cliftyhanger
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| posted on 26/11/16 at 02:44 PM |
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Zetec/st170 main and big end torques
Just putting my engine back together, and struggling to find info on the big end and main bearing torques. And added to that seems some are saying
they are stretcg bolts and should be replaced, but can;t find normal ones for sale, only ARP.
Can anybody point me in the right direction here? Std bolts will be fine, and besides, the mains are marked up as 10.9, so appear to be normal bolts
(as opposed to stretch)
Cheers
Clive
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chris
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| posted on 26/11/16 at 04:32 PM |
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I tried to find tappet gaps for my St170 engine
Turns out it's a state secret and risked life imprisonment if I carried on with my enquiries
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obfripper
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| posted on 26/11/16 at 07:56 PM |
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The ford etis shows 'refer to relevant section' in the st170 engine torque specs section, and then doesn't have the relevant section
for rebuilding the bottom end.
If you are replacing with arp bolts you will need arp's own torque specs with arp lube, or a bolt stretch gauge and the correct bolt stretch
value.
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
I will have a look at the older pc tis discs to see if it's a website omission or if the section was never published for the st170.
The bolts are stretch, but there is a possibility that the bearing cap bolts may have a limited reuse capacity, as the head bolts are also stretch and
can be reused twice before replacement and should be dot punched to indicate previous reuse.
Main dealers will be able to supply standard bolts, pumaspeed or burtons may supply them.
Dave
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cliftyhanger
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| posted on 26/11/16 at 09:28 PM |
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That is really useful info.
Seems it is easier to find specs (and parts) for a 1960's engine than a 15 year old ford one (guess because so few actually get rebuilt)
I have now ordered a set of ARP BE bolts, and will reuse the mains. Still a bit confused with the 10.9 spec on those, and they just don't look
like stretch bolts. Ho hum.
Cheers
Clive
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Hornet
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| posted on 27/11/16 at 08:58 AM |
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Never worked on the st170 just the duratec and sima ze. If the 170 is the ladder type bearing carrier then I wouldn't worry about using same
bolts. Not a lot of stress on them. The big end bolts are your main concern and as you state, you have bought arp ones
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