How tight is too tight for wrist pins?
04-05-2015, 07:39 PM
#1
Burning Brakes
Thread Starter
How tight is too tight for wrist pins?
I bought a set of LR wrist pins for my new engine. I have two sets of pistons and am planning to use 3 from one and 1 from the other as this gives the best match in weight and size.
The problem is that while the new pins slide freely in the three pistons, but I had to use force on the fourth. After working it for a while it loosened up enough to where I can press it in/out with one finger, and rotate it in the bore with some effort. of course the piston had been heated by my hand by then. All the pins are the same. The other pistons in the second set are the same. The old pins slide in/out by themselves.
Will it free up or do I have to ship the piston out for honing?
The problem is that while the new pins slide freely in the three pistons, but I had to use force on the fourth. After working it for a while it loosened up enough to where I can press it in/out with one finger, and rotate it in the bore with some effort. of course the piston had been heated by my hand by then. All the pins are the same. The other pistons in the second set are the same. The old pins slide in/out by themselves.
Will it free up or do I have to ship the piston out for honing?
04-05-2015, 10:24 PM
#2
Rennlist Member
Yes, something needs to be done. Since it is not a press fit, it needs proper oil clearance.
I bought a set of LR wrist pins for my new engine. I have two sets of pistons and am planning to use 3 from one and 1 from the other as this gives the best match in weight and size.
The problem is that while the new pins slide freely in the three pistons, but I had to use force on the fourth. After working it for a while it loosened up enough to where I can press it in/out with one finger, and rotate it in the bore with some effort. of course the piston had been heated by my hand by then. All the pins are the same. The other pistons in the second set are the same. The old pins slide in/out by themselves.
Will it free up or do I have to ship the piston out for honing?
The problem is that while the new pins slide freely in the three pistons, but I had to use force on the fourth. After working it for a while it loosened up enough to where I can press it in/out with one finger, and rotate it in the bore with some effort. of course the piston had been heated by my hand by then. All the pins are the same. The other pistons in the second set are the same. The old pins slide in/out by themselves.
Will it free up or do I have to ship the piston out for honing?
04-06-2015, 08:16 AM
#6
Three Wheelin'
If edges of the pin opening have even slightest deformation (for example from removing the pins), these are exactly the symptoms that you are describing.
I would first check the pistons for damage and deburr the edges.
I would first check the pistons for damage and deburr the edges.
04-07-2015, 11:47 AM
#7
Burning Brakes
Thread Starter
Thanks.
It is definitely too tight when centred as well so it can't bee the edges. I measured all my OEM wrist pins.
They are 23.90mm all of them. The manual says 24mm - 0.004mm so I would consider them to be on the small side but within spec. These pins fit without issue. The LR pins must be slightly larger, but I'v not yet mic'ed them.
I've found two good 24mm reamers. What do you think? Could I possibly be able to use them to open the bore slightly? I could use my lathe as a guide to hold the piston and reamer straight and true, but I would turn the reamer by hand. (I could use an old piston pin to set up the piston and slide it off of the pin onto the reamer when I'm satisfied with the setup).
It is definitely too tight when centred as well so it can't bee the edges. I measured all my OEM wrist pins.
They are 23.90mm all of them. The manual says 24mm - 0.004mm so I would consider them to be on the small side but within spec. These pins fit without issue. The LR pins must be slightly larger, but I'v not yet mic'ed them.
I've found two good 24mm reamers. What do you think? Could I possibly be able to use them to open the bore slightly? I could use my lathe as a guide to hold the piston and reamer straight and true, but I would turn the reamer by hand. (I could use an old piston pin to set up the piston and slide it off of the pin onto the reamer when I'm satisfied with the setup).
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04-10-2015, 02:32 AM
#8
Rennlist Member
it's a quick fix with a rod machine in an automotive machine shop. Isn't there one available to you? They get honed, not reamed. Ask them to fit all the new pins to your pins to your pistons: .001-.0015" (inches) clearance.
