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Piston pin "end play" ? How much is ok ??
Posted: Fri Nov 20, 2020 3:59 pm
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 ??
Re: Piston pin "end play" ? How much is ok ??
Posted: Fri Nov 20, 2020 4:28 pm
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
Re: Piston pin "end play" ? How much is ok ??
Posted: Fri Nov 20, 2020 8:13 pm
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
Re: Piston pin "end play" ? How much is ok ??
Posted: Fri Nov 20, 2020 8:25 pm
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.
Re: Piston pin "end play" ? How much is ok ??
Posted: Fri Nov 20, 2020 9:10 pm
by Chipster
?? Don't round lock need a chamfered end on the pin.
Re: Piston pin "end play" ? How much is ok ??
Posted: Fri Nov 20, 2020 9:22 pm
by modok
probably,
I just read the title and answered. Maybe will read all the words later.
Re: Piston pin "end play" ? How much is ok ??
Posted: Sat Nov 21, 2020 3:51 am
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.
Re: Piston pin "end play" ? How much is ok ??
Posted: Sat Nov 21, 2020 4:15 am
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
Re: Piston pin "end play" ? How much is ok ??
Posted: Sat Nov 21, 2020 2:43 pm
by MadBill
Surely 1/8" clearance turns the pin into a tiny, patient battering ram?
Re: Piston pin "end play" ? How much is ok ??
Posted: Sat Nov 21, 2020 4:38 pm
by digger
machine a couple spacers if you cant get a longer pin?
Re: Piston pin "end play" ? How much is ok ??
Posted: Sat Nov 21, 2020 5:40 pm
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..
Re: Piston pin "end play" ? How much is ok ??
Posted: Sat Nov 21, 2020 6:20 pm
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.
Re: Piston pin "end play" ? How much is ok ??
Posted: Sat Nov 21, 2020 8:30 pm
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..
i'd want symmetry otherwise load transfer is skewed
Re: Piston pin "end play" ? How much is ok ??
Posted: Sat Nov 21, 2020 9:50 pm
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.
Re: Piston pin "end play" ? How much is ok ??
Posted: Sun Nov 22, 2020 12:29 am
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?