Hi fellow f4i owners,

I'm gathering a shopping list of parts to buy for my engine and wondering if the head bolts are reusable (the 10 "9mm" cylinder mount bolts w washers) or are they the stretching torque-to-yield kind
I looked in the service manual, it only tells me to apply oil and install them. I guess that might mean it's reusable, but don't wanna assume and be wrong. anyone know?

Also on a side note - the manual says the head bolts are 9mm but I've taken apart 2 f4i heads and they're 12 mm (if I remember correctly). Same with the "6mm flange bolts" they are deff not 6mm. Like wut??

Thanks all and have a good day

 

you'll be fine reusing them. just dont over tighten them when torquing them. dont want to strip out the threads on the case.
i figured those bolts were 10mm, maybe 9, But you use a 12mm socket on the head of them. and 6mm bolts have a 10mm head on them....assuming thats what causing your confusion.

 

Stretch bolts should be replaced. Once they stretch, they're done.

sjona2011 is correct about the bolt sizes. The size of the bolt refers to the diameter of the bolt, not the size of the wrench that fits the head.

 

So they're not stretch bolts?

Oh yeah the bolt size thing makes sense now lol.... just naturally assumed they meant the bolt head mm. XP

 

What is the tightening procedure in the manual?

If they just tighten to a spec, they are not stretch bolts.
If the tighten to a spec then tighten more by degrees of rotation, then they're stretch bolts.

 

"Tighten the 9-mm bolts in a crisscross pattern in two to three steps in the specified torque (TORQUE: 47 Nm (4.8kg/m, 35 lb/ft)"

So I guess that means they are not stretch bolts, and are ok to reuse.

Thanks 74demon! Good info for the future as well

 

I've not seen the type that quote a spec then degrees. Where can such bolts be found usually?

 

Many headbolts are like that now. The tightening procedure will be something like; all to 30, back off 2 turns, tighten to 36, then all 90 degrees, then all another 90 degrees.

All bolts stretch though. They are like torsion springs. I'm even seeing aluminum bolts more these days. Those are one time use because once they twist, they don't unwind and will break if they are torqued further.

 

I imagine it's a lot of stress on the threads.

 

i think even re-usable head bolts deserve to be measured for stretch...