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Holeshot71 · 09-03-2019, 11:43 AM

Sounds just like an exhaust leak!

chiphead · 08-20-2019, 09:54 PM

Quote:

Originally Posted by gtofreek

I'll say it again, that noise is not piston slap. The pistons are 2618 material and they require a minimum of .0045" clearance and when I measured them they are at .0047" after honing it. It's not piston slap. Doesn't even sound like piston slap. Anyone that's heard piston slap would know that.

Confirmation of piston material is helpful. My motor made a dull double knock noise at TDC and BDC, especially when engine wasn't warmed up. Since (most? all?) 8 cylinders were doing it, it had a rhythmic double rap that I got used to. I just didn't hammer on it before it warmed up. When water temps were up, the noise would be hard to hear, kinda like Sirrotica said.

I'm not saying this is piston slap for sure. One of those videos Joe posted had a double knock sound on the driver's side that sure mimics what my motor would do, just louder.

I can't imagine what else could make this noise and not come apart. Sure it sounds like it's coming from the rear of the engine near the oil pump drive. There's not much there unless the driveshaft is smacking the block d-shaft loop hard enough to make that much noise???

chiphead · 09-23-2019, 03:35 PM

Quote:

Originally Posted by chiphead

Confirmation of piston material is helpful. My motor made a dull double knock noise at TDC and BDC, especially when engine wasn't warmed up. Since (most? all?) 8 cylinders were doing it, it had a rhythmic double rap that I got used to. I just didn't hammer on it before it warmed up. When water temps were up, the noise would be hard to hear, kinda like Sirrotica said.

I'm not saying this is piston slap for sure. One of those videos Joe posted had a double knock sound on the driver's side that sure mimics what my motor would do, just louder.

snip.....

Just sayin...... *GRIN EMOJI*

74SDformula · 09-22-2019, 08:46 AM

Quote:

Originally Posted by gtofreek

I'll say it again, that noise is not piston slap. The pistons are 2618 material and they require a minimum of .0045" clearance and when I measured them they are at .0047" after honing it. It's not piston slap. Doesn't even sound like piston slap. Anyone that's heard piston slap would know that.

Looks like someone made an assumption here.

grivera · 08-20-2019, 08:34 PM

My 08 Tacoma with 4.0 engine has had piston slap since new - common with these engines - and sounds different than the tapping in Joe's engine.

Sun Tuned · 08-20-2019, 11:03 PM

Any chance this thing might have a cam drive gear pressed on the back of the cam?
Any chance it's pressed/ machined not quite right causing an elliptical deal?

Runout check on it if it comes out...

STEELCITYFIREBIRD · 08-21-2019, 01:36 AM

Quote:

Originally Posted by Sun Tuned

Any chance this thing might have a cam drive gear pressed on the back of the cam?
Any chance it's pressed/ machined not quite right causing an elliptical deal?

Runout check on it if it comes out...

Would that be a viable, probable cause, for rapid wear of lower distributor bushing?

With that, have you checked for a repeat failure there?

grivera · 08-21-2019, 07:16 AM

Quote:

Originally Posted by Sun Tuned

Any chance this thing might have a cam drive gear pressed on the back of the cam?
Any chance it's pressed/ machined not quite right causing an elliptical deal?

Runout check on it if it comes out...

It's a Lunati billet roller cam and gear is not press on type

Va68goat · 08-21-2019, 01:18 PM

grivera,
Paul did say the old gear had some wear. He may be able to elaborate on that.

Dragncar · 08-20-2019, 11:37 PM

The 461 I am doing now will make a little noise until warm. .006 piston to wall. .004 is what Ross wanted and said add another .002 if hard blocked. It is. .002 more ring gap too.

Sirrotica · 08-21-2019, 07:38 AM

They have spun the engine over with the distributor removed and observed for runout, reported no runout.

MarkS57 · 08-21-2019, 08:31 AM

Quote:

Originally Posted by Sirrotica

They have spun the engine over with the distributor removed and observed for runout, reported no runout.

I thought he same- the cam gear run out could be an issue but it looks true in the video they took. Its a real reach but it might be possible the cam gear teeth (or distributor gear teeth) might not be machined right such that the cut depth & width of the teeth changes along the circumference of the gear effectively pushing against the other gear when a narrow cut engages the other gear...like a said...its a real reach.

Anyway, listened to the videos of the knock again last night, to me, the sound and timing are that of a bad lifter tap..but its a roller so???

grivera · 08-21-2019, 08:50 AM

It's a shame that [before shipping it back] Paul didn't take a video/audio on a run stand with engine idling considering the history of this engine

Holeshot71 · 08-21-2019, 09:40 AM

Feel like I'm kicking a dead horse here but has anyone taken a length of hose and listened around where the exhaust manifolds bolt to the heads? Specifically around cyl #8 and #2 flanges? This has been brought up by several people but don't think it's ever been answered?

Sirrotica · 10:08 AM

Since the thread started it was suggested numerous times, and has been thoroughly checked more than once, from the owner, and the people doing the diagnostic work, there isn't an exhaust leak.

The noise is most pronounced in the distributor area and seems to be a metallic rapping. It has been listened to with a long rod and a mechanics stethoscope and when the engine was returned to the builder and disassembled there was a lower bushing destroyed in the distributor which was replaced by the manufacturer.

I wasn't aware that the latest guy doing the diagnostic work had pulled the distributor and noted that the newest gear was showing a uneven wear pattern after only 2 hours run time. There is a possibility that even though there is no runout of the drive gear on the cam as observed through the distributor hole, that there is a manufacturing defect of the teeth as far as the helical cut of them.

HWYSTR455 · 08-21-2019, 10:40 AM

It's def not piston slap, I can attest to that, and have heard piston slap on a multitude of engines.

Although the cam gear was observed and considered not having a runout issue, that was a visual inspection, and could technically still have excessive runout. But that's a big reach there, I have never seen that, and I've done a lot of cams.

Looking closer at the vid where they turned it over with the dizzy out, not sure if it's an optical illusion, but the moment the starter is engaged, it looks like the cam gear kicks to the rear for a moment. It might show a little wear on the very corner of the tooth where it kicks out, too. Maybe slow the vid down?

https://www.youtube.com/watch?v=dDZKHIOGWcE

Maybe someone else can chime in and see what I'm seeing? That might explain the gear wear, but still can't see how that would cause a knock. It would have to kick the shaft over considerably, and consistently, and would need to have the shaft bushing worn out for it to go far enough to make contact. Or that's what I'm thinking.

More I think about pin knock, doesn't that actually change when you pull the plug wire? I think it gets quieter when you pull the plug wire?

.

Va68goat · 08-21-2019, 04:53 PM

Sun Tuned,
I like the idea of opening up this motor and checking out the camshaft. On the other hand, my friends that were helping me before are out of the equation for now. Now that Paul and Jeff have their tech, everything will go through them. One thing I don't want to do is spend a lot of time diagnosing things that have been checked 8 times before the tech was involved. As for the distributor, I believe Paul checked that out when he discovered the bad bushing and I'm confident that Paul would have verified that it was straight. But remember, we ran this engine with a different distributor that had another gear on it and it still made the same knocking noise. When we tried the other distributor we also used different plug wires.

STEELCITYFIREBIRD,
Not that I know anything about engines but I always had a feeling that the distributor bushing was the result of something that is causing the knock, not the source of the knock. As I mentioned before, I understand checking everything that it could be but I think it's about time to get inside that motor. Me or my friends aren't touching this motor at this point. I think it's awesome that Paul and Jeff have the tech coming to my house and we're not getting in the middle of that so I'm at their pace. It's been 2 years and a ton of money, I can wait a little longer.

STEELCITYFIREBIRD · 05:04 PM

Definitely worth a revisit with good lighting and/or HD 4K pic/video...and some probing WTF that is...or is not.
I looked at a HFT cam I had handy in hand, definitely the only "counterweight" in that area should be last cam lobe. Roller lobes are centered to lifter bores more than hydraulic lobes.
Went out to a fresh Pontiac short block on stand in my shop, last lobe is nowhere in sight thru dizzy hole with HFT cam, roller lobe should be further toward front than HFT!

Agree HWYSTAR, Definitely their should be nothing in sight thru the dizzy hole but a gear.