Speed pro2355 coated piston

[Rayzor]

Can you guys share what piston to wall clearance your running with these? The box calls out .0015 minimum. My machinist bored for .002  I heard from someone that this is way to tight and need .005 minimum.  What gives?

[BSB67]

0.0035".  But that was 30 years ago.

[c00nhunterjoe]

In my experience, despite the .0015-.002 speedpro calls for; the skirts will get torn up on a street car. .003-.0035 if i were using them. But i would go with a different brand that is lighter.

[Rayzor]

The short block is all ready put together.  Looks like I'm going to have to tear it apart and re block.

[c00nhunterjoe]

Wait and see what rons experience may be with them.

[Rayzor]

In my experience, despite the .0015-.002 speedpro calls for; the skirts will get torn up on a street car. .003-.0035 if i were using them. But i would go with a different brand that is lighter.

So you have seen these pistons bite the dirt from being run at the listed clearance? I have been searching for a definitive answer. Some say the added clearance is built in to the coating, others say run it tight at listed 001 and another camp says I need a foot of room.   My block is .60 over and the bore was set at    .002 over that size. 4.381 if I remember correctly.  Help!

[BSB67]

It was not uncommon for the skirts to gall from getting a little hot when installed at the recommended spec.  Again, 30 years ago. 

[RTsehibb]

I went through the same thing in 2016. 

Do a search on this board for, "2355 piston to wall clearance."  I got great advice from the engine guys here (Thanks Ron and others) as they confirmed what my machinist said - there should be at least .0035 to be on the safe side and that's what we did on my coated (Sorry made in India) 2355's that were 40 over (69 440 Mag bored with deck plate).  Supposedly the newer alloys don't expand as much so they say.  My machinist did warn it may be noisy when cold.  It is noisy but more of that is from the pushrod oiling holes in the Johnson lifters (Oiling holes that I don't use) and they tend to bleed all the way down when the engine is static for a week or more.  So do I hear piston slap? Not really but I did work on airplanes for many years so my hearing is shot!

I can tell you that after warm my engine runs great and smooth.  Having the correct compression pistons makes an amazing difference in torque and neck snapping power.  Those 2355's were a great choice for a forged piston at that price on Amazon.  The only other problem we had were finding piston rings for them (40 over) but I found Keith Blacks that worked. 

Overall, I'm very happy with the 2355's but I'm still at only about 200 miles on the rebuild so time will tell.  I'm sure it will roast the 275/60's if I pushed it - effortlessly.

Good luck with your build,

Randy

[Rayzor]

Well I guess that sums it up, I need to pull it apart and have it honed  open a couple thousandths.   Not sure what that will do to my ring gap as the top ring is already at .024.

[BSB67]

Here is one of my 35 year old pistons that was installed with 0.0035" after about 30 or 40,000 miles, and probably 200 passes at the track

[c00nhunterjoe]

Here is one of my 35 year old pistons that was installed with 0.0035" after about 30 or 40,000 miles, and probably 200 passes at the track

Any eyebrows on thos pistons?

[BSB67]

Nope.

SpeedPro/Power Forge L2286P.  

Search it and let me know what you find.  

[c00nhunterjoe]

No need. Those are the basic old school trw NHRA 440 piston comparable to my 2257s that were in my 383... although mine had eyebrows from valve kisses... lol.

[Challenger340]

Well I guess that sums it up, I need to pull it apart and have it honed  open a couple thousandths.   Not sure what that will do to my ring gap as the top ring is already at .024.

Di you file the rings to .024" gap ? or were they that way OOTB ?

The reason I ask is because if they were .024" OOTB with no filing ? that would indicate your Bores are already likely above nominal Bore dimension ? ie: .031" instead of .030" etc ?
Remember here,
the math Pi factor being 3.14 means for each extra .001" extra/above nominal Bore dimension as above, the ring end gap opens around .003" (Pi).... and those rings typically show an OOTB Ring End Gap with NO filing on a .030: Bore of about .016" to .018"..... meaning if yours are .024" - .018" = .006"/.003" = 2 or .002" and maybe your Bores are already at .032" ?

Just saying here....
we like to run the L2355's up around .003" minimum as well for safety.... meaning we typically have to take the bores over nominal Bore dimension by .002" or so and those (.024") end gaps are typically what we see ?
Check closely.... yours may already be there ?

Another factor;
Was the Engine Honed with a Torque Plate ?
A Torque Plate when installed usually "distorts" the Cylinders .001" to .0015"..... and in severe cases(thin walls) can do so .003" or more, the same way the Cylinder Head distorts the Cylinders when it's installed ?

Many Shops that don't have a T/Plate for a BB Mopar just ADD an extra .001" or so clearance when Honing as a safety factor to compensate ?
and....
that may be why you are seeing the .024" end gaps ?  because they may have added the extra clearance for NO T/Plate and you do in fact have .003" Piston clearance ?

[Rayzor]

Well I guess that sums it up, I need to pull it apart and have it honed  open a couple thousandths.   Not sure what that will do to my ring gap as the top ring is already at .024.

Di you file the rings to .024" gap ? or were they that way OOTB ?

The reason I ask is because if they were .024" OOTB with no filing ? that would indicate your Bores are already likely above nominal Bore dimension ? ie: .031" instead of .030" etc ?
Remember here,
the math Pi factor being 3.14 means for each extra .001" extra/above nominal Bore dimension as above, the ring end gap opens around .003" (Pi)....
and those rings typically show an OOTB Ring End Gap with NO filing on a .030: Bore of about .016" to .018"..... meaning if yours are .024" - .018" = .006"/.003" = 2 or .002" and maybe your Bores are already at .032" ?

Just saying here....
we like to run the L2355's up around .003" minimum as well for safety.... meaning we typically have to take the bores over nominal Bore dimension by .002" or so and those (.024") end gaps are typically what we see ?
Check closely.... yours may already be there ?

Another factor;
Was the Engine Honed with a Torque Plate ?
A Torque Plate when installed usually "distorts" the Cylinders .001" to .0015"..... and in severe cases(thin walls) can do so .003" or more, the same way the Cylinder Head distorts the Cylinders when it's installed ?

Many Shops that don't have a T/Plate for a BB Mopar just ADD an extra .001" or so clearance when Honing as a safety factor to compensate ?
and....
that may be why you are seeing the .024" end gaps ?  because they may have added the extra clearance for NO T/Plate and you do in fact have .003" Piston clearance ?

Correction they are .026 right out of the box. Block was not honed in with torque plates either. I do not own a bore gauge so I only have the info wrote down. And that was pistons were 4.379 and finished bored at .381. I pulled a piston and with my Ebay digital mic I get 4.377 at bottom of skirt below coating. Middle of pin get .378

[Challenger340]

Well I guess that sums it up, I need to pull it apart and have it honed  open a couple thousandths.   Not sure what that will do to my ring gap as the top ring is already at .024.

Di you file the rings to .024" gap ? or were they that way OOTB ?

The reason I ask is because if they were .024" OOTB with no filing ? that would indicate your Bores are already likely above nominal Bore dimension ? ie: .031" instead of .030" etc ?
Remember here,
the math Pi factor being 3.14 means for each extra .001" extra/above nominal Bore dimension as above, the ring end gap opens around .003" (Pi)....
and those rings typically show an OOTB Ring End Gap with NO filing on a .030: Bore of about .016" to .018"..... meaning if yours are .024" - .018" = .006"/.003" = 2 or .002" and maybe your Bores are already at .032" ?

Just saying here....
we like to run the L2355's up around .003" minimum as well for safety.... meaning we typically have to take the bores over nominal Bore dimension by .002" or so and those (.024") end gaps are typically what we see ?
Check closely.... yours may already be there ?

Another factor;
Was the Engine Honed with a Torque Plate ?
A Torque Plate when installed usually "distorts" the Cylinders .001" to .0015"..... and in severe cases(thin walls) can do so .003" or more, the same way the Cylinder Head distorts the Cylinders when it's installed ?

Many Shops that don't have a T/Plate for a BB Mopar just ADD an extra .001" or so clearance when Honing as a safety factor to compensate ?
and....
that may be why you are seeing the .024" end gaps ?  because they may have added the extra clearance for NO T/Plate and you do in fact have .003" Piston clearance ?

Correction they are .026 right out of the box. Block was not honed in with torque plates either. I do not own a bore gauge so I only have the info wrote down. And that was pistons were 4.379 and finished bored at .381. I pulled a piston and with my Ebay digital mic I get 4.377 at bottom of skirt below coating. Middle of pin get .378

.026" ring end gap right out of the box.... if accurate ? and I am NOT doubting you.... IMO, would be indicative of a somewhat bigger Final Bore dimension than the 4.381" mentioned ?

Try this if you can ?
remove one Piston.... and carefully remove the rings from that Piston.
Then insert the Piston into it's Bore upside down.... putting the Piston into the Bore head first about 1/2 down into the cylinder while you hold onto the Connecting Rod.
Then using a Feeler Gauge.... do you have one of those ?  
Press the Piston skirt tang on one side tightly against the Cylinder.... and while doing so insert a .003" Feeler Gauge strip on the other side of the Piston Skirt Tang up between the Cylinder Wall and Piston Skirt Tang and see if it will go in ? or a .002" strip... or a .004" strip... whatever fits ? Oil helps to avoid galling the Piston skirt coating.
Suffice to say.... whatever feeler gauge strip fits ? that's your Piston to Wall clearance.

[Rayzor]

Brilliant I will see if I can source up some feelers that read that low. Mine stop at 006 thanks
I found a cheapo bore gauge on amazon for 20 bucks   I think I will scoop that up as well.

[Rayzor]

Well I guess that sums it up, I need to pull it apart and have it honed  open a couple thousandths.   Not sure what that will do to my ring gap as the top ring is already at .024.

Di you file the rings to .024" gap ? or were they that way OOTB ?

The reason I ask is because if they were .024" OOTB with no filing ? that would indicate your Bores are already likely above nominal Bore dimension ? ie: .031" instead of .030" etc ?
Remember here,
the math Pi factor being 3.14 means for each extra .001" extra/above nominal Bore dimension as above, the ring end gap opens around .003" (Pi)....
and those rings typically show an OOTB Ring End Gap with NO filing on a .030: Bore of about .016" to .018"..... meaning if yours are .024" - .018" = .006"/.003" = 2 or .002" and maybe your Bores are already at .032" ?

Just saying here....
we like to run the L2355's up around .003" minimum as well for safety.... meaning we typically have to take the bores over nominal Bore dimension by .002" or so and those (.024") end gaps are typically what we see ?
Check closely.... yours may already be there ?

Another factor;
Was the Engine Honed with a Torque Plate ?
A Torque Plate when installed usually "distorts" the Cylinders .001" to .0015"..... and in severe cases(thin walls) can do so .003" or more, the same way the Cylinder Head distorts the Cylinders when it's installed ?

Many Shops that don't have a T/Plate for a BB Mopar just ADD an extra .001" or so clearance when Honing as a safety factor to compensate ?
and....
that may be why you are seeing the .024" end gaps ?  because they may have added the extra clearance for NO T/Plate and you do in fact have .003" Piston clearance ?

Correction they are .026 right out of the box. Block was not honed in with torque plates either. I do not own a bore gauge so I only have the info wrote down. And that was pistons were 4.379 and finished bored at .381. I pulled a piston and with my Ebay digital mic I get 4.377 at bottom of skirt below coating. Middle of pin get .378

.026" ring end gap right out of the box.... if accurate ? and I am NOT doubting you.... IMO, would be indicative of a somewhat bigger Final Bore dimension than the 4.381" mentioned ?

Try this if you can ?
remove one Piston.... and carefully remove the rings from that Piston.
Then insert the Piston into it's Bore upside down.... putting the Piston into the Bore head first about 1/2 down into the cylinder while you hold onto the Connecting Rod.
Then using a Feeler Gauge.... do you have one of those ?  
Press the Piston skirt tang on one side tightly against the Cylinder.... and while doing so insert a .003" Feeler Gauge strip on the other side of the Piston Skirt Tang up between the Cylinder Wall and Piston Skirt Tang and see if it will go in ? or a .002" strip... or a .004" strip... whatever fits ? Oil helps to avoid galling the Piston skirt coating.
Suffice to say.... whatever feeler gauge strip fits ? that's your Piston to Wall clearance.

Ok so the feeler gauge story, With the piston down in bore to about midway threw pin I can get a .0025 gauge in pretty smooth. I can get a 003 in with a little wiggling but it feels more like a inference fit. verdict?

[BSB67]

If you can get 0.003" in there, that means you have 0.003".  A feeler gauge won't fit if there is an interference fit.

[Challenger340]

[/quote]
Ok so the feeler gauge story, With the piston down in bore to about midway threw pin I can get a .0025 gauge in pretty smooth. I can get a 003 in with a little wiggling but it feels more like a inference fit. verdict?
[/quote]

Bingo
There's your Piston to Wall clearance, run it....

[NavyDad]

Is that .026 ring clearance going to cause blow by? Seems like to much.

[Rayzor]

Good question. Anyone have any input on max ring gap?

[Challenger340]

Is that .026 ring clearance going to cause blow by? Seems like to much.

In my experience NO.... because the top ring is exposed to far more heat/expansion which closes up the ring end gap substantially.   
Seen LOTS run that way, doesn't seem to affect them at all.

[alfaitalia]

This page has some interesting info on ring gaps....

https://www.aa1car.com/library/ring_end_gap.htm

[firefighter3931]

My old 446 used the older (non coated) 2355's and we set the wall clearance at .005 using the one thou clearance for every inch of bore diameter rule of thumb. This was a street/strip type build. I believe the newer coated version does not expand as much as the older non-coated piston so you should be good to go with the measured clearances.

I don't see an issue with that ring gap either....


Ron