[STEELCITYFIREBIRD]

Piston slap is usually most pronounced on a cold engine and then quiets down as expansion equalizes .
With that I assume it possible, like Paul said; collapsed in service. But when you fit the pistons, they are either in spec or not, and this builder is noticeably obsessive compulsive for detail!! (good for you!)

A good test would of been to kill a cylinder at a time and see if the noise goes away or lessens. Wrist pin and piston slap noise are most prominent on the power stoke.

Condition that could be a contributing/casual factor for collapsed skirt in service;
Running the engine high rpm or hard under load or unloaded/free rev it high/hard... COLD. Commonly done to show your buds what your hot rod sounds like.

These long stroke motors usually have comparably short skirts, don't know if that amplifies this condition, but I theorize it would.

[STEELCITYFIREBIRD]

Do you plan to run it Paul, or dig right in??

[PDC]

Originally Posted by mgarblik

My guess is the speculation will be over within a month, after Paul has the engine back in his possession. Can you believe over 20,000 views of this thread? Allot of people will learn something from this. Sorry for the time and expense the principals involved have to deal with. Every engine problem has a solution.

20,000 views of a thread where an engine developed an issue and - if anything - the entire event has only elevated Paul’s well-earned reputation in this community. All in all, this is a really good group of members. My bet is that the issue is something that no one could have predicted or prevented. I’m eager to see the first burn-out video once the engine is nestled back in the engine bay.

[chiphead]

My 400 had mild piston slap with 2618 forgings at .005" skirt to wall. Sounded like a rhythmic dull slap/rap above the pan rail on both sides. It would go away once water temp went over 150F. Never caused an issue and pistons were still good on teardown.

In this case, I bet it's windage tray tapping the pan or lower dipstick tube or an errant rod bolt. Much worse and it would start making metal by now. Part of the noise is exhaust, but there IS some sort of "metal making contact" sound riding under the exhaust noise.

[gtofreek]

Originally Posted by STEELCITYFIREBIRD

Do you plan to run it Paul, or dig right in??

I'm tearing right into it. We have to pay to use a dyno to run it, and without mufflers, I'm not sure we'd even hear it on the dyno. Looking back at the dyno video's I made, you cannot hear any noise.

[grivera]

Shame there isn't a run-in stand available.

[Va68goat]

Ok....Let's play a game. Since I have received so much help and input from the guys on the forum...let's have some fun! My motor arrived at Paul's shop today. I just ordered this 12 inch aluminum Pontiac sign on eBay. The first forum member to correctly guess what the problem was with the motor will receive this sign for free. I'll pay the shipping!

Because of this thread, I have met some good friends and I've learned a lot about cars. I can't tell you enough how great Jeff and Paul have been. I wouldn't hesitate to have Paul do another motor for me. He is a true professional.

Post your guess!

[indymanjoe]

windage tray..my best guess

[Dragncar]

Originally Posted by chiphead

My 400 had mild piston slap with 2618 forgings at .005" skirt to wall. Sounded like a rhythmic dull slap/rap above the pan rail on both sides. It would go away once water temp went over 150F. Never caused an issue and pistons were still good on teardown.

In this case, I bet it's windage tray tapping the pan or lower dipstick tube or an errant rod bolt. Much worse and it would start making metal by now. Part of the noise is exhaust, but there IS some sort of "metal making contact" sound riding under the exhaust noise.

The 461 I am doing will have a little piston noise until its warm. .006 It has to have a extra .002 because the block is filled. Same with the rings.
The Ross FTs need .004 then + .002 so I am ready for a little noise.

Then I get to hammer the pedal and make some more noise!

[torqhead]

piston slap as I said previously

[wbnapier]

Oil Pump pick up.

[gtofreek]

I'll go out on a limb by saying with 99.9% confidence that it is not piston slap.

1. It does not sound like piston slap.
2. I setup the pistons with the minimum .0045" clearance that they call for, and I use a torque plate with the same type gasket that I used to assemble with. I've setup a lot of engines with these pistons at .0045" and never had a noise from them. Plus I've honed thousands of blocks over the last 26 years so I'm pretty good at it. I hone to the tenth of a thousandth of an inch so I can say with confidence it had .0045" clearance.

My best guess at this point is possibly a piston pin trying to gall in the pistons bore, but I set those up at .0008" clearance, so they shouldn't be trying to gall. Or possibly a piston skirt collapsed for some reason.

In any case, I will be going to work tomorrow and tearing it down, so I should have an answer for you all tomorrow. My biggest fear is that I won't find anything obvious, so I think it's going to take a very close examination of everything.

[STEELCITYFIREBIRD]

UnderdahoodWoodpecker
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[TedRamAirII]

Windage Tray. Does it have a crank scraper?

[400 Lemans]

Crankshaft counter weight making slight contact on block.

[Va68goat]

TedRamAirII,

Yes...It does have a windage tray but we have checked the spacing of the windage tray!

[torqhead]

Originally Posted by gtofreek

I'll go out on a limb by saying with 99.9% confidence that it is not piston slap.

1. It does not sound like piston slap.
2. I setup the pistons with the minimum .0045" clearance that they call for, and I use a torque plate with the same type gasket that I used to assemble with. I've setup a lot of engines with these pistons at .0045" and never had a noise from them. Plus I've honed thousands of blocks over the last 26 years so I'm pretty good at it. I hone to the tenth of a thousandth of an inch so I can say with confidence it had .0045" clearance.

My best guess at this point is possibly a piston pin trying to gall in the pistons bore, but I set those up at .0008" clearance, so they shouldn't be trying to gall. Or possibly a piston skirt collapsed for some reason.

In any case, I will be going to work tomorrow and tearing it down, so I should have an answer for you all tomorrow. My biggest fear is that I won't find anything obvious, so I think it's going to take a very close examination of everything.

Paul, in no way was I implying you would have done something wrong. I have the upmost respect for your work even though I haven't had you do anything for me personally....... yet....

Anyhow, if a piston skirt collapsed causing piston slap wouldn't that still count ... I know this is definitely an interesting one for all of us and confident you'll figure out what the hell it is!

[ponchjoe]

I’d mag the windage tray

[cnc]

I'm goin rod issue.....due to oil starvation for some reason.....It's a guessing game right .....
Been through this twice ......not fun.....
Hope Paul figures the issue out.....

[wrench]

I think you will tear it down and find absolutely nothing wrong. I hope I'm wrong, easy to fix if you find an issue, but I like that sign, lol. So that's my guess.