Conrod Bolts/nuts...

[matty_gti 20]

Well my 8v 1.6 - 1.9 conversion is under way, i thought id just get everything replaced, but i didnt think my wallet would get this dented , o well.

 

Any way, ive got some 8v 1.9 balanced pistons/rods, and i hear that the conrod bolts are the stretch type?, because my first idea was to use my 1.6 conrod bolts but if there the stretch then maybe not.

 

I allso have a lightend and balanced flywheel and crank (which is getting reground as i type this), becasue i would ideally like the car to rev a little higher that the standerd 6250rpm, is there a big need to go for the ARP conrod bolts or shall i just go with the standerd bolts from Peugeot?, and do i need to buy new nuts for the bolts or are they all supplied as a set?.....and if any one knows the best place to buy the ARP bolts and any prices....

 

ThAnKs

[Sandy 189]

I had an ARP bolt strip its thread the other day (before reaching peak torque, correctly lubricated etc etc) and have since had other engine builders confirm that they've had issues. possible the quality isn't what it was. I'd stick with new OE ones if I were you, the Peugeot ones are better than average and haven't let me down yet.

[jim21070 2]

I had an ARP bolt strip its thread the other day (before reaching peak torque, correctly lubricated etc etc) and have since had other engine builders confirm that they've had issues. possible the quality isn't what it was. I'd stick with new OE ones if I were you, the Peugeot ones are better than average and haven't let me down yet.

 

 

I have heard that some ARP bolts are a few thou' too long and bottom out in the thread bore, hence the stripping before full torque is reached.

 

Recommended to shorten them a tad...

[matty_gti 20]

ok, im getting it now. just outa interest what does OE stand for?

 

And when i buy the new bolts from Peugeot (only £40 or so), is there any prep work before fitting, i.e, lubing them up??, if so how much and what is the best way of tightning them?, Ive heard tighten/loosen them to 3/4 of the torque specified 3 times, and them do it to the correct full torque?.

[jackherer 543]

OE = Original Equipment

[matty_gti 20]

Thanks for the tech info

[Sandy 189]

Use a graphited grease on the thread and nut face, first time you tighten them, tap them all lightly with a small hammer, then repeat tighten then full torque.

[PumaRacing 1]

I had an ARP bolt strip its thread the other day (before reaching peak torque, correctly lubricated etc etc) and have since had other engine builders confirm that they've had issues. possible the quality isn't what it was. I'd stick with new OE ones if I were you, the Peugeot ones are better than average and haven't let me down yet.

 

Well I've certainly never had a problem with ARP bolts breaking and I find it vanishingly unlikely that there ever would be such. They manufacture out of higher strength materials and to a higher quality of finish and checking than anyone else in the business. I'd want an awful lot of verified independent evidence before concluding that an ARP bolt had failed during fitting rather than the fitters torque wrench was out of calibration of he'd missed some other factor. They don't supply most Nascar and F1 teams for no good reason.

 

Of course anyone can have a one in a million random failure but that's no reason to decry the entire company.

[M3Evo 0]

I have heard that some ARP bolts are a few thou' too long and bottom out in the thread bore, hence the stripping before full torque is reached.

 

Recommended to shorten them a tad...

 

But there isn't a threaded hole in the rods, the bolts are a bolt and nut arrangement so shortening them won't achieve anything!

 

Don't forget to check that the head of the bolt sits properly on the rod as the packaging warns you to check this for good reason!

 

We had to have a chamfer put on the Mi16 rods we assembled using ARP bolts!

[Sandy 189]

Glad to hear you've not had any trouble Dave, I was expecting the obvious "my error" reply, but not from you. That's a cheap shot and perhaps a slight on the quality of my work.

 

This one (the last of eight succesful 7 were ok) just pulled the thread, not entirely, but enough not to torque smoothly and make me dissemble to look and see what was wrong. I was working to 35lbft as is recommended, having only the previous day had a conversation with someone (with a great deal more experience than me) that habitually uses 45lbft, but I prefer to stick to the recommendations, being well aware of the risks of not operating to specs.

[matty_gti 20]

You have a very fair point indeed, its all about having experiance.

 

I know people have there own way of tightning the bolts but is there a 'best' way?, and do i use greese on the threads 'n' nut face or engine oil?

[M3Evo 0]

Seem to recall that the ARP ones come with their own lube.

[petert 554]

If you aren't using a rod stretch guage and logging the results you're probably wasting your time with the ARP bolts anyway. Better off using new OE bolts.

[pug_ham 242 3 Cars]

I asked Shenpar this a few years ago when I was rebulding my engine & they'd never heard of many oe ones failing so for the cost stick with them.

 

Graham.

[PumaRacing 1]

If you aren't using a rod stretch guage and logging the results you're probably wasting your time with the ARP bolts anyway. Better off using new OE bolts.

 

Nonsense. If you're using a high quality bolt which successfully takes more torque than an OE one then by definition you've achieved a higher clamping force and a joint which will survive at higher rpm.

 

It might be nice in an ideal world to use stretch as a means of optimising a bolt's position on its yield curve but that's no reason to suggest a lower grade bolt is preferable to a higher grade one if you don't have a bolt micrometer.

[petert 554]

Have you done a yield test to determine the limits of the OE bolt? On the XU engines I've seen blown up, (broken rods, spun bearings, etc.) the cap is always still securely clamped to the rod, within spec. It's been my observation that other parts tend to fail first, or cause a spun bearing, thus money is better spent elsewhere first.

[niklas 1]

It doesn't differ that much between new OE bolts and ARP bolts...

[matty_gti 20]

If you aren't using a rod stretch guage and logging the results you're probably wasting your time with the ARP bolts anyway. Better off using new OE bolts.

 

So with the OE ones i dont need to measure the stretch?

 

Just to make sure i can only find the torque settings in the 'older' haynes manual

 

Main bearing caps nuts and bolts- 49Nm

Big-end cap nuts- 49Nm

 

Do i just tighten them right up to the torque?

 

With the Main bearings caps do i need to replace the bolts???

 

When fitting the Main cap No 1 it says oil pretty much every thing, should i cover all the other main caps (mateing surfaces,thread) 'n' bolts in oil?

 

When fitting big-end caps do i keep the mating surfaces clean except for the bearings which will be coverd in oil , and the thread which ill just lightly oil......doesnt say in the ye old book.

 

Sorry with all the stupid questions

[niklas 1]

It doesn't differ that much between new OE bolts and ARP bolts...

 

Money-wise

[PumaRacing 1]

Have you done a yield test to determine the limits of the OE bolt? On the XU engines I've seen blown up, (broken rods, spun bearings, etc.) the cap is always still securely clamped to the rod, within spec. It's been my observation that other parts tend to fail first, or cause a spun bearing, thus money is better spent elsewhere first.

 

Have we been discussing just this specific engine or the generalities of ARP vs OE?

 

The std XU nut/bolt being a 9mm fine thread one is a very strong item anyway. Most XU engines aren't going to need anything stronger. The same sized bolt/nut is used in the Ford Pinto. The 91mm piston in that weighs a ton and the rod isn't light either. A std bolt will cope with that much weight at 8000 rpm. With the much lighter XU parts I doubt if the std bolt is going to worry too much at anything under millions of cycles at 9k rpm.

 

I certainly wouldn't bother with ARP in an 8v XU road engine. In fact I wouldn't even bother with new OE bolts. At 6.5/7k you aren't going to use up the fatigue life of a std 9mm bolt until hell freezes over.

 

This is not the same thing as saying OE bolts are just as good as ARP ones which clearly they aren't or that other types of engine might not need better bolts than std.

 

Engines with 8mm bolts like the CVH, K series and Zetec obviously have a much lower margin of safety for a given rod/piston weight than engines with a 9mm bolt. Then there's the Vauxhall XE engine which has 9mm bolts but inexplicably they are coarse thread not fine so they are much weaker than they need be. This is such a basic design point I fail to understand why it was done. Mind you I dislike most of the design points in that engine.

 

The other thing you have to take into account is the material the std bolt is made from. Most engines use 10.9 grade steel. The Rover K series uses 12.9 which is nearly 20% stronger. How much stronger again ARP bolts are depends on material spec for each application. For Nascar and F1 applications they have materials which are nearly twice as strong as a 10.9 grade steel but they don't use that for common or garden road engines.

 

The final thing most people are unaware of is that required bolt strength varies with the square of engine speed. If you are going to tune an engine such that it revs to 8k instead of 6k that's a 33% increase in rpm. That means you need a bolt 1.33 x 1.33 = 1.78 times as strong to give you the same fatigue life as std.

 

Just putting a 20% stronger bolt than std into an engine and thinking it's then bulletproof no matter what you do to it is about as wrong as you can be.

[Anthony 1,000]

On the XU engines I've seen blown up, (broken rods, spun bearings, etc.) the cap is always still securely clamped to the rod, within spec

I've seen two XU9J4 engines where the big end bolt has failed and caused the bearing cap to come away from the rod on one side - however, given that I suspect that on atleast one of those engines old rod bolts had been reused multiple times and driven very hard, it's prehaps not entirely suprising...

[Miles 331 1 Cars]

The OE bolt I;ve got here you can see how bad the construction of it is as it's in 2 bit's, but it's just a standard part and you can;t ask for more from it.