i took my car to a muffler shop today to have my y pipe and catback installed on my lt's. after they installed them. i noticed a knocking sound coming from the engine. the mechanic noticed it too and chech for exhaust leaks. he didnt find any. he said it might be in the valvetrain. i have 1.6 rr, new lifters. everything on the engine is brand new. it has less than 20 miles driven. i think it did it the first time i turned on the car. but it was hard to tell because open headers were too loud. what could be causing the knocking?? theres also a screeching sound coming from under the car when i put it in reverse and sometimes does it when im driving down the road. if im at a red light, then start going, it'll screech. then i let go of the gas for a second and step on it again and it goes away. i have a 168 tooth flexplate and its an a4. clearance from flexplate to bellhousing is very very small. like a cm. what could these noises be coming from??

 

Could the screeching be either the serpentine belt or the tires?

Also, the y-pipe could be hitting the k-member.

Im just hoping for easy answers for ya

 

With the car running go underneath the car and feel with your hand the oil pan might be hitting it or the windage tray why type of pan you have?I hope it something very simple Bro.

 

its not the belt and i wish it was the tires. i couldnt any sign of the exhaust hitting anything. i have the stock pan but the shop said they clearanced it out. it sounds like a wood pecker pecking on wood. i think its coming from the bottom. when i described it to one of my buddies, he said it could be a spun bearing.

 

Do a oil change on it right away,Check for any shavings in the oil.I would not start it up anymore till you can see what is causing the problem.

 

My short block was also clearanced by the engine builder but when I fired it up #1,#2 & #7 rods were hitting the pan . I would check that first then check to see if your exhaust system is hitting anywhere since you just had it done, Then it may be spun bearing

 

The rods will hit the windage tray. I bent mine up a little bit and it cleared fine. With the stock oil pan none of the rods seemed to hit and def isn't making any knocking sound. But I figured I'd give you something else to check if you have to take the pan off. Does the car run ok?
If you used a bigger cam and the rods weren't checked for enough clearance a few of them will hit the cam. I forget exactly which ones do though. other than that it maybe a spun bearing, but again you'd notice your car running a little worse
Hope you find it good luck with it

 

it doesnt run all that good. its hard getting it to 30 mph. after that i guess it gets a little better. i did do an oil change and i didnt see any metal shavings. it has a 503 comp cam and the builders said they had clearanced everything. they're coming to my house on monday to check it out.

 

I feel for you brother. I had a couple questions. Did you put the motor together?? If so, did you spin the crank with the oil pan on.? What kind of rods are you using? Mine hit heavily and I ended up going with a Canton pan (which I love). Either way...... I dont think its the valve train, can't see how you would get knocking from there. You say the motor has only 20 miles on it?? Well let us know buddy. Good luck. I hate to say what I think it is but how well do ou know this engine builder??

 

a local speed shop put it together. im using 6" eagle h beam rods. the owner of the shop has been in business since the late 60's. he knows his stuff. they did say they clearanced the pan. how can i check what it is without tearing down the engine again?

 

You have to pull the pan, period Hope it's only rods hitting "something". The lack of power spells out one thing, spun rod bearing. Happened to me, same symtons. We all make mistakes & it sounds like someone made some putting your engine together? What I've seen is a shop owner who lets his help do the work & then you have problems.

 

I had a problem of screeching and kncoking coming from the engine. The knocking was kind of hard to hear and it only screeched every once and a while. Car ran real bad too, wouldnt idle the greatest and ran poor. Sorry to say but it turned out to be spun main and rod bearings. I know this isnt what you wanted to hear but Thats what my problem was. I hope it is something else for ya that one of these guys mentioned but just to show you it could be major so driving needs to be minimal in it!

 

thanks for all the info. hopefully, ill find out what it is tomorrow when they come check it.