I need a set of ears, long post and not a normal noise

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My427stang
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Re: I need a set of ears, long post and not a normal noise

Post by My427stang »

Not a whole lot found with measuring the pistons

4.075 across all 8 with the micrometer flush with the end of the skirt, at the .50 measuring point, all were 4.074, 40 degree garage temp

Zero'd my bore gauge, checked them all nothing wild, as garage warmed up, checked again, tightest is .0055 after a few hundred miles, no taper, loosest is under .0062, looser than I put it together, but well within spec for the pistons. Could chalk it up to summer temps in the garage when measuring the pistons plus breakin, but nothing jumps out

Overall height of the piston at the skirt is 2.325 and compression height is 1.33, these numbers are not that important, but it does show a pretty short piston by FE standards

Here is what the base of a couple cylinders look like, I cannot feel these marks, and they don't measure with the bore gauge, but odd for only a few hundred miles, the last one isn't as "shiny"

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70 Mustang, 489 FE, TKO-600, Massflo SEFI, 4.11s
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Re: I need a set of ears, long post and not a normal noise

Post by travis »

My very first 351w build years ago had a very similar noise issue your describing. After it driving me nuts for a month and not being able to find it even after multiple tear downs, it gradually progressed to a random knocking at idle...apparently that’s when the crack in the flex plate got big enough to make noise with no load on it at idle. Maybe look for cracks around the flex plate/flywheel area?

Although those marks on the bottom of the bores are definitely suspicious...
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Re: I need a set of ears, long post and not a normal noise

Post by My427stang »

travis wrote: Thu Feb 22, 2018 1:42 pm My very first 351w build years ago had a very similar noise issue your describing. After it driving me nuts for a month and not being able to find it even after multiple tear downs, it gradually progressed to a random knocking at idle...apparently that’s when the crack in the flex plate got big enough to make noise with no load on it at idle. Maybe look for cracks around the flex plate/flywheel area?

Although those marks on the bottom of the bores are definitely suspicious...

Thanks Travis, I do appreciate it, but two different flywheels, one new, 2 different pressure plates and discs, all new bolts, plus crankshaft magged...a bit embarrassed to say for a guy who did this for a living for a long time, but I started getting into pure parts replacement and guesswork.

I agree, those marks make me think the piston is flopping around at the bottom of the stroke too.
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70 Mustang, 489 FE, TKO-600, Massflo SEFI, 4.11s
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Re: I need a set of ears, long post and not a normal noise

Post by grant6395 »

So there is only a thou between measurements from the bottom of skirt to .500 up? Is that where the piston manufacture wants the measurement taken? Seems like not a lot of "barrel" to the pistons. Imho
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Re: I need a set of ears, long post and not a normal noise

Post by My427stang »

grant6395 wrote: Thu Feb 22, 2018 2:31 pm So there is only a thou between measurements from the bottom of skirt to .500 up? Is that where the piston manufacture wants the measurement taken? Seems like not a lot of "barrel" to the pistons. Imho
That is correct, the taper of the skirt reduces toward the ring lands. If I measure at the .500 point , I can almost walk the mic off the bottom of the skirt, it gets noticeably looser toward the ring pack as well\

and yes, .0500 is where Probe said to check, .0045 preferred, .003-.007 acceptable
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Re: I need a set of ears, long post and not a normal noise

Post by cjperformance »

I would like to see PB back down at .0045"/.005" tops.(what coolant temp do you run it at?)

What is pin clearance?

Get your rods checked for straightness.

Do pistons have any bore contact marks up above the top ring?
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Re: I need a set of ears, long post and not a normal noise

Post by Mark O'Neal »

I have no idea what it is, but there should be no piston noise at .0045.

What's the oil pressure doing? I had one do something like that that turned out to be a crack along the oil gallery.
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Re: I need a set of ears, long post and not a normal noise

Post by My427stang »

Mark, thanks, no issues with pressure, and 2 different blocks, both pressure tested.

Its a stumper

Some additional pictures of the skirts

Image

Image

Image
Bullock's Power Service, LLC
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Re: I need a set of ears, long post and not a normal noise

Post by cjperformance »

Can you access a new piston of the same # to compare skirt profile?
If not just have the block honed to clean up and make sure the bores are spot on and order a different brand piston!
OR try the abradable coating it may do the trick, i have not used it so cant say but others say it seems to work.
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Re: I need a set of ears, long post and not a normal noise

Post by My427stang »

I don't think anyone sells these anymore, however, I will likely go back to Diamond or try Racetec with a 4032, it's not a race engine, it'll be happier and more stable with a 4032 and .0025-ish clearance.

Heck if I could get a cast or hyper it'd live in the truck the way it's run, that's the bummer in this build, took a lot of time and cash for something that doesn't need to be that cosmic :)
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Re: I need a set of ears, long post and not a normal noise

Post by MadBill »

How far do the skirts come out of the bores at BDC? It looks a little like they may be rocking. Pistons with a higher gauge point generally fare better in strokers.
I'd still recommend the Line2Line process. Cheaper, no worries about re-balancing, can't hurt if it's not the problem, can only help if it is...
Felix, qui potuit rerum cognscere causas.

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Re: I need a set of ears, long post and not a normal noise

Post by kimosabi »

Definitely piston rock judging by the pic of the bottom of the skirts and the cylinders. Maybe the skirts are soft, collapse a little when hot, skirts out of bore at BDC or whatever. Maybe you really need to run offset pin. Is the block plate honed?

Not very helpful here, just thinking out loud. I'd just blueprint everything again, new pistons definitely. Checking rods for straightness someone mentioned is a good tip too.
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Re: I need a set of ears, long post and not a normal noise

Post by Mark O'Neal »

MadBill wrote: Thu Feb 22, 2018 9:20 pm How far do the skirts come out of the bores at BDC? It looks a little like they may be rocking. Pistons with a higher gauge point generally fare better in strokers.
I'd still recommend the Line2Line process. Cheaper, no worries about re-balancing, can't hurt if it's not the problem, can only help if it is...
That's what I'd like to know next. The cylinders look like a 408 Cleveland with a 6" rod.
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Re: I need a set of ears, long post and not a normal noise

Post by My427stang »

I'll mock one back up and take some pics/measurements.

There is nothing unique about this engine or block though, 2 different 390 blocks, 4.25 stroke SCAT, 6.70 SCAT I beam rods. Pretty much the most common of FE strokers.

I don't have a reason why it did it, but I am growing more comfortable on the "what". Next thing is to compare skirt length, shape and dimensions to an Racetec and Mahle. Would like to find something different before I throw good money at it a third time. I wish I had some manufacturing specs to figure out if they have rolled and are just soft or ???

I'd love to try the Line2line, but for 300 bucks or so for a set of 8 after shipping, not sure I have the faith in these pistons to trust a 3rd build when I can add 200 bucks and go with a 4032 with a metric ring pack

What I would do, and may do sometime, is bring them as tight as I can on a fresh build and see if I can find a crank/rod combo that stays entirely in the bore. Just need to see what is worth doing for fun and the cost. A longer rod/shorter stroke combo could work despite the currently unstable setup.

Unfortunately, in all the FE strokers I have done, or buddies have done, I haven't seen a second set of these pistons in use, so I don't have a reference for how quiet they are normally cold or if I somehow have a unique situation
Bullock's Power Service, LLC
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Re: I need a set of ears, long post and not a normal noise

Post by Mark O'Neal »

The skirt design we used on that piston was developed by Ford Motor Company. They are quiet. They have always been quiet.

You might want to contact Barry Robotnick at Survival Motorsports. He specializes in FE motors and may have some insight for you. He has also used hundreds of sets of Probe pistons in these applications which makes him aware of any quirks in combinations.

The SRS Series was also made of the same 2618-t6 everyone uses on forgings made by the same forging house everyone uses. Since I have never seen a single complaint of this nature, you would have had to have gotten the only "soft" forgings in the batch....of at least a thousand. That would be incredible bad luck. If the parts are soft, they would have had to have been heated to a very high temperature and normalized.
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