Bolts Vs Studs

Indycars

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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
 
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
 
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!
 
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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:
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
main cap studs, studs are NOT torqued into the block!

studs are screwed into the block for the full thread length then backed out 1/2 turn,
STUDS are installed through the main caps, before the nuts and washers are installed,
I generally oil the threads on the lower stud threads in the block,
but no loads are applied to the studs until the threads in the block are full length engaged,
into the block and the washers & nuts on the studs are tightened.


UN-machined SBC blocks have a nominal 9.0" deck height,
its very common to have the deck on a previously undecked block actually measure 9.022"-9.025"

SBCprintCustom2.jpg





UN-machined BBC blocks have a nominal 9.8" deck height,
its very common to have the deck on a previously undecked block actually measure 9.822-9.825

BBCbott.jpg



How to Install ARP Main Cap Studs​


Serious race engine builders mostly use high strength ARP studs to anchor the main caps.
Studs provide a more even clamping force with higher tensile strength than most bolts and they are less highly stressed in the block .


1. Clean and inspect ALL threads in the cylinder block thoroughly. After initial tank cleaning, dry the block and inspect threads closely. Chase the threads with the appropriate size ARP thread chaser if necessary.
2.
To prepare the threaded holes select a small stiff bristle nylon cleaning brush as found in engine brush kits available from online retailers.
We prefer to scrub the main cap bolt threads with a brush and brake cleaner and then blow them out with air to get them spotlessly clean prior to assembly. At this point you should also ensure that the main cap mounting surfaces are spotlessly clean and free of any nicks, burrs or other contamination. This step is important to ensure perfect seating of the main caps.
3. Clean and inspect ALL studs and verify all dimensions. Remove all shipping lubrication from the studs until they are squeaky clean.
4. Screw the studs into the appropriate holes HAND TIGHT ONLY! While not specified by the manufacturer, we prefer to brush a very thin coating of ARP Ultra-Torque fastener assembly lube on the threads. Do not over-tighten the studs in the block.
Note: If permanent mounting of the studs is desired, Loctite may be applied to the threads.
If you do this the fasteners must be final torqued before the Loctite sets up.
main cap stud install

5. Install the main caps and check for proper fit and alignment.
Splayed bolt main caps require outer stud installation after each main cap is installed.
Install the inner studs and use them as a guide for the main cap.
Tap the cap into place and then install the outer studs. (USE A DEAD BLOW MALLET)
6. Use a small application brush to coat the stud threads and washers with assembly lube and install the nuts finger tight.
Whether using ARP fasteners or others,
we recommend ARP Ultra-Torque fastener assembly lubricant to ensure consistent torque readings.
Lubing with regular motor oil is discouraged due to inconsistent clamping forces. (THIS IS REFERING TO THE UPPER FINER THREADS< NOT THE
CORSER STUD THREADS IN THE BLOCK
7. To apply the proper preload to the studs follow the manufacturer’s recommendations.
Torque the nuts in three even steps until you reach the recommended torque spec.
Note: clamping forces will change when installing new studs. Check the main bearing housing bores for proper size and out of round condition. In most cases align honing the mains with the new studs properly torqued will be necessary to ensure proper fit and clamping forces.
Editors note: If you found this article helpful, please click HERE to let them know and to order you copy of their 2013 catalog.




61G0MlyI29L._AC_SL1000_.jpg

stressx4.png

the answer depends on what your intending to do with that engine build and your budget.
think through your choices carefully.
chevy rates the two bolt SBC blocks at 350hp, but everyone has seen two bolt blocks built to produce 450 hp,
and stand up to that power level for short term stress.
the stock two bolt main cap block works ok up to about 400-maybe occasionally 450hp, if its only run hard occasionally.
adding splayed main caps aids the lower end rigidity, but its likely to cost you over $600 in parts and machine work costs
and might allow that original block to handle 500hp-550hp
(yeah I hear all the screams about guys who swear they build 500 hp sbc engine with two bolt main caps all the time)
theres a huge difference between hitting 6000 rpm plus occasionally vs regularly, and pushing 500 hp every once in awhile,
and running an engine hard/frequently at that power level like a dirt track cars engine! STRESS IS CUMULATIVE
if your intention is to build a daily driver , get main cap studs and use the block,
if your intention is to run the crap out of the engine added splayed main caps and spending $600 plus on caps and machine work might make sense, if your goal really exceeds 500 hp or you want a heavy use of nitrous buy a Dart or BOWTIE 4 bolt block
DART blocks are built with better quality cast iron, higher nickel alloy and have much thicker castings

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/


Since you have studs, can you measure the stretch instead of measuring the torque

since you can't get access to the other end of the stud ,
(unlike rod bolts)
as its threaded into the block web,
even if you placed a dial indicator stand
Amazon.com
71MN5pwVnpL._AC_SL1500_.jpg

on the block and use the dial indicator on the stud, you don't know how much movement is related to stud stretch or block web deformation as the load is increased. on the block web and main cap being squashed

63521_W3.jpg


.https://www.cpgnation.com/how-to-measure-bolt-stretch-for-proper-torque/

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

http://garage.grumpysperformance.co...onnecting-rod-rod-length-too-stroke-info.510/


https://www.hotrod.com/articles/using-rod-bolt-stretch-tool/

.https://www.cpgnation.com/how-to-measure-bolt-stretch-for-proper-torque/

www.enginelabs.com

Video How To: Measuring Rod Bolt Torque And Stretch - EngineLabs

In this quick-hit video how-to, Real Street Performance's Jay Meagher shows how to measure rod bolt stretch, and provides a number of tech tips in the process.
www.enginelabs.com
www.enginelabs.com
www.motortrend.com

How to Use Rod Bolt Stretch Tool Stretching Exercise - Car Craft Magazine

Car Craft magazine takes a closer look on why to use a a rod bolt stretch tool
www.motortrend.com
hotrodenginetech.com

ARP Rod Bolt Stretch Gauge How-to - Hot Rod Engine Tech

Most engine builders concede that torquing rod bolts during final assembly is no longer an accepted practice. While no doubt adequate for general engine rebuilding where loading rarely approaches that of competition levels, basic rod bolt torquing simply cannot account for...
hotrodenginetech.com
main-caps.png

Stretching Exercise

Quote Reply
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Last edited:
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 ?
 
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.
 
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
 
t6nisson Writes:

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

the Girdle in your above Pic looks like a good design

i just do not like its made of aluminum
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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
 
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
 
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
 
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?
 
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 !!!
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_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst ( DragStrip Simulation Software )
PipeMax ( Engine Simulation Software )
http://www.maxracesoftware.com
 
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
 
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.
 
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
 
Larry Meaux Writes:

1 more thing i forgot to mention is "Taps"
icon_e_smile.gif


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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