6.125 rod and piston question
06-19-2019, 11:28 AM
#1
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6.125 rod and piston question Hello, I'm new and I hope I posted this in the correct place. I'm new to LS engines also but I am researching and learning. I'm building a 6.0 that I'm going to bore for 6.2 pistons. My question is if I run a 6.125 rod instead of the stock 6.098 rod can I mill the difference (.027) off the top of the pistons instead of buying custom pistons with relocated pins?? I searched for hours on the interned and found nothing except the custom piston option. I am going to run the engintech stock, cast P5076 pistons. No boost, or NOS, just pump gas, and I'm not going to spin it, it's going in a 78 C10 show truck that will not drive much. I'm looking in to running the 6.125 rod since I want to run a floated rod and new 6.098 rods are very high compared to the 6.125. Any ideas if milling .027 will be ok? Thanks..
06-19-2019, 11:36 AM
#2
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The bigger problem you'll find is the 6.125 rods all have .927 pins. Take a look at our new Pro LS offerings. We've got combinations for every rod (with common pin) and 4" stroker versions too at a good price.
06-19-2019, 11:41 AM
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Thanks for the reply, I will look into that. I did see that pin size is going to be an issue also. It's hard to find a shop here in the Dallas area that does the hone and bushing install on press rods, and re-size also so if I have to buy new ones it may as well be the 6.125's.
06-19-2019, 11:52 AM
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That is correct. Rods these days have become relatively inexpensive compared to the cost of bushing a rod. The other problem is the powdered metal rods have cracked caps that makes it hard to find bearings when you resize. The least expensive LS 6.125 rod is the Scat SCA-6612521.
06-19-2019, 11:57 AM
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That is correct. Rods these days have become relatively inexpensive compared to the cost of bushing a rod. The other problem is the powdered metal rods have cracked caps that makes it hard to find bearings when you resize. The least expensive LS 6.125 rod is the Scat SCA-6612521.
06-19-2019, 12:04 PM
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No problem. Standard bore mid-compression piston for a 6.2 is part number SUM-2999274065-2. They run $599 a set and the matching rings are another $99. They aren't listed on the site yet as the 6.2L lineup is new to the Pro LS offerings, but will be within a couple weeks. Here's a link to the video on them if you want to spend more time on the internet today. Let us know the chamber volume you're running and we'll double check the compression ratio for you.
06-19-2019, 12:37 PM
#7
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No problem. Standard bore mid-compression piston for a 6.2 is part number SUM-2999274065-2. They run $599 a set and the matching rings are another $99. They aren't listed on the site yet as the 6.2L lineup is new to the Pro LS offerings, but will be within a couple weeks. Here's a link to the video on them if you want to spend more time on the internet today. Let us know the chamber volume you're running and we'll double check the compression ratio for you.
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06-19-2019, 01:38 PM
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Our 6.2's are primarily designed with a 2cc dome to hit 11 out of the box with a 70 chamber. A 63cc chamber would net 11.9:1 which sounds a little stout for what you are wanting to do maybe. A flat top with valve reliefs would get you about 11.25:1. The DSS DMS-1820CSX-4065 would be your least expensive option there. Mahle is a bit more expensive, but MLE-930223165 would fit the bill too.
06-19-2019, 01:43 PM
#9
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Our 6.2's are primarily designed with a 2cc dome to hit 11 out of the box with a 70 chamber. A 63cc chamber would net 11.9:1 which sounds a little stout for what you are wanting to do maybe. A flat top with valve reliefs would get you about 11.25:1. The DSS DMS-1820CSX-4065 would be your least expensive option there. Mahle is a bit more expensive, but MLE-930223165 would fit the bill too.
06-20-2019, 08:04 AM
#10
If you won't be beating on this engine, and your only reason for wanting aftermarket rods is for floating pins, you can hone factory rods without bushing them. Just be sure to address pin oiling (usually a drilled top/center hole and two bottom holes, one on each side of the beam). It's been done successfully on many, many, high horsepower BBC 's that I know of. Heck, that's "the way it was" back in the 60's and 70's before aftermarket bushed rods became more available and affordable.
06-20-2019, 11:32 AM
#11
Our 6.2's are primarily designed with a 2cc dome to hit 11 out of the box with a 70 chamber. A 63cc chamber would net 11.9:1 which sounds a little stout for what you are wanting to do maybe. A flat top with valve reliefs would get you about 11.25:1. The DSS DMS-1820CSX-4065 would be your least expensive option there. Mahle is a bit more expensive, but MLE-930223165 would fit the bill too.
06-20-2019, 12:52 PM
#12
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If you won't be beating on this engine, and your only reason for wanting aftermarket rods is for floating pins, you can hone factory rods without bushing them. Just be sure to address pin oiling (usually a drilled top/center hole and two bottom holes, one on each side of the beam). It's been done successfully on many, many, high horsepower BBC 's that I know of. Heck, that's "the way it was" back in the 60's and 70's before aftermarket bushed rods became more available and affordable.
06-20-2019, 01:25 PM
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A very well rounded line. 4.8, 5.3, 5.7, 6.0, 6.2 displacements. Boost and mid compression pistons each. 4 sizes each. Gen. 3 rod, Gen. 4 floating rod, 6.125 rod and 4" stroke 6.125 rod each. Something for everyone basically.
06-20-2019, 04:32 PM
#14
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If you won't be beating on this engine, and your only reason for wanting aftermarket rods is for floating pins, you can hone factory rods without bushing them. Just be sure to address pin oiling (usually a drilled top/center hole and two bottom holes, one on each side of the beam). It's been done successfully on many, many, high horsepower BBC 's that I know of. Heck, that's "the way it was" back in the 60's and 70's before aftermarket bushed rods became more available and affordable.
06-20-2019, 08:04 PM
#15
.002 is a little loose for my tastes. I wouldn't go over a thou. One thing that I think you're not thinking about.........is piston retention. Without the press fit rod, you're going to need spirolocks or circlips. That requires machining the piston. Something that I would only trust the best of the best to do. That's not plain old boring or honing. It's fairly intricate. And.......as your current pins are giving you about twice the clearance you should have, that requires order new pins of the correct size. After all that, you're at the cost of an offshore set of bushed rods. Or spending even more to have the factory rods bushed, then fit to the pins. All of this......to alleviate something that is no problem at all and has been run for decades and decades to monumental rpm, and survived a half million miles of street time..........there's utterly no issue at all with press fit pistons. Think of it this way: a press fit piston is still floating on the pin at both ends. By floating them, you're just adding an extra articulation point in the middle. But the outer ends are still floating.
06-20-2019, 08:14 PM
#16
Thinking more about this, another option may be to just order larger pins, and have them offset fit to the pistons by the .027". Sort of like offset grinding a crank back in the day before stroker cranks became so economical.
06-20-2019, 09:40 PM
#17
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I'll sure consider staying pressed, most of my old motors were pressed and lasted for years. My new pistons do have the retainer grooves and locks though, I suppose I could use the original .945 pins and hone the small rod end to get the half a thou clearance.
06-21-2019, 08:52 AM
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Nevermind on that as soon as I posted that I realized I can't use my original .945 pins in the new .943 pistons. lol
06-21-2019, 04:16 PM
#19
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Well I used a telescoping gauge and actually measured the small end hole of my factory rods, so I'm getting .943 which makes sense since a .945 pin was pressed in. So my new pistons with .943 pins slip right in. I should have measured in the first place but I assumed the hole was .945 since the pin was .945. New pistons do have the locks so I believe this should work.