Timing chain slap/noise when fully warm...

[Cakes]

I have been dealing with a knocking/slapping when my motor has been fully warm. Many people have told me my bearings could be the culprit, which I am not ruling out, but I checked them when I did my rear main, with the mechanic at my side, and they seemed normal for an engine with 40k on it. I have no noise at idle but when the engine is free revved from 2000-2500 it will make a slapping/knocking noise and then as rpms go higher the noise goes away. I know the previous owner replaced the timing chain with a double roller from ATR(Cloyes) and I am fairly certain that chain is for the stock line bore(they do make one for .005 and .010 line bore) The reason I say for a standard one is because the engine was rebuilt my GM (under warrantee) and I dont know if the engine was aligned bored or not. Also on the ivoice from ATR, I did not see a new cam button purcahse so I am assuming he used theold stock one. I have been trying to figure out where the noise has been coming from using a stethoscope and I think I have pinpointed it to the timing cover. A bearing just doesnt make sense to be because it only does it when its warm and at a particular rpm...even holding steady at say 2500 and then if I blip the throttle the noise will occur and then go away. Any ideas/help/insight is greatly appreciated! Thanks for your time!

 

[turbosam6]

My car does the exact same thing. Weve cut the oil filter and nothing. Oil pressure stays up too. Wierd thing is its so intermittent. I can never get it to do it when the engine builder looks at it. Sorry I can't help more, but hopefully someone else can.

 

[Cakes]

Turbosam6, mine does it everytime no matter what I do. I raced it 3 times like this (flame me) and I drive from Agawam, MA to Maine in 95 degree weather and it still does the same thing and I have no probs. I am worried about it alot and I dont want to do anymore go fast parts until I fix it. Thanks for your insight. Do you still race it like that? I wish I could just have an answer so I could fix it. I hate just opening up the engine just to "look" for an answer. Oh well I may have to do it! Thanks for your help!

 

[salvageV6]

I'd go in the cam sensor hole and see if you can check for the proper tension on the chain or missing tensioner.

Good first test before taking the front cover off.

 

[Cakes]

SalvageV6, I am willing to do that but I do not have a cam sensor set tool so I wouldnt be able to get it back to normal. Also from what I understand a double roller doesnt need a tensioner, correct? If its there, could this be cause for concern? Thanks!

 

[jastrckl]

don't use a tensioner with a double roller. the chain will eat the tensioner and gum up the works.

 

[Cakes]

I know a tensioner is not supposed to be used with double roller but I am not sure if the owner before me used one. I didnt see a new one on any invoices and I presume in the instructions they state not to use the tensioner. The cam button I am not sure about. If my engine needs a rebuild I dont think I can wing the money and would mroe than likey be forced to sell.

 

[turbosam6]

Yeah, I race mine like that. Screw it, either its gonna break or its not. Its a double roller, pretty sure with no tensioner. It was built by a reputable TR guy, and whenever I take it to him, its quiet. Can you hear it when cruising? Mine sometimes after driving for a good while will set off the knock gauge, then when I turn off the radio and listen it will be tapping.

After I make a pass, I can hear it when I get back to the pits, but it hasn't set off the knock sensor like that. I just let it idle with the fan on after a pass, and it will go away in less than a couple minutes. So I figure if its bearings or something I would have oil pressure problems or it would at least get worse with time. But its actually gotten better, probably just wore something away! These motors are generally loud, with the few exceptions. I wouldn't have noticed to much if I didn't have the knock gauge. Weirdest thing is when you're doing 75-80 down the interstate (Hell yes with the slicks!), the damn knock gauge goes nuts for a second, then resets and is cool for 5 minutes or so. WTF??? I've been all over this thing with a screwdriver to my ear, and best I can tell is it sounds valvetrain related. Not deep, like a rod, but like lifter tap. But when I pull the valve cover its all good. Note, mine seems to come from the driver side. Hell if I know, I'll just take the dump cap off and try to drown it out! Good luck, I'm eager to see what you find.

Just out of curiousity, if the chain has some slack in it, what do you do about it?

At least mine goes away when I'm on it, damn false knock would piss me off!

 

[Cakes]

I dont seem to get any knock when in gear(or at least I cant hear any) but if I am at say 30-40 mph and put it in neutral and rev I can hear the slap/knock. Its weird. I even power broke it in my garage to see if I could hear it and nothing. It seems logical that once the timing chain heated up that it could have some slack and hit something inside the timing cover but its just a shot in the dark. I guess if I found out my engine was line bored when rebuilt and I knwo for a fact a standard Cloyes Double roller was used that could lead me to believe it could be a bit long. I guess the onyl way to get rid of it is to get a new steel GM timing set and use the tensioner and spring and it will take out all the slack. I just want it fixed so I can go run some times with confidence that my engine will survive.

 

[turbosam6]

I sure wouldn't trust a GM timing chain I don't think. I don't understand why a line bore changes the chain length? Isn't centerline still centerline? It shouldn't matter how big the journal is. Unless it isn't bored on the centerline. I don't get it?

 

[Cakes]

Sorry I didnt mean GM, I mean GM style (i.e. Steel gears and teeth) I dont know why it makes a difference if your engine has been line bored or not.....maybe because if it has the crank is a bit further up or something....not sure on that one. I just want the warm knocking to go away. Ive driven it for a while but who knows if and when it would turn into something worse. Thanks again!

 

[turbodave231]

Line bore or hone moves the centerline of the crank up further into the block. If align honed the centerline will be rasied about .001 to .002". If the block is align bored more material is removed from the caps and block and the centerline will be raised much more.

If your block was honed or bored, a short chain is needed or it could be sloppy and cause a problem.

It sounds like you need to do some exploritory surgery to find the root cause of the noise. Ticking/knocking isn't normal from this area. If the double chain is loose replace it. Stock style replacements with the dampner work just fine. Thats exactly what I run.

I recently found a similar noise to be a lifter lobe #3 exh going away. The noise was loudest right at the cam sensor not the valve cover like you would think.

BTW setting your cam sensor is no big deal. you don't need an expensive tool, just a voltmeter and a little persistence.

 

[Cakes]

turbodave231, if I removed the cam sensor could I see if the timing chain had any slack or do I need to remove the whole front cover? Im going to do more "listening" when I am home next to see if I can pinpoint anything more. When I used a good stethoscope I found the noise to be coming from the timing chain area, so that was my first idea. Another question....if I go through all the trouble of doing a timing chain swap should I maybe consider doing a cam swap as well since I will be right there. I know the stock cam is good into the 11s but I do now have a 3200 stall and I was just curious if it would be a good idea. Its 95% street 5% track but more fun on the street is always the goal! Thanks!

 

[salvageV6]

Ooops missed the double roller part.

Hey you going to Cottons outing/winter party sat. 22nd?

I can bring the cam sensor tool with me and a few wrenches.

Prolly get about 100 opinions on what your problem is too.

Might be able to get an estimate at fixing it and a cam install too.

Worth thinking about anyway.

 

[Cakes]

SalvageV6, I dont think I will be going to the party as I am at school although I am close. Right now being as student cash flow isnt that high since last year I dumped a large chunk of my cash over to Jack for a Strip Tranny and Art Carr Torque Convertor. I took it to Jack and he said I need a rebuild and I took it to the mechanic I work for and he thinks if it were bearings I would have blown the engine a long time ago since I have taken it to the track 3 times after I noticed the knocking. Thanks for the offer though

 

[REDS HOT AIR]

timing chains stretch soon as you fire them.

the design of the v6 makes the cam jump back and forth at all times

If it is line bored it definatly needs a shorter chain

rollmaster double rollers are best on the market for these motor ..they have machined gears that dont wear like cast gears and chain is pre stretched when you get it so it dont loosen up once you install it.

I tried several chains and all got loose with very few miles till I went with a rollmaster and finally got rid of my chain slap noise .

like you said it is noiseyest between 2 and 3000 rpm.

mines gone now ..

its really not going to hurt nothing but if you want to get rid of it get a rollmaster chain.

you cand search for it ...I know Lee thompson runs them also since he's the one who recomended it to me ..

 

[Cakes]

Thanks Red, now the big question......do I save for a cam to match my Art Carr Convetor or leave the stock one alone?? Thanks again!

 

[JCotton]

I took it to Jack and he said I need a rebuild and I took it to the mechanic I work for and he thinks if it were bearings I would have blown the engine a long time ago since I have taken it to the track 3 times after I noticed the knocking. Thanks for the offer

Cakes,

Nooooo, I didn't say you need a rebuild, I said, I would have to explore to find the noise since it was internal. I don't do rebuilds unless necessary. The last thing I need is another motor job here. You can debate what your noise is until the cows come home, bottom line, exploring the internals is the only way you will diagnose it. Anyone that can tell you what your noise is over the internet is a magician and needs to do this full time. If enough people respond, someone will be right, sooner or later.....