Any machinists or LS1 gurus around here?

[FoFittyFoSS]

I'm wanting to upgrade my rod bolts in my 98 LS1 motor as they are known to be a weak link. I'm getting conflicting info on the need to resize the rods. They are fractured cap rods so they are not resized in the typical fashion. They can however be honed, and a slightly thicker bearing be used, (.002" I believe). Any ideas?

[squirrel]

Re: Any machinists or LS1 gurus around here?

You'd almost want to swap bolts and measure them to see how round they are, eh? Probably folks have gotten different results...probably because some engines got abused more than others?

You could see how round they are before swapping bolts too..

[FoFittyFoSS]

Re: Any machinists or LS1 gurus around here?

Yeah lots of different opinions on LS1 tech. Don't know if I trust the accuracy of my measurements and didn't want to have to pull the heads. Engine is on a stand right now. Problem with the bigger forums are lots of "experts" with different answers, it gets difficult to figure out who is in the know, and who is blowing smoke. Pretty sure the guys swapping there rod bolts are running them hard.

[squirrel]

Re: Any machinists or LS1 gurus around here?

The only way I know of to measure the rod bores accurately is on a rod bore gage, which is usually attached to the resizing hone... at the machine shop....

[fabricatordave]

Re: Any machinists or LS1 gurus around here?

press in rod bolts or cap screw type?????????????

[SpiderGearsMan]

Re: Any machinists or LS1 gurus around here?

those are powdered metal rods
I would go with a nice H beam rod from the aftermarket
have not seen em fail in the dealer after 12 years of the LS

[Brad54]

Re: Any machinists or LS1 gurus around here?

Going to bigger bolts in the LS1 rods is a lame fix.
As you said, the rods can't really be "resized" because they're the fractured caps. Honed with the slightly bigger bearings... seems like too much to chance there.
You'll have money in the machining, and you'll have a bunch of money in the new fasteners.

Plus, when you're done, they're still the powdered metal rods. Stock, the rods are rated by GM for 500 horsepower.
If you just can't bring yourself to buy good rods, buy someone else's take-out rods. In 2005, GM put bronze bushings in the pin end, with the beefier bolts.

You'd be better off buying cheap import I-beam or H-beam rods with decent fasteners for nearly the same money.

-Brad

[min301]

Re: Any machinists or LS1 gurus around here?

those are powdered metal rods
I would go with a nice H beam rod from the aftermarket
have not seen em fail in the dealer after 12 years of the LS

This is a good recommendation, if you ask me...

[TC]

Re: Any machinists or LS1 gurus around here?

Actually the HP limit on the rods is more like 700hp, but the real factor is the rpm you'll be spinning, 7000+ and your going to want to change the rod bolts, and if your making 600hp+ at that point I'd change the rods to.

People have to realize that a crate motor LS1 makes 400hp and even NOS in it instructions says that a LS1 can take a 150 shot with no problem, so right their the motor would be making 550hp. But then a lot of this might have to do with the traction your getting and how much load is being put on the parts.

[SpiderGearsMan]

Re: Any machinists or LS1 gurus around here?

if you are in there , doesn't hurt to change the rods
unless you are broke like me , but then you would not have a fancy LS1 - you would be doing someone elses

[std]

Re: Any machinists or LS1 gurus around here?

If you're going with the same size bolt but better quality, and torque it to the factory spec, why would you need to resize it? What would make the bore any different then what it was?

I'd put the new bolts in and run it.

[TC]

Re: Any machinists or LS1 gurus around here?

If you're going with the same size bolt but better quality, and torque it to the factory spec, why would you need to resize it? What would make the bore any different then what it was?

I'd put the new bolts in and run it.

I actually feel the same way. How does changing the bolts change the bore size??

[Tom Slick]

Re: Any machinists or LS1 gurus around here?

If you're going with the same size bolt but better quality, and torque it to the factory spec, why would you need to resize it? What would make the bore any different then what it was?

I'd put the new bolts in and run it.

I actually feel the same way. How does changing the bolts change the bore size??

Normally you would press them out and it's an interference fit, requiring some juice and no great way to hold the rod still while you pressurize the sides. I guess it could make the rod part of the big end of the rod not a perfectly round half any more. How close is "good enough" when it goes to 7000 after a missed 3rd gear shift?

[FoFittyFoSS]

Re: Any machinists or LS1 gurus around here?

Thanks guys, good things to think about here. As far as the bolts are concerned, they are the same size, but the torque specs are higher because they are stronger bolts. This is a 1998 LS1 and the rod bolts were different than later years. Don't mind building the bottom end but If it's possible to just slap in bolts versus pulling heads, ete. etc. That's what I would rather do. From what I've read these are the strongest production rods GM has ever produced. The rod bolts are the week spot. They are shotpeened from the factory I'm told. Hell, it's on a stand, I'm just gonna take the damn thing appart.

[SpiderGearsMan]

Re: Any machinists or LS1 gurus around here?

arp wants you to torque with a stretch gauge
powder meatal came in about 1993 on the northstars
head and main bolts are torque to yield - which means - throw em away after you use em once