ARP ? Rod bolts
 

New rod bolts. ARP or our hosts ones.
A 67 S 911 used as a runabout
Lyndon

What is the cost difference between the ARP kit and the 12 bolts and 12 nuts? What is your intended use of the motor/car? How much do want to risk?? The difference appears to be about 37 bucks. You won't regret going with the ARP.

Cheers

I'd go with ARP for similar $$, hands down.

Note that due to the higher torque value of the ARP bolts, you should have the rod big ends checked with the ARP's and resized if needed.

We use ARP bolts whenever possible. We even devised a simple machining process that allows us to use 2.7/3.0 ARP bolts in 2.2 rods. ARP never made a bolt for that application so a little ingenuity was required. We even use the ARP/Wrightwood bolts to replace the factory bolts in the Pankl titanium GT3 rods.

Nothing, except Carrillo rods leaves our shop without ARP rod bolts.

A side note about Carrillo bolts: although Carr bolts are infinitely stronger, WMC bolts are still a stellar choice for most Porsche flat six applications. Sometimes "more" is just "more" hype.

Agree 100% Henry. Just assembled this 930 shortblock this morining with Carrillo rods and WMC bolts. Even the water cooled Porsche motors we build get Carrillo rods with their WMC bolts.




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Cheers

[SARCASM]

My engine architect, William Knight, must be stupid and subject to hype. After all, he uses 2 MSD ignitions with 2 coils, he uses 993 Twin Turbo head studs, and he prefers CARR fasteners for his higher performance builds.

What a tool I am for listening to his advice.

[/SARCASM]

Ok I'm going with ARP 204-6003
To my surprise they vary from 160 to 280 from two well known suppliers in the USA. Am I missing something here ??
1967 911S
Also can I confirm this 204-2802 is the correct flywheel Bolt kit ???
Lyndon

Scott,

You have clearly done lots of research. But I have to ask, what is your point with the post above? If William prefers the CARR bolt, he can post and say so? CP/Carrillo has good info on their site about the properties of each fastener.

Cheers

Here's a little bit of science for those who think for themselves sans the need for the “cool kids” approval. Most engine builders here agree that ARP rod bolts are a great upgrade for factory rods.
It is very interesting that the standard bolt in some well-regarded rods are either ARP 2000 (Manley, Pauter, etc.) or H11 (Cosworth and WMC Carrillo). Are all these bolts being upgraded on the builder side during installation? I'm a little surprised the CARR/625 bolt is almost viewed as a 'must have' for the Carrillo rods by some “cool” builders. These happen to be some of the lightest rods which one would think would place less stress on the bolts compared to the heavier rods from other manufacturers.
What I call that is “hype”.
I guess you have to ask yourself: are you taking your engine apart 15-18 times and/or is your 1250 hp engine going to be increase to 1500hp?

Of course for some inexperienced drivers, over-revs are a common occurrence so the best bolt might be the better choice.

BTW: My reference to "cool kids" is simply a metaphor for hero worship. When it comes to technical issues, the data someone offers and the experience they bring to the specific discussion is far more important than "who" that person is.

Jeff, you probably know this but I am posting to help people unlike you or Henry, I actually use all 4 bolts, The ARP, ARP 2000, WMC, and CARR.. It depends on the application.
The deal with using CARR bolts over and over is something I don't agree with. I may use the three times, WMC once, ARP once, ARP 2000 maybe twice.. The factors that dertermine the bolts used, Pauter uses both ARP and ARP 2000, CP uses WMC and CARR. I like the WMC bolt in most applications as it saves about $350 but the main difference in the bolts is the clamping force. It is directly proportionate to the tensile strength of the bolt. on a 70 mm stroke is is much less critical than an 80 mm stroke, the piston weight is another big component along with RPM obviously. Race motors where we change rod bearing's and rings before a rebuild often benefit from the CARR bolt.. Most DE level street hot rods do not need premium bolts..
One more tip for nonprofessionals the longer stroke means the piston is traveling faster at the same RPM. secondly in my opinion the number one reason new builds fail prematurely is people changing there stock rod bolts to ARP rod bolts without correcting the roundness of the rod.. Hope this helps some new people keeping the air-cooled world alive as there are definitely not enough qualified people to do this anymore.

Why....Concerned about fatigue? The primary reason to replace a rod bolt it that it has been torqued to yield. When you reach yield, the bolt length will grow making it out of spec.
If the bolt is tightened using the stretch method and the unstressed bolt measures within spec, why would it be necessary to change?

Just a fine line between yield point and Elastic region. Also I have less comfort on too many uses on high RPM high Stress motors that are very expensive to rebuild.

So sizing the rod doesn't count as "one" use?

If you are changing to ARP bolts for example in a stock a rod, it counts for 1 stretch cycle.

I understand your reasons for posting William. NO issues. I agree with pretty much all of what you have said.

Further, if someone is rebuilding a motor without resizing the big end, regardless of their bolt choice, they deserve what ever happens... :)

Cheers

I've decided to buy a set of pauter rods
They come with bolts and I don't need to resize my S rods.
I will know they are perfect and it's the last time I will need to look at my bottom end.
PS engine is running well but it's getting a birthday soon.
Lyndon

Interesting choice: When engineers and engine builders get together to discuss rod designs the conversation centers around strength vs weight, materials and grain structures. They explore the benefits of H beam vs I beam vs A beam. They never seem to include the X beam design. Why is that?

Isn't the point of using the highest quality bolts predictability? The manufacturers offer guidelines for how much stretch is acceptable. How many times those numbers can be achieved and how much horse power you can reasonably achieve using their products. These numbers are publish by engineers not end users.
I get a kick out of your reference to "High stress motors" when the bolts manufacturers are quoting numbers like 10,000 rpm and 1250 to 1500 hp.

Jeff one of the biggest causes of failure are guys upgrading to an ARP bolt without correcting the big end. They get there rods done then change bolts, cars usually live 70 to 100 miles. I have seen it about 10 times. other issue is cam sprockets.. I hope we can all help keep people from having issues..

Sprockets ??
Big ends ?
Could you elaborate on theses. I don't want to get it wrong.
Lyndon

I agree William. There is no "low cost" rebuild that will stand the test of time. Regardless of the quality of some of the product choices.

Cheers

Sorry, The chain/cam sprockets do not go face the same 123 faces inwards, 456 faces outwards. If you make them the same the chain chews metal off the sprocket. The reason is the cylinders are offset, this was done to help align the chains straight.

Ok. I think that is pretty obvious.
The big ends??
I take it with the ARP tension the big ends are resized at this torque as it may or make them out of round ?
Lyndon

Yes, for example if you true the rods at 20 LB and change bolts to 40 LB. it is not the same any longer. On the sprockets you may say it is pretty obvious but when Motor Mi---- was in business I dont think they ever got it correct once.

Ive got real reservations that my ARP bolts would have been installed properly. I’ve got 4000 miles into the car today. In folks collective experience, would the failure have already happened? Sounds like it based on Williams experience

Perverse as it sounds, think we’re all learning a lot from the debates playing out between Winders and Henry. It’s teasing out some very reputable perspectives on all sides. Occasionally there are some curse words. Every now and again, there’s good humor. Play on I reckon and thanks for taking the time to hash it out.

Before anyone jumps down my throat, I have great respect for winders and his research, field testing and patronage. Without him and folks like him, there wouldn’t be a need to push the envelope. Same for Henry who needs no re-introduction.

Henry - when you refer to 1250-1500 HP motors, are you referring to drag motors? Do those guys reuse ARP (or other bolts torqued with a stretch gauge) until the gauge says they have stretched more than the few thousandths specified as OK?

Up until now I haven't seen any engine builder or mechanic say that rod bolts which haven't stretched shouldn't be reused.

Nobody mentions the nuts that I recall, though. Porsche just says replace their bolts and nuts.

Glenfield if it made it 4000 miles.. your most likely good I would say 95%

Thanks William. Much appreciated

^^^, over stretched (over rev) or improper installation means imminent failure. We have seen engine last between -60-90 secs where a bolt was over stretched (similar to not stretched or torqued correctly on install). My own GTI lasted 52 seconds on track before I had 2 large holes in the block and parts of pistons and wrist pins sitting on the under tray. Many thanks to the provider of the TCU tune in the DSG gearbox.... :)

Thanks William. Much appreciated

Glad to help, have had many calls through the years where the car ran great about 60 miles. Last one was guy named Buzz. Pretty orange 73' with 3.0. Not sure where it was built.. WK

Pauter seems to have pretty good marketing because I still don't get their design approach that is the opposite of every other high-performance connecting rod out there.

https://www.f1technical.net/forum/viewtopic.php?t=27372

I've heard that often. Long standing customers in the VW drag and off road world, among other things, making for brand loyalty? I can't say I have seen reports of their rods failing, at least more than other rods. Mine haven't, but that's hardly definitive. Cost was a factor for me.

It was state of the art for.:::/
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