Topic: 400F Heavy Duty Cylinder Studs - Do I really need them?

[ag12680]

Folks -

I searched on this topic and did not find an answer on 400s.

Building a lightened cafe 400F with an ebay 466 kit, APE lightened crank, deleted kickstarter, modern ignition, aftermarket exhaust etc.  Everything else in the motor (cam, valves, head) is stock.

Love the work APE did on my crank, but I'm after a mild yet reliable power increase leaving room for more down the road to do more with the head and carbs if I want to throw more $ at the project.

Given this scenario, I would appreciate input on whether HD studs/nuts are worth the additional costs for this build?

Thanks much,

Andy --

[neevo]

Keen to see what the experts say on this.

[afkrejci90]

Well if you are looking to do stuff to the head for more power down the road, why not spend the ~$100 or whatever the cost for the insurance that your engine will be held together with quality studs over stock.  Since you have the engine apart already, put them in now so you don't create more work later. 

[Tim2005]

I'd certainly consider them, but do APE studs actually have a higher torque setting than stock ones?  There was an unanswered thread on that somewhere, also about what nuts to use. Also changing studs does of course mean removing the old ones, which can be very difficult indeed, so it'd be useful to know what benefit APE confirm they will bring before deciding. 
BTW, are you doing anything to raise the compression, and will you be running an oil cooler?

[Jerry Rxman Griffin aka MuthaF'er]

You don't NEED but it's a good idea on a built engine that gets the xtra abuse. Stock studs stretch. At least on the 750s.

APE studs, upper and lower, are torqued to 20 - 22 lbs which is higher than stock. I used new Honda nuts. 

[kyre]

I used them for my 466 build. I'd go for it, they aren't expensive and very we'll worth it. I only torqued mine down to 19ft lbs since I was afraid of stripping even though they are rated for 20-22.  I believe stock is 16 or 18 ft lbs.  nuts are stock. ZERO head leaks.

Removing the old studs was a pain though! I ended up renting a stud remover from autozone and it worked great. Just dont expect to re-use the stock studs as the remover will chew them up. Double nutting did nothing on removing for mine.

[ag12680]

Thanks for all the helpful input guys.  I'm going for them on the basis of future mods and to reduce the possibility of any leaks with the 466 kit.  Will skip using their nuts though.

This is an eBay kit that does not raise compression as far as I know.

Fortunately, the stock studs came out cleanly with some "encouragement" and patience.  Just have to know when to walk away in the heat of the moment...!

Leaks were the tipping point.  I don't like leaks and had not planned to run an oil cooler unless my temps show otherwise.

Again, appreciate the advise from all...

Andy --

[specweld]

If your beefing up a 400/4 motor, I would be more concerned about the con rods than the cylinder studs, the very least you should do is have the standard rods polished to take away any sharp edges(especially on the shoulders).

Standard rods do have a nasty habit of snapping on over bored engines.

My honda 400 is bored to 500, has 11-1 compression, produces 63 bhp and runs on standard cylinder studs, but it does have special rods made by Robson Enineering (uk).

hope this helps.

[70CB750]

After reading stories here, I would not use them.

You are better off with original proven studs and retorque them.

I don't remember ever hearing about original studs to snap on torquing.

Are the HD studs threads rolled or cut?

[ag12680]

Thanks for addressing the rod issue.  I'll look into what can be done stateside.  Want to stick with the stock rods.  Wow, what's your cylinder wall thickness at that bore?

The HD studs are from APE.  I don't know if they are rolled or cut.

More to ponder.  Have not ordered yet,

Thanks again,

Andy

[Jerry Rxman Griffin aka MuthaF'er]

APE are rolled. They are stronger than stock bottom line. Yes, some of the 750 guys have talked about snapping them. I'm not sure that any of these guys have mentioned the amount of torque they are applying to cause this?! I've been into mine a few times and no issues. Does Kibblewhite do 400 studs?

Specweld may be the only 400 guy I've heard that has special rods. It doesn't hurt anything except perhaps your wallet. Stronger rods are insurance at the least.

How does sharp edges affect the strength of rods?? That's the impression I got from that statement.

[Old Scrambler]

Jerry and others.............sharp edges and machining-marks offer the potential for the beginning of a fault when the rods are subjected to more than standard loads. Think of it this way.......the sharp edge is actually a very thin piece of steel and could begin to weaken after normal heat-cycles. By shot-peening and polishing the rods, you eliminate the weakest part of the rod.  Often times the after-market performance rod is only slightly beefier than the standard unit.........but it sure is pretty

[afkrejci90]

  Often times the after-market performance rod is only slightly beefier than the standard unit.........but it sure is pretty

I'd have to disagree, my Carrillo's make the stock 750 rods look like tooth picks.

[thirsty 1]

Jerry and others.............sharp edges and machining-marks offer the potential for the beginning of a fault when the rods are subjected to more than standard loads. Think of it this way.......the sharp edge is actually a very thin piece of steel and could begin to weaken after normal heat-cycles. By shot-peening and polishing the rods, you eliminate the weakest part of the rod.  Often times the after-market performance rod is only slightly beefier than the standard unit.........but it sure is pretty

I call Bullhsit. There isn't any reason a sharp edge on a rod or any other piece of metal going up and down will effect the strength of a rod. As for the head studs I'd go stock and torque them to the recommended torque.

[70CB750]

Yeah, back in the day, russians did not trust their metallurgy - for a good reason I say - so on the russian tank everything was beefy, LOL!  But that's not what good engineering is about.

Sharp edge or a nick can be and often IS the starting point of a failure.

[specweld]

Andy, bike has special liners intstalled to keep the thickness required, if you bore the standard liners to 56.5 the wall thickness becomes too thin.

Jerry and Thirsty 1, try a little research on 'NOTCH EFFECT' and 'POLISHING CON RODS'

Below result of using standard rods in beefed up 400/4s

I have been racing my cb400 since 1977 and  know of many people who have snapped standard rods.
As I got the impression you don't intend to race it , that's why I made the suggestion to at least polish.

Hope this helps.

[Tintop]

Not sure that's an approved method for welding up a head.

[kmb69]

I call Bullhsit. There isn't any reason a sharp edge on a rod or any other piece of metal going up and down will effect the strength of a rod. As for the head studs I'd go stock and torque them to the recommended torque.

Wikipedia:

In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.

Fatigue occurs when a material is subjected to repeated loading and unloading. If the loads are above a certain threshold, microscopic cracks will begin to form at the stress concentrators such as the surface, persistent slip bands (PSBs), and grain interfaces.[1] Eventually a crack will reach a critical size, and the structure will suddenly fracture. The shape of the structure will significantly affect the fatigue life; square holes or sharp corners will lead to elevated local stresses where fatigue cracks can initiate. Round holes and smooth transitions or fillets are therefore important to increase the fatigue strength of the structure.

Duh!

[specweld]

Tintop,

managed to find all the pieces and weld it all back together, back on track within half an hour ,,Honest...

[turboguzzi]

wow, thirsty, using the BS word here is a bit harsh. dont take my word for it though, just read some metallurgy texts on stress raisers or stress concentration in cyclically loaded parts and you might change your mind...

Andy, like others here, would recheck priorities. seen a few 400s explode also here in italy so would have spent my pennies on rods rather than a lightened crank... honestly, a lightened crank is something you do when you are searching for the last fraction of second accelerating out of turns or sprinting out of the blocks, never seen that as crucial on the street. Heck, i even road race with stock cranks....

[Tintop]

Tintop,

managed to find all the pieces and weld it all back together, back on track within half an hour ,,Honest...

 

[Doctor_D]

Jerry and others.............sharp edges and machining-marks offer the potential for the beginning of a fault when the rods are subjected to more than standard loads. Think of it this way.......the sharp edge is actually a very thin piece of steel and could begin to weaken after normal heat-cycles. By shot-peening and polishing the rods, you eliminate the weakest part of the rod.  Often times the after-market performance rod is only slightly beefier than the standard unit.........but it sure is pretty

I call Bullhsit. There isn't any reason a sharp edge on a rod or any other piece of metal going up and down will effect the strength of a rod. As for the head studs I'd go stock and torque them to the recommended torque.

Of course this was nothing other than a vanity move...

[afkrejci90]

I call Bullhsit. There isn't any reason a sharp edge on a rod or any other piece of metal going up and down will effect the strength of a rod. As for the head studs I'd go stock and torque them to the recommended torque.

Wikipedia:

In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.

Fatigue occurs when a material is subjected to repeated loading and unloading. If the loads are above a certain threshold, microscopic cracks will begin to form at the stress concentrators such as the surface, persistent slip bands (PSBs), and grain interfaces.[1] Eventually a crack will reach a critical size, and the structure will suddenly fracture. The shape of the structure will significantly affect the fatigue life; square holes or sharp corners will lead to elevated local stresses where fatigue cracks can initiate. Round holes and smooth transitions or fillets are therefore important to increase the fatigue strength of the structure.

Duh!

Exactly this^^^  This is the reason high pressure tanks have rounded ends to evenly distribute the stress.  An example, scba bottles are subject to extreme temperatures and quick temp changes and they can over pressurize more than the normal bottle pressure at room temp, corners could make them susceptible to failure.

[70CB750]

Just nick a rubber band and watch where it brakes.

There is whole science around steel parts breaking and i spent too much time in CVUT labs to ignore that.

[thirsty 1]

wow, thirsty, using the BS word here is a bit harsh. dont take my word for it though, just read some metallurgy texts on stress raisers or stress concentration in cyclically loaded parts and you might change your mind...

Andy, like others here, would recheck priorities. seen a few 400s explode also here in italy so would have spent my pennies on rods rather than a lightened crank... honestly, a lightened crank is something you do when you are searching for the last fraction of second accelerating out of turns or sprinting out of the blocks, never seen that as crucial on the street. Heck, i even road race with stock cranks....

Ya that was a bit harsh. I had alittle to much Cool-Aid last night. Sorry dude. Stress risers are bad news.