How hard is it to rebuild a 4.6 DOHC?

Venompower

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To say I have gone through a range of emotions since Saturday would be an understatement... when doing the first oil change since purchasing my Mustang I found glitter in the oil, no large flakes, or chunks, but everything I have read has been doom and gloom. Trying to figure out the best way to move forward, the engine isn't ticking or knocking... there is a slight miss at idle but I associated it with the tune as it's slightly lean at idle.

I requested a test kit from Blackstone, hoping that it will at least point to what the glitter came from so I can narrow the search.

Would love feedback about what you would do in this situation, as well as get some feedback on how difficult it is to assemble a 4.6 DOHC long block...

If it does need a rebuild I'll be trying to keep costs down and use as much as possible from the current engine, basically have the heads inspected/freshened and new springs added, and then have the block bored and forged rods and pistons added. Depending on cost I'd prefer to have the shop reassemble the engine, but if that becomes prohibitive based on cost I may need to try and tackle it myself???
 

RAU03MACH

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i am fairly new on a 4.6 i have put about 3 of them together not bad at all
5.0 302 is almost the same concept but the over head cams are critical when timing
and having the right tools is a pluss
 
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Venompower

Venompower

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i am fairly new on a 4.6 i have put about 3 of them together not bad at all
5.0 302 is almost the same concept but the over head cams are critical when timing
and having the right tools is a pluss
The ability to put the long block together might be huge if this ends up being bad enough to necessitate a rebuild.

I'm talking to a trusted local shop right now to see what they think.
 

RAU03MACH

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that is for 4valve 4.6
my next one is going to be the 3 valve 4.6 in that 05 i just picked up
just going to go through the engine to make sure all is good
 

RAU03MACH

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my mach swap on the 98 gt running good , a little noisy but runs like a champ
my cobra engine is holding up verey well
but i do want to check out see what makes the 3 valve tick
 

cobrajeff96

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From what I've heard from pros, you're much better off having a professional shop do this if rebuilding o the bottom end rotating assy is required. It's actually the exact reason I chose not to bulletproof my original Teskid motor and just do a Coyote swap. The cost to gain ratio is massively in the Coyote's favor when it's all said and done.
 
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Venompower

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I messaged the owner of local shop that has done some great work on friends cars, and he advised he believes this is from a bad powder coating job where the powder is starting to chip off the cam covers. Aluminum Oxide is used as blast media and is non magnetic. So before I lose my mind, I'm going to put some easy miles on it and change the oil again and see what it looks like and what the oil test shows.
 

cobrajeff96

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Sounds fair, and really all of the busy stuff inside a motor is going to be mostly steel. I just worry about that glitter embedding itself into any bearing surface and potentially scarring things up. But yea don't jump the gun, just be easy on her and change that oil.
 

lwarrior1016

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The pistons are aluminum and can leave residue like that. Does it have piston slap when started up cold that goes away when warm?

With as fine as that is, I wouldn’t be scared that it’s doing damage.
 
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Venompower

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The pistons are aluminum and can leave residue like that. Does it have piston slap when started up cold that goes away when warm?

With as fine as that is, I wouldn’t be scared that it’s doing damage.
No piston slap on cold starts… the only noise it makes is slight miss at idle but the tune has the AFR at 16 to 17 at idle, and as soon as any throttle is applied the AFR’s are perfect, and under full throttle are in the 11’s.
 
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Venompower

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Drove the Cobra to work this morning, its 30 something miles one way... no weird start-up noises, car did great never exceeded 3.5k rpm, air conditioning is nice to have lol... supposed to rain all weekend, but I'll put some more miles on next week. I got the Blackstone test kit yesterday evening, would you recommend testing the old oil or the new oil, or both by requesting another kit? I think you are supposed to capture the oil mid stream while draining and I obviously can't do that with the old oil.
 

BHernandez

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I have a 2V 4.6L. I had the silver glitter start at about 140K. After much searching and diagnosis, I've discovered the cause. Thrust bearings. How, or if, to repair is really up to how you drive it. I'm old now, so I don't treat it like I did when it was new. The car has nearly 200K on it now and aside from a small rattle on cold starts it runs just fine. No misses. No odd noises. Of course, I rarely take it over 4,000 RPM anymore but the occasions that I have I've haven't noticed any rattles of any kind. As far as how hard it is to repair or rebuild geos; the 4.6 design is based on the 2.3 4-cyl. Hence the "Modular" designation. You'll need a few specialty tools, available from any parts store or RockAuot.com, but aside from that it's pretty straight forward. Your bigger concern should be a good machine shop. Keep the bore to a minimum and if they're good they can save the crank. Like I said, I haven't fixed mine and I don't drive it hard or even often. It's mostly a weekend car for me now. I stay on top of the oil changes and use only Mobil 1 full synthetic. I have no issues with hopping in it and making a 400-600 trip without worry of being stranded by the car.
 
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Venompower

Venompower

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I have a 2V 4.6L. I had the silver glitter start at about 140K. After much searching and diagnosis, I've discovered the cause. Thrust bearings. How, or if, to repair is really up to how you drive it. I'm old now, so I don't treat it like I did when it was new. The car has nearly 200K on it now and aside from a small rattle on cold starts it runs just fine. No misses. No odd noises. Of course, I rarely take it over 4,000 RPM anymore but the occasions that I have I've haven't noticed any rattles of any kind. As far as how hard it is to repair or rebuild geos; the 4.6 design is based on the 2.3 4-cyl. Hence the "Modular" designation. You'll need a few specialty tools, available from any parts store or RockAuot.com, but aside from that it's pretty straight forward. Your bigger concern should be a good machine shop. Keep the bore to a minimum and if they're good they can save the crank. Like I said, I haven't fixed mine and I don't drive it hard or even often. It's mostly a weekend car for me now. I stay on top of the oil changes and use only Mobil 1 full synthetic. I have no issues with hopping in it and making a 400-600 trip without worry of being stranded by the car.
If the thrust washer was wearing out, wouldn't the particles be magnetic if they are made of steel? I know the bearing material is an aluminum alloy, but I thought the washer was steel?
 
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lwarrior1016

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The trust washer is the same material as the main bearings. It has to be softer than the crank, and is a wear item. Heavy pressure plates will strain a thrust washer on start up.
 

lwarrior1016

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Recommendations if this were the issue?
The only thing you could do is rebuild it with a new thrust washer. But you may be chasing a non issue. I’d flush it with a couple oil changes (cheap oil, really close intervals like only a couple hundred miles). Then put some good oil in it and see how it looks. Just make sure to listen closely to it.
 
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Venompower

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I’ll be 60 miles into the new Mobil 1 5w-30 I put in by the time I get home, I’ll try to drive it a couple times next week and then do the first change and inspect the oil.
 

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