700r4 noises or 383 stroker piston slap?
 

Hey and good day.. Thank you for your time and help.. I recently put a new engine in my truck and did a 700r4 conversion.. I have a noise that has developed in my motor that seems is going to make me have to pull it out and have it torn down.
But, I remember that before or just when the noise started I took my truck back to the shop where they put the Transmission in and had them rotate the flexplate 180 to see if we could get it to balance out bit more. I didn't think about this until today and now I am wondering.
I went and picked up my truck and started it up and heard this noise that sounded much like a rod noise to me and or a very loud clapping type noise that I had thought I had heard developing slighly before dropping the truck off at the transmission shop.
Research has lead me to believe that it may be piston slap. It is 383 built by Smeding performance, a highly recomended builder by Edelbrock and a brand new engine from the block up.
I have pulled a wire at a time and the noise never disapeared. The noise seems to be coming from the back of the motor. As soon as the motor gets up to running temp the noise is all but impossible to hear.
My question is about the Trans. Is there something in the Torque converter and or flex plate set up that could be causing this type of noise? Any and all experiences with engine noise or 700r4 noise is greatly appreciated.
I hate to pull the motor if it is a trans problem. What came to me today while thinking about pulling the motor was remembering that the noise was seeming to just start occuring at about 350 miles on the new engine and trans.
and I remembered when I picked up the the truck after they had turned the flex plate that the noise was terribly loud. But went mostly away after warming up.
The truck hadn't sat any longer than it had in the previoius days/weeks before I picked it up at the trans shop. Tempuratures about the same, mid 40's.. So I am wondering because of that time I picked it up and noticed it being so very loud, could it be transmission related. And of course any engine related noise advice very much appreciated.

Thank you thank you for any help..

Please check your flexplate to converter bolts or nuts. I've had a converter sound just like a rod knock because it was bangin against the flexplate. the studs or bolts will slam back and forth in the flexplate holes and make a hell of a racket. It will change under load or as the temperatures climb to normal operating temp. I would check this before I yard out the motor, considering you just had somebody else work on that particular part. I would also see if they added any weights to the flexplate to balance it. the weights could be coming into contact with your block, trans, or starter.

I agree, it really sounds like a loose converter.
If they are all tight, and the noise is still there, then crawl under again, and unbolt the converter all together and push it back towards the tranny. Then start the engine again and see if the noise is still there. If it is, then it's in the engine...if it is gone, then the tranny is to blame.

Yeah, could be a loose converter for sure. My buddy had a flexplate bolt break and come through his floor, because he didn't have time to check the noise out. Another thing it could be, although unlikely with a fresh trans, is the front pump in the 700R4 being shot. My Z28 had a bad front pump in the 700R4, and it sounded like a really bad rod knock until it warmed up, exactly what you mentioned. Just a few ideas for you, good luck!

And some one please correct me if I am wrong, but I have never heard the sound of piston slap being compaired to a rod knocking. I'm thinking they are totally different.

engine noises
 

See if anything on here helps


http://remanufactured.com/Engine_Noi...gnosis_101.htm


VetteVet

Is a 383 externally ballanced??

some are...some aren't

Hey everyone, thank you so much for your input, I am going to check out all of these suggestions. I will update when I do some investigating.

About the noise.. I did a lot of research and quite a lot of reading and I found that nearly everyone that was told it was piston slap in the end, always stated it sounded like a rod knock. The noise in my rig certainly does. But a rod knock would not go away when warmed up. That is why the piston slap consensus started making a lot of sense. I am so hopeful that the knock is coming from one or more of the suggestions you guys gave me here. The only thing that I have a hard time seeing easily is that with the transmission problems, how they would tend to go away when warmed up.. Unless like piston slap just enough expansion is gained to swell the plates up to the bolts or etc. etc. I sure hope it is that simple let me tell you. Quite a hassle if not..

Here is a couple of leads talking about the Chevy buy back of newer trucks because of Piston slap.. Many were bought back under the lemon law. I read in a few places that some of these same people likened the noise to rod knock in every case.. I didn’t take the time to search all of those out, but I did find one guy that likened it to rod knock in his camaro but was told it was piston slap.

Anymore input, in the slightest degree is welcomed. Thanks again. Very much..

Stringpickin/Barry

http://www.2carpros.com/topics/noises.htm

http://www.mylemon.com/Piston%20Slap.html

Didn't see anyone ask if your motor has forged pistons or not. If it is equipped with forged pistons, that may explain the knock. Forged pistons are known for making a little noise until they come up to temp.

Just a thought.

Spark knock?
When I installed my 383 I had to switch to high octane gas because of the flat top pistons.

Hmmm, interesting...I have honestly never heard of it sounding like a knock.
And I was tryin NOT to learn anything today. :rolleyes:

piston slap
 

This website has a sound of an engine with piston slap and it sure don't sound like a rod knocking to me. Believe me I know what a rod knock sounds like.
VetteVet



http://www.pistonslap.com/site_map.htm

Hey JB,, not forged pistons. I am wishing I would have went that way about now. The specs might have been a bit tighter. Mrein, have been running premium, ouch.. Longhorn, and Vette. yes, I know, i have heard a couple of rod knocks myself in my time and sure enough I had spun a rod bearing. When I listen to this, if I have piston slap, it must be I have possibly one very bad piston, two at most. Because it sounds fairly timed consistant with one cylnder per rev. Hard to tell that, but compared to the sound file I listenend to at the site you sent me too, the noise could be said to have qualities like that but less happenings of it and a much stronger clap. I do have an .mpg sound file of my trucks knock, can I upload it for you all to hear?? I just went to advanced options to see if I could load a sound file, and doesn't look like I can do it. Would be glad to send it to anyone who would like to take a listen if you email me at stringpickin@sbcglobal.net. Thanks every one..

I had a very similar problem. Serious knock sound. Not an experiance engine man... To my un-trained ear, I thought it was a rod. I have a brand new GM crate. Fresh rebuild 700R4. Sound developed very quickly on my way home from an errand. Sound was pretty much at idle and went away around 1000-1200 rpm.

To make a long story short my TV cable was way out of adjustment. I have the factory style cable and evidently the lock on the collar was not completely engaged and allowed the cable to slip out of adjustment.

I have the bowtie overdrives tv cable bracket. Adjustment procedure is simple enough. Ensure w.o.t. is attainable from throttle pedal. Adjust all slack out of t.v. cable. Push throttle pedal to floor, you will here clicking as the t.v. cable adjusts itself. Then the part not in the instructions: Make sure the lock button on the cable is engaged.

Hope this helps.
Rich

Edit: Not sure why this cable caused the problem. Know this is the only input to control pump pressure though.

Any updates?

Hey hey Wing,, funny you should ask. I was just looking at the relplys in my inbox from the thread and thought I should let them know what I found out. Last friday took my truck over to the tranny shop and put it up on the rack. Checked everything out, everything was tight, but rotated the TQ any way, just for the fun of it. Anyway, I have not started the truck on a cold morning as of yet, as I have been very busy behind schedule on a cabinet job and working way to many early and late days. However, I have no hope that we found a problem, so therefore I am inclined to believe even when I do start it up, it will still be there. By the time I had gotten the truck over to the shop the noise had completely disapeared also. The warmer the mornings are the quieter the noise is, and the shorter duration it lasts. Basically same spot I was at before checking out the tranny. It seems it is an engine noise that happens when cold and quits when warmed up. Back to piston slap? I was sure hoping to see something strange going on under that cover. oh well.. Thanks again.. looks like I am going to change oil and cut the filter and inspect for metal.. Keep on looking until I end up pulling out the engine I guess. Real drag considering this is the second one. Had a brain of a mechanic destroy the last one by cutting and air cleaner with a jig saw and bolted it to the intake and let the engine suck in all of the metal chards. 1 brand new 4 thousand dollar motor destroyed. Now the replacement has this knock. Oh man, what a night mare..

I had the rod knock piston slap dilemma with a bored and stroked 289. Everyone thought it was a rod but it went away with temperature increase. It had forged pistons and piston slap is much more common with forged pistons since they are set up a tad looser that cast pistons. You can determine if it is piston slap by adjusting the timing to zero when you start it cold. The noise gets worse with increased timing and will all but disappear when the timing gets to 0 degrees. Mine did and that solved the mystery. This was after I had already pulled the pan and replaced all of the rod bearings which were perfect!!!!!! Just my 0.02!

Thanks Stllookn.. There is a test that one of the guys here pointed me in the direction of at one of the sites that had the recorded sound of piston slap that has a test that involved pulling a few of the plugs on the number one bank and adjusting the piston to certain positioin and then rocking the crank back and forth via the fan belt and pully. I may give that a whirl. I have to re-read it to get the test set up correctly. But it has something to do with getting number one to the top and when you rock the crank you can hear the clank if it is there.. What did you do with your situation? Just run it. Does it still clank in the cold mornings? thank you..

I had two pistons that were making noise. At first pulling the plug worked on one worked when the timing was at the normal advance...thus all the experts and myself decided that this was the "bad rod". It checked out perfectly when I pulled the pan. When I buttoned it back up and reinstalled the dizzy at with a little more advance (by accident) without retimining it...then it was louder and a second and third piston started making noise. These all had new bearings with perfect tolerance! When I got the timing set and moved it back to zero...NO NOISE...even at cold start-up! Just a little more information that you probably don't need but it may help.

So, your saying timing was the problem? You never replaced pistons or etc. A new timing set and correct advance was the fix?

Just curious what flex plate did you use with the 383? a regular 350 or a 400.

Stringpickin - Are you sure the noise is coming from the bottom end of the engine or tranny? I've have bad lifters make similar noises at the top end of the engine. A bad lifter will make all kinds of noise when cold or starved for oil. Once warm and oiled, the noise will go away. If its a new engine, a poor break in could have damaged the cam as well. Just thought I'd add more food for thought! Good Luck.

Cleskie,, hey,, well, it sounds mainly as it is coming from the back and low end. I had thought it could have been a cam lobe or lifter break in problem as you noted. I have not ruled out the possibility of a collapsed lifter. But it is a pretty solid thunk to be a lifter. I hate to pull the motor and have it not be readily apparent what the problem is. Some one suggest I pull the filter and use a pipe cutter on it and open it up and inspect for metal. I am going to do that once I get a spare hour. In the midst of a huge contract of cabinets building, so making it very hard to squeeze any mechanic time in. I feel as if I should drive it long enough to either blow up or become apparent as to what is wrong. If it blows up I get a new engine out of the deal, as it is under warranty. If it is something that requires a rebuild is a drag because I paid big bucks for a BRAND new motor, not a used part in it. Block, heads, bolts etc. And a 400 flex plate for NeonLarry.. So a rebuilt motor means all of the geometry that I paid for in a brand new motor is no longer there. So,,,, a bit of a hassle here. and this too shall pass eh. I am still thanful for many other blessings that I most certainly have, so must keep it in perspective. But what a pain.. lol .. Thank you

Stingpickn: Just got done reading your profile. ...The furniture building and theoretical physics part.... rang a bell. Did you just get done building a house?

Hey ChickenWing,, no, have not just got done building a house. Just got done a few months ago with a very expensive super fancy kitchen I built and installed in Arizona, from northern Ca.. Man do I like your signature too. The goverment is supposed to be run by the people not some (rich and corrupt) people.. It almost seems impossible that if a Tea party had to happen the modern weapons would nearly make it impossible. Oh well, one world system coming our way whether we like it or not.. interesting times. Forget about the weapons, who needs the hi tec weapons when the blindness of the majority of the people to see the real garbage that is going on is so prolific. Sorry,, didn't mean to turn our Kool Truck board in to a dialog on the rich getting richer.. lol.. consider it done.. ............

string, the problem with the 289 was piston slap...timing only makes the noise more or less noticeable, that is all. It is also a way to diagnose piston slap. If you retard the timing to 0 degrees you will likely lose considerable performance depending upon what your timing is supposed to be.

UPDATE.. The engine is being broken down by Smeding Performance. Lets hope the problem is easily found.. hope hope hope.. string

Hey! You never called me up for the engine pull!

I had nearly the exact same symptoms in my recently-rebuilt, low-mileage 350 and th350. Drove me nuts. The flex plate LOOKED fine, just by looking with the cover removed. However, I unbolted and slid the torque converter back and found that the center bolt holes on the flex plate - where it bolts to the crankshaft -- were broken out. You might not see this if you just unbolt the converter from the flex plate to rotate the converter on the plate. You have to be able to see the center of the flex plate.

UPDATE: The Motor is broke down. Being it only had approx. 900 miles on it, wear marks were basically non-existent because the noise happened only when the motor was cold and disappeared when up to running temp. What they found was when they measured the cylinders. Approximately 4 cylinders are over sized by enough to cause a few pistons to slap inside the holes. But was not easily seen because at the top of the cylinder they measure within spec. just barely. So when they measure down inside where the piston rings had been running against the bore the measurement was notably larger than allowed specs. So the consensus is, before the ridges of the Honing of the bore were knocked off the cylinder bore was within spec. So my consensus is this. The engine should have never been put together with the specs that close to the outside acceptable tolerance.
If they would have measured the bores before they put the motor together they would have found that it was on shaky ground. My opinion they would have and should have come to that conclusion. Anyway, they are going to take the now seasoned block, and bore it 30 over and rebuild it from the ground up. He assured me that he doesn't want it back again and they are basically going to blueprint it as they put it together this time.
He said they have never had this happen to them before. Apparently they never measure the bores on the brand new blocks they purchased from GM. Apparently they come bored and honed ready for assembly, then they just throw their parts in them. He said they measure the pistons to make sure they are within spec across the board, but had never found it necessary to measure the blocks. Oh well. I got the one that was a little too sloppy. What an expensive waste of time this has been for me. I cannot wait until it is in my truck and running correctly, with zero knocks. Anyway, that is the scoop. Thank you everyone for your input and concerns... Barry

YES!!! Engine has been picked up from the builders and is enroute and to be delivered monday afternoon. I might be able to use my truck for the bluegrass festival after all. What they did for me is, Took the brand new (broken in and now seasoned block) which is good because block will react very evenly now when she gets hot again. Serious race engine builders prefer a seasoned block to build, so I am going to go with it being a good thing. The builder told me that he basically blueprinted the motor for me. Told me he knows I am going to be listening even closer now, so he made sure it went together perfect. Anyway, I will be very happy to get her back and in and running. Maybe I will finally be able to enjoy my rebuild and restore of my chevy.....with a motor that aint clankin.. won't that be nice.. Will let you know how the start up goes.. ciao for now..

My experience with piston slap, -I sold a low mile 305 from a 77 Nova because it scared me. That buyer ran the crap out of it in a 69 3/4 gmc and it never failed. I found later that that year commonly had piston slap. I had a rebuilt chev 350 that I put 60-70 K on before selling to someone who put it straight in a car. I have a 189 K LT1 thats slapping away and runs like a striped @$$ ape. I have a 40K Cad 500 (in 86 chev pu)that started slapping around 5-10 K. It's getting a tad louder but still fades and is gone above 1200 rpm and warmed up. That engine works really hard pulling a car trailer and putting up with my having fun. It is disappointing I know, -I used to worry alot. But I haven't personally heard of a failure from it. Just my experience and 2 cents.

When ya gonna install it?

Hey Cadiac.. Yeah, from what I have read, it is not usually ever a problem that is going to lead to catasrophic engine failure. I have found some reports that seem to say it does shorten engine life depending on degree of slap. More severe slap more possibility of the rings are torqued causing premature wear. Some motors with piston and stroke ratios where it allows the rings to get down in to the area of the cylnder where the slapping has occured can cause early wear. But generally as you say, they run for many thousands of miles. Of course my beef is I spend 4K on a brand new motor for my rig, and I am supposed to accept knock knock knock as being an acceptable situation? nope.. I want that baby to run like a sewing machine. Try to convince someone if you are selling it, ah shucks its just piston slap, no biggy.. then also if you have other noises clanking and bangin what happens if some time down the road another noise develops but you can't hear it cause you think everything is piston slap. You could destroy your motor because undiscovered noises in the early stages. And not to mention, how can they possibly last as long when they are beating up on themselves. Quite a hassle to have it fixed and costing me down time and costs. But, I will have it running right when done I hope.. in theory.. hopefully worth the trouble.. lol

hey wingman of the chicken,,, well,, being delievered monday afternoon at the shop where I paid the guys to pull it.. I half thought about towing home dropping it in over here. Kind of a long story, you know how people break things and never admit to it. Well, to keep the ground fertile I basically had to say, okay yeah yeah, your right, you guys couldn't have done that. thats the short version.. lol.. So, to save possible earthquakes I am going to have them drop the motor in, and if they seem to give me any troubles then I will tow it home and hook the rest of it up myself. Right now it would be hard to take it away from them when they have stored it over there for over 3 weeks.. But if things start getting goofy I won't hesitate to bring it home and button it up on tuesday or wednesday.. you chompin at the bit?

Ya if i spent a bunch for a premium/special rebuild, -they would have it back in there shop.

lol, naw.... If ya needed me, I'd clear my schedule for a day.