Massive Engine Knock on All Startups

[sonic]

that sound s like a header leak not internal engine.

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[96gt4.6]

It is possible no doubt, and I do agree a thorough check of the header to cylinder head areas for leaks would be worth doing before getting too involved, as indeed it really is hard to accurately diag via video/ect.

Keep us updated!

 

[racingmason]

It is possible no doubt, and I do agree a thorough check of the header to cylinder head areas for leaks would be worth doing before getting too involved, as indeed it really is hard to accurately diag via video/ect.

Keep us updated!

I should note I have a smoke machine and tested the header area and saw no leaks. I did this by removing the exhaust at the collector flange and pumped smoke in. I didnt see any leak out if the head to header area but it made it all the way through the blower and out the air intake. Is there another way to check for a header leaker. I dont see soot anywhere around the header flange and the exhaust is fairly sooty.

On 14psi it's running e85 and on 13 psi its 93. Its daily driven on 93 octane and 13 psi. The tune is set to make about 600 hp on 91 octane since fuel is inconsistent and I very rarely got wot on 93 octane.

 

[96gt4.6]

Everything I can tell in that video just sounds like internal engine to me, and indeed it sounds like you have checked about everything as far as leaks/ect. Normally an exhaust leak that bad is very apparent on the header flange/cylinder head as black streaking/soot/ect, and you can usually feel exhaust coming out around it during the concern if you have it in the air.

My professional opinion, let it cool, get a scan tool that can cancel cylinders (unplugging coils while running can damage the pcm), and start killing cylinders 1 at a time until you hit the one that makes the noise change. Then, carefully inspect that hole through the plug hole with a scope, and just for safe measure the exhaust port on that hole.

In that second video, you can really hear the metallic. My gut just screams internal engine, but could be wrong without hearing in person.

 

[F1scamp]

Adding a restriction sometimes helps finding a leak, try blocking one of the tips, and running the car while watching the gasket area, or just pull the header back and check the gasket. You said you just did an oil change, any sheen, or shiny pieces in the oil?

 

[96gt4.6]

Everything I can tell in that video just sounds like internal engine to me, and indeed it sounds like you have checked about everything as far as leaks/ect. Normally an exhaust leak that bad is very apparent on the header flange/cylinder head as black streaking/soot/ect, and you can usually feel exhaust coming out around it during the concern if you have it in the air.

My professional opinion, let it cool, get a scan tool that can cancel cylinders (unplugging coils while running can damage the pcm), and start killing cylinders 1 at a time until you hit the one that makes the noise change. Then, carefully inspect that hole through the plug hole with a scope, and just for safe measure the exhaust port on that hole.

In that second video, you can really hear the metallic. My gut just screams internal engine, but could be wrong without hearing in person.

 

[racingmason]

Everything I can tell in that video just sounds like internal engine to me, and indeed it sounds like you have checked about everything as far as leaks/ect. Normally an exhaust leak that bad is very apparent on the header flange/cylinder head as black streaking/soot/ect, and you can usually feel exhaust coming out around it during the concern if you have it in the air.

My professional opinion, let it cool, get a scan tool that can cancel cylinders (unplugging coils while running can damage the pcm), and start killing cylinders 1 at a time until you hit the one that makes the noise change. Then, carefully inspect that hole through the plug hole with a scope, and just for safe measure the exhaust port on that hole.

In that second video, you can really hear the metallic. My gut just screams internal engine, but could be wrong without hearing in person.

What type of scan tool are you talking about? Where can I rent or buy one that's not $7k.

 

[96gt4.6]

Higher end Snap-On and such should work, and I agree no need to purchase equipment just for this. Easiest method is to pay a shop the minor fee they would charge for such a service, or just skip to scoping all 8 cylinders and hope to find something to go off of. My bet is once you find a way and start to cancel cylinders, you will hit one that lightens the noise up. I really hope I am dead wrong for sure on this, but it just soooo much sounds like metallic internal engine in those videos. Have you tried (safely!) being under the car while it is doing it to help isolate where/which side/ect? Is there any change when the clutch is pushed in?

 

[racingmason]

Higher end Snap-On and such should work, and I agree no need to purchase equipment just for this. Easiest method is to pay a shop the minor fee they would charge for such a service, or just skip to scoping all 8 cylinders and hope to find something to go off of. My bet is once you find a way and start to cancel cylinders, you will hit one that lightens the noise up. I really hope I am dead wrong for sure on this, but it just soooo much sounds like metallic internal engine in those videos. Have you tried (safely!) being under the car while it is doing it to help isolate where/which side/ect? Is there any change when the clutch is pushed in?

No change with clutch pushed in. I will put it up on stands tonight and have the wife start it in the morning and crawl under it. It's on the drivers side for sure and more towards the back. I'm going to check the welds on the headers just to be sure but kooks is a good product. There's a mustang shop here I can see if I can get it in for an hour of diagnostic.

 

[Jay-rod427]

I agree with some that's cracked header. Definately not rod knock imo. improves when warm as the metal swells and closes the gap. Drivers side is easy just take the header off.

 

[racingmason]

I agree with some that's cracked header. Definately not rod knock imo. improves when warm as the metal swells and closes the gap. Drivers side is easy just take the header off.

I will most likely do that this weekend. It is easy once I pull the blower off which takes me 5 mins since I've done it so many times. I'm hoping a weld failed but I won't hold my breath.

 

[DavidHuff]

Buy a Mechanic Engine Stethoscope on eBay for $8.00 and check your headers for leaks.
If you have a header leak you will know it very quick.
I have used a Stethoscope on my 1987 Buick Grand National to find header leaks and this tool works.

 

[greengoblin31]

yeah in these cases i take a 1/2" or 5/8" heater hose and put it up to my ear and i go fishing with the other end at the exhaust flange or welds to 100% rule out if i hear any leaks.

i hope you don't wind up needing a motor OP

best of luck

 

[racingmason]

yeah in these cases i take a 1/2" or 5/8" heater hose and put it up to my ear and i go fishing with the other end at the exhaust flange or welds to 100% rule out if i hear any leaks.

i hope you don't wind up needing a motor OP

best of luck

I will look at that tomorrow. It's hard with the Kenne Bell because it covers that side of the engine. The evap is also relocated on that side along with the 5 inch intake. I'll play around with some heater hose tomorrow.

Nothing would make me happier than it being the cometic gasket. I think its quicker to pull the blower and just remove the 8 bolts and pull the header back and swap the gasket and see. But I havent seen any soot around the head or flange when I last had the blower off.

 

[racingmason]

Well I checked with heater hose for a header leak and didnt hear anything. I pulled the blower and intake and checked for soot and the bolts were all torqued down. I picked up a factory gasket and will swap it tomorrow just in case. I'm leaning towards something in the bottom end. I went back and looked at the dyno videos from a year ago after my buddy said he heard something rattling. I had put it off as non important at the time as the KB motor mounts had lowered the oil pan onto the casting Mark's of the steering rack. I added a spacer to each side and filed down the Mark's. If you listen closely you hear a metallic rattle and it's from the same side of the car. Occurs around the same rpm up to 3k. I know it wasn't the exhaust as I check it every month for tightness and alignment. I have the borla gt350 exhaust and am really anal about the quad tips being center in the valence. The only way to do it was to ensure proper clearance from the balance and line everything up. The only thing I thought it could be is the header hitting the steering shaft as there is not alot of clearance but I was able to verify on a lift it doesn move that much and the engine is centered in the bay. Possibly could be a small stone that got into the kmember or the beginning of the engine noise. Below is the video of the rattling.

 

[F1scamp]

I don't think that's an engine rattle either. Nice thing is parts are so cheap for these things. When my stock motor went, I bought a factory shortblock for around 1600. Gaskets, headbolts, bearings, timing components brought it up alittle but I believe it was right arounf 2k. Check the bearing clearances and open up the ring gaps on the new shortblock if that is what it ends up being.

 

[racingmason]

I don't think that's an engine rattle either. Nice thing is parts are so cheap for these things. When my stock motor went, I bought a factory shortblock for around 1600. Gaskets, headbolts, bearings, timing components brought it up alittle but I believe it was right arounf 2k. Check the bearing clearances and open up the ring gaps on the new shortblock if that is what it ends up being.

The roads are real abrasive where I live and I'm constantly cleaning pebbles out of the rear valance and fender wells up front. I'm sure one is lodged where it is causing harmoics.

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