Need help finding engine knock

[Slow old poop]

We're ready to tear into the motor to find a baffling problem. We hope somebody out there can help.

BACKGROUND
When we first got the car, it had no balance shafts, ran 110-120 psi oil pressure, and blew off three oil filters. We ported the oil filter housing, got it down to about 100 psi. Then, when we installed a 2.3 stroker motor, AMS recommended their balance shaft replacement kit, which puts part of a balance shaft back in, and restores some load on the oil pump. This has worked perfectly for a year, with oil pressures in the 80 psi range, and no more blown filters. Until last weekend at Iowa Speedway.

We observed 110 psi oil pressure up on the banking at 20 psi boost and, sure enough, blew another oil filter.

After replacing the oil filter and the oil, checking it over pretty good, making some test pulls on the highway, we went back out.

After a few laps, we heard a knocking noise that sounded like a blown downpipe, so we came in. At the time, IT SEEMED THAT there was no loss of boost, no loss of power, and no loss of revs. Just noise. (I could be wrong, but I can usually feel or see when I lose power)

Initial investigations could not find the source, so we put it on the trailer and brought it home.

DIAGNOSTICS SO FAR

Water temp was up slightly when we came in.
Alternator belt damaged--beat up and torn, but whole
No damage to plugs, no weird indications on plugs
We cannot hear any engine knock if we turn it by hand.
We cannot hear any engine knock if we pull the plugs and crank it.
Cold compression is 140, 150, 170 and 150 (throttle not open--AMS says 150 is normal for a stroker motor)
With plugs in, one at a time, we hear the knock under cranking only when the plug is in cylinder 3, and the knock appears to be coming from 3.
We pulled the pan to look for damage. The pistons, rods, bearings and whatnot all look OK from underneath. We only pulled the bearing cap on 3, though.
We pulled the cam cover, but can find no damage.

It's baffling. We have no clue.

The most promising theory was that the balance shaft kit failed. If it did, we posited, that would cause the oil pressure to run up to 110 and cause a knock sound similar to what we hear. Alas, the balance shaft SEEMS OK, from what we can see from underneath.

The other baffler is: what do high oil pressure, a torn alternator bolt and engine knock have in common?

AMS says it may be the cam but, short of disassembling it, we can't find anything wrong.

We are ready to tear into the motor, but my fear is that we can pull the motor, pull the head, and examine everything, yet still not figure out what's making it knock.

Therefore I ask you, my brothers, to suggest additional diagnostic methods to employ on the engine whilst it is stil in the car and can be cranked with the starter.

If we trailered it down to an engine builder, what tools do they have that we don't have? (borescope, stethescopes, lefthanded diffraction spectrometer, or whatever)

Jon, Mike, Brent and Dan: If I forgot something, please chime in.

 

[dilbertgonebad]

I am begining to fear that it may be pistion slap, (though this is not a sound with which I am familar)

 

[stealthTT]

I am begining to fear that it may be pistion slap, (though this is not a sound with which I am familar)

Oh I hope not! Here's the only "test" I know for piston slap:

1. Turn motor over and memorize the sound.
2. Pull the spark plug.
3. Put a couple squirts of oil in the cylinder.
4. Replace the spark plug.
5. Turn the motor over again.

If the sound is muffled, there's a good chance it's piston slap. The oil will lubricate the metal on metal contact of the piston hitting the cylinder wall.

But, I would think the piston would slap with or without the spark plug installed.

 

[drivemusicnow]

How was the alternator belt torn? This would indicate why it was failing.

Here is my thought process: If you only get the knocking noise in cyl 3, and only when the spark plug is in it would make sense that there something compression related that is the problem. Now, I don't see how anything other than the piston ring or piston skirt hitting the wall would make the knocking noise. Reason being that anything else, IMO, would be there without pressure as well. Piston slap could be pressure related as if there isn't anything trying to push past the rings... (a little out there, but nothing else makes sense)

The other thing to note, is that based on your numbers, it seems like cyl 3 has the highest compression.

I guess if it was me I'd do stealthtt's "piston slap" test, as well as a good leakdown test on all the cylinders.

I'd also pull the oil filter housing and/or just the pressure relief valve and see if anything is out of the ordinary.

 

[Slow old poop]

How was the alternator belt torn? This would indicate why it was failing..

Damifino. Mike the Mechanic says it's just a coincidence.
I think the pulley is pulled in a little, but everybody else swears it is in the normal position.

Here is my thought process: If you only get the knocking noise in cyl 3, and only when the spark plug is in it would make sense that there something compression related that is the problem. Now, I don't see how anything other than the piston ring or piston skirt hitting the wall would make the knocking noise. Reason being that anything else, IMO, would be there without pressure as well. Piston slap could be pressure related as if there isn't anything trying to push past the rings... (a little out there, but nothing else makes sense)..

We looked in there the best we could, but could not see anything. We agree with you, but can't figure out what could have gotten in there. Also, the plug is not damaged.

The other thing to note, is that based on your numbers, it seems like cyl 3 has the highest compression. I guess if it was me I'd do stealthtt's "piston slap" test, as well as a good leakdown test on all the cylinders. ..

Well, we did the test cold, and didn't hold the throttle open, so it wasn't the most perfect compression test.

I'd also pull the oil filter housing and/or just the pressure relief valve and see if anything is out of the ordinary.

Good plan. Like maybe the relief valve got blocked somehow with debris, and that would account for the sudden increase in oil pressure?

Thanks for your help.

 

[Defiant]

Are you running a solid pulley? I'd wonder if its keyway has been beaten out.
I seriously doubt it's piston slap. Unless you've broken or cracked one, they aren't that loud.
It coming after losing a filter, and pressure, make me suspect a rear balance shaft bearing. I can't correlate that to the noise being mutable with the third cylinder, however. Same with the crank pulley. The third cylinder turnoff situation sure makes it sound like a rod bearing. Could it be a wrist pin? Are you running squirters? Do you have a borescope you can check the piston crown with?
I sure don't like the sound of blowing off filters. May be time for a dual-mount setup.

 

[stealthTT]

Are you running a solid pulley? I'd wonder if its keyway has been beaten out.
I seriously doubt it's piston slap. Unless you've broken or cracked one, they aren't that loud.
It coming after losing a filter, and pressure, make me suspect a rear balance shaft bearing. I can't correlate that to the noise being mutable with the third cylinder, however. Same with the crank pulley. The third cylinder turnoff situation sure makes it sound like a rod bearing. Could it be a wrist pin? Are you running squirters? Do you have a borescope you can check the piston crown with?
I sure don't like the sound of blowing off filters. May be time for a dual-mount setup.

He's using all stock pulleys, but good idea.

With the noises dependance on installation of #3's spark plug, I thought for sure they'd find a bad rod bearing on #3. But they said it looked okay.

I thought it might be the balance shaft bearing, but they said it looked okay as well.

He is running squirters. He installed brand new ones at the last rebuild and clearanced them for the 2.3 stroker.

Is it possible to tap the oil pump or filter housing for fittings and use a remote-mount oil filter like a Canton? I know we could use a sandwich-type adapter, but that seal could pop just as easily as an oil filter's seal.

 

[Slow old poop]

We looked at all the main bearings and #3 rod bearing. Everything looks OK on the bottom end.
We pulled the cam caps on #3, and they look OK too.
We poured oil into #3, and the noise did not change. I hope that rules out piston slap.
I am still with Defiant on the balance shaft, but we have no way of checking it. A failed balance shaft explains everything--sudden high oil pressure and a deep knock.

What we plan to do now is button it back up, put it on the trailer, and take it to a machine shop where, we hope, somebody can diagnose it.

Otherwise, it looks like we'll have to pull the engine and pull the head.
*sigh*
Rich

 

[drivemusicnow]

He's using all stock pulleys, but good idea.

With the noises dependance on installation of #3's spark plug, I thought for sure they'd find a bad rod bearing on #3. But they said it looked okay.

I thought it might be the balance shaft bearing, but they said it looked okay as well.

He is running squirters. He installed brand new ones at the last rebuild and clearanced them for the 2.3 stroker.

Is it possible to tap the oil pump or filter housing for fittings and use a remote-mount oil filter like a Canton? I know we could use a sandwich-type adapter, but that seal could pop just as easily as an oil filter's seal.

If you have the external cooler style oil filter housing, than you could machine a plate to fit into the filter location, tig weld it in place, and just use some AN lines to put a filter in line with the cooler.

 

[Defiant]

I know we could use a sandwich-type adapter, but that seal could pop just as easily as an oil filter's seal.

A seal mounted inside a machined adapter will be much more secure that those rubber rings in thin steel oil filter bases. And, if you're using it to halve the stress by going to either a second or a grown-up sized oil filter, all the better.
I always loved that Datsuns would take a Ford V-8 filter.

 

[stealthTT]

A seal mounted inside a machined adapter will be much more secure that those rubber rings in thin steel oil filter bases. And, if you're using it to halve the stress by going to either a second or a grown-up sized oil filter, all the better.
I always loved that Datsuns would take a Ford V-8 filter.

I guess the oil filter base could "flex" more than an adapter would. That makes sense.

I do like the idea of machining a plate and welding it on as drivemusicnow suggested. Well, let's see if the balance shaft is to blame for the high oil pressure, so we can see if there's any money left in Rich's piggy bank for a remote setup with a "grown-up sized oil filter", as you so eloquently put.

 

[Slow old poop]

If there's any money left in Rich's piggy bank for a remote setup with a "grown-up sized oil filter", as you so eloquently put.

After blowing four oil filters, with the mess it causes, the worry and anguish, not to menion losing a session and pissing off my fellow competitors, I would do ANYTHING to stop blowing filters. What do I gotta do? What can I buy? I druther pay for a guaranteed solution than to try porting the filter housing again and hope it works.

 

[stealthTT]

After blowing four oil filters, with the mess it causes, the worry and anguish, not to menion losing a session and pissing off my fellow competitors, I would do ANYTHING to stop blowing filters. What do I gotta do? What can I buy? I druther pay for a guaranteed solution than to try porting the filter housing again and hope it works.

Good point Rich.

So what do you guys think? I like the idea of welding on a machined plate with AN fittings. So we'll need a piece of aluminum, stainless hose, AN fittings, AN adapters for the oil cooler.

Then we can either use an inline filter like this:

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Or use a canister filter like this:

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I guess we'll have to see what fits. Anyone have any hints or suggestions?

 

[lethal_vr4]

Rich,

Personally, I would use a sandwitch plate for a remote oil lines. It will be similar to the one I was showing Brent in the garage last night. I would not recommend welding anything on just yet as it is not going to solve any high oil pressure issues, just mask the symptoms.

 

[drivemusicnow]

You already have the external oil cooler filter housing right?

You need 2 of these adapters from summit to adapt from the oil filter housing to AN line, (I use -12 which is just overkill, but my intent was to use a huge oil cooler and lines to help lower my oil pressure)

Some high quality braided stainless line: Linky

I'm not sure how you're runing your air to oil cooler, if it already has fittings or not.

I like the inline filter you posted, however I'm not sure what the filtering capabilities would be. I'm not sure what would be best, but I'd try and find a 20 micron or better filter.

 

[drivemusicnow]

Rich,

Personally, I would use a sandwitch plate for a remote oil lines. It will be similar to the one I was showing Brent in the garage last night. I would not recommend welding anything on just yet as it is not going to solve any high oil pressure issues, just mask the symptoms.

The problem of blowing off filters is an effect of high oil pressure that I wouldn't neccesarily want to use as a symptom. I personally don't like the sandwhich plates (just a personal preference), but you may be able to safety wire/ lock it in place at least.

 

[lethal_vr4]

You already have the external oil cooler filter housing right?

Correct, Rich has the external oil cooler OEM oil filter housing.

 

[stealthTT]

I'm not sure how you're runing your air to oil cooler, if it already has fittings or not.

I think it has hose fittings with clamps, so we'll need to take those out and put in AN adapters. I like that much better than relying on clamps!! The clamped hoses show signs of leakage, but nothing major.

I like the inline filter you posted, however I'm not sure what the filtering capabilities would be. I'm not sure what would be best, but I'd try and find a 20 micron or better filter.

The Canton's are rated at 8 microns and still maintain 45gpm due to their depth filtration system and increased size. Lot's of racers use them. I plan to pick up a Canton spin-on (direct replacement) that uses a similar filtering media for my Stealth. They're $90 upfront and then $12 for replacement filters. But I think it's worth it to remove the bypass and increase the filtration of smaller particles. Our main bearings are tiny compared to the torque they see, so the oil system is a huge issue for our platform.

 

[Defiant]

The Canton's are rated at 8 microns and still maintain 45gpm due to their depth filtration system and increased size. Lot's of racers use them. I plan to pick up a Canton spin-on (direct replacement) that uses a similar filtering media for my Stealth. They're $90 upfront and then $12 for replacement filters. But I think it's worth it to remove the bypass and increase the filtration of smaller particles. Our main bearings are tiny compared to the torque they see, so the oil system is a huge issue for our platform.

Eh, I guess. I've alway thought an oil filter is more a "too late" device than of much actual use. But I've never scrapped a motor from oiling issues, so I've not been indoctrinated.

 

[Slow old poop]

We trailered it up to a machine shop yesterday, and the guy thinks it may be a wrist pin, but wants us to do a leakdown test to identify any possible valve problems. We are hunting all over, trying to buy, rent or borrow a tester. Motor comes out Saturday. We'll pull the head, and see what's broke.

The machine shop says one cause of the sudden high oil pressure might be a stuck valve in the oil pump. Geez, if we can't fix the pump, what do we do? I hate to buy a replacement pump from Mitsubishi, because I've heard too many horror stories about those pumps. Ideas, anyone?

Rich

 

[stealthTT]

Eh, I guess. I've alway thought an oil filter is more a "too late" device than of much actual use. But I've never scrapped a motor from oiling issues, so I've not been indoctrinated.

Well...yes and no. If the bearings go bad and become shrapnell, I'd rather the oil filter catch it instead of it running into my oil cooler, turbos, heads, etc. A normal oil filter will bypass when it fills up allowing all that shrapnell to bypass the oil filter. But a normal oil filter will also bypass under other conditions. It works purely on differential pressure opening a rubber valve. Pressure pulses from rapid acceleration, cold oil, poor manufacturer tolerances, a piece of gunk wedging the valve open, etc. can allow dirty oil to bypass your oil filter and you'd never know it.

For $90 upfront and about $12 at every other oil change, it's worth it to me. I look around at what real racers are putting on their cars, research it, and then hope I'm helping to keep my motor a little more safe in an abusive racing environment.

 

[stealthTT]

We trailered it up to a machine shop yesterday, and the guy thinks it may be a wrist pin, but wants us to do a leakdown test to identify any possible valve problems. We are hunting all over, trying to buy, rent or borrow a tester. Motor comes out Saturday. We'll pull the head, and see what's broke.

The machine shop says one cause of the sudden high oil pressure might be a stuck valve in the oil pump. Geez, if we can't fix the pump, what do we do? I hate to buy a replacement pump from Mitsubishi, because I've heard too many horror stories about those pumps. Ideas, anyone?

Rich

The valve he's talking about is most likely the pressure relief valve. I've never heard of those getting "stuck" on a mitsubishi, but if someone can break it, you can.

See ya this weekend to tear that motor out and give it a "what for"!!

 

[Slow old poop]

Whew!

Would you believe...loose flywheel bolts!!!?? Nobody thought of that one, not even an engine builder.

The garage elves (my fabulous crew) pulled the motor Friday night, took off the trannie, and found the loose bolts. They loc-tighted them, tightened them up, put the trans back on, and ran the starter---and the noise was gone!

To address the high oil pressure problem, Brent the Fabricator remounted the oil cooler so it actually will get some air flow (the idiots who built the car mounted it against sheet metal, so only a fraction of the cooler was getting air flow. It's a pretty big cooler. Brent mounted it inside the LF fender, so it will get full air flow.

We are also changing over to 10W30 oil, from the 20-50W we've been using.

If all goes well, and the car starts up with no problems, we are going to try to make it to Putman for the NASA event this weekend.

 

[Defiant]

Bizarre. But, cheap and easy.

 

[Slow old poop]

Bizarre. But, cheap and easy.

Cheap yes. Easy no. We are still putting it back together. The motor comes out a lot easier than it goes back in. We are down to the piddly stuff now, but it is still time consuming, nitpick work.