So, I'm pulling into my apartment complex in my 97 Cobra. I speed up a little to get to the speed bump and when I reach 2000rpm I hear a knock. WTF? I find out after driving around to better hear it that it only knocks between 2000 and 4000rpm. First thing I did was check the oil, it was a quart low, I topped it off. Knock still there. I changed my oil from 5w30 to 10w40 both full synthetic. No help. I don't have any loss of power or anything except that knock. Most people are telling me that it's the crankshaft bearings. Is their an EASY way I can tell if this is the problem? I don't really know what I'm doing and I'm not ripping apart the engine. If this is the problem about how much would this cost to fix? *sigh* I miss my car.
It could be worn crank shaft, or rod bearings. If that's all it is, then it's as simple as pulling the engine down, checking the journals for wear and replacing them. Unfortunately, the DOHC assembly isn't as "simple" as it would be for an OHV. Not only does the engine have to be removed, but so does the timing cover and drive chain assembly. If you plan on doing it yourself, get a hold of a detailed shop manual and someone with in depth automotive experience to assist you and make a weekend out of it. If you're paying a shop to do it, prepare to pay though the nose for labor, cause it ain’t gonna be cheap. If you've got some extra cash to spare, this might be a good time to spring for a forged bottom end upgrade, in the even you want to start adding some "real power" to your engine later on down the road. If this all sounds like it’s going to be too much for you, I’d be on the lookout for a low mileage Cobra engine to replace yours with. It may cost you a little more than a refurbish of you old one, but in the end a swap is a lot simpler and faster than a complete rebuild. Not to mention it’s a nice time for an upgrade.....Late model Cobra or Mach 1 engine anyone? Barring all that, have you tried "Seafoaming" the engine? Might be worth while to do before you go digging into it?
Do you have, or can you post a recording of the sound? Might help some people in the know on here. Plus if it is making the same sound as mine I can point you in the right direction. BTW take out the oil you put in, it way too thick for our hydaulic lash adjusters. Put 5w30 back in.
