Engine Knock help

[elks]

jeep straight 6 258 motor. Complete fresh rebuild. Done the work in my shop and is the 4th engine I have built. Other 3 have several thousand miles no issues. This engine was doing great. Break in went well 500 miles no problem. The owner did an oil change on Friday and went out on Saturday. At 750 miles or so engine developed a knock. Cold start after a few hours knock happen for just a split second. Engine idles good, and run under torque find until the 3500 mark. The 258 was built for low end torque and should be considered red lined at 4000 or so.... So the knock is only at the very top RPMs and on a cold start.

What is most likely cause? I am thinking oil in lifter letting it deflate? Noise is definitely not up in rocker arms but lower in engine. It sounds more like a hammer hitting that a tick when you get a rocker arm out of adjustment!

Owner filled with 5 quarts oil and 1 bottle Lucas oil stabilizer. Weird it started after the oil change. With only 700 miles on engine the owner said old oil looked new and no noticeable metal fine of chunks.

 

[76k5blazerr]

This is a Chevy forum, drop a 350 in the jeep, problem solved.

 

[diesel4me]

Chevy engines can knock too...

It could be a bearing with excessive clearance,that makes a woodpecker knock sound until oil pressure reaches it and takes up the space...
If the engine was just rebuilt,why put Lucas in it ?...that is great stuff for quieting down a loose old worn engine,or reducing oil consumption,but its extreme thickness may delay the oil from pumping up to critical areas on cold starts...

It may be excessive crankshaft end play also...it often gets ignored during a rebuild,and can make that kind of noise..

I had a customer years ago who bought all the parts to rebuild a 302 Ford engine --after it was all assembled and run a few days,it developed a cold start knock,that went away,until the engine was run a good 20 minutes or so--then the oil pressure would drop a good 20 lbs,and you could hear a slight knock at idle,and the lifters would start ticking ever so slightly..sometimes the oil pressure gauge would flutter with the engine idling too,like it was pulsing through the oil passages..

The guy had rebuilt many engines and knew his stuff,and being a perfectionist,he decided to pull the engine back out,and all apart..
He discovered the main & rod bearings he bought,were actually standard size,despite the boxes being marked .010 undersize..he failed to look at the stamped numbers on the bearings themselves,and just put them in,assuming they were in the correct boxes..

 

[Blue85]

During this oil change...did it receive a Fram filter?

 

[76k5blazerr]

Chevy engines can knock too...

It could be a bearing with excessive clearance,that makes a woodpecker knock sound until oil pressure reaches it and takes up the space...
If the engine was just rebuilt,why put Lucas in it ?...that is great stuff for quieting down a loose old worn engine,or reducing oil consumption,but its extreme thickness may delay the oil from pumping up to critical areas on cold starts...

It may be excessive crankshaft end play also...it often gets ignored during a rebuild,and can make that kind of noise..

I had a customer years ago who bought all the parts to rebuild a 302 Ford engine --after it was all assembled and run a few days,it developed a cold start knock,that went away,until the engine was run a good 20 minutes or so--then the oil pressure would drop a good 20 lbs,and you could hear a slight knock at idle,and the lifters would start ticking ever so slightly..sometimes the oil pressure gauge would flutter with the engine idling too,like it was pulsing through the oil passages..

The guy had rebuilt many engines and knew his stuff,and being a perfectionist,he decided to pull the engine back out,and all apart..
He discovered the main & rod bearings he bought,were actually standard size,despite the boxes being marked .010 undersize..he failed to look at the stamped numbers on the bearings themselves,and just put them in,assuming they were in the correct boxes..

Was just making a joke

 

[dyeager535]

Ping or knock?

I'll relate my story, no idea if it's valid in your case or not.

Been chasing a coolant loss for quite awhile (I rarely drive the truck) and just recently with a fairly cold engine I get some pinging under load. Seems to clear up after the engine warms up, then no issues. Note that being injected, timing retards either before I hear anything, or immediately after, so I'm not "hearing" the full effect. I noticed the system can't retard enough to eliminate the ping if I don't decrease the engines load though, so it's a substantial problem.

Fixed a few minor leaks, even made an overflow catch can so I know that doesn't vent fluid. Still losing coolant, I'm sure now that it's a head gasket. Also been losing oil pressure, guessing that is related to putting a lot more strain on the reciprocating parts/bearings trying to compress coolant. Also lost a substantial amount of MPG. Very, very slow consumption rate, I can go a few tanks of gas before the overflow goes dry.

Last I tested pressurizing the coolant system and compression, no leaks to cylinders or external connections (after I tightened a couple clamps) but it's now obvious it's getting into a/the cylinders, even if it tests fine. It's worse now though, losing more fluid and the pinging is relatively new. Enough age on the engine I'm not confident new head gaskets will seal, and with significantly lower oil pressure, I think the engine needs replaced anyway.

 

[elks]

Yes he did put a Fram filter on it.

As far as the Lucas treatment. I had suggested he get an additive designed for engine break in and run it with his oil changes for a little while (for the first 500 miles). Why? Because that is what the machinist said to do... Unfortunately I did not recomend lucas but was looking more at a true break in additive.

I am having swap out the fram filter and and see if that might help. But we are likely just going to pull it in and go through the entire thing. Will it be obvious when we find it? When building it I speced and checked everything including end play on the crank but I do not have notes for end play on the cam shaft? Would that be a possible cause?

Just trying to research and find a good direction for us to head.

It is definitely more of knock that a ping or a tick.

Could a loose or stretched timing belt cause a knock in the condition described? I also want to get it hooked up to an oil pressure gauge and verify oil pressures at the high rpms....

 

[diesel4me]

It could be the Fram filter--some lack an anti-drainback valve,and most straight sixes have the oil filter sitting sideways instead of up,which can let oil drain back into the pan overnight if there is no anti-drainback valve,and cause the knock upon the next cold start,till oil pressure builds up...but if it keeps knocking after its warm at higher rpms I'd say it has other issues also..

I think a 258 has timing gears or a chain,not a belt...

I have had small blocks with timing chains so sloppy they wore through the timing cover,but only "knocked" slightly intermittently..

One of my 350's I thought had a loose timing chain when I heard a knocking clicking noise from that area--after I replaced the chain and gears,the noise was still there..turned out the mechanical fuel pump had a loose pin on its rocker arm and it was sloppy,also the push rod that operated it was scalloped out on the cam lobe end...replacing the pump and push rod silenced it.....wish I had checked that first..!