Bolts Vs Studs

Indycars

Administrator
Staff member
Below is a discussion about why bolts such as main bolts and head bolts are better than using studs. This is completely contrary to what I have heard for years. Even David Vizard as made comments in his book about using bolts over studs and is supported by Larry Meaux of MaxRace Software (PipeMax).

Book titled "How To Build Chevrolet Small Block V8 Heads"
By David Vizard
Page 122 ( pages 117 to 123 )
Year = 1991
Motorsports International
Powerpro Series

I thought it would be beneficial to post the thread here for discussion. I will post a part of the thread every few days, it is still an active thread on the MaxRace forum and is starting on it's 3rd page now. The link is below, but you need to be an owner of his software to login and view the forum.

Below is the thread from the MaxRace Software forum .........

http://maxracesoftware.com/bulletinboard/viewtopic.php?f=26&t=1431

t6nisson Writes:

First, I apologize for my bad English. I try my best to be understandable for you.
Also try to keep my questions short.

The objective is to keep stock 440 bbm block alive around 900-1000hp.
There seems to be no free information available for my questions.
No budget for aftermarket block, but opportunity to machine parts on my own.
So I am interested in main cap design for 2 bolt mains.
Thinking 7075 aluminum?

#1 BCR style aluminum main caps with girdle

p1030751.jpg


#2 Pro-gram style with cross bolting. Needs milling the already weak main webbing a little bit.
mopp_1012_05_o%2Binstalling_pro_gram_mopar_big_block_main_caps%2Bcross_block_holes.jpg


#3 Dvorak style mains, needs milling lot of the webbing and thru side of the block and aluminum seems like a wrong idea for something like this? In dvorak website, they say "Will withstand 1500 plus horsepower" which is hard to believe.


BilletCapsAngle.jpg


MainKitInstall1.jpg


So.. What would you do?


And also want to thank you Larry and all the others around here for all the information.
icon_e_smile.gif
 

Indycars

Administrator
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Larry Meaux Writes:

the Dvoark mains look like steel or ductile iron
are you saying Dvoark is aluminum caps ???

i would prefer using Steel or Ductile Iron Main Caps than anything made out of aluminum Caps/Girdle

your last picture with Main Caps that have those sharp step cuts on sides
will be places a crack or fracture can start from !

and i also much prefer Bolts than Studs in all Engine locations !!!

Studs cause more distortion of round holes than Bolts
and that is why no Rod Company will use Studs in strictly racing type Connecting Rods .

When CompCams 1st started making Rods they used Studs
and stated in National Dragster Ads and Magazines how much better Studs were than Bolts
then they started having many Rod failures
then later published 2-3 page National Dragster Ads stating they reversed course and changed
their Rods to Bolts ... issued "Apologies" in many Magazines/National Dragster

a Stud acts more like a LEVER than a Bolt will do
and thereby will distort the material it is bolted into thru its leverage distance
the longer the Stud, the greater the distortion

all the finest race Rods in the world use Bolts ... no studs .
cannot mantain a round hole with Studs

if you want too use Studs then :
1- use .001"+ more main bearing clearance
2- Torque Studs at least 15+ more lbs than you would similar Bolts
_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst ( DragStrip Simulation Software )
PipeMax ( Engine Simulation Software )
http://www.maxracesoftware.com
 

Indycars

Administrator
Staff member
t6nisson Writes:

No, dvorak mains are not aluminum.

Good to know. Just a lot of mopar people are saying, that the aluminum is the way to go.
For me it seems strange to use aluminum, because of different properties of steel and aluminum to act together.
I somewhat understand, when people are talking about crank shock dampening with aluminum? That crank can move a little without cracking the main webbing?

In all engine locations? Very interesting to hear that.

Thank you for your time!
 
Last edited:

Indycars

Administrator
Staff member
Larry Meaux Writes:

that's exactly what i also thought people would be thinking
icon_e_smile.gif


if you know you are going to be making that kind of Torque/HP increases
then you will have more distortions to contend with ( reason you are thinking going route in your Pics )

the more distortion...the greater main bearing clearance you need

that .002" to .0025" Internet stuff will not work if you are getting/planning on that much distortion of 900-1000 HP .... to 1500+ HP

we just made 2050 HP on BBC 632cid yesterday at 7900 RPM 1550+ TQ ( cold box NOS setup ) Top Sportsman Class
we had .005" Rods .0055" Mains
thats the tightest we run on that TQ and HP level with NOS

on 892 cid BBC Hemi all aluminum engine with Studs
we run .006" Rods / .007" Mains

*********************


all the bearings failures on my Dyno from other Engine Builders/Racers
has been that .002" to .0025" Internet stuff

We do not have any Bearing failures !!
all our engine bearings look brand new .
_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst ( DragStrip Simulation Software )
PipeMax ( Engine Simulation Software )
http://www.maxracesoftware.com

 
Last edited:

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
having taken a great deal of engineering classes in college , I can point out a few flaws in the discussion
first , Id point out that your comparing APPLES TO ORANGES ,
if your comparing rod BOLTS to studs in connecting rod applications

rod bolts are designed to have some stretch,
most of the length or in a few cases half the rod bolt is designed to slide in the rod this allows the stress, (tension )
forces to be distributed over a large percentage of the connecting rod fastener body,
and as long as the bolts elastic limits are never exceeded
they perform as intended, BUT if you use of a STUD in a connecting rod
all the stress is concentrated at the shear plane between the two connecting rod components
as a stud is threaded into both sections, leaving only the single stress point.

point two
when using a main cap or main cap girdle steel is far stronger than aluminum and has
a far higher and longer term endurance limit
main cap studs allow the whole threaded length in the block to hold the tension stress,
while the unthreaded length extending through the main cap or through the main cap and stud girdle under it absorbs the shock and stress loads.
but use of aluminum main caps do have the ability to reduce or cushion the impact stress on crank bearing over a short term.
this is also why nitrous engines frequently use aluminum connecting rods, but remember the aluminum connecting rods,
in a race engine and crank bearings are considered a replaceable wear item like brake shoes or fan belts and they get replaced on a regular basis

stressx4.png


http://mitsubishilinks.com/fsm/arp_catalog_rodbolts.pdf

http://garage.grumpysperformance.co...connecting-rods-pistons.247/page-2#post-99062

http://garage.grumpysperformance.co...market-4340-connecting-rods.13321/#post-72047

http://garage.grumpysperformance.com/index.php?threads/rod-bolts-rpm-vs-stress.341/

http://garage.grumpysperformance.com/index.php?threads/rod-bolts-rpm-vs-stress.341/
 

Indycars

Administrator
Staff member
BUT if you use of a STUD in a connecting rod
all the stress is concentrated at the shear plane between the two connecting rod components
as a stud is threaded into both sections, leaving only the single stress point.

The shear plane you refer to, is that the surface between the rod and the cap ?

How can a stud be threaded into both the rod and cap, don't understand that point ?
 

Unforgiven

solid fixture here in the forum
A bolt has two forces to deal with... stretch and twist , where a stud only has to deal with stretch.

I'm not sure if this is relevant to the story but it is what I was taught in college engineering about 40 years ago.
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
they don't use studs in rods they use bolts yes I could have worded the response clearer





most stock rods use rod bolts press fit through the rod and the rod caps are held with threaded nuts applying clamp force
sca-25700_w.jpg
s-l640.jpg

rod bolts are either threaded through the cap into the rod body like above

or through the rod body and threaded into the rod caps to supply clamp force

in all cases the section with the clamp shoulder on the bolt is on the section without the threads
studs don't have a clamp shoulder on the ends opposite the threaded section so clamp force due to bolt stretch can,t be maintained
svw-3ag15052u_xl.jpg
 

Indycars

Administrator
Staff member
t6nisson Writes:

If we forget about aluminium and studs...would you use girdle to tie it all together?
 

Indycars

Administrator
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Larry Meaux Writes:

the Girdle in your above Pic looks like a good design

i just do not like its made of aluminum
icon_e_sad.gif



when main bore distort/elongate vertically
causing main caps to pull away horizontally from block's crankcase webbing,
the Girdle and things like side bolting of Main Caps help greatly to prevent or reduce that

same help from Splayed Main Cap styles
_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst ( DragStrip Simulation Software )
PipeMax ( Engine Simulation Software )
http://www.maxracesoftware.com
 

Indycars

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FoxChassis Writes:

Larry do you still prefer bolts over studs on aluminum heads/Dart block ? Customer is ready to purchase one or the other.
Dwight
 

Indycars

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Staff member
Larry Meaux Writes:

I like Bolts everywhere on the Engine , except maybe for Valve Covers , and maybe Oil Pan , things like that

the Stud's Bore distortion shows up more on Small Block Chevy , and a little on BBC engines
on most OEM 400 SBC cast-iron Blocks , Studs will cause cracks to form on the Block Decks to water hole between the Intake Port Pair's Bolthole
but a Headbolt will usually not cause a crack or distort the Bore anywhere near as much as a Stud .

Studs require at least 10+ Lbs greater Torque to clamp the Headgaskets as much as a Headbolt does ,
same for Main Caps .... and if you use Studs on Main Caps ,
make very sure you Honed or Align-Bored Mains with Studs installed + torqued to 10+ Lbs Torque greater than Bolts

All the Connecting Rod Companies i know will not use Studs on their best Hi-RPM Pro Rods
.... you cannot maintain a round hole with Studs ... Studs act like a "Lever"... they will transfer distortion thru leverage distance
_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst ( DragStrip Simulation Software )
PipeMax ( Engine Simulation Software )
http://www.maxracesoftware.com
 

Indycars

Administrator
Staff member
Talperian Writes:

This is very interesting Larry, do you know of any links to further literature I can read on this subject?

In my BMW I6 world. We are having trouble 11mm ARP L19 studs distorting/cracking the cast iron block deck to the nearest water holes, just as you said. However, we need the extra clamping force to keep the heads from lifting under boost. Any suggestions?
 

Indycars

Administrator
Staff member
Larry Meaux Writes:

yes, just use ARP Bolts instead of Studs !

Bolts give you same clamping forces as Studs ... but with 10 to 15 Lbs less Torque
so you think you have more clamping force with Studs ... but its just an illusion !
icon_e_smile.gif


David Vizard did some great testing on this , on Headgasket / Block Decks , Studs -vs- Bolts
i sadly found out much too late on my very own , that everything thing he wrote about it was true
and the Studs and Bolts used in his test , i also used many of those same Bolts + Headgaskets he tested ,
and came to exact results he stated ... much respect for Vizard in those tests !

a little more info from a Rod Manufacturing Engineer that came by my Shop years ago ,
not only explained why they use Bolts instead of Studs .... but that they always try to move the Rod Bolt holes as close
as physically possible to the Rod's Big End Bore diameter ... in other words , as close as possible to Rod Bearing OD or Big End Bore ID
Reason : the further the Bolt holes are from the Big End Bore ID ... the more distortion there will be at the Big End Bore ID
in more words : it creates a pivot point / pivot distance , like a Rocker Arm , and can cause more distortion like a Lever effect .

he had a nice picture with very detailed drawings + forces info showing effects as you moved the Rod Bolt Holes closer or further away from Big Bore End

moving the Rod Bolts / Rod Bolt Holes as physically close as possible .... only applies to Rods and Main Caps
but not to Cylinder Bores ... just to clarify the difference !!!
icon_cool.gif

_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst ( DragStrip Simulation Software )
PipeMax ( Engine Simulation Software )
http://www.maxracesoftware.com
 

Indycars

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Staff member
foxchassis writes:

I have seen where guy's have poured 4" thick decking plates out of aluminum. I think this was so they can
use long studs to help control the distortion while machining.
Dwight
 

Indycars

Administrator
Staff member
Talperian Writes:


I cannot wrap my head around how a bolt would achieve the same clamping force at a lower torque. I need to find some literature or pictures/details on this to better understand.

I figured connecting rods used bolts because you can directly measure the bolt stretch, which is a direct indication of the tensile force. Whereas with a stud you couldn't do this.

Unfortunately I can't fine a metric bolt of ARP2000 grade or better on ARP's website to try. I'll give them a call and pick their brain.
 

Indycars

Administrator
Staff member
Larry Meaux Writes:

just to clarify : typical Small Block Chevy Cyl Heads = OEM 7/16-NC Bolts @ 65 Lbs Torque w/Torque Wrench
but i use ARP Bolts OEM 7/16-NC Bolts @ 75 Lbs Torque w/Torque Wrench ( so i'm torquing HeadBolts + 10 Lbs more )
even with the Chevy OEM Bolts , i'm just at barely 75 Lbs Torque w/Torque Wrench
.... i also Torque-Plate Hone with those Torque Wrench settings on HeadBolts .

Aluminum Rod Manufacturers will not use Studs ... even though Studs would better protect the aluminum threads in the Rods !
they use things like serrations or serration rows across parting lines to help keep Rod Caps from moving around
... but never use Studs ... just bolts .

Look what happened to your Block Decks with a Stud .
probably would not have happened with a Bolt or not as bad .

any movement of the Stud at the top-end ... the forces get multiplied thru the Studs Length or distance ,
so at the bottom of the Stud in the threads of the Block ... its greater distortion !

Bolts have more leeway ... things can expand + move around a little and a Bolt has leeway to move around
without transfering as much block distortion as a Stud .

the Leeway is = to many ARP and OEM Headbolts have reduced diameters located in the length of the HeadBolt
Studs are usually very close to same diameter thru out its length

try this with a Block but no Cyl Head on , just a Stud screwed down bottoming out in threads on the Deck surface
now move the Stud by hand at the very top of the Stud .... theres no leeway or hardly any ,
so any movement at the top of the Stud on a live running full-throttle run ... gets amplified distortion transfered to the Deck , according to the length of the Stud
the greater the Stud length ... the greater the potential distortion .

Do the same with a HeadBolt ... now theres much more leeway or slop
A HeadBolt also gives you more room inside the Cylinder Head's HeadBolt Holes,
this is great if you've maxed-out Intake Ports and had to press-in or install HeadBolt Tubes or Sleeves
like between SBC Intake Port pairs .

if you Torque both a Stud and Bolt to the same Lbs Torque ... the Bolt has more clamping force
reason : most Head Studs are NC-threads into the Block , but NF-threads at the other end , the Nut end
_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst ( DragStrip Simulation Software )
PipeMax ( Engine Simulation Software )
http://www.maxracesoftware.com
 

Indycars

Administrator
Staff member
Larry Meaux Writes:

1 more thing i forgot to mention is "Taps"
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i use only H1-Limit Taps in NC and NF
they cost a few $ Dollars more,
and i've even ordered special H1 Taps with minus 0.002" all the way to some at minus 0.004"
... these cost about $40.00+ USD more Dollars than just H1 Limit Taps

H1 Limit Tap usually will just clean "crud" out of Holes as it Taps , but can also remove a little metal too , but it depends on OEM Thread fit ?

the H1-Limit Tap is usually what OEM Factories use on Blocks , etc.

what you get at local Automotive or HardWare Stores are H3 to H5 Taps or even greater plain ordinary Taps
a H3 or H5 will definetly cut material out of the Threads in th Block , making for a much looser fit , possible thread failure !

an H1 minus -0.002" or -0.004" only will just remove crud or silicone or Loctite , etc, absolutely no metal removed

could be an "L" coded Tap when its below H1 ? ( or L-limit Tap )
but the H1's i get that are - minus 0.002" or -minus 0.004" still have H1 etched on them , just with extra specs etched
i guess it depends on Tap manufacturer ??


_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst ( DragStrip Simulation Software )
PipeMax ( Engine Simulation Software )
http://www.maxracesoftware.com
 
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