Head bolts

ChrisJC · Post by **ChrisJC** » Thu Apr 10, 2008 7:25 am

I'm in the process of changing the head gaskets on my RV8, and I'm using stretch bolts with the Range Rover Classic EFi front cover.

Now, the alternator bracket fixes onto the front-lower head bolt on cylinder 1, which is a special bolt with a short threaded extension above the bolt head.

In the past I've fitted a conventional (i.e. not stretch) bolt in this position, and stretch bolts elsewhere.

I'd like to fit a stretch bolt in this position too, is there such a thing as a stretch bolt with the threaded extension to take the alternator bracket?

Ta,

Chris.

badger · Post by **badger** » Thu Apr 10, 2008 10:56 pm

No such thing Chris. For what it's worth, I see more rover engines with head gasket failure through the workshop that have stretch bolts than "normal" bolts. The stretch bolts release their clamping force over time and cannot be re-torqued. My personal preference for a bullet-proof build is an ARP stud kit, second choice being the early type non-stretch bolts.

ChrisJC · Post by **ChrisJC** » Fri Apr 11, 2008 7:30 am

Interesting.

I've had two engines fail, both banks, cyls 5 & 6 leaking to the outside. Both had tin gaskets & stretch bolts. One 10.5:1, one 12:1, running LPG.

I've changed one to composites & stretch bolts and am in the process of doing the other.

So I'd not recommend tin + stretch bolts. Either that or I'm incompetent (not impossible!)

Chris.

sidecar · Post by **sidecar** » Fri Apr 11, 2008 9:44 am

How much do the stretch bolts cost? If they are getting on for a ton then you may aswell by the ARP studs!

I Fitted studs to my 4.6 and a must say that they were a very nicely made bit of kit. I only torqued them to the standard setting as I think that the clamping force that they produce is greater due to them having a very high tensile strength. (Even non stretch bolts must stretch to a degree, this reduces the clamping force).

No more torquing into ali threads....my pet hate!

Pete

ChrisJC · Post by **ChrisJC** » Fri Apr 11, 2008 11:55 am

Set of 20 cost about £25 from eBay.....

Chris.

sidecar · Post by **sidecar** » Fri Apr 11, 2008 12:35 pm

ChrisJC wrote:Set of 20 cost about £25 from eBay.....

Chris.

I see!

badger · Post by **badger** » Wed Apr 16, 2008 7:57 pm

Yep, that's £25 every time..... as opposed to £90-something from ReelSteal once only.
Normal bolts do stretch, as do studs, but only within their elastic limit. Stretch bolts are deliberately deformed beyond the elastic limit which is why they are once-only use.
As to torque, you can go to 70lbft but no further or you risk pulling the ally threads from the block! Be aware though that the finer thread on the nut end of the stud gives a far higher clamping tensile force in the stud at the same torque as an equivalent coarse thread.

ChrisJC · Post by **ChrisJC** » Wed Apr 16, 2008 8:05 pm

Possibly talking at cross purposes here.

The £25 from eBay is for stretch bolts. I've fitted the stretch bolts everywhere apart from the one odd bolt where I've reused the old non-stretch bolt.

BTW, I don't like the stretch bolts because the first ones you wind in are quite tight as the compress the gasket, but the end ones always seem relatively easy as the gasket is already compressed.........

Chris.