1.094 vs 0.990 Piston Pins- Weight Saving or Not?

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JGC403

JGC403

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Is there actually a weight savings when switching to the smaller Chevy size pins when all is said and done? I had some custom pistons made about 15 years ago or so and I was considering switching over to the smaller pin size, the representative of the manufacture said that it was pretty much the same weight, because of the extra material in the piston for the smaller pin that it didn't save any weight. So is this true? Any engine buiders out there have experience using both pins sizes in Mopar Big Blocks, when adding everything up to balance the engine is the weight savings with the smaller pin cancelled out by more material in the piston?
 
If you do it correctly you save a bunch of weight. But you have to know how to do it. Taking a factory 440 rod and bushing it down to 0.990 isn't the correct way.
 
Pin metal is very strong and usually very heavy, the additional AL to neck down to a .990 is nothing. I would think the .990 pin has a much larger selection as its a very popular platform, BBC. As well as the rod selection and price Chevy vs Mopar specific.
 
I have a set of ross pistons for .990 pin, that are 400+ grams lighter than the trw's they are replacing.
 
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I was able to find some weights on rods and piston pins but not the piston. I think the weight savings is very little, if any.

Molnar Connecting Rods H-beams
-6.760" length
-Big End Bore: 2.500”
-Big End Width: 1.017”
-Pin End Width: 1.140”
-Bolt: 7/16 ARP2000
-Pin=
-1.094"= 852
-0.990"= 849

So with the rods, same manufacturer everything the same width, length, even the bolts. Between the 1.094 and the 0.990 pin there is only a 3 gram difference. Sure there are lighter rods out there but I wanted an apples to apples comparison.

Mahle piston pin:
-Length- 2.52"
-Material- Steel

-1.094= 153 grams
-0.990= 148 grams

So again same manufacturer same length. There is only a 5 gram difference between the pins.

JE piston pins:
-Series 51
-Length-2.930"
-5115 low carbon steel

-1.094= 170 grams
-0.990= 151 grams

Here your up to a 19 gram difference. But I still think the weight savigs would be used up with the extra aluminum in the piston.

The only thing I can't find is the exact same pistons with the different pin size. To compare.

So when everything is kept as similar as possible. If you were building an engine and you had the choice to use either pin I don't think there is actually a weight savings. In some instances there is an advantage to using the smaller pin, for example if you were building a stroker and the pin is close to the oil ring a smaller pin would get the oil ring a little futher away. But for weight saving I don't think there is any.
 
Utilizing the .990 pin allows use of a big block Chevrolet connecting rod which have 2.200 (vs. 2.375) rod journals. The smaller rod journal helps with clerance issues when you get into the 4.150 or greater stroke crank, especially in a low deck application. The addition benefit of weigh savings and component cost/availability make it a better deal than using stock 1.094/2.375 stuff.


JGC403 said:
I was able to find some weights on rods and piston pins but not the piston. I think the weight savings is very little, if any.

Molnar Connecting Rods H-beams
-6.760" length
-Big End Bore: 2.500”
-Big End Width: 1.017”
-Pin End Width: 1.140”
-Bolt: 7/16 ARP2000
-Pin=
-1.094"= 852
-0.990"= 849

So with the rods, same manufacturer everything the same width, length, even the bolts. Between the 1.094 and the 0.990 pin there is only a 3 gram difference. Sure there are lighter rods out there but I wanted an apples to apples comparison.

Mahle piston pin:
-Length- 2.52"
-Material- Steel

-1.094= 153 grams
-0.990= 148 grams

So again same manufacturer same length. There is only a 5 gram difference between the pins.

JE piston pins:
-Series 51
-Length-2.930"
-5115 low carbon steel

-1.094= 170 grams
-0.990= 151 grams

Here your up to a 19 gram difference. But I still think the weight savigs would be used up with the extra aluminum in the piston.

The only thing I can't find is the exact same pistons with the different pin size. To compare.

So when everything is kept as similar as possible. If you were building an engine and you had the choice to use either pin I don't think there is actually a weight savings. In some instances there is an advantage to using the smaller pin, for example if you were building a stroker and the pin is close to the oil ring a smaller pin would get the oil ring a little futher away. But for weight saving I don't think there is any.
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TRW rat pin is 151 grams. TRW bbm pin is 225, the heaviest in my trw book. Guess which is the heaviest piston in my old trw book? The low compression 440 piston.
 
Jeremiah said:
Utilizing the .990 pin allows use of a big block Chevrolet connecting rod which have 2.200 (vs. 2.375) rod journals. The smaller rod journal helps with clerance issues when you get into the 4.150 or greater stroke crank, especially in a low deck application. The addition benefit of weigh savings and component cost/availability make it a better deal than using stock 1.094/2.375 stuff.
Click to expand...

You can get rods with Mopar journals and either Mopar size or Chevy sized pins.

Molnar had the bobweight listed for their cranks. Both cranks are the same stroke one had a Mopar rod journal size the other had a chevy rod journal size. The bobweight listed for both those cranks was the same. They didn't have the weight of the crankshafts listed.
 
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The only way mopar pins weigh nearly the same as rat pins, is if they are thinner wall. The factory stuff is very heavy, so factory replacement is heavy. The goal is to get lighter parts. Most of the newer pistons for mopars are designed around 990 pins.
 
33IMP said:
TRW rat pin is 151 grams. TRW bbm pin is 225, the heaviest in my trw book. Guess which is the heaviest piston in my old trw book? The low compression 440 piston.
Click to expand...

33IMP said:
The only way mopar pins weigh nearly the same as rat pins, is if they are thinner wall. The factory stuff is very heavy, so factory replacement is heavy. The goal is to get lighter parts. Most of the newer pistons for mopars are designed around 990 pins.
Click to expand...

Your not taking into consideration bore size. What is the bore size of the "rat pin" and whats the bore size for the BBM pin. Bigger bore is going to have a longer pin typically. That is why I looked up pins that are the same length just the different diameters. Cause If I have piston made for a Mopar, but the only difference is if I went with the Mopar pin size or Chevy, the pins will be the same length.
 
JGC403 said:
Your not taking into consideration bore size. What is the bore size of the "rat pin" and whats the bore size for the BBM pin. Bigger bore is going to have a longer pin typically. That is why I looked up pins that are the same length just the different diameters. Cause If I have piston made for a Mopar, but the only difference is if I went with the Mopar pin size or Chevy, the pins will be the same length.
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Im comparing the rat pin that im using in the ross pistons designed to use a rat pin, 151 grams, with the stock, or trw pin used in a stock 440. My point is, if you use stock length mopar stuff, a LOT of weight can be saved if the pistons are designed for the shorter, lighter pin. Exact same bore size.
You want light? Put in small block chevy pins. My tool steel pins in my small block are 85 grams.
 
33IMP said:
Im comparing the rat pin that im using in the ross pistons designed to use a rat pin, 151 grams, with the stock, or trw pin used in a stock 440. My point is, if you use stock length mopar stuff, a LOT of weight can be saved if the pistons are designed for the shorter, lighter pin. Exact same bore size.
You want light? Put in small block chevy pins. My tool steel pins in my small block are 85 grams.
Click to expand...

I don't care about stock stuff it's getting replaced regardless. What I am saying is if I have a set of custom pistons made with either the Mopar sized pin or the chevy sized pin they would be the same length and therefore the only thing that comes into play would be the diameter. And the weight savings is a wash.
 
JGC403 said:
I don't care about stock stuff it's getting replaced regardless. What I am saying is if I have a set of custom pistons made with either the Mopar sized pin or the chevy sized pin they would be the same length and therefore the only thing that comes into play would be the diameter. And the weight savings is a wash.
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You have convinced yourself that more metal weighs the same as less metal. I wont change your mind.
 
I recently bought a used set of Crower rods on Marketplace.

The seller said they were all built to Mopar stock specs.

I got them home and they had .927 Chevy pin bores. I got back to the seller...sez he had no idea. He offered to help pay for any machine work needed to fix the issue.

They are at my machine shop right now getting the pin bores machined to match my new RaceTec pistons.

I weighed a .927 pin and my stock .984 pins and there was 8 grams difference...but the wall thickness is not the same.

In a stock application thats not much.
 
So I went to the Ross Pistons website and looked at two Mopar pistons #99499 & #99500. Both exactly the same except one has a .990 pin and the other has a 1.094. If anyone is curious enough they can do the same.
 
IQ52 said:
So I went to the Ross Pistons website and looked at two Mopar pistons #99499 & #99500. Both exactly the same except one has a .990 pin and the other has a 1.094. If anyone is curious enough they can do the same.
Click to expand...

Thank you that is what I was looking for. Didn't think of going to a manufacturers website, was looking at Summit, and Mancini. Couldn't find what I wanted there.

So the piston with the Chevy pin is slightly heavier at 563 grams. With the Mopar pin 555. So with the pins the Chevy size is 709 grams. The Mopar 713 grams. So they are very close. The way that people talk about switching to the Chevy pin there is automatically a lot of weight savings. But looks like with a typical off the shelf piston that isn't the case. I'm not saying that it doesn't all add up a couple grams here and there. So get whatever is cheaper.
 
You are so focused on one item that you don't see the big picture.
 
AndyF said:
You are so focused on one item that you don't see the big picture.
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Really, what's the big picture? I'm using a stock cast iron crankshaft for this build. I'm trying to reduce rotating weight. Trying to balance cost vs weight reduction. The original question was if there was any weight savings going to the Chevy size pin, there is but not a lot. Connecting rod is a little lighter. It all adds up. Never said I wouldn't use the Chevy pin size. Just wanted to see if there was actually any weight savings.
 
IQ52 said:
So I went to the Ross Pistons website and looked at two Mopar pistons #99499 & #99500. Both exactly the same except one has a .990 pin and the other has a 1.094. If anyone is curious enough they can do the same.
Click to expand...
When Diamond puts a bigger hole in their piston, it gets lighter.

The question is; does the piston manufacturer actually lighten/removes more material from the same piston when it has a smaller pin bore, and does the rod manufacturer make the pin end smaller for the smaller pin. If the piston and rod manufacturers don't do this, all else being equal on the pin other than diameter, the net reciprocating weight difference is small.

Do what is easiest. I wouldnt go out of my way chasing one or the other.
 
JGC403 said:
Really, what's the big picture? I'm using a stock cast iron crankshaft for this build. I'm trying to reduce rotating weight. Trying to balance cost vs weight reduction. The original question was if there was any weight savings going to the Chevy size pin, there is but not a lot. Connecting rod is a little lighter. It all adds up. Never said I wouldn't use the Chevy pin size. Just wanted to see if there was actually any weight savings.
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If you are using a stock cast crank then it doesn't matter. Just use what fits.
I assumed you were building a stroker engine. I haven't used a Mopar pin size in an engine in over 20 years but I don't build cast crank stocker stuff. So carry on.
 
Used to work in shop where I could stay over and work on my own stuff. I made H13 pins in 1.094 size but, thin wall and justified it as larger diameter being stronger. It went into a 440 with Wisecco pistons and stock forged crank, with shotpeened stock rods. 7500 rpm was available but, not necessary because, the heads would not move the air.
 
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