New Rod Bolts

[leadrsa729]

Hi Everyone -

I just received new rod bolts and nuts for my 72 911 engine rebuild. I just tried to test fit one of the rod bolts by just dropping it into the cap of one of my rods. The bolt does not seat all the way flush to the cap, and seems to need a lot of force to get it to do so but I'm afraid to try. Is this normal? do you have to tap these down all the way during final install to get the threads to show through the bottom, or did I get the wrong part sent to me. I just triple checked the correct part number, and it matches what was sent to me. the part # I'm using for a 72 911 is 914.103.171.00

Thanks All,
Sanford

[KTL]

The shank of the bolt acts as a guide to align the cap with the rod end. So they're a light press fit to precisely align the two parts of the rod.

[leadrsa729]

Hi Kevin -

This is not going in all the way no matter how hard I push with my fingers. So I basically have the wrong bolts then?

Thanks,
Sanford

[Trackrash]

A picture would help. Are these factory rod bolts? How do they compare to the old ones?

[leadrsa729]

Hi -

Here are pics that show how far they go in pushing by hand:





I had to tap out the old rod bolts with a small hammer.

Thanks,
Sanford

[leadrsa729]

see if this works -

https://photos.app.goo.gl/jaXoPi8O1U8MkI0Q2

https://photos.app.goo.gl/wYocNHEIuvXQXSiF2

[KTL]

Tap them in with a plastic mallet. It's a tight fit to make sure both the rod and cap align precisely

[leadrsa729]

Thanks Kevin! This whole process is so nerve wracking! I'm competant enough when it comes to brake jobs, valve jobs, carb tuning, bearing replacement, etc., but this engine rebuild has me frazzled! I'm so afraid I'm going to do something wrong.

[Trackrash]

How hard was it to remove the old bolts? Should be tight, as mentioned, light tapping from a mallet should do it.

Do the new bolts look the same as the old ones?

[KTL]

Just hang with Souk on this one Sanford. He'll give you an education you'll never forget?

(but you may regret................ )

[Tippy]

Align the bolthead, and smack it down with a soft hammer of choice.

Yes, it's a snug fit.

[smokintr6]

remember, if it's a one time use bolt you will have to throw it away if you use the new one to check bearing clearance via plasti gauge

[cgarr]

Brass block to support the cap and tap it in with (I use a brass hammer) stock bolts go in hard


Sent from my iPhone using Tapatalk

[Neil Harvey]

Originally Posted by smokintr6

remember, if it's a one time use bolt you will have to throw it away if you use the new one to check bearing clearance via plasti gauge

FYI to all, Porsche rod bolts for these engines are not a stretch "one time" bolt.

When rebuilding the rods and assembling the engine, the rod bolts will be stretched minimum 3 times.

Once after installing new bolts and resizing the big end, 2nd time when measuring the bearing inside diameter and a 3rd time when installing on the crankshaft during assembly.

As long as the bolt returns to its relaxed length, you are good to go. As for how many rebuilds, that's down to use, engine maximum speed observed and your risk management.

[smokintr6]

Originally Posted by Neil Harvey

FYI to all, Porsche rod bolts for these engines are not a stretch "one time" bolt.

When rebuilding the rods and assembling the engine, the rod bolts will be stretched minimum 3 times.

Once after installing new bolts and resizing the big end, 2nd time when measuring the bearing inside diameter and a 3rd time when installing on the crankshaft during assembly.

As long as the bolt returns to its relaxed length, you are good to go. As for how many rebuilds, that's down to use, engine maximum speed observed and your risk management.

They don't appear to be a necked torque to yield bolt, but the factory manual does say to discard them every time, and other Porsche models do not get the same treatment. Per the factory 944s can reuse the bolt but not the serrated nut. I forget if the 911 is a torque angle spec, but if it's not, you do get a different clamp load for each of those torque applications as the threads wear smooth against each other. This can be observed with the behavior of an ARP fastener as you run it through 3 torque cycles using the stretch method. I think some ARP fasteners want 5 cycles of loading before installation if you're using a torque wrench, for accurate clamp load. It's also not easy to track the relaxed length of the stock bolt down to .001" since it doesn't have a nice machined surface to measure from. I also don't like that Porsche rod bolts changed mid run of the 3.6 per a service bulletin. Very different torque procedures but the bolts appear mostly the same. Porsche even allowed for the types to be mixed within an engine, though not mixed on a single rod. Anyway, it sounds like you have enough experience to be comfortable using the Porsche bolts. I don't build engines often, so when I do I prefer the aftermarket bolt system because there's zero ambiguity. There's a very detailed installation process that's clear to follow, and using a stretch gauge you know if the bolts are permanently deformed, and you can be 100% confident in your repeatablilty

[Tippy]

As over the top as Neil goes on rebuilds and chris_seven has stated here about reusing rodbolts, I'd feel pretty confident they are reusable.

Personally went with ARP because I wanted to go to a higher RPM than the factory redline and the 3.2 uses the smaller bolts.

[smokintr6]

Originally Posted by Tippy

As over the top as Neil goes on rebuilds and chris_seven has stated here about reusing rodbolts, I'd feel pretty confident they are reusable.

Personally went with ARP because I wanted to go to a higher RPM than the factory redline and the 3.2 uses the smaller bolts.

I never said they weren't reusable. I said that Porsche says to discard them, and that you have to know what you're doing to reuse them safely. Something a builder would be comfortable with, but not necessarily a weekend warrior that's only provided with the instruction to throw the bolts away.

[Tippy]

Originally Posted by smokintr6

I never said they weren't reusable. I said that Porsche says to discard them, and that you have to know what you're doing to reuse them safely. Something a builder would be comfortable with, but not necessarily a weekend warrior that's only provided with the instruction to throw the bolts away.

The statement wasn't directed at you, rather there's a lot of 'golden rules' this board follows that other's using science (chris_seven) or pure long time expertise (Neil) prove as myth.

You nailed it on the head about weekend warrior vs pro, but I see pro's usually take the safest route due to liability.

[leadrsa729]

Thanks everyone for all the detailed information submitted. I feel much more confident in the rod bolts sent to me, and will continue to move forward. I'm definitely more the weekend warrior for sure. I've done a top end rebuild on this same motor before, but this is the first time diving into the bottom end.

[Neil Harvey]

There are a lot of myths and folk lore in this world and engine building is full of it. I don't expect the DIY owner to know or understand a lot of the science and knowledge we have gained over years, either.

There is nothing wrong with being safe and using new bolts. Porsche may state to use new ones as they do not know every circumstance and they surely are using CYA mentality here. Plus they want to sell parts.

Hopefully, coming on this forum along with other experts I hold in high regard, like Steve at Rennsport Systems, we can help those in need and looking for sound advice.

There are many ways to achieve the same result but only one "right".