Open Road

Greetings, there is a TSB for early GTS engines regarding the connecting rods. Porsche recommends replacing them with a later style with a reinforced section near the bearing. I am faced with opening my GTS and replacing the rods when I drill the piston lands for drain oil back holes.

My question is regarding OEM vs Aftermarket connecting rods. Is there an advantage to going aftermarket? Are they lighter and cheaper?

I’m n the same questionable phase on two gts engines and am researching. Have the 2R on hand for one but looking at options for the 2nd.

No, seriously. Interested in the answers but don’t have anything other than barely formed opinions.

Looks like GTS rods are ~$300 each. Call it $2500 for the set with new nuts. But, that might be an out-of-date price.

I think a set of Carrillo rods will be no less than that. (I could look at my pre-2020 receipt, but that as useful as the price of gas in 1971.)

Add to the current cost of a set of Carrillo rods, the cost of a thread stretch gauge and needing about 4 times as long to assemble the short block as a result.

But, IIRC the Carrillo rods were lighter than stock.

Well.... yesterday there was a set of OEM rods available, they just came back into stock. I was leaning toward those but I delayed too many hours and now they are gone, Price ~$220each. So now there are no OEM's available for the moment.

lighter rods won't really help with the heavy piston's and wrist pins from factory. I'd recommend going stock if you can find them.
Often this type of thread reminds others, oh hey I need to order some rods. holy crap there is only one set available? I better grab them now~!

Thanks for the insight to use the OEM rods @maddog2020 .

I was able to find a dealer that was able to confirm there is a set available in Germany. So I ordered them and will need to wait to see if they actually arrive in 4-6 weeks. I'll update the post when I have them.

The conn rod replacement is part of the motor rebuild to address excessive oil consumption as many GTS owners experience. I plan to replace the rods, headgaskets/valve guides, and drill the pistons. I start a new thread on that work since I have many questions.

@maddog2020 do you have a recommendation of aftermarket pistons for the GTS? I figure the machining costs to drill into the existing pistons might make aftermarket a viable option

have you opened up the engine yet? drilling factory pistons is going to be the best option. once you get into aftermarket pistons, then you are going down the rabbit hole that entails coatings, tolerances outside the stock tolerance groups and th list goes on, until you start looking at bore condition and that is a whole other rabbit hole on its own.

maddog2020 wrote: ↑Tue Aug 22, 2023 3:48 pm have you opened up the engine yet? drilling factory pistons is going to be the best option. once you get into aftermarket pistons, then you are going down the rabbit hole that entails coatings, tolerances outside the stock tolerance groups and th list goes on, until you start looking at bore condition and that is a whole other rabbit hole on its own.

This X 3 decades of 928 mods -^

You can only use actual Mahle (Germany (Porsche)) pistons in a 928 block. All the other options for coatings or even Mahle Motorsport (US) pistons will probably kill the motor. My “machine shop” guy has tried all the combinations in 3 decades of building the inline-4 motors: It’s either Porsche pistons or throw it all away and Nikasil the block.