Piston pin or piston slap

[davidcam69]

Can you feel by hand a lose piston pin? I have 4000 miles on a rebuilt 440 with KB hyper pistons. They are full floating. It has a knock when
cold and goes away (almost) when hot. Could be a piston slap but with the KB hypers I didn't think they would expand much. I just tore it down
and everything looks good by just eyeing it. Can't feel any slop in the rod pins. I changed the lifters and went to roller rockers but no change.
I thought for sure I would find a loose pin.

[Eldovert]

You should be able to feel a loose pin
How much clearance do you have between pistons and cylinder?  sure sounds like cold slap.
You could check by sticking the pistons down the cylinders with a feeler gauge for a go-no go measurement.

[davidcam69]

Eldovert, that's kinda what I thought on a loose pin. If its not pin then it has to be piston slap. Its only one and pretty much goes away after engine
is completely warmed up.  I think I will take it to my new shop and have them check it out. My old shop retired awhile back. This is my numbers
matching engine so I want take good care of it.     Thanks

[Challenger340]

Yeah KB's will rattle around a bit at .0035" to .0040" Piston to wall clearance.... quieter once warmed up.

Run 15w-40 or 20w-50 to shut 'em up if you don't wanna listen to them.   Do the new guys have a BB Mopar Torque Plate and used it when honing or NO ?

[davidcam69]

The old shop and new shop used hone plate. I used the KB hypers  because I thought they would be quieter than forged and pretty much a stock
build. Its 40 over now and I'm running 20 50 Z rod oil now.  Not sure what to do now. Can I get an accurate measuring it myself with a feeler gauge?
What would be the maximum clearance?   Only one is making noise when cold and I hate it.     Thanks 340 for your reply.  














     

[Challenger340]

The old shop and new shop used hone plate. I used the KB hypers  because I thought they would be quieter than forged and pretty much a stock
build. Its 40 over now and I'm running 20 50 Z rod oil now.  Not sure what to do now. Can I get an accurate measuring it myself with a feeler gauge?
What would be the maximum clearance?   Only one is making noise when cold and I hate it.     Thanks 340 for your reply.  

one Piston rattling around would drive anyone bonkers.... imo, far better when all are noisy and at least there is some consistency ?

Hypers are the high silicon alloy version of a Cast Piston... the extra silicon makes them strong/hard and somewhat more thermally stable in sizing from cold to hot so that tighter Piston to wall fits can be used.

Same goes for Forged Pistons these days.... in that not all forgings are 2618 base alloys anymore and noisy
wherein
most Manufacturers are now offering 4032 HIGH Silicon Alloy Forgings for the stock applications, Cam & Barrel structure designs, that are just as thermally stable and run just as quiet as the Hypers.
Case in point would be the L2355F Forged Piston offering from Federal Mogul made with 4032 Alloy, which calls for a Piston to wall clearance of .00125".... that right.... one and 1/4 thousandth of an inch.  We typically fit them a little looser up around .0025"-.0030" , but they are a Forged Piston and run dead nuts quiet.

Best way to measure your current Piston to wall clearance is with a mic reading of the Piston skirt.... then transferred onto a dial bore gauge, albeit engine dis-assembly is req'd.

You may have some success with a feeler gauge silding it up between the skirt and the cylinder wall on the still assembled engine with just the oil pan off,  however, it can be very frustrating with such a thin ribbon feeler gauge ?

Have you tried 'shorting' the sound out.... or making the sound 'change' when running the cold Engine.... by removing spark plug wires one at a time to determine which Cylinder is the noisy culprit ?
I like to remove/loosen each plug wire first so as to make it easier to pull each one away one at a time while running.... use gloves and rubber insulated pliers to minimize getting zapped yourself.
If it's a Pin or Piston slap.... when you find the offending cylinder it should change from a quick/sharp Dbl 'wrap' to a very light thud.

[flyinlow]

Is the use of 4032 alloy a recent change?  A dozen years ago I used SRP pistons that called for .005 clearance. I assume they where 2618 alloy. Now the JE website says most of its SRP's are 4032.

[Challenger340]

Is the use of 4032 alloy a recent change?  A dozen years ago I used SRP pistons that called for .005 clearance. I assume they where 2618 alloy. Now the JE website says most of its SRP's are 4032.

I don't believe the use of 4032 base alloys is anything new for Manufacturers.... and some tend to distinguish their 4032 Forgings into lower priced piston offerings from their name 'brand' 2618's ?
although,
with JE/SRP 2618 Forgings can be found within the SRP line on some applications.

For example:
as you said "JE" brand being mainly 2618 with most of the SRP line being 4032(some 2618 application specific, typically higher CR domes)
Wiseco mainly 2618.... ProTru being mostly 4032 offerings
etc

I have not heard/seen of a .005" recommended Piston to Wall clearance for a 4032 SRP BB Mopar offering ?  Is there a chance your SRP's were "2618" alloy ?

[flyinlow]

Is the use of 4032 alloy a recent change?  A dozen years ago I used SRP pistons that called for .005 clearance. I assume they where 2618 alloy. Now the JE website says most of its SRP's are 4032.

I don't believe the use of 4032 base alloys is anything new for Manufacturers.... and some tend to distinguish their 4032 Forgings into lower priced piston offerings from their name 'brand' 2618's ?
although,
with JE/SRP 2618 Forgings can be found within the SRP line on some applications.

For example:
as you said "JE" brand being mainly 2618 with most of the SRP line being 4032(some 2618 application specific, typically higher CR domes)
Wiseco mainly 2618.... ProTru being mostly 4032 offerings
etc

I have not heard/seen of a .005" recommended Piston to Wall clearance for a 4032 SRP BB Mopar offering ?  Is there a chance your SRP's were "2618" alloy ?

That's what I was wondering if they used 2618 in the past and recently switched to 4032 for less noise or cost reasons?

[Challenger340]

Is the use of 4032 alloy a recent change?  A dozen years ago I used SRP pistons that called for .005 clearance. I assume they where 2618 alloy. Now the JE website says most of its SRP's are 4032.

I don't believe the use of 4032 base alloys is anything new for Manufacturers.... and some tend to distinguish their 4032 Forgings into lower priced piston offerings from their name 'brand' 2618's ?
although,
with JE/SRP 2618 Forgings can be found within the SRP line on some applications.

For example:
as you said "JE" brand being mainly 2618 with most of the SRP line being 4032(some 2618 application specific, typically higher CR domes)
Wiseco mainly 2618.... ProTru being mostly 4032 offerings
etc

I have not heard/seen of a .005" recommended Piston to Wall clearance for a 4032 SRP BB Mopar offering ?  Is there a chance your SRP's were "2618" alloy ?

That's what I was wondering if they used 2618 in the past and recently switched to 4032 for less noise or cost reasons?

Most all of the '2618' alloy SRP Pistons I have seen were "Domed" Pistons(BB Chev) or Higher Compression intended applications ? where there still exists substantial potential for 'detonation' in operation, which is a weak spot for all higher Silicon content 4032 alloys same as KB Hypereutectics, because as the silicon makes them stronger, it also makes the alloy more brittle and prone to cracking ?
Hence....
why 4032 Forged Pistons have the advantage in thermal stability for tighter fit and quieter running .... the 4032 alloy Forgings are also NOT Recommended for anything more than very very light boost(max 6 psi)....   or maybe just a 100hp shot of Nitrous..... that's it, that's ALL !

I have not seen a Flat Top SRP Piston in anything other than 4032 alloy. This is not to say they were not produced.... just that I personally have not seen them.

The only learning curve and my intention here..... is to pass along the advancements made in Forged Piston alloys and 4032 offerings from manufacturers as it relates to 'quieter' running potential...... the trade-off being only good for VERY low Boost/Nitrous

[davidcam69]

Yes I started  pulling plug wires at the very first and the knock sounded like it was coming from 1 3 or 5. I run a firecore  distributor and Rev-N-ator control
box. when I pulled no 3 wire the engine died. It restarted and ran poorly for a bit. I pulled the same wire and it died again. It would not restart again. Killed
the ICU. Sent it back to RT Garage and they sent me another, no problem.  I was out on a cruse and was talking to a friend about my problem and pulled the same wire and the engine died. Would not restart. Killed that ICU. Got another from RTG with no problem.  They could not tell me why this was happening. Needless to say that I don't do that anymore. I do have my engine tore down. Im going to take it to my shop and have them check it out.

Thanks for your input 340. I always enjoy your post.           

[flyinlow]

Try  grounding the plug end to the block or through a spare sparkplug that is grounded. This will reduce the stress on the ignition system. 

[flyinlow]

Is the use of 4032 alloy a recent change?  A dozen years ago I used SRP pistons that called for .005 clearance. I assume they where 2618 alloy. Now the JE website says most of its SRP's are 4032.

I don't believe the use of 4032 base alloys is anything new for Manufacturers.... and some tend to distinguish their 4032 Forgings into lower priced piston offerings from their name 'brand' 2618's ?
although,
with JE/SRP 2618 Forgings can be found within the SRP line on some applications.

For example:
as you said "JE" brand being mainly 2618 with most of the SRP line being 4032(some 2618 application specific, typically higher CR domes)
Wiseco mainly 2618.... ProTru being mostly 4032 offerings
etc

I have not heard/seen of a .005" recommended Piston to Wall clearance for a 4032 SRP BB Mopar offering ?  Is there a chance your SRP's were "2618" alloy ?

I sent a question to JE pistons  about the alloy maybe being different when I bought mine . A Senior Sales Technical Associate from JE replied that as far as he knew the SRP number I used where always made from 4032 aluminum. The recommended clearance is .0035 ".

So my pistons are a little lose... Oops.

[Challenger340]

I don't believe a 4032 Alloy long skirt 440 Piston(2.067" CD) that has been fit at a Piston to Wall Clrc of .005" would be overly noisy ? probably minimal noise if at all audible ?
that said...
anyone may indeed be able hear a 4032 short skirt Piston like those used in a 451 Engine(1.32" CD) not just when Cold.... but also even once warmed up to full operating temps as well in a mufflered street Car ?

Just say'in....
satisfactory operation of many Piston Alloys/Design parameters of the Piston can extend far beyond the actual Piston to Wall Clearance utilized ? and relative Piston Skirt length that any clearance is then spread over is a factor as well ? and if your .005" clearance is spread over a long skirt 440 Piston it's far more forgiving.

Forget 'noise' for a moment.... and now also think about the Piston "ROCK" in the Bores which is what you are hearing as Piston "slap".... as it pertains to Piston RING Sealing functions/efficiencies therein/Blowby etc. ? I mean if the Pistons are rattling around as the platform holding the Rings then easy to see ring "seal' is also somewhat diminished right ?

That's why it's so important with Strokers/many Shorter Skirt Piston applications to pay close attention to Boring/Honing/Piston fitting as per the intended application ?



A little off topic here..... and only provided as reference to correct Piston "fitting" as per Piston Alloy present when unsure ?

Be Aware !
* ALL Pistons are typically manufactured dimensionally SMALLER than their intended Bore Size..... by the amount of the minimum Rec'd Piston to Wall clearance.
For example here:
a 4032 alloy SRP Forged Piston manufactured/built/intended for a 4.350" Bore Engine... Rec'd for a minimum .0035" Piston to Wall Clrc...... will typically measure/Mic at 4.3465" (4.350 - .0035 = 4.3465)
and
a 2618 alloy JE Forged Piston manufactured/built/intended for a 4.350" Bore Engine.... Rec'd for a minimum .005" Piston to Wall Clrc..... will typically measure/Mic at 4.345" (4.350 - .005 = 4.345)
So from the above it's pretty easy to see ?
that the Pistons themselves if Mic'd ? are telling the Machinist WHAT they are..... and the intended minimum Piston to Wall that should be used ?
Because ....
the ONLY way any Machinist can then provide .005" Clearance when fitting a 4032 alloy SRP Piston that is built .003" to .0035" down from the intended Bore size(typical)... is to then enlarge/hone the Cylinders well past the nominal Bore Size by the extra .0015" to .002" ....  to get to the .005" clearance ?
THAT oversizing procedure.... and the Pistons themselves when measuring...  should have been telling somebody/goober that something is wrong when doing it ?

The definition of 'minimum' Piston to Wall Clearance being: that which is required for satisfactory usage in most all mufflered STREET applications..... ie: NON Racing, Extended High RPM/Compression/Boost or Nitrous.

If you are RACING/extended HIGH rpms/HIGH Compression/Boosted or Nitrous then YES... and extra .001" to .003" Piston to Wall Clearance is Rec'd with the caveat that you will expect some audible Piston Slap and be carefully applying extra Ring End Gap as well anyways(some blowby expected)

[davidcam69]

Good information here!  Thanks

[justcruisin]

I have a set of 4032 SRP's in a 3.75 stroke 440 - 2.062CH, they are in at .004" wall clearance. You can hear them on start up but once fully warmed up they quiet down nicely.

[Challenger340]

I have a set of 4032 SRP's in a 3.75 stroke 440 - 2.062CH, they are in at .004" wall clearance. You can hear them on start up but once fully warmed up they quiet down nicely.

May I ask what weight of Oil are you using ?

[justcruisin]

10w40 brad penn I was using a 5w30 synthetic from oil extreme but it made my rear main leak go from bad to really bad. Even with the 5w30 the pistons were not overly noisy when fully warmed up. I run an xe/hl cam which also kicks up noise but different from the piston noise but I guess could mask some piston noise..  I will be pulling the engine shortly to pull the crank and try to fix the leak and doing a cam swap to a SFT.
The SRP's were for a 4.360 bore and mic at 4.3565".

[Challenger340]

Synthetics... while wonderful lubricants, tend to exacerbate even small leaks by being just too slippery for the older Engines sealing/gasket technology.
We've seen that even some light 'sweating' around a Valve Cover for example ? can and will turn into a full blown LEAK once the switch to a Synthetic Oil is applied ?
Hence... we don't use Synthetics around the older generation Engines "std" Gasket designs.


Sry to hear of your main leak.... NO fun.

Dunno how confident you are feeling tackling the Main ? 
pm me if ya feel like it..... and I may have a few ideas we've used ? and we always 'test'(hang the Engine) for the Main Leak to make sure it's sealed prior to re-installing as nobody likes doing things more than once.

[justcruisin]

Hey thanks, I will. I will be pulling the engine in about a months time. I will contact you then, thanks again.