[Grandpa#3]

Hello Gents, I need some help. I am tearing down a 1992 968 to replace rod bearings and WYIT things. I have heard the 92 rods are p/poor at best and should be replaced with 951 Turbo Forged Rods. I can't remember what year has the best Forged Rarst Rods. Any help will be greatly appreciated.



Cheers,

Larry

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[Grandpa#3]

Well I got the help I needed real fast. I harp all the time that SEARCH is your friend. I should have remembered my own advise. Thanks anyway if you took the time out to read my post.



Cheers,

Larry

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[Cloud9...68]

Hi Larry,



To what extent are you tearing down your engine? For me, what started as a plan to replace a few leaking seals, maybe rod bearings, and possibly a head refresh, has turned out to be an engine extraction, complete tear-down, with new pistons, rods, ceramic coating of the pistons, combustion chambers, valve seats, and exhaust ports, etc. A very slippery slope, indeed! On the suggestion of Mike Lindsey of Lindsey Racing, I went with Pauter forged rods. I had inquired about the 951 rods, but they're apparently very hard to come by - at the time, anyway, there were none available, so I went with the Pauter's. Plus, I'd heard the 951 rods are pretty heavy, and since I'm planning to track the car extensively, that didn't appeal to me. You might want to give either Mike Lindsey, Pete Fitzpartick of RS Barn, or Karl Poeltl of Racers Edge a call for advice and opinions. Best of luck.

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[jfrahm]

The early 944NA rods, 944.103.101.3 RARAST are nice forged rods and supposedly got used in the late 951. The early 951 rods are supposed to be somewhat stronger, 944.103.110.0 RARAST. They weigh exactly the same as the 101.3 rods (I weighed them.)



Some have found 110.0 rods in later 951 engines and I do not know where the cutoff was. I have found the 101.3 in 1986 NA motors, I do not know where the cutoff is there either. Many said it was much earlier than 1986.



Rods to avoid are the non RARST 944 rods that replaced the 101.3, and the 968 1R rods. The cast 944 rod seems fine in 944NA motors but but not strong enough for boost.



The 1R rods have been bent in 968 and 928GTS engines but there seems to be little info on how this was accomplished. Normal street use does not seem to be a problem. They were replaced with a rod that had more meat in the transition between the beam and the big end.



There are S2 and 2.7NA rods out there too I think, I do not know anything about them.



I recall a TSB that said to replace all the 1R rods in any engine that had a rod cap taken off or something to that effect. There is supposed to be good data on the 968 engine numbers that got the 2R rods. My blue car is supposed to have the 2R rods but i have not looked.



-Joel.

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[flash]

i am just about to venture into this very area. i need to replace my early rods too, and am trying to decide what to put in there. however, i am particularly concerned about the extensive harmonics calculation that went into the mass of the rods, so i am concerned about changing that. it's not something that you would feel, but rather something that could cause other issues that you wouldn't know about until it was too late.



what are the weights on the pauter rods?

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[flash]

jfrahm - above you said to avoid the rod that replaced the 1R rod. why? they did that to correct the stretching problem. was that a typo?

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[jfrahm]

I think you misunderstand. The comma indicates a list.



Avoid:

The non-RARST 944 rods

1R Rods.

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[flash]

ah - got it - i read it as a list, but as avoiding things that replaced both the 101.3 and the 968 1R. the missing semi-colon is what threw me - no worries - thanks

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[jfrahm]

Actually on further thought the 2R rods are pretty meh so you might as well avoid them also. I see little point when there are lots of alternatives. I think they are sintered rather than forged rods and while perhaps lighter not likely stronger than the proven 101.3 and 110.0 rods. I do not know if they are lighter, cost saving was more likely the effort. I have sets of both the 110.0 and 101.3 rods and weighed them, they weigh the same which I believe was to allow for interchangeability. I think the cast 944 rods weigh the same as well, I have a set of these but have not weighed them and they still have pistons attached.



If someone has a 1R or 2R rod please toss it on the scale.



I also think the 944S2 rods are the same as the early 968 rod and I recall there was a supercharged S2 that blew the bottom end at one point.

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[flash]

what is meh?



i'm trying to find a replacement that weighs the same as the early rod. i don't want to mess with the harmonics. i figure that if they said to replace the 1R with the 2R that they did the math and figured there was no problem there. but, to change to a lighter rod, i would then need to remove mass elsewhere to compensate, and then change the balance shafts to work with that................



you get where i am going.



i have to tear down my motor to re-ring it to cure an oil burning issue, and while i am in there i think i want to change the rods.



so, the hunt begins

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[jfrahm]

"meh" is a slang term used to indicate indifference, disinterest, etc. It is not quite as contextually versatile as "dude."



I suppose if 2R rods were a different weight than 1R there might also be different balance shaft part numbers. Given that in the past Porsche made the effort to keep rod weights the same for interchangeability I would imagine the 2R weighs the same as the 1R but you can always weigh them and see. As long as they are used in sets of 4 I dunno if it matters much compared to the weight that might be removed when balancing the crank. Plus people run aftermarket rods which are significantly lighter than stockers.



-Joel.

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[flash]

never heard that term. i wonder what the origin is?



anyway, i agree that if the rods were different weights, there would probably be different shafts. i seem to remember somewhere reading that they were the same, even though they were made differently.



i know that people use lighter rods, and even lighten the crank, but that is on a race motor which gets torn down frequently, and already has things done to mitigate harmonics damage. i don't want to do that on a street motor, even though it is supercharged.



hence why i am looking for a set of rods that weigh the same as the 1R rods. i just don't want to make any significant changes to something that i already know works

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[DaveN]

That's the cost of not having kids Bob. <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" /> You miss out on a teenager looking at you after you said something profound and hearing "meh". I know you're OK with the sacrifice <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" />

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[Grandpa#3]

Hello Gents, I wish to thank all of you for the great amount of insight on all the connecting rods available for use in the 968 engine. A chip might be the only thing I will be adding. I do not worry how the harmonic balance might be affected by using the 86 951 rods. I will be replacing all four rods so that may help on the balance. Being that I am retired kind of limits what money I have to play with every month, so brand new rods are out of the question for me. I have no plans for using the car for track. It's normal driving for fun, but I did learn how to drive on the Autobahn. <img src="/forum/images/smilies/968/EmoticonCar.gif" class="smilie" alt="" />



Cheers,

Larry <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" />

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[jfrahm]

Hi Larry,



I would not worry about the 1R rods in your case. I would be more worried about disturbing the ring package. Re-ringing and re-bedding new rings without the pixie dust on the old pistons might do more harm than good. Some say you should scuff the bores, some say don't... I dunno.

Neither of us have bent a 1R rod so maybe it's better to just keep the revs in check, buy quality gas and not worry about it.



In general I feel if you are at the point of swapping rods and re-ringing you are should be doing a serious build. Otherwise you are much better served with a good used running long block. No one puts them together like the factory and trying to get close to that process costs a ton of money and time.



Rod bearings, rod nuts, Reinforce the oil pickup tube, do the usual top-end stuff, cambelt stuff and go drive.



Cheers,

-Joel.

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[flash]

yeah- i've only see 2 stretched 1R rods (which is what happens). all reports i have ever heard of are the same failure. the connection point stretches, which leads to the rod becoming too long and then getting bent. all reports have been in sustained high rpm cases, such as racing.



the only reason that i want to change them is because i expect to subject the engine to sustained high rpms



as for balance, even if all four are the same weight, if they differ from the 1R weight, i would be concerned about the harmonics causing or accelerating things like the well known oil pickup tube problem.

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[Rap]

You sure meh isn't ehh

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[flash]

if only the kids would read 1984

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[DaveN]

Only kides before 1984 CAN read <img src="/forum/images/smilies/968/dry.png" class="smilie" alt="" />

FWIW. When I had my engine rebuild for the SC my friend, a 30 year Porsche mechanic, didn't prep the cylinder walls before the new rings. I think he felt the break-in process was more inportant than anything else.

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[Cloud9...68]

I agree that the 1R rods should be fine for all but sustained high rpm use. These engines aren't really that highly stressed. Max (formerly of RS Barn) once told me the only time he'd seen the early rods fail was when a bearing froze. So, regardless of the mechanism, it's a very unlikely occurrence. As far as the bores, Lindsey racing told me to leave mine alone.

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