I would not bother rebuilding an impreza engine with standard rods.

the sti pistons are more than decent, it is and always was the rods that cause the problem.

Rods dont have to be as expensive as you make out. I paid much less than that for my billet rods.

[Edited by Adam M - 8/2/2002 9:48:51 AM]

 

the standard rods are forged steel as far as I know.

is it possible/practical/cheap to get them cleaned up and shotpeened?

actually submanz's suggestion doesn't sound as bad as I first imagined. Although tapped threads might not be so smart.

Carrilo use SPS bolts I thing, which Mr Carrol seems to think highly of in Engineer To Win, but maybe things have moved on.

Paul

[Edited by Pavlo - 8/1/2002 8:21:24 PM]

 

Yes this helps, thanks steve.

What's involved in re-circling the rods? Is this a regrind? Would it need bigger shells? Or is a just a case of bending them into shape.

A combination of bolts, surface smoothing and shot peening sounds like it might be worthwhile.

Anyone got some low mileage rods for sale? Adam?

Can I measure the stretch with a modified micrometer, just use a ball bearings at each end of the bolt.

Cheers

Paul

[Edited by Pavlo - 8/1/2002 11:10:02 PM]

 

as subject, what's the deal with these? Do arp do any, i have heard not. Any alternatives? Is it a standard bolt that can be replaced with an aero spec item?

All info gratefully recieved.

Paul

 

They bore out the conrods and tap then use bigger high strength bolts

 

that doesn't sound so good to me, stronger bolts, weaker rod...

I haven't seen the bolts yet, but it they are standard hex head bolts, I would have thought arp do something, or maybe even Unbrako or similar.

Paul

 

paul, what havent you seen, the standard bolts?

if so, do you want me to take a piccy of mine in a bit

 

Why do you want to uprate them???

Your not upping the revlimit?? or are you thinking for when you change the pistons to just put better ones in because youve got it in bits?

David

 

I am thinking for the future, with lighter pistons etc. Having read a number of posts on the MLR regarding bearing shells spinning an whatnot.

Uprating the bolts can't be a bad thing all in all.

cheaper that spending £600+vat on billet steel rods

Paul

 

david,

i am leaving mine as standard, and keeping the rev limit the same.
doing the pistons and a few other bits at the moment, but at a later date will fit steel rods, flywheel etc

p.s. you going to TOTB at elvington on sunday?

cheers
ian

 

much less than £600 +vat? that sounds like it could in the ball park.

If you can bear to mail the details I would be more than grateful.

Paul

 

And me..

Yes Im off to york weather permitting.

David

 

You can use mini cooper arp bolts, but you have to ream the bolt holes 3/8, about .020 bigger, then recircle the rods as the bolts act as dawls to locate rod and cap 20 thou will not affect strenght
you also have to mill .040/1mm off the nut seat on the cap. Sounds like a lot of fluffin about but its not that bad, but steel rods is the way to go if you can get them at a good price.
Steve.

 

Pavlo you could use a bolt, but then your relying on the material of the rod to take the thread stress over the arp material 170,000 or 190,000 psi, although the bolt will be more than up to the job would say, you will still need to recircle the rod. Big end clearance say .002 if that cap moves as little as .001 half a *** paper you have half the clearance and a rod housing that is not round. Recircle 4 rods £25 + vat. A few good points with arp is that you can take a static measurment of the bolt, log it, next time you rebuild check measurment if more than .001 static lenght bin it, only expect this with B/E failure. Many people use a stretch gauge to tighten rod bolts expect 5-6 thou stretch on a rod bolt, to much or to little stretch and bolt will fatigue and will FAIL, all a torque figure is, is a predetermined amount of stretch, manufactures rely on the threads and the seat of the bolt being coated with a 30 grade light oil for the figures given, lots dont bother. ARP stretch gauge £70 there are centres machined in the bolts for these measurments. Hope this helps steve.

 

Pavlo you could use a micrometer with b/bearings, just with a stretch gauge you see the stretch as you tighten the nut so you will not over stretch the bolt, so with a mic extra care will have to be taken. When recicling a rod you remove .002 of the cap and rod on a cap and rod grinder (made for the job), then set the rod housing size on a 3 way measuring device which measures size and ovality, so you have in effect made the hole oval, then hone the rod round again checking size and ovality. This will drop the piston down the bore half the total material removed.
Steve.

 

Std size bearings are still used as rod I/D is machined back to std. Arrow precision wiil shot peen 4 rods for about £40+vat ask for Dave Correy.01455 234200
Steve.

 

of course, remove material from the cap!!

I am used to 2 stroke rods without a split BE.

Are the operations you mention something you can do? If so mail me with some prices etc.

Thanks

Paul

 

Paul YHM mate.

 

SMG Can I have mail, or paul could you forward me details..

David

 

David YHM mate.