly, 5 and 7 have seen some water when looking at the valves but not so much with the cylinders. Do you see any red flags here, or can I just proceed with clean up of the block and putting new parts on?
picture order is 1-3-5-7-2-4-6-8
Valves in a separate post (10 pic limit)
cylinder 1.jpeg
cylinder 3.jpeg
cylinder 5.jpeg
cylinder 7.jpeg
cylinder 2.jpeg
cylinder 4.jpeg
cylinder 6.jpeg
cylinder 8.jpeg
 
Valves pics same order. This stuff will be thrown away.
 

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Oil burner, why replace the heads and not rebuild? Is the crosshatching visible on cylinder walls? Vertical scores and shiny smooth no good.
 
scoflaw said:
Oil burner, why replace the heads and not rebuild? Is the crosshatching visible on cylinder walls? Vertical scores and shiny smooth no good.
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1. Not my wheelhouse by any stretch, I've not found anyone who cares more than me what the end result is.
2. Speed. All new for about the same price as a rebuild. I've got to be at St. Pete Yacht Club in a couple of weeks.
3. I'll look closer for the crosshatching, but I remember seeing more shiny than lines. The engine oil level hasn't dropped per se, but the pressure is lower than Starboard.
 
370Dancer said:
Valves pics same order. This stuff will be thrown away.
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Interestingly enough, Cylinder 5 and 6 which are both the 3rd cylinder from the front of the motor both show signs of water ingestion. There is some pitting and rusting on the valves. If you compare that to the cylinder pictures (hard to tell the exact order) the piston tops may also be cleaner. This would lend itself to some potential water ingestion (bad gasket or exhaust reverb).
 
Which is why I am satisfied with replace all, and just run it. This boat isn't going to be my first love for many more years.
Probably what I will change is either adding the elbow extension pipes, fresh water flush with high rev antics before shutdown, or both (or neither).
 
One more question for the smart ones.
The MAG MPI Horizon is somewhat unique in that there is no valve lash torqueing per se. Each rocker bolt is set to 40 ft lbs. However, it uses hydraulic lifters. There are many vids that talk about setting zero lash by turning the engine 1/4 turn, and continually adjusting rocker arm bolts for zero lash until you get around a couple of times.
Also, the service manual 23 does not discuss "soaking" the lifters in oil to fill them up. Instead it's just cover rockers, bolt ball, pushrods, and lifters with oil when installing, and torque the rocker bolt to 40 ft. lbs. No engine rotation or any of that.
What's your take on this? From page 3A-33:
Rocker Arm Stud Kit
These engines use a net lash or non-adjustable rocker arm system. Torquing the rocker arm
bolt to 40 lb-ft (54 Nm) sets the valve lash. When rebuilding these engines with a net lash,
machining of the cylinder deck surface or cylinder head surface or grinding the valve seats
or valves may cause an incorrect valve lash condition. The most common problem is that
the valves will not close completely after the bolt is torqued.
The kit can be used to convert the engine from a non-adjustable to an adjustable valve lash
engine. There are 8 studs and 8 nuts in each kit. The valve lash is 1 turn down from “0” lash.
Valve Adjustment
No adjustment is required. Valve lash is automatically set when rocker arm bolts are torqued
to 40 lb-ft (54 Nm).
 
It likely won't be required if the heads are just machined. Usually required when a larger cam is installed.

See here - http://garage.grumpysperformance.co...ck-chevy-gen-v-vi-to-adjustable-rockers.4564/

I forgot to mention it, but those intake manifold gaskets definitely aren't original - they look like Felpro gaskets to me. So at minimum the intake has been off. You could measure the bore and compare to see if it's ever been bored out. Refresh my memory, but did you ever do a leak down test?
 
You adjust like they are adjustable, lifter on cam heel, then you check as you go. Tighten the nut to get 0 lash then it should be 1/2 to 1 turn when you hit 40 lbs. If your not in that range your gonna have a problem.
 
Just did a deeper inspection and found a couple of things. Some cylinder gasket water issues, right at 4/6 and 3/5, so that's starting to explain the water in the cylinders. Wasn't burned through, but definitely visible.
2nd, that changes the schedule somewhat is he did find some scoring on the cam at 8 for sure, where the pushrod had punched through the rocker a couple of years ago, and light scoring on a couple of others. So, we're this far, time to finish tearing the front off, and move the water lift to swap it out. Now, can I find a cam soon enough in today's environment? bleah.
 
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