ST170 crankshaft main bearing torque

[MarkBzero]

Hi,

I have looked on the internet and I am getting different results.

Does anyone know the torque setting when fitting ERA sump to ST170? I have to undo 4 main cap bolts to fit the windage tray.

Any help appreciated.

Thanks Mark

[maca]

Hi Mark,

Detalis from LOCOSTBUILDERS.CO.UK

These tightening values are for standard bolts in a us focus svt, the engine is identical to the st170 lump.
Main bearing cap bolts

Stage 1: 25 Nm
Stage 2: 60 degrees

Connecting rod bearing cap bolts

Stage 1: 35 Nm
Stage 2: 90 degrees
 

[MarkBzero]

Thanks Maca, I was not sure if this applies when I am replacing the bolts with the ones from Tiger Racing. They say 60 lbs ft. I feel more comfortable with angle guage.

[maca]

Please note! they say that the bolts are stretch bolts so may have to be replaced?

Regards Martin

[MarkBzero]

Thanks Maca, I have a spare engine if it goes bang!

[Bob Tucker]

I am coming at this from zero knowledge of this engine, but it seems odd that the conrod bolts are far tighter than the mains bolts, or is that all to do with different stretch properties?

Just interested.

 

[brumster]

Your main end bolts are typically much bigger though, plus they're not getting flung around at several thousand rpm I would just suspect the loading on the rods is higher than the crank caps, but that's just my FingerInTheAir-o-meter working rather than anything quantifiably backed up by science

[MarkBzero]

9 hours ago, brumster said:

Your main end bolts are typically much bigger though, plus they're not getting flung around at several thousand rpm I would just suspect the loading on the rods is higher than the crank caps, but that's just my FingerInTheAir-o-meter working rather than anything quantifiably backed up by science

I agree, plus the Conrod is only 2 small bolts versus 10 for main end bolts and much larger. 

I will try on the weekend and follow Tiger Racing instructions I have a calibrated torque wrench. What could possibly go wrong.....famous last words.

[Bob Tucker]

Well those figures are backed up here too, but it does seem to refer to ARP bolts

https://www.focaljet.com/threads/torque-specs-zetec-engine.510001/

[MarkBzero]

3 hours ago, Bob Tucker said:

Well those figures are backed up here too, but it does seem to refer to ARP bolts

https://www.focaljet.com/threads/torque-specs-zetec-engine.510001/

Thank you.

[Bob Tucker]

Just for interest I'm building a modified Redtop (again) using ARP bolts everywhere.

The settings are 32 ft lbs big end bolts, and 65ft lbs mains studs.

[brumster]

4 hours ago, Bob Tucker said:

The settings are 32 ft lbs big end bolts, and 65ft lbs mains studs.

I am guessing you're saying that for the fact the mains studs seem higher than the big end bolts but do you not have instructions on 2 or 3-stage angle-based tightening *after* that inital torque setting?

[Bob Tucker]

A bit off topic now, so I'll leave the thread for the OP's st170 question after this.

Thats the final figure. I tighten in 3 equal (ish) steps, finishing up at 32 and 65.

But I stress they are ARP non-stretch bolts/studs, so no direct comparison for stretch bolts.

The rod end bolts torque figure  seems crazily low, but this is the 4th redtop ive built, all using ARP rod bolts.

One was even designed for 8k rpm with forged rods, & is still running strong (right Kevin?)

https://tech.arp-bolts.com/instructions/109-6001.pdf