Name that sound (broken cobra)

MalcolmV8 · Post by **MalcolmV8** » Sun Nov 23, 2008 11:52 am

http://www.youtube.com/watch?v=RLIav2AbM4k

Yes that's my car. I broke something.

usmcrp1044 · Post by **usmcrp1044** » Sun Nov 23, 2008 7:21 pm

You have a little person in your engine knocking to get out? or maybe it's just one of those bearings...

Where does the noise actually come from?

MalcolmV8 · Post by **MalcolmV8** » Sun Nov 23, 2008 7:35 pm

I'm pretty sure it's a rod knocking but oddly enough the sound is loudest at the tranny. I think it's just resonating though cause pushing in the clutch or putting it into a gear etc. has no affect on the noise what so ever. Sucks.
Looking at the plugs it looks like I went a little lean and probably had some detonation and destroyed a rod bearing from the shock load.
It was a cold night, 40F, and apparently my fuel system was not strong enough for the extra cold dense air and a bunch of WOT back to back runs from 40 to 160 did it in.

cgrey8 · Post by **cgrey8** » Sun Nov 23, 2008 7:43 pm

That's in the engine or in the tranny? It sure sounds like it's coming from the tranny or from the clutch.

Has this thrown a Check Engine Light? Does the engine run different now? The engine noise just sounds too smooth to be a problem with the engine itself. But that's just what it sounds like to me...obviously not what's actual.

MalcolmV8 · Post by **MalcolmV8** » Sun Nov 23, 2008 9:54 pm

There is no check engine light but I don't see why it would have one either. The noise is definitely loud from the tranny but when I push the clutch in and put the tranny in gear there should not be a single spinning gear or shaft in the tranny at that point right? Doing so makes no difference on the noise.

It actually still runs fine. On the way home after it started making that noise and before I realized it was a metal on metal noise I raced a friend several times and it still ran strong as ever. Got home and the noise actually seemed gone. Fired it up the next day and it's the loud metal on metal type sound you hear now. It's definitely loud under the car. If you stand over the top of the engine with hood popped you almost can't even hear it.

What a bummer, a rebuild will be around $6k minimum from what I've researched. Stock replacement short blocks can be had for around $4k but they have the same short comings and weaknesses so need to build for some real power. Especially since I plan on putting a kenne bell in the near future.

The stock 03 cobra motors have very tight piston to wall clearance. In the order of 0.001 to prevent any piston slap and keep the motors real quiet. Unfortunately put huge amounts of boost in them or do high speed runs (like WOT in 5th or 6th) and you produce so much heat that the pistons expand to much and wear off the teflon coating and ruin themselves.
Another major weakness were the heads. Ford since revised them so they didn't have cooling issues on cylinders 7 & 8. I had installed a cooling mod to let the coolant out of the back of the driver's cylinder head but there are other mods there were made. I think I read the valve guides were improved and they also went from 4 spark plug threads to 8. Not sure what genius thought 4 aluminum spark plug threads on a super charged motor was a good idea. I've seen on the forums where the plugs blow out and go right through that metal plate over the valve covers. One guy even had it blow a scoop off his hood and it landed on his windshield.

So anyhow the idea is to get down to a bare block, make sure my forged steel crank is still good, and the forged rods, get new pistons .020 over and machine with more clearance than factory in the bores. I will probably have to live with piston slap on start up but I'm told I'll easily hold 700 rwhp at that point. Oh and the new revised heads apparently are a must.

This is just following what the other guys are doing on the cobra forums and what's working for them. I'm still researching.

Warpig Racing · Post by **Warpig Racing** » Sun Nov 23, 2008 9:55 pm

I assume it does it in park? How about all the gears? How about with the clutch disengauged?

MalcolmV8 · Post by **MalcolmV8** » Sun Nov 23, 2008 10:01 pm

Warpig Racing wrote:I assume it does it in park? How about all the gears? How about with the clutch disengauged?

When you say park do you mean neutral? It's a stick shift of course (got a clutch). yes it does it in all gears. In fact gear, or neutral, clutch in or out etc. seems to make no diff on the noise at all which really blows. I'd so rather have a blown tranny than motor.

Warpig Racing · Post by **Warpig Racing** » Sun Nov 23, 2008 10:23 pm

Haha. Yeah, that was retarded on my part.

have you tried listening closely? I usually use a 1" wood dowl rod. You can place it on different places on the motor and tranny and put you ear up to it. the vibrations will be transferred to your ear and you will be able to isolate the noise. It's an old school method but it is effective.

have you drained your oil to see if you have shavings in the oil? Could do the same with the tranny. Gotta drain them anyways before you pull it.

MalcolmV8 · Post by **MalcolmV8** » Sun Nov 23, 2008 10:41 pm

I tried a screw driver briefly and it seemed to be coming out the tranny but I couldn't be sure. I had my 8 year old push the clutch in and out while I was under there and didn't notice a difference in noise. I was tempted to have him put it in gear too but if that little foot popped off the clutch in gear I'd have a car on my head so I decided to pass on that test

I have not drained the oil yet. I'm gonna drain the engine oil soon. I went to get some mobil 1 yesterday and they had a sign up due to hurricane ike supplies are limited so I found some castrol syntec in the right weight. Reason been I'll need to put oil back in to continue testing or possibly even drive it somewhere for more trouble shooting.

I've been so busy lately I may even have to take it somewhere to get the motor pulled. Or just leave it till next summer and then pull it and rebuild it.

cgrey8 · Post by **cgrey8** » Mon Nov 24, 2008 5:12 am

You've eliminated it being in the tranny for sure. But you have not eliminated it being in the area of the clutch and flywheel. Hopefully it isn't internal to the engine, but it sounds like you are expecting that.

As for the cooling on the number 7 & 8, a guy at work with a Cobra had that problem while it was still under warranty. They replaced the head and he put that cooling mod on to prevent that from happening again. But his is mostly stock. He's got a few very minor mods, but it's mostly stock. He's trying his best to talk himself into buying a KB or Steig V port job similar to what you got. The problem is he just doesn't drive it hard as-is. The only reason he'd be doing the mods is just for braggin' rights. He's also a bike rider and he admits that there's nothing he could do to that car to make it even close to what his bike can do as far as accel and speed.

Oh and the tight piston clearance...not a performance decision at all. That's an emissions decision. The tight clearance and the piston mods that put the 1st compression ring up closer to the top of the piston. The attempt is to reduce the amount of raw fuel that gets between the piston and the cylinder and doesn't burn...but does make its way out the exhaust. I wouldn't guess that the emission effect AFTER the CATs would be that big, but it was enough for them to make those mods. Another very negative side-effect of putting the compression ring closer to the combustion is it makes them even less resistant to predetonation. I wouldn't be surprised if there are aftermarket pistons out there that lower the compression ring to more traditional levels.

cjcnomor4 · Post by **cjcnomor4** » Mon Nov 24, 2008 6:26 am

sounds like a rod or rod bearing. disconnect injectors one at a time while running to see if you can pin it to a cylinder. even with that the end result will be the same.

MalcolmV8 · Post by **MalcolmV8** » Mon Nov 24, 2008 9:16 am

CJ, do you think I could pull the k-member (I know probably a massive job isn't it? and pull the oil pan and remove the rod cap and just put a new bearing in the bad one? I know if the rod and crank are damaged or scored that won't do me much good but that may get me back on the road so I can at least drive the car till I have cash to rebuild.

cjcnomor4 · Post by **cjcnomor4** » Mon Nov 24, 2008 11:18 am

you would need something to hold the engine from the top. I'm not 100% sure you can get rod bearings for it. possibly aftermarket. if theres any bluing on the rod, you're done. I had an 06 milan 2.3 4v a few months back with a #4 rod knock. had the pan and rod cap off in under 1 hour, only to find that ford doesnt offer a rod bearing. the lowest level of service is a short block. you have a forged crank in that thing so it may be ok. there are two 12mm bolt holes on the rear of the rh head and the front of the lh head, you could use an engine hoist to hold it while the front subframe is out.

MalcolmV8 · Post by **MalcolmV8** » Mon Nov 24, 2008 11:34 am

So the entire lower subframe has to come out. Wow. Would it be easier to just pull the motor out the top? or is there any benefit to pulling the subframe?

cjcnomor4 · Post by **cjcnomor4** » Mon Nov 24, 2008 12:50 pm

if you pull the subframe, k-member, whatever you want to call it, you can leave the trans in it. you wont have to mess with the exhaust, drain the cooling system, evac a/c. shouldn't even need to be aligned either. if you find you have to pull the motor, all of that would have to go together again to get it out the top.