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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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#27 ·
Thanks carsavvycook......

Interesting comment you make about the torque converter. I bolt it to the ring gear and it is tight against it.
Then the motor mount holes line up and the transmission mount lines up, so I cannot see how I could have the torque converter not seated all the way. And I am sure the transmission lines are crimp free and have no blockage. I tape off the lines with a baggie and a rubber band all the time the truck sits awaiting the engine. But I will double check that. Thanks.
As I said, I have yet to pull the crank out, so I expect to see things not doing well there either. The excessive end play of the crank cannot be doing good things to all of those parts hanging on to the crank.
The knock was certainly coming from #5. The inserts are almost totally eaten away. Any idea what could have caused this?
So far, no sign of heat, blueing or anything like that at all. The crank rotates freely with no rods on it, but I suppose that means nothing........pg
 
#29 ·
I would have to agree with the rods being out of round, the crank not being balanced or the engine builder set it up with excessive clearance. If the bearings were set up at say .0045 to .005 play and a high pressure pump was used to compensate for the oil pressure drop I think you would see these patterns after some time.

It wouldn't be apparent right away but once the bearings started to wear the problem would get exponentially worse. Good thing you caught it when you did though or it would have ruined the crank eventually.
 
#30 ·
Double_v23 said:
I would have to agree with the rods being out of round, the crank not being balanced or the engine builder set it up with excessive clearance. If the bearings were set up at say .0045 to .005 play and a high pressure pump was used to compensate for the oil pressure drop I think you would see these patterns after some time.
It wouldn't be apparent right away but once the bearings started to wear the problem would get exponentially worse. Good thing you caught it when you did though or it would have ruined the crank eventually.
Yes, that makes sense. Was the crank balanced? I have no idea. The engine idled and ran smoothly at all times.
Now that I have opened it up I see holes on the counterweights of the crank in places, and in other places on the counter weights I see raw weld filling a portion of some of the holes. The result of balancing? Is that what the factory does? Somehow it seems like a raw way for a manufacturer to finish something like a crank.
One thing is for certain.....the bearings are shot after only 15K miles, and that is just not right. I have baby-ed this engine and changed the oil every 3000 miles, and always using a new filter.
I see felt tip markings on the rod and main caps denoting measurements shown in the thousandths, so somebody did some measuring. If they went to that trouble you would think they would have fit up the engine correctly. Apparently not though.
That is one more reason I have decided to try to do it myself. People are willing to take your money, but reluctant to give you what you have paid for. Oh well, it's live and learn regardless what our problems may be......pg
 
#32 ·
piniongear i agree with u there are alot of people out there that will give u a shotty product and then u are *** out in long run, and would have been better off doing it urself. Its almost like then reused a crank instead of giving u a new 1 but it is hard to tell when u have 15k on it but I am really interested in seeing the crank pics. I had a rod halve up on me cuz the guy over torked the whole motor it was amzing that it lasted as long as it did........hmmmm know thinking about it my rod went about 3 months or 15k something like that cuz when i bought the motor guy said there was 5 on it so really 10k and then i put 5k on then it went and destroyed the crank and rod but saved the rest some people are just not honest to bad to here that about #5 and u do take some great photography.


I think that the rod pin got so hot that its probally not the exact same as others now.
 
#33 ·
74chevy454 said:
piniongear i agree with u there are alot of people out there that will give u a shotty product and then u are *** out in long run, and would have been better off doing it urself. Its almost like then reused a crank instead of giving u a new 1 but it is hard to tell when u have 15k on it but I am really interested in seeing the crank pics. I had a rod halve up on me cuz the guy over torked the whole motor it was amzing that it lasted as long as it did........hmmmm know thinking about it my rod went about 3 months or 15k something like that cuz when i bought the motor guy said there was 5 on it so really 10k and then i put 5k on then it went and destroyed the crank and rod but saved the rest some people are just not honest to bad to here that about #5 and u do take some great photography.
I think that the rod pin got so hot that its probally not the exact same as others now.
Yes, I have to wonder about that pin in hole #5. No sign of any extra heat but then I have not removed the pin yet either. The #5 big end bearing was so worn out that I am astonished that it knocked only when the rpm was up. I guess that is just a sign of how these engines can take a beating and still keep running on.
With the rods removed I can grab the harmonic balancer and give the crank a spin and it still rotates after my hands leave the balancer. In other words, it turns freely.
My next step is to remove the crank and we will see what that brings to light.
Before I took anything apart, I went over every bolt and nut to check what they were torqued at. Everything was exactly correct with the torque values stated in the factory repair manual.
More photos to come within a few days. I have to get a balance removal tool and some pullers for the cam and crank sprockets before I can make much more progress..........pg
 
#34 ·
The factory did not add weight by welding in plugs like that so I would say that your engine was balanced during the rebuild.

I would think that they set the clearances too loose. What oil pump was in the motor? Does it have a plug that you can change the pressure spring in it? What color is the spring if it is changeable?
 
#35 ·
Double_v23 said:
The factory did not add weight by welding in plugs like that so I would say that your engine was balanced during the rebuild.
I would think that they set the clearances too loose. What oil pump was in the motor? Does it have a plug that you can change the pressure spring in it? What color is the spring if it is changeable?
The oil pump is a Melling High Output pump. I am uncertain if I can change the pressure on it.
In a talk with a Melling tech guy, he did not mention that feature when I called him concerned with the 55lbs when I first installed the engine 3 years back......pg
 
#37 ·
carolinarednecknc said:
have you checked the roundness of the pistons one of them could possibly be a little oval before the engine heats up and the piston rings expand causing it to knock till the engine heats enough for the piston rings to fix the gap just a theory but a possibilty :welcome:
Well the bores look good and the piston skirts look like they just came out of the box.
I believe the knock was coming from the big end of #5 rod since the insert is all but gone. Thanks for your comment......pg
 

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#38 ·
Back with some crank photos....

This morning I removed the camshaft and crank.
The crank bearings were worn about the same as the rod journal bearings, i.e., lots of copper showing, except for #5 at the rear. It was mostly silver colored.
Here are the 5 main journals, starting with #5 and going to #1.
I will add some more pics in the next reply......pg
 

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#39 ·
Here are the pics of the crank journals for the rods.
First pic is for #1/#2,
then #3/#4,
then #5/#6, Notice #5 (on the right side). This is the worst rod of the bunch.
#7/#8,
and last shot is of the weld put into the crank to achieve balance I assume.

Next pics will be of the crank Main journals......pg
 

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#40 ·
Here is the rest of the crank main journal shots.
First pic is #1 main, then #2, #3, #4 and #5

The next (and last post of pics) reply has the assembled crank caps showing the bearing wear in them. For some reason the cap bearings show more wear than the upper block bearings......pg
 

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#45 ·
Jmark said:
Thanks, I'll be stopping by there sometime soon. I know where it is but don't know much about it, but will make a few calls too. It's actually right across the street from the shop that did my other engine about 15 years ago.
And since you did find the receipt and can verify the builder, I see no problem listing his company name for future searches on him. From what i've seen from your engine, it's a dirtbag company, www.fivestarengines.com
here is his BBB sheet.
Mark
Thanks Mark.
I did some more looking myself this AM and found some complaints on Ripoff Report regarding Five Star Engines.
I filed a report myself and told it as it is. I cannot blame Five Star since I have 3 years and 15K miles on the engine, but at the same time the engine should last what, 100,000 miles if built properly?

I bought my engine from Chris and he always gave me excellent customer service every time I called him, which was a number of times. So, in all fairness, please tell him that along with the photos of the junk they sold me.

In 2005 I got an email from a stranger who had bought a Five Star 350. His question was....'Have I had any problem with my engine?'
He told me that he and a number of others have engines with serious problems from Five Star.
My reply was that at the time I only had 5K miles on it and had no problem. But, as you may imagine, I did not sleep well for the next few nights until thought of the email was forgotten (somewhat anyways)

I would appreciate hearing how the visit went after you get by there......pg
 
#46 ·
It almost looks like something went wrong in their cleaning process that left crap in the oil galleys. The was everything is worn is very strange. Almost looks like something abrasive was floating arround in the engine. I wounder if there cleaning tank somehow got poluted.

That engine looks more like a 200K engine than a 15K engine
 
#47 ·
T-bucket23 said:
It almost looks like something went wrong in their cleaning process that left crap in the oil galleys. The was everything is worn is very strange. Almost looks like something abrasive was floating arround in the engine. I wounder if there cleaning tank somehow got poluted.
That engine looks more like a 200K engine than a 15K engine
I can not agree with you more on the engine condition. What in the world could cause such damage to all of the bearings, yet show no signs of heat anywhere, nor is there, or ever has been, any metal in the oil which is changed along with a filter every 3K miles.
This one has me really puzzled.
I finally got a lead from the husband of a friend of my wife's. He owns and drives a Chevy oval track car and he gave me the name of the automotive machine shop that builds his engines.
I called the shop this morning and described the mess. He said I may want to consider a short block rather than put money into the machine work. He would line bore everything, turn the crank and then I would put it all together.
He said the cost is going to perhaps be the same as a short block.
Maybe, but with a short block I may be right where I am today in a couple of years, since I do not know who built it.
This 1992 van is only the 4th car or truck I have owned since 1965. So that tells you I run them quite a long time.
I will take the block and parts to the machine shop tomorrow and see what he says after looking it over..........pg
 
#48 ·
piniongear said:
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
Looking at the rod bearing that's your knock. That's the upper, what does the lower half look like?

.010 is telling you it's a turned undersize crank. What is the surface quality, at 15000 miles it should be smooth if not polished. The journal needs to be consistently circular from end to end as well. I'd expect roughness since it's been eating the bearing and that stuff has been circulating. Telling what is bad machining from damage done by the bearing will be hard to tell apart at this point.

What do the mains look like?

What is the condition of the thrust bearing? And what is the crank's fore and aft clearance on the thrust bearing?

Operation can lead to excessive bearing wear, what I see here is also typical of an engine operating under high loading at low RPMs. The problem that lugging causes is that the load in the bearing is high and the oil flow low. A solution is gearing up so the engine spins faster making more oil flow or installing a high volume pump to get the pressure/flow up at lower RPMs. This talk about 10psi per 1000 RPM is gross generalization more suitable for grocery getters than vehicles that work for a living. This is not an issue of type of oil (synthetic versus mineral) nor to some extent even the weight. It's an issue of putting enough oil thru the bearing to both support the development of the hydrodynamic wedge that floats the bearing above the journal with enough strength that forces on the rods aren't greater which just blows the oil out the clearance, the other is enough oil flow to take the heat out of the bearing and journal. In the latter case the greater the forces in the bearing/journal the higher the local heat being generated. Good oil flow is necessary to take this heat out.

Bogie
 
#50 ·
Jmark said:
One last question and opportunity for more pictures! LOL What shape are the cam and cam bearings in? Ok, or trashed lobes too?

Mark
The cam looks pretty good. The bearings are not worn to the copper like all of the mains and rods.
The lobes look good too, although I am far from an expert. They show some signs of wear.....like I cannot say this is a new cam because you see wear or tracks on the lobes.
There is one lifter that I could not get out however until I removed the cam.
This is also from my old friend cylinder #5.
The bottom of the lifter is concave. Very concave. All the rest of the lifters came out easily and are dead flat across their bottoms.
I don't know if the concave will show, but I will take a photo of it and stick to this post..... (It shows)
The bad lifter base is really fished tailed out. The spread is so great that it would not come out of the block topside. The edge is sharp like a razor. The other lifters by comparasion, have a nice smooth beveled edge to them....pg
 

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#51 ·
piniongear said:
The cam looks pretty good. The bearings are not worn to the copper like all of the mains and rods.
The lobes look good too, although I am far from an expert. They show some signs of wear.....like I cannot say this is a new cam because you see wear or tracks on the lobes.
There is one lifter that I could not get out however until I removed the cam.
This is also from my old friend cylinder #5.
The bottom of the lifter is concave. Very concave. All the rest of the lifters came out easily and are dead flat across their bottoms.
I don't know if the concave will show, but I will take a photo of it and stick to this post..... (It shows)
The bad lifter base is really fished tailed out. The spread is so great that it would not come out of the block topside. The edge is sharp like a razor. The other lifters by comparasion, have a nice smooth beveled edge to them....pg
These pictures are photos of the kiss-of-death for the lifters and cam.

Questions to be asked are:

- is this damge from eating scraps of bearing material from the crank?

- is this the failure that took out the crank bearings?

- are these two seperate and unrelated failures?

I can't answer any of that, but at this point I'd seriously be considering scrapping the old motor and replacing it completely.

Bogie
 
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