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Recap: Ellwein Engines 383. Less than 10k on engine and not thrashed.

Engine had a knock between 2500-3500 on part-throttle acceleration. After a lot of testing, pulled the engine due to metal in filter. Crank and rods were checked by machine shop and confirmed ok. Cam and lifters not so much, which was the source of the metal in the filter. New billet cam. New LT1 lifters. New King bearings installed on crank and rods. None of the bearings showed any signs of being spun or having anything other than grit damage, and even then - Karl said he'd have re-installed the bearings and been done with it. I changed them anyway. Clevite cam bearings installed. Machine shop said the block did not even need a hone, so I let it ride. Fired it up last week and dialed in the tune a bit more. Checked compression across all cylinders and its 200-205. Leakdown was around 6%. Took it out of the garage for the first time yesterday and got it smogged. Car passed smog by a country mile.

Drove it to work this AM, which was the first time its been more than 5 miles and driven for any length of time on the interstate since the install. Temps all good, oil pressure is stellar, car generally runs excellent. Repeated environment where it knocked before I pulled it and the knock is still there. I am at my wits end.

Spitballing some ideas regarding the sound:
1. Too much rod side clearance. Karl said he noticed that the rods had more side clearance than he was used to seeing.
2. Piston pin. All of the pistons were removed, cleaned and inspected and everything appeared fine. No excessive side-play on the small end. Nothing binding. No cracks in pistons.
3. Pistons rocking in the bore on the bottom-end of the stroke. Would that not have been apparent when everything was out? Seems to me were this the case that it would show evidence of this on the skirts and/or the bore.
4. Possible that the sound is coming from the trans? I can't test this easily because the noise does not happen when driving it around town - only on the interstate, only between 1800-2500, and only on part/light throttle acceleration.

Anyway, what do the guru's think? What did I miss?
 

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1. Too much rod side clearance. Karl said he noticed that the rods had more side clearance than he was used to seeing.


4. Possible that the sound is coming from the trans? I can't test this easily because the noise does not happen when driving it around town - only on the interstate, only between 1800-2500, and only on part/light throttle acceleration.
#1. what size rods, 5.7" or 6"??...by Karl saying a little to much side clearance...like how much...xxx?

#4...given the motor has had a full colonic the trans is something to consider as a cause.

drive a few hundred miles and look at oil and cut open filter.....while there may be some "build residue" see what is in oil & filter

Maybe the initial finding of metal was concurrent with whatever is causing the knock and you just caught that before more major carnage but the knock is being generated elsewhere in drive train (tranny)

just spit ballin like you Dan...
 

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Dan, I'm going to go back to this where I had mentioned about the cylinders being short on some late blocks. http://www.impalassforum.com/vBulletin/7-concerns/1307130-interesting-me.html
I found this too. Does anyone else's 383 sound a like a diesel? - ChevyTalk - FREE Restoration and Repair Help for your Chevrolet
Just reading these and other comments, I see people describing their 383 sounding similar to a diesel. Would that be close to your sound? It might be something to look at. The block # is 880 that seems to be the offender.

Mark: Snowman-33
 

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#1. what size rods, 5.7" or 6"??...by Karl saying a little to much side clearance...like how much...xxx?
#4...given the motor has had a full colonic the trans is something to consider as a cause.
drive a few hundred miles and look at oil and cut open filter.....while there may be some "build residue" see what is in oil & filter. Maybe the initial finding of metal was concurrent with whatever is causing the knock and you just caught that before more major carnage but the knock is being generated elsewhere in drive train (tranny)
6" rod. Not sure on the exact side-clearance, but it was enough to make me think twice. I reached out to Karl about it and he agreed that some of the newer SCAT rods he's using have 'a bit more' clearance than they used to. I think you are onto something in just driving it for a bit and seeing what comes out of the filter.

Can you find a hoist? Since it's only part/light throttle may be able to duplicate in air.
The trick is that its part throttle, under load. In the garage, it does not do it at all - no matter the RPM.
Dan, I'm going to go back to this where I had mentioned about the cylinders being short on some late blocks. http://www.impalassforum.com/vBulletin/7-concerns/1307130-interesting-me.html I found this too. Does anyone else's 383 sound a like a diesel? - ChevyTalk - FREE Restoration and Repair Help for your Chevrolet Just reading these and other comments, I see people describing their 383 sounding similar to a diesel. Would that be close to your sound? It might be something to look at. The block # is 880 that seems to be the offender.

Mark: Snowman-33
That is awesome info. Awesome in that it may mean big issues for me, but at least there could be a f-ing answer. YES it sounds like a diesel. The knocking is something else, though, but the diesel sound has been there since day 1 - I even asked Karl about it after first start. My very first thought was that it sounded like a piston or pistons rocking in the bore. I will check on the casting #'s when I get home.

THANKS!
 

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6" rod.


The trick is that its part throttle, under load. In the garage, it does not do it at all - no matter the RPM.


/QUOTE]

6"...certainly "less prone" to side loading that 5.7" rod...was just a thought

Given the noise does not occur at any RPM just with car sitting but "under light load/accell" at 1800-2500 rpm...have you tried to "power brake" it to see if the knock appears under this commanded load??

if so to me that would indicate more a drive line (tranny or TC) issue than the motor.

Is my 383 "louder" than the stock 350....yes and no. We all know RR have a "sound" (sewing machine) which to me is ironic as a needle bearing/roller tip rocker, you would think, would be quieter than a stamped piece of metal rubbing the tip of the valve but that is what it is. Headers seem to amplify motor sounds normal or not. "Diesel" sound is not what I have ever experienced though and inside the car the motor is not noticeable at all in terms of any sounds

Have you scanned the car while it is making this noise to see if any timing is being pulled?
Do you think this noise could be "grounding" under load (like exhaust hitting something)??

man if that was the case would it ever be a ah ha moment to see some witness mark somewhere (x member)

If noise is there under a "power brake" condition...with car securely raised and blocked while someone was power braking it you could see under wtf may be grounding or maybe better hear location of noise but be uber careful being under the car during this process
 

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A few times when I worked as a mechanic, was able to find noises on a lift.
Using the brakes as a load, and spinning them up to 55-65.
Need to be very careful obviously, and trust the person in the car.

Being an avg. Joe, might prove difficult to find a shop willing to let you be a part of this process though?
Finding a GOOD shop to assist might be worthwhile to locate/verify the source of the noise. Maybe someone on here has access to a lift, or is willing to lend a hand?

Obviously we can't hear it, but I'd shy away from putting any real miles on it w/o knowing for sure something bad isn't going to happen.
Chewing up new engine parts is both frustrating and costly.
 

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I have had weird noises at 68 MPH on my GM truck .. light throttle it would get very more amplified .. more pedal it would drop off.. it was the drive shaft U joints .

never did it at other speed just at that speed .. U joint was seized . 2K RPM.
 

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Engine had a knock between 2500-3500 on part-throttle acceleration.


Repeated environment where it knocked before I pulled it and the knock is still there. I am at my wits end.
Dan, you're hearing this..we can't

Is this noise a "knock" like what you heard from what appeared to be wearing lifters/cam lobe (often sounding more like a tick vs knock though)

or is this a KNOCK like sound more associated with a rod bearing or piston slap

I am assuming the car was at full operating temp when you duplicated the test drive and heard it. Did you by chance do a drive immediately after start up before engine gets to full temp and hear it?

I know describing by a word vs hearing it leads one to think about what they interpret a sound to...well sound like

Is this more a harmonic/vibration kind of noise or a = rhythmic to rpm "rod knock" sound?

weird it is just within a short rpm range...although from my understanding that rpm range is where sbc do or can exhibit harmonics...maybe just enough to reveal what you note is a slight "side clearance" of the rods??
 

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There is a product available at NAPA called anti stutter/shudder for the trans. I have had similar issues with a trans, and I thought it was the engine until I put the product in the trans. It went away instantly.
 

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How about this: At 1800 rpm you TC is locked, the cam doesn't like being there and you get the knocking sound when lightly accelerating. Once you hit 2500 rpm the cam start working, making torque and you loose the knock. You have 3.42 rear which may put your rpm too low in OD. I'd bet that's what you are hearing.

An engine knock is usually going to happen throughout the rpms.
 

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Here is a link to a video I shot this morning. You can hear the knock.
https://photos.app.goo.gl/TyZTv3DsKJCPCc736

I checked the casting #'s and its the correct casting. At this point, I suspect that its either the rod end-play, or a piston rocking in the bore on the bottom of the stroke
 

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Have you ruled out spark advance? Stock bins push a lot of timing in part throttle conditions. I see you've tuned it and if you're using that that new def that seemed buggy for a number of people, it might be your issue. Cap your spark tables at 20 deg, or set max advance to 20 and see what it does.
 

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Ok, I will give that a try.

Out of morbid curiosity, I went out and drove it this weekend with eehack running. I disabled individual cylinders during the knock, and it had no effect.
 

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Dan

well from this side of the internet we can now hear the noise you have described.....but not as acutely as you hear it in car

While it could be your rod end play or piston rocking (Karl would be better experienced to reply on that) have you gotten under the car yet while someone power brakes the car at that RPM to mimic the load/RPM range the noise occurs?

with a stethoscope would the noise be more prominent source from oil pan ....or TC cover.....or tranny itself??

The noise only happens when you are in "OD" and "lightly" apply gas in the 1500-2k RPM range??

My thought is not to dismiss this as a engine only sound source until further inspecting/listening

The spark advance programming idea is out of my wheelhouse but certainly worth a check

Sadly after replacing your cam & lifters this did not resolve your initial core noise....but that parallel issue alone was brewing inside the motor and you caught it before considerable damage occurred
 

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I have had engine knock over the years that sound to me is not a piston knock.

sound like rapping noise in drive train .. probably not flywheel/flex crack but it has that sound .
 

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From what I hear in that video it doesn't sound like a rod knock or piston slap. That almost sounds transmission related.

Although anything is possible I have a hard time believing that the engine would make the same noise after taking it apart, inspecting and rebuilding.
 

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Got the car out in a quiet, desolate area and loaded up the car in gear with the brakes applied. I tried all sorts of throttle positions and loads. Some with the brakes applied but loose enough to let it roll, some with the car locked-down at a stop, some with loads of throttle and medium brakes, etc. While the light piston slap was there (as it has been since day-1) the knock in the video did not reappear. It only appears on the road, which would point to a driveline issue.

The driveshaft was replaced with a Denny's shaft since I thought it may be the u-joints. It obviously is not. I also checked the mount and fasteners associated with the trans when the engine was out. No problems found.

I will roll back some timing via eeHack and go for a spin to see what it does.

Thanks for the input everyone. You are talking me off the ledge.
 
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