5100 series Chromoly wrist pins

Are the 5100 series standard type wrist pins good for 700 HP street type stroker build? Im looking at using a .990 dia .180 wall pin in a 545 with SR-71 heads with hyd roller

poweredbyford wrote:Are the 5100 series standard type wrist pins good for 700 HP street type stroker build? Im looking at using a .990 dia .180 wall pin in a 545 with SR-71 heads with hyd roller

They are suitable for that much HP and a whole lot more.

Ok thanks, i cant seem to figure out why the manufacturers act like they're a stock replacement type pin not good for alot of HP.

Probably because most of them are .150 wall?

Mark O'Neal wrote:Probably because most of them are .150 wall?

That's my guess too.

5100 steel wrist pins are made in China by the millions and used by "almost" every aftermarket piston manufacturer. They have a near zero failure rate for the quantity made. Using a thicker wall pin will reduce the flex which is the major cause of pin failure ( by itself). Using a higher quality steel ( read more expensive) will buy increased cycle life but pin failure from fatigue life is very uncommon so extending fatigue life could be a waste of money. Horsepower / power adders, piston weight and RPM should be the factors considered when choosing a pin and wall thickness.

I've made them from 8620. 9310, and 5115 over the years and had no issues with any of them. We did use pins from Taiwan that were 9310, the quality was quite good. One piston manufacturer simply states that theirs are 52 Series. I assume a variety but I never cared enough to ask.

Most limit OTS pistons to a .150 wall. Autotec has .180 and .200 available (no cost upgrade) 51 series. Unfortunately they use weird lengths so you can't use them on anyone else's pistons.

Also, to sort of address your question, 8620 has better wear resistance than 9310, but 9310 is stronger than 8620.

Mark O'Neal wrote:I've made them from 8620. 9310, and 5115 over the years and had no issues with any of them. We did use pins from Taiwan that were 9310, the quality was quite good. One piston manufacturer simply states that theirs are 52 Series. I assume a variety but I never cared enough to ask.

Most limit OTS pistons to a .150 wall. Autotec has .180 and .200 available (no cost upgrade) 51 series. Unfortunately they use weird lengths so you can't use them on anyone else's pistons.

Also, to sort of address your question, 8620 has better wear resistance than 9310, but 9310 is stronger than 8620.

What materials are best for thin/taper walled pins for a guy wanting a lighter rotating assembly? How thin is acceptable for the various applications?

dfree383 wrote:

Mark O'Neal wrote:I've made them from 8620. 9310, and 5115 over the years and had no issues with any of them. We did use pins from Taiwan that were 9310, the quality was quite good. One piston manufacturer simply states that theirs are 52 Series. I assume a variety but I never cared enough to ask.

Most limit OTS pistons to a .150 wall. Autotec has .180 and .200 available (no cost upgrade) 51 series. Unfortunately they use weird lengths so you can't use them on anyone else's pistons.

Also, to sort of address your question, 8620 has better wear resistance than 9310, but 9310 is stronger than 8620.

What materials are best for thin/taper walled pins for a guy wanting a lighter rotating assembly? How thin is acceptable for the various applications?

Tools Steel S7, H-11, H-13. For a less expensive version 52100.

We used to use a lot of .090 and .120 wall stuff, but the demand is pretty much gone. If it were me I'd use an H-13 taper wall. Thickness depends on specific applications. Most of them seem to come from Trend.

I will say this. Those of us with cars at Probe all used .150 wall 8620 standard pins up to 17lbs of boost and around 700 FWHP. None of the cars ever had an issue....until we sold them. It's mostly about oil and tune. I do like to use both forced and broached pin oiling wherever I can.

.

From a quality and feature point of view I prefer Molnar......but it depends on what I'm doing. I use everything from a RPM/Scat to Manley/Crower. Molnar gets the beam offset correct for the engine the rod is being used in, as opposed to just shoving a Chevy rod in it and calling it a day. Besides....I like Tom.

In general I think forced ping oiling is nonsense. Fluids always follow the path of least resistance. The path of least resistance is pretty much never a hole drilled from the oil ring groove to the pin, or the rod bearing to the pin. Ford had Roush test our pistons with and without forced pin oiling and they supported that conclusion. The determination was "it didn't make any difference."

A lot of this stuff is opinion and perception, which is why I don't post all that much here. Oh, and the perception part is the reason I put forced pin oilers in the pistons. Not having them, from the customers point of view, is worse than having them and I see no reason to argue the point.

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Mark O'Neal wrote:

dfree383 wrote:

Mark O'Neal wrote:I've made them from 8620. 9310, and 5115 over the years and had no issues with any of them. We did use pins from Taiwan that were 9310, the quality was quite good. One piston manufacturer simply states that theirs are 52 Series. I assume a variety but I never cared enough to ask.

Most limit OTS pistons to a .150 wall. Autotec has .180 and .200 available (no cost upgrade) 51 series. Unfortunately they use weird lengths so you can't use them on anyone else's pistons.

Also, to sort of address your question, 8620 has better wear resistance than 9310, but 9310 is stronger than 8620.

What materials are best for thin/taper walled pins for a guy wanting a lighter rotating assembly? How thin is acceptable for the various applications?

Tools Steel S7, H-11, H-13. For a less expensive version 52100.

We used to use a lot of .090 and .120 wall stuff, but the demand is pretty much gone. If it were me I'd use an H-13 taper wall. Thickness depends on specific applications. Most of them seem to come from Trend.

I will say this. Those of us with cars at Probe all used .150 wall 8620 standard pins up to 17lbs of boost and around 700 FWHP. None of the cars ever had an issue....until we sold them. It's mostly about oil and tune. I do like to use both forced and broached pin oiling wherever I can.

Back in the day...I had a set of Probe custom pistons [Ross] with the C&A H11 pins with .120" wall. Never an issue with the 3.74" stroke and ~ 7,000 rpm jet boat...never an issue. But, after doing a 572" 4.600 x 4.300" drag race deal with the same pin the pin bores looked like shit...at some point you sent me .150" wall pins and the issue went away. Everything is application driven. What is learned is that ...if... a guy wants to get a few gm. of wt. out of the bob wt. don't be looking very hard at the piston pins.

And, as John Winger said (loudly)....."That's a fact, Jack"

Seen a race motor going together quite a few years ago, the builder was using custom ordered Titanium pins. They were almost solid! They did'nt weigh hardly anything. But I always thought that Titanium was a rather brittle kind of material. I don't know if it has the same amount of "flex" that other steel alloy's have before it cracks or breaks, maybe that is why it was so thick? I don't know, but it was interesting to say the least.

Ti has a relatively poor bearing strength. I toyed with putting a Ti "plus" n a .020 thick tool steel shell back in the 80's, but Moe got bored before I got all that far. With the coatings they have today, It's probably a lot more doable.

I'm not all that certain that 30 grams makes all that much difference in usable power output.....or 10 lbs in a crank for that matter.

52100 alloy is "Timken bearing steel" according to many. It is "through hardened" and IMHO a poor choice for pin material. Through hardening makes the material ''glass like" . in structure. In other words when the pin gets to it's yield point , it shatters. It also has a wear problem with synthetic oils. It wears and the pin bore doesn't. As I said before pin flex is the downfall of wrist pins the same as any metal subjected to flex.
For those of you who are on the light weight pin program , think about the additional flex that the thinner pin allows which translates into less power transfer to the crank. I spent several years testing with Nascar teams and light weight pins did NOT produce more power. Once the minimum weight rules were imposed , everybody went to thin wall 927 x 2.250 pins . Now they are .708 x .180 for increased stiffness while maintaining minimum weight. Thickness ( or "modulous of elasticity") is very important even when it comes to C350 material , THE high end steel for wrist pins. Adding a "diamond like carbon coating" will increase pin life by incredible amounts and end pin wear / galling issues completely.