Engine Knock

[Jprevat]

Hello again yall!

Im hoping yall can help me with this very last (fingers crossed) piece of the puzzle.

My 1997 4.3GL rebuilt engine is getting a slight knock after being run over 3000 rpms for a few minutes at a time. It can idle around all day with no problem at all. This knock is not audible if i am above idle speed. After I slow back to idle within 2 minutes the knock completely subsides and I run quiet until I throttle back up. My oil pressure is about 45 at warm idle and around 65-70 around 3000 rpms. I am also sitting dead center in the middle of the safe range on my dipstick.

I have heard rod knock doesnt go away so I am thinking this may be a pushrod/rocker issue. I have a basic puralator filter on there but it looks like I need to change that out for something better. Im thinking I will retorque all of my rocker arms but should I change my nuts? What other points of interest should I be checking out?

Thank you all ahead of time guys!

 

[alldodge]

A knock is louder then a rocker. Rocker noise from a collapsed lifter would be more of what folks call a tick.

Did you buy the rebuild or have it rebuilt?
Having 45 psi for a standard build with the motor warmed up I'm thinking the bearing gap may be to close unless you installed a high volume oil pump

 

[Jprevat]

Knock may very well be too strong of a word. When I look up engine knock on youtube its nothing like that. Ill see if i can make it knock and get a video of it. I bought the rebuild. It has a turned crank and new bearings throughout. I guess thats why Im so confused. I am also using a standard volume oil pump because I thought the tolerances would be too tight on a newly rebuilt engine to warrant a high volume unit.

 

[alldodge]

With standard tolerances it should not have a high volume so you should be good in that area.
What weight oil you running?
Did it come with lifters, in other words a long block?
Was it bought from a local of big outfit rebuilder (no names necessary) I'm trying to find out if there is a quality rebuild issue or just a fluke

 

[Jprevat]

I picked it up from a small shop but the guy does really good work. I have 5w30 in there now but i was getting only a little higher pressures on SAE30 and decided to try something lighter just to see if it would change. It was a shortblock but I put in new lifters. I used my old pushrods though and im hoping maybe that could be my problem. The rotating assembly actually turned over pretty easy on the stand and I had a another mechanic I trust check it out and help me with assembly and he said everything looks good.

 

[alldodge]

It wouldn't be the first time that new lifters collapsed, maybe time will get them to stay up. Hope is just a weak seal on a lifter which may fix it self

 

[Jprevat]

That would be absolutely wonderful if that were the case. I pulled all of my pushrods out to check them out yesterday and they seem to be in good shape with no blockages. Some of my rockers had a little play in them so I retorqued them all back to 20 lbs. Im going to pick up a better oil filter and see if that helps anything. If nothing else I will pull the engine again and see whats going on but im trying to avoid that if I can.

 

[Jprevat]

Ok guys so I retorqued everything up top. I pulled my oil filter off today and it was only half full of oil. Is that normal? I drained the oil out through a filter element and even though the oil was a good bit darker after a few hours use this weekend I have no shavings or particles in the oil. This time I filled the filter completely with oil in hopes of eliminating any air pockets.

My oil pressure gauge does not react when I turn on my key now but I am getting oil up to the heads so I think I have a sending unit or gauge problem but thats not pressing at the moment.

If I had a bearing problem I would have a knock no matter what right? It couldnt just stop spinning at low rpms could it?

 

[alldodge]

my oil filter off today and it was only half full of oil. Is that normal?

What filter are you using and how is it located?

My oil pressure gauge does not react when I turn on my key now but I am getting oil up to the heads so I think I have a sending unit or gauge problem but thats not pressing at the moment.

Could very well be the sender/gauge issue. Get a mechanical gauge and install where the electric one is

If I had a bearing problem I would have a knock no matter what right? It couldnt just stop spinning at low rpms could it?

If you had a spun bearing it would not go away

 

[Jprevat]

Thank you for gettting back to me so quickly. I hate to admit it but it was an orange can Fram that was on there for the past 5 hours of run time. Was getting the same knock with the basic red purolator filter I was using before hand.

It is located on the rear port side of the engine right up against the bell housing.

I will be picking up a mechanical gauge to see whats going on and to see what my true oil pressure is.

Well that does make me feel better about my bearings.

I cut open the old oil filter and found very little metal. As in not enough to even what I would expect from breaking in a rebuilt engine.

 

[alldodge]

Not of fan of those filters, but my question was not for what manufactured filter your using, it was to find out if the filter that was being used had a anti-drain back valve or not. This is the reason I wanted to know the type (which would include the number)

 

[Jprevat]

Oh ok I understand now. It was a Fram PH3980. I have heard that their drain back valves are not to be trusted though.

 

[alldodge]

The PH3980 does have an anti drain back valve, so that is good. The filter should have been full of oil

So far as their drain back valves not being up to others, I cannot say. I stopped using Fram because there quality is lacking. Cut some of my new ones open and found one which the pleats were not full bonded together. This would allow crud to get into the bearings. From then on I stuck with Wix. I have a couple cases of Penzoil filters which are made by Fram, and I need to give or throw them away.

 

[Jprevat]

It does have the valve but it just seemed really strange the top ofthe filter was dry and it only being half full of oil. Makes me think that maybe my oil system was catching air due to the filter or that maybe I have a blockage of some sort. I had it planed off and pulled it straight on the trailer without waiting on the sound to go away before killing the engine so now Im thinking the two are related.

 

[Jprevat]

Ok so I pulled some of my old lifters and replaced them with some of my factory ones. Idled great and ran up around 30 mph for a few minutes with no issues at all. no knock, nothing. So I decided to push it up and out to 42 mph and had no knock after a minute or two then I ran it up to 47 mph for a bit and the knock came back after I idled down the sound stayed there. I think my lifters may be turning in the guides.

I also went around and pulled all the plug wires one by one and the sound never went away so I guess its not in my bottom end.

I am looking at Lunati and Trick Flow lifters and a new set of guides.

Im very close to pulling the whole engine again and pulling it apart if this doesnt do it.

 

[Jprevat]

Would Melling lifters be a good stock replacement? I used a Melling oil pump and they seem to have really good reviews. I guess im just hoping for a little direction.

 

[G_Hipster]

...20 ft lbs is not the way to set valve lash. These are roller lifters you are talking about?

 

[alldodge]

Mellings should be fine, even thou the offshore folks have been having trouble with them, but they are above 600 HP and 6K RPM also. I forget which ones they are going to now

 

[Jprevat]

...20 ft lbs is not the way to set valve lash. These are roller lifters you are talking about?

I was under the impression that my 1997 Vortec heads were the non-adjustable type. The stock nuts arent nylock style and my studs have shoulders.

 

[Jprevat]

Mellings should be fine, even thou the offshore folks have been having trouble with them, but they are above 600 HP and 6K RPM also. I forget which ones they are going to now

Hmm I hope they can stand up to my little 4.3, but I honestly thought the Sealed Power lifters would but I was definitely wrong there. Thank you for the input Dodge. Ill put the order in today for new pushrods and lifters. I got so happy when there was no noise all the way up to 40mph just for it to resurface and crush my hopes 5 minutes later.