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I need some help with my 350 Chevy engine...

15K views 79 replies 14 participants last post by  CNC BLOCKS NE 
#1 ·
My first post after doing my intro.
The problem:
I purchased a 350 rebuilt engine 3 years back for my 1992 Chevy van.
After 15K miles the engine suddenly developed a knock. The knock occurs when the engine is just beginning to shift into second gear.
The engine burns no oil and runs and starts well.
I removed the engine and have begun starting to take it apart.
So far I have found no problem except for one thing:
Cylinders 2 through 8 had spark plugs that looked white and clean.
Cylinder #1 had a jet bleck spark plug.
After I removed the heads I saw that cylinders 2-8 had identical brown color on the exhaust valves. Cylinder #1 all valves are jet black.
Cylinder walls look OK, but I have not removed the pistons and rods yet. Engine is very clean inside. No sludge, metal particles or any sign of damage anywhere. I removed the oil pan and all looks OK there as well.
Anyone have an idea of what I need to look for to ID this knocking? I really am in need of help here........pg
 
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#2 ·
Jmark.....
Thanks for the quick reply.
I thought to check the flywheel carefully for cracks, but it looks good.
My description of it knocking when it gets ready to shift may have been a little misleading. When I sit there in neutral and bring the rpm up to about 2500 the knock begins. And it sounds like a rod knocking too.
Maybe when I get the rods off the crank I will see some kind of damage. This is not my first time to work on a Chevy, but it is the most serious problem I have encountered.
In other words, I am in deeper than ever before and I still don't have the pistons out yet. :sweat: ........pg
 
#3 ·
piniongear said:
Jmark.....
Thanks for the quick reply.
I thought to check the flywheel carefully for cracks, but it looks good.
My description of it knocking when it gets ready to shift may have been a little misleading. When I sit there in neutral and bring the rpm up to about 2500 the knock begins. And it sounds like a rod knocking too.
Maybe when I get the rods off the crank I will see some kind of damage. This is not my first time to work on a Chevy, but it is the most serious problem I have encountered.
In other words, I am in deeper than ever before and I still don't have the pistons out yet. :sweat: ........pg
Rod knock is the typical double knock. But pin knock and piston knocks are also double knocks they differ from rod knocks in tone but not frequency.

Piston pin knock like rod knock happens as the piston and rod assembly change direction and the slack of excessive clearance is taken up. Piston knock is typically from a cracked skirt which flexes every time the piston changes direction and the skirt snaps across the bore clearance between its thrust and non-thrust sides.

It's often hard to tell the difference between these unless you've heard them a lot.

Bogie
 
#4 ·
Jmark and Bogie.....
Hot and humid in Houston Texas? Ha-Ha, no worse than living in a swamp 347 days out of the year. I had the engine in the garage part of the shop after I got it out of the van. I have a 30 inch wall fan there and noticed sawdust on my motorcycles that are parked in there. The fan is swirling the dust around and it is humid!
So my first activity on the engine was to roll the engine on the stand to the air conditioned shop in the next room. Ah-hhhh. Better now, and no dust!

Bogie.....
Thank you for the comments.
This knocking may happen for a few seconds when I crank the engine cold, then it goes away until the engine gets to around 2500 rpm.
The knocking is not a heavy thud-thud-thud, but rather a higher pitched clacking sound. I had a harmonic balancer come loose on an old 318 Dodge I had and this sound a bit like the same kind of noise. In fact I crawled under the van to check the torque on the balancer when I first heard the knocking. It was/is tight though.

Now what you say about a possible piston crack or wrist pin problem has my interest because of the #1 cylinder looking so black compared to the other 7 which look all alike and are tan colored. I would post a pic if I knew how to do that.

So, when I get the rods out I will look at #1 first and closely.
I will let you guys know what I find. I am hoping to find something, and as bad as it sounds, it would be a blessing to find a cracked piston.
Thanks guys.........pg
 
#5 ·
Got the ridge reamer today....

The Lisle 36500 ridge reamer showed up today. I know it is a reamer, so I should only turn it clockwise. I assume I use a generous amount of cutting oil too? The cutter is carbide so I am not sure.
Nothing in the instructions tells me to lube it.
I am really eager to have a look at the #1 piston.......pg
 
#6 ·
piniongear said:
The Lisle 36500 ridge reamer showed up today. I know it is a reamer, so I should only turn it clockwise. I assume I use a generous amount of cutting oil too? The cutter is carbide so I am not sure.
Nothing in the instructions tells me to lube it.
I am really eager to have a look at the #1 piston.......pg
With only 15K miles, you should not have to Ridge Ream that cylinder. :welcome: A sharp knife should get the black carbon build-up off of the top of the cylinder wall. JMO and experience.

Pictures of that piston would be nice. The way I know how to up-load them, is to scroll down to "Manage Attachments"(while posting), and click on it. This will take you to a upload page. You need to make sure your pictures are downsized, edit in your picture manager, then simply hit "browse" and click on the picture/pictures, and click on "upload". These will show up under your "post" when you are done.

How others on here, get their pictures in their post, I have not figured out yet. :sweat: :welcome:
 
#8 ·
yep, right when the trans shifts it knocks. Basically when there is little load on the engine and the revs are around 2-3000. Had this happen a couple of times. Ended up to be a weak oil pump (spring was bad not holding enough psi).
The fact that #1 is black would make me think a different problem. Hope you dont have to dig to deep and come up with maybes :sweat:
Just having 15000 should not need ridge reamer.
 
#9 ·
OK, I got the number piston out this morning.
To start with:
I checked the crankshaft end play and it was .015. The book tells me it should be .002 to .006, so that is a negative.
I checked the side clearance of #1 rod and it was .015 gap. Book says .006 to .014, so I am just a little wide on that.

You guys were correct in saying I did not need a reamer. But I used it anyway and one rotation cleaned it to the metal.
Now for some photos:
The first pic is of the insert in the cap. It is stamped .010. Does this tell me the bearing is .010 oversize (that the crank journal has been ground down) .010?

The next two pics are of the rod inserts. They look really worn, considering the engine has only 15K miles on it. Half of the ebarings have copper color showing and the other half have silver showing.
Can anyone give me an idea if the bearings may be bad or not? They look very bad to me, but I hae no experience with this kind of thing.

I will do another post with photos of the piston and bore. Hang tight.....pg
 

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#10 ·
Here are the shots of the piston and bore.
The piston looks really good to me. No cracks. No scuffing, and the skirt walls look like I just took the piston out of the box.

The bore looks good too. Hard to take a photo of it, but the walls are smooth top to bottom. There are a couple of light lines on the wall which seem to match light lines on the piston.

Back to the crank: I forgot to mention that the journal feels a bit rough if I drag a fingernail over it. I did not get a shot of it, but it certainly is not smooth as it would be if it were freshly ground. Again, I do not know what 15K miles will do to the surface. Oil has been changed every 3K miles.

I sure hope you guys have something to tell me about this. Meanwhile, I will continue to remove rods and pistons I guess.......pg
 

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#11 ·
More pictures of other cylinders/pistons/ and bearings would be nice.

That cylinder, and rod bearing looks to me that the rod is bent, or the rod journal on the crank, is ground crooked. The rough scoring on the crankshaft, and bearing is from debree, or some lack of oil pressure at some point. It does not look blackened from lack of oil over a long period of time.

Number one cylinder is the last to get oil pressure in a SBC, or BBC for that matter.

From what I can see of the top of the piston, it does not look like a ring problem. If it was, the quench area would be washed clean of carbon. I would look more into a valve guide, valve seal, or intake gasket leak.

JMO
 
#12 ·
wow

In my experience that looks like bad oil pump or oil pressure but like carsavy said we kinda need more pics of other pistons and rods.


I bought a bbc that was supposed to have 10k when i got it and drove about 5k or 3 mnths before a rod bearing halved up on me and destroyed a crank.......welll **** happens so that motor was a 454 when that happened now 468 with edelbrock performer package and that thing lopes boy sounds almost to big of cam but there is no such thing as to much heheheheh.
 
#13 ·
Thank all of you guys for your comments! Yes, I too thought the rod bearing looks worn out, The wear seems to be on one side only (the rod, or upper side) although the cap bearing is not too pretty either.
As I remove more pistons I will post the results.

For whatever it is worth, this engine was a rebuilt engine that I bought on Ebay from an outfit in Arizona. The photo was taken in June 2005 as I was ready to install it in the van.

The engine came with a high output oil pump and the oil pressure has been 55 psi since the day I fired it up. At first I thought that was way too high, so I called the people I bought it from and they told me that perhaps the bypass was not working on the pump (?) but they would send me a replacement pump and apologized for the extra work I had to do to install it.

Meanwhile, as I was waiting for the replacement pump I called the oil pump company. He told me this pump is a high output pump and the bypass was set at 60 psi. Since I had 55 psi he told me everything was OK. The replacement pump arrived and I just put it away and never installed it.

I do not know if 55 psi is a problem on a small block engine?
OK, I will be back later with more results. Thanks.........pg
 

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#15 ·
Thanks carsavvycook......
I was not sure about the oil pressure. I have always owned Chevys and all of them show 20 psi when I stop for a red light, then gos up to 40 psi running down the road. I am talking about a standard oil pump.

Today I hope to get more rods removed from the engine.
#2 will be the next one to come out. Since it shares the same journal as the #1 I am curious to see what it looks like.
I will be posting some photos of what I find........pg
 
#16 ·
carsavvycook....

I removed the rest of the pistons/rods a few minutes ago.
All of the inserts look as bad as the #1 rod, except for #5.
#5 is so worn out that the insert even feels half as thick as the rest of them.
Both inserts will not even sit in the rod and cap as I try to bolt them together.
Another thing......The wrist pin is almost stuck in the piston. The rod will stand straight up by itself. I can move it all the way from left to right but it is tight.
Have not taken any photos yet, but will do so later.

So I am at a total loss as to what has caused this engine to crater like it did.
It looks like a crank regrind on all 4 journals is going to be required and a new set of inserts as well.
Boy, am I going to have fun trying to fit that stuff together! (NOT)........pg
 
#17 ·
Jmark said:
Yikes, don't like hearing that part! Hope it's not from anyone I know! LOL
BTW...55 is fine oil pressure. I have a stock Melling M55 and it runs 60 cold, 45 hot.
Yes, a Melling is what is on my engine. I could not think of the name of it.
The engine was purchased from a shop in Phoenix as I recall. I have the paperwork around here somewhere.

They sold the engine for $2395 and you pay the freight or $2495 with free shipping. No block exchange was required. I took the shipping included option and the freight truck pulled up in front of my house with a lift gate on the back.

$100 to ship it from Arizona to Texas? That always bothered me. It just seemed like I got the engine much to cheaply.

I had one customer email me and asks if I had any problems with my engine. I said I did not (this was at about the 5000 mile mark) and he said a number of customers he knew had 'serious problems' with theirs. That bothered me also for a while, until I forgot about it. Ha-Ha.....Wake up call now ringing.
pg
 
#18 ·
man that sucks, I hate to hear that alot of people are having problems with certain builder.............hmmmm something smells fishy, and they probaly wont or dont have a good customer service policy.....I stand by my work and have not had a comback yet knock knock on wood heheheh even thou i only believe in karma. :(
 
#22 ·
Bates K...

bates_k said:
Just an opinion, but it looks like the rod weren't resized...

K
What do you mean by 'looks like the rods were not resized?'
Under the inserts, most of the rods look like there was some kind of machining done to both the rods and caps. Almost like the .010 inserts needed to seat a little deeper to gain proper fit on the crank.
I am just really ignorant about how this fitting should be done though........pg
 
#23 ·
piniongear said:
What do you mean by 'looks like the rods were not resized?'
Under the inserts, most of the rods look like there was some kind of machining done to both the rods and caps. Almost like the .010 inserts needed to seat a little deeper to gain proper fit on the crank.
I am just really ignorant about how this fitting should be done though........pg
Well, the caps and rods are machined when they're manufactured, when they're rebuilt,
they need to be resized, Mainly because of all the time they've spent going up and down,
will oval shape the bore in the big end. That picture you posted looks just like that type
of work...

K
 
#24 ·
It looks like they didnt balance the crank, and even thou some manufacturers say they come ready to go is bs. I bought a scat crank and had a machine shop put it together 4 me as I had more money then time 4yrs ago and come to find out the machine shop didnt check it and when i started it up it felt like a train was coming by as the whole truck shock violently, so took back apart because machine shop said it wasnt thier fault, and balanced whole motor even thou I was able to exchange the crank due to family friend scat at first said they wouldnt take it back put they did in long haul so I just got screwed the 1500 I paid the shop.......but I guess it was a 1500 lesson becuz now I balance everything but maybe its overkill but I think its worth it.


How does the crank look?
 
#25 ·
Thanks for your comments so far guys....

OK, this morning I removed the remaining rods and pistons.
All big ends have damage.
Rods 1,2,3,4,6,7,&8 are about the same. Lots of copper color showing.
Rod #5 is a bit different than the rest however.
The insert in #5 feels like it is about half the thickness of any of the other inserts. Both the insert in the cap and in the rod on #5 will not even sit in place while I bolt the cap and rod together.
Another problem with #5 is the piston pin is tight in the piston. All others swing freely back in forth in the pistons. I wonder what caused that? Ecessive pounding on the big end bearing? I am at a loss.

First photo is a group shot. The pistons are arranged in this order. starting from left to right:
Front row....#8, #6, #4, #2.
Back row.....#7, #5, #3, #1
Notice how all rod inserts show the copper color, except #5. Pretty much the same.
Next is a couple of close up shots of the #5 rod insert, or what is left of it.
Notice how the rod stands straight up. That is a too tight piston pin.

I am certainly open to any comments you guys may care to make as to why this could happen in only 15K miles? I think I need to start looking for an automotive machine shop because the crank needs attention.

I still have to remove the crank from the block. Lord only knows what I will find there! Since the crank has .015 end play rather than the .002 to.006 stated in the factory manual I am almost afraid to look at it.
Suggestions appreciated, I am all ears..........pg
 

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#26 ·
The "tight" piston in #5 tells the "story". This was your knock.

It will be interesting to see picture's of the main and thrust bearings, and the crankshaft.

This may hurt some. :nono:

If the forward surface of the Thrust is worn/hot/burnt/blue. The torque converter was not "seated" all the way in,(you should not be able to put a finger between it, or the transmission housing) or it also could be, what I like to call "ballooning", of the torqure converter expanding in size. This can also be caused by a restriction in the transmission cooler lines. A bend or crimp is enough to do it.

JMO

Been There; Don't ask :D :D :D
 
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