700r4 noises or 383 stroker piston slap?

[stringpickin]

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..

[screamin_c102]

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.

[Longhorn Man]

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.

[68 Stepside]

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!

[Longhorn Man]

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.

[VetteVet]

See if anything on here helps


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


VetteVet

[Deuce]

Is a 383 externally ballanced??

[Longhorn Man]

some are...some aren't

[stringpickin]

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

[jbw0127]

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.

[mrein3]

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

[Longhorn Man]

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

[VetteVet]

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

[stringpickin]

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..

[chickenwing]

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.

[chickenwing]

Any updates?

[stringpickin]

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..

[stllookn]

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!

[stringpickin]

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..

[stllookn]

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.

[stringpickin]

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

[neonlarry]

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

[cleszkie]

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.

[stringpickin]

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

[chickenwing]

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?