Speed-Talk is running on www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Piston pin "end play" ? How much is ok ??

General engine tech -- Drag Racing to Circle Track

Moderator: Team

BillK
Expert
Expert
Posts: 614
Joined: Wed Aug 26, 2009 8:30 pm
Location: Beautiful Southern Maryland
Contact:

Piston pin "end play" ? How much is ok ??

Post by BillK »

Hey guys,

One of my customers has a set of brand new forged pistons that he brought by for me to look at. The pistons use round wire lock type pin retainers. On this set of pistons the pins can move back and forth almost 1/8" Every set of decent pistons I have seen have very little if any movement of the pins.

The rods are full bushed H beam rods.

The place he bought the pistons from is telling him it will be fine. I called one of the piston manufacturers who I use and they basically said the same thing for a street engine.

I am just curious what you guys have seen and what your opinions are on it. I dont feel comfortable with it myself.

Any thoughts ??
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

www.enginerepairshop.com
piston guy
Expert
Expert
Posts: 959
Joined: Mon Sep 10, 2012 1:55 pm
Location: Anaheim, CA

Re: Piston pin "end play" ? How much is ok ??

Post by piston guy »

Bill ,
Wire lock applications always end up with end play because the lock has have enough space to go into the groove and once it snaps down into the groove "some" end play results. "I" see .015 as a minimum and have run as much as .050. .125 is IMHO too much and a .050-.100 longer pin should be used to reduce the play to a "safe" number. I have seen this happen from time to time and the longer pin is a great fix. The other fix is contacting the manufacturer regarding the issue. Hopefully DCal will chime in. He has about double my experience. He said .017-.023 on another thread.
"Spirolocks" Must NOT be run with that much end play EVER. The pin WILL blow the lock out of the piston. Spirolocks should always 0 to .010 MAX end play
ProPower engines
Guru
Guru
Posts: 8121
Joined: Sun Jan 21, 2007 1:16 pm
Location: Victoria BC Canada

Re: Piston pin "end play" ? How much is ok ??

Post by ProPower engines »

BillK wrote: Fri Nov 20, 2020 3:59 pm Hey guys,

One of my customers has a set of brand new forged pistons that he brought by for me to look at. The pistons use round wire lock type pin retainers. On this set of pistons the pins can move back and forth almost 1/8" Every set of decent pistons I have seen have very little if any movement of the pins.

The rods are full bushed H beam rods.

The place he bought the pistons from is telling him it will be fine. I called one of the piston manufacturers who I use and they basically said the same thing for a street engine.

I am just curious what you guys have seen and what your opinions are on it. I dont feel comfortable with it myself.

Any thoughts ??
I have seen this issue as well a few times with pistons bought at a discount or off the internet and were supplied with pins that were too short.
The end result was the round wire lock popped out of the grove and the pin walked out and did a number on the bore before the piston pin boss broke up and the resulting damage to the block it was a complete do over.

These were bought from an internet seller but he bought and assembled all the parts I just bored and decked the block
Real Race Cars Don't Have Doors
User avatar
modok
Guru
Guru
Posts: 2657
Joined: Sun Jun 06, 2010 1:50 am
Location:

Re: Piston pin "end play" ? How much is ok ??

Post by modok »

With tru-arc clips should be .004-.016 end play.
Measure the pin length and check the squareness of the ends of the pins.
Chipster
New Member
New Member
Posts: 40
Joined: Fri Feb 09, 2007 11:21 am
Location: Pitch Forks, ND

Re: Piston pin "end play" ? How much is ok ??

Post by Chipster »

?? Don't round lock need a chamfered end on the pin.
User avatar
modok
Guru
Guru
Posts: 2657
Joined: Sun Jun 06, 2010 1:50 am
Location:

Re: Piston pin "end play" ? How much is ok ??

Post by modok »

probably,
I just read the title and answered. Maybe will read all the words later.
Mark O'Neal
Guru
Guru
Posts: 1507
Joined: Tue Mar 06, 2007 7:23 pm
Location: Torrance, CA
Contact:

Re: Piston pin "end play" ? How much is ok ??

Post by Mark O'Neal »

Chipster wrote: Fri Nov 20, 2020 9:10 pm ?? Don't round lock need a chamfered end on the pin.
Yes.
BCjohnny
HotPass
HotPass
Posts: 1121
Joined: Sun Feb 26, 2006 6:07 pm
Location: England

Re: Piston pin "end play" ? How much is ok ??

Post by BCjohnny »

Maybe further for explanation's sake ....... the chamfer on the pin puts a vector angle pressure on the round wire clip and actually locks it tighter into the groove

FWIW 0.125" is too much, I prefer pin length where the minimum clearance to snug the clip in is enough
"If an honest man is wrong, after demonstrating that he is wrong, he either stops being wrong or he stops being honest." Anon
User avatar
MadBill
HotPass
HotPass
Posts: 14808
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: Piston pin "end play" ? How much is ok ??

Post by MadBill »

Surely 1/8" clearance turns the pin into a tiny, patient battering ram? :?
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
digger
Guru
Guru
Posts: 2066
Joined: Sun Jan 27, 2008 6:39 am
Location:

Re: Piston pin "end play" ? How much is ok ??

Post by digger »

machine a couple spacers if you cant get a longer pin?
User avatar
MadBill
HotPass
HotPass
Posts: 14808
Joined: Tue Nov 15, 2005 10:41 am
Location: The Great White North

Re: Piston pin "end play" ? How much is ok ??

Post by MadBill »

A single 1/8" one would do, but tricky to machine and it would have to be chamfered to lock the clips in place.. :-k
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
User avatar
af2
HotPass
HotPass
Posts: 6692
Joined: Sun Jan 28, 2007 4:42 pm
Location: Grass Valley, CA :Northern Foothills

Re: Piston pin "end play" ? How much is ok ??

Post by af2 »

piston guy wrote: Fri Nov 20, 2020 4:28 pm Bill ,
Wire lock applications always end up with end play because the lock has have enough space to go into the groove and once it snaps down into the groove "some" end play results. "I" see .015 as a minimum and have run as much as .050. .125 is IMHO too much and a .050-.100 longer pin should be used to reduce the play to a "safe" number. I have seen this happen from time to time and the longer pin is a great fix. The other fix is contacting the manufacturer regarding the issue. Hopefully DCal will chime in. He has about double my experience. He said .017-.023 on another thread.
"Spirolocks" Must NOT be run with that much end play EVER. The pin WILL blow the lock out of the piston. Spirolocks should always 0 to .010 MAX end play
Exactly. Even the wire lock will hate the extra clearance. .050" max.
GURU is only a name.
Adam
digger
Guru
Guru
Posts: 2066
Joined: Sun Jan 27, 2008 6:39 am
Location:

Re: Piston pin "end play" ? How much is ok ??

Post by digger »

MadBill wrote: Sat Nov 21, 2020 5:40 pm A single 1/8" one would do, but tricky to machine and it would have to be chamfered to lock the clips in place.. :-k
i'd want symmetry otherwise load transfer is skewed
BillK
Expert
Expert
Posts: 614
Joined: Wed Aug 26, 2009 8:30 pm
Location: Beautiful Southern Maryland
Contact:

Re: Piston pin "end play" ? How much is ok ??

Post by BillK »

Thanks for the replies so far guys. Every piston I have seen with wire locks has had virtually no clearance. We have been doing quite a few late Hemis with Mahle pistons and those locks just barely go in.

I am going to try to get in touch with the piston manufacturer Monday. Part of the problem is my customer bought this entire rotating assembly about 4 years ago . He had a stroke shortly thereafter and is just now feeling good enough to try and put it together. I am going to take the one piston I have off the rod and see if there is a pin available the correct length.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

www.enginerepairshop.com
User avatar
af2
HotPass
HotPass
Posts: 6692
Joined: Sun Jan 28, 2007 4:42 pm
Location: Grass Valley, CA :Northern Foothills

Re: Piston pin "end play" ? How much is ok ??

Post by af2 »

BillK wrote: Sat Nov 21, 2020 9:50 pm Thanks for the replies so far guys. Every piston I have seen with wire locks has had virtually no clearance. We have been doing quite a few late Hemis with Mahle pistons and those locks just barely go in.

I am going to try to get in touch with the piston manufacturer Monday. Part of the problem is my customer bought this entire rotating assembly about 4 years ago . He had a stroke shortly thereafter and is just now feeling good enough to try and put it together. I am going to take the one piston I have off the rod and see if there is a pin available the correct length.
What piston?
GURU is only a name.
Adam
Post Reply