ARP ? Rod bolts

[Lyndon302]

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

[Jeff Alton]

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

[stownsen914]

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.

[Henry Schmidt]

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.

[Jeff Alton]

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.






Cheers

[winders]

Originally Posted by Henry Schmidt

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.

[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]

[Lyndon302]

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

[Jeff Alton]

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

[Henry Schmidt]

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.

1722 (AMS 6304) is the steel used by ARP for it’s ARP 2000 a 220 ksi material (tensile strength). The next step would be H11, which ARP calls L19. Carrillo WMC bolts are made from this material. Those are getting up to 240-250 ksi. Carrillo Carr bolts are made from an aged 625. This is a 260-280 ksi material.
So basically H11 gets you an extra 10% of tensile strength as compared to the ARP 2000 and Carr bolts are basically 15% higher.

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”.

Carrillo
WMC bolts are generally good for 15-18 torque cycles and Carr bolts are good for an infinite number if the stretch method is used.

WMC Rod Bolts

High quality, aircraft standard fastener
Asymmetrical Threads
⅜” (9.65mm) diameter
Supports up to 8,500 RPM and 1250 HP

CARR Rod Bolts

High quality, aircraft standard fastener
Asymmetrical Threads
⅜” (9.65mm) diameter
Supports up to 9,000 RPM and 1500 HP

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.

[KNIGHTRACE]

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.

[Henry Schmidt]

Originally Posted by KNIGHTRACE

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.

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?

[KNIGHTRACE]

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.

[cgarr]

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

[KNIGHTRACE]

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

[Jeff Alton]

Originally Posted by KNIGHTRACE

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.

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

[Lyndon302]

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

[Henry Schmidt]

Originally Posted by Lyndon302

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?

[Henry Schmidt]

Originally Posted by KNIGHTRACE

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.

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.

[KNIGHTRACE]

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..

[Lyndon302]

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