Gen I Connecting Rods in a LS Build
Thread Starter
Joined: Nov 2007
Posts: 413
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From: Albuquerque, New Mexico
Gen I Connecting Rods in a LS Build I actually have an identical post over in the Advanced Engineering Forum. I need to know what modifications are necessary to use Gen I rods in an LS build. I have an expensive, nice set of 6.25" long Crower titanium rods that I was going to use in a Gen I build but got pulled into the allure of building LS motors and have really never looked back. Because the rod length is unusual, I'm not going to get my money out of them by selling them so I might as well look into the modifications that will make them usable for me. Can anyone detail these mods?
Depending on the specs on the rods and the combo you're trying you should have no problems using them . LS rods are an on center design whereas SBC rods have a little offset , some have a little some have more . Old LS builds commonly used 6.125 SBC rods before dedicated rods were made . If your rods are designed for 2.100 journals all you'll need are custom pistons . You won't be able to do a long stroke unless you using a taller deck height as it will push the pin way up into the ring package . I'd like to see pics of these Ti rods , I wish I could afford those .
I have been running 6.125 SBC rods in my boosted 370 since like 2003 with no probs. If you can figure out a piston that will work with the rest of your combo, you should be good to go.
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Verdad Gallardo Thread Starter
Joined: Nov 2007
Posts: 413
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From: Albuquerque, New Mexico
Did you run them right out of the box or was there modifications to perform before you could use them?
Others...don't be concerned with rod length. I have the proper piston part number with the proper compression height to work with the longer rod. My only concern is the rod itself...particularly the offset. It appears from what I the responsed that the factory makes the rod with a pin offset but do the aftermarket companies generally do the same thing. I'm contacting Crower in hopes that the pin is machined on center with these rods.
As long as the window in the piston is wide enough for the rods small end to have clearance on both sides when installed the SB rods will work fine. I typically look for .050 clearance although I have run them tighter. Watch the draft in the forging if the inner pin boss is not machined, you will have less clearance at the top of the boss in that type of piston.
Kurt
Kurt
Thread Starter
Joined: Nov 2007
Posts: 413
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From: Albuquerque, New Mexico
As long as the window in the piston is wide enough for the rods small end to have clearance on both sides when installed the SB rods will work fine. I typically look for .050 clearance although I have run them tighter. Watch the draft in the forging if the inner pin boss is not machined, you will have less clearance at the top of the boss in that type of piston.
Kurt
Kurt
Thanks for the response. I'll check those features.
The biggest difference in sbc rods and ls1 rods is what was stated before...ls1 rods are centered on the big end of the rod. if you look at the rod from the side you will notice a slight offset. What you want to do is do the best you can with moving the rods around to make the rod as centered on the wrist pin as possible so as to not create a lot of side load on the piston. Do this BEFORE pressing the pistons on the rods. You will need to mark them after getting them right. The other difference between the 2 are that sbc rods are chamferred (beveled) on one side of the big end due to the way a sbc crank is machined on the journal. i believe ls1 rods are not at all. On an sbc the chamferred side HAS to face the outside of the rod journal...it won't matter on an ls1. The MOST important thing is to get them as centered as possible on the wrist pin. I have built a few like this and have had no issues. i would not use them on a large stroker motor because of the natural side load on the pistons.
FormerVendor
Joined: Nov 2001
Posts: 3,065
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From: Houston, Tx.
You need to machine the pin end of the rod on the non chamfered side back about .040 and you should be fine on most of these deals. We used to only have SBC rods and you just make them work. The inboard pin boss pistons are tighter to make fit and the older school pistons like Diamonds side ribbed piston models fit old school rods fine with no work due to the wider pin boss spacing.
Thread Starter
Joined: Nov 2007
Posts: 413
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From: Albuquerque, New Mexico
There not much to look at especially compared to the Eagles but they are about 100 grams lighter. You might also notice that there is no chamfer on the big end of the Ti rods...curious. Anyone want to comment on why?
Racer7088 and Taspeed...thanks for your help. I appreciate everyone's input.
Racer7088 and Taspeed...thanks for your help. I appreciate everyone's input.
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
If you have a normal aftermarket crank with a fillet in the corner you will have to have the rods chamfered and the bearings clearanced or narrowed there as well or you might have a bad surprise!
If you are running an OEM GM LS7 or any LSx GM OEM crank with a rolled fillet you don't need a chamfer.
If you are running an OEM GM LS7 or any LSx GM OEM crank with a rolled fillet you don't need a chamfer.
I am in the same boat, as I just purchased some Lunati Pro Mod SBC 6.125" connecting rods and was wondering if there are any more words of wisdom to making SBC connecting rods work with an LS1 w/stock crank and forged pistons?
Last edited by ZexGX; Dec 29, 2010 at 10:48 PM.
Yea that could be a little work if the rods need to be machined to fit an aftermarket crank. Not sure what crank you are looking to use, but check the different compression heights on ls1 pistons and do the math to see if anything off the shelf would work. Like a piston set up for a 4.125 stroke and 6.200 rod etc, etc. It might not be ideal where it ends up compression height wise, but if it's in the hole some a thin headgasket might make it work.
For my LS1 piston/SBC rod combo, there is 0.220" clearance between the piston and the small end of the rod (this is with the small end pushed flush with the piston on one side, so if it was centered it would be 0.110" on each side). Is there some sort of machine work that has to take place? Does the small end of the piston have to be offset a certain amount on the wrist pin when installed? I'm pretty new at rotating assembly knowledge, so any help would be appreciated.
Pistons: Diamond Racing P/N 11503
Rods: Lunati P/N LAE1
Pistons: Diamond Racing P/N 11503
Rods: Lunati P/N LAE1
