Well, after I did the rope thing the other day, where I was trying to replace the valve springs, and the rope got cut when I was pulling it out of the cylinder. Wel, I had turned the motor over a few times so I could get to the rope out piece by piece, and now I have a knocking noise. I got under the car with jacks, and you can hear, with a tool up to the oil pan a slight knocking noise. When warm it goes away.
The motor is a 396 with SRP pistons, Eagle rods and a forged crank.
The knocking is hard to explain as it goes away after warm, and it isnt really a double knock. ANyway, besides pulling the motor to verify anything?
There is no metal in the oil, so that is good.

 

ugh... you may have bent a rod doing that...

Short of dropping the pan, I donno what to suggest.

 

Regardless, I beleive she needs to come out and be looked at.

 

I would pull the pan ! That way you can check the rod and the piston skirt . The rope trick forces the piston to pivot at the pin, trying to force it out of square and this normally cracks the skirt ! You can also take off the rocker arms on that cylinder to see if the valves close all the way , maybe a valve is bent or something in the valve train .

 

Okay, sounds good. Fairly easy to pull the pan?

 

i never hurt anything using rope, dammm bad luck

 

I think it was the turning over of the motor with the rope inside. Its going to be a long couple weeks coming here soon.
New Cam time,

 

Is the noise only at the front of the engine near the timing chain?
After the engine warms up it goes away? I have had the same noise for over 10,000 miles .
It's not realy like a knocking noise but like a knock squeek?

 

Youcan get underneath it and hear it, and it does go away after warm up.
If I pull the pan, should I be able to "see" something? Cracked skirts? I could also do a compression check, see if there is any evidence of a cylinder leaking?

 

You can get underneath it and hear it, and it does go away after warm up.
If I pull the pan, should I be able to "see" something? Cracked skirts? I could also do a compression check, see if there is any evidence of a cylinder leaking?
Also, the motor does not vibrate. So that should eliminate the bent rod?

 

Seems funny to me that the noise goes away. Bent is bent, and broke is broke. Are you sure it's not just a lifter making noise? Did you try it more than once? Sometimes something, most often carbon, can bounce around on piston and make a gawd awfull noise that will make you think you have a bad rod bearing or wrist pin. Perhaps a few rope fibers would do the same thing. If it were mine, I'd assume IF I'd done serious damage, the damage is done already and can't hurt it much anymore. I'd then look for easy solutions short of pulling the engine or pan. Like, pull the spark plug out of the cylinder in question and give the engine a few spins without starting it to try to blow any junk in that cylinder out. Button it up and try again. If the noise is still there, get some top engine cleaner and give that a try. Not sure how you're supposed to get it in there on a vette. I've always used it on vehicles with carburetors so it was easy to dump it down the throat. Perhaps remove the plugs and squirt it in the cylinders with an oil can or something. Fire it up and try it again. If the noise is still there, remove the valve cover. Get some of those rocker arm oil hole pluggers at the auto parts store so you can run it without spraying oil all over the place with the cover off. Start it and see if there's valve movement that in the same rythem as the noise. If you can't tell by looking, take the handle of your hammer or something and push down fairly hard on the push rod side of the rockers one at a time. If the valve train has anything to do with the noise you should be able to make the noise better or worse that way. For all you know the cylinder you got the rope stuck in may not even be the source of the noise. At this point if you want to satisfy your curiousity a little you can remove the push rods on that cylinder and give them a roll across your work bench. Then you'll know if they're bent or not. I'd do all those things and maybe check the valve adjustment all around and call it good. If the noise is still there after all that, I'd run it anyway. If there is something really the matter, it will get worse before long. I'd be assuming I'd be paying for an overhaul or long block replacement anyway so there's not much to loose buy trying it. It also eliminates the possablity that I'd pulled the engine and overhauled a bunch of stuff for the sake of carbon knock or a sticking lifter. That's what I would do. Not saying that's what you should do. My advice is free and no warranty is expressed or implied. I never tried the stuff rope in the cylinder method before to hold valves closed, always used air. From your experience I know I'll stick with air. So thanks for that. Best of luck to you.

 

pretty good thought to go with...

 

I will give it a try today, thanks, Steve

 

Hello Steve,

Consider trying to find someone with an automotive borescope. With that, you MAY be able to check the top end without removing parts (spark plug excluded). With a good scope, you can check out the top of the piston, see what is going on around the vavles, etc. I suspect you have some debris stuck in the suspect cylinder.

For additional information go Google-then "automotive borescopes" and enjoy. Wish I had one. You may be able to call around and check various shops and see what's available. I'm sure they would let you check the scope and show you what is there. If push comes to shove, try some local aircraft repair facility. Non destructive engine inspections are quite common in the piston driven airplane world.

Kinda fun peeking around those cylinders. Hope everything works out and let us know.

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