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+--- Thread: Head bolts (/showthread.php?tid=3651)
Head bolts - Yianni - 09 Nov 2012
Hi all:
When installing new head gaskets with existing heads should I use new head bolts? I realize that they have been stretched, but can they still be used again? The manual does not specify. Also, does anyone have a better torque procedure than what's shown in the Delorean manual?
Thank you all for any input
Yianni
Re: Head bolts - Guinney1971 - 11 Nov 2012
Martin G or RichH are probably best to answer this, but I'd say yes to changing the
head bolts, especially after all these years.
We fitted new ones to #2292 when the heads were done in 2003.
Re: Head bolts - tgraham - 12 Nov 2012
Quote:When installing new head gaskets with existing heads should I use new head bolts? I realize that they have been stretched, but can they still be used again? The manual does not specify. Also, does anyone have a better torque procedure than what's shown in the Delorean manual?
This is similar to an oil discussion - you'll get a lot of (different) answers and (strong) opinions
Here are mine:You can reuse the existing bolts as long as they're in good shape (make absolutely sure the threads are good). It's a good idea to run an M12-1.50 tap through the threads in the crankcase to clear out any debris, but if you keep on going, you can actually tap more threads towards the bottom of the holes - just clean everything out really well when you're done (use brake cleaner and compressed air). In some cases you can extend the threads quite a bit! But by ensuring that the threads go completely through the crankcase, you won't stand a chance of "bottoming out" the bolt's thread when you torque them down.
The DMC manual is derived from Volvo (and maybe others) manuals from the 1970s. Take a look at the B28F manuals linked from here, which are from the 1980s (really modern!): http://goo.gl/BFSy8 It includes a new torque pattern and if you're rebuilding the engine, it's definitely worth a read in its entirety. There used to be some PDFs of Renault manuals lurking around somewhere too, probably from Martin.
Also, instead of the angle torquing procedure from the DMC and Volvo manuals, an alternate procedure is to torque the bolts to 25-50-75 ft-lbs (incrementally, following the pattern you choose). Make sure you use a good torque wrench and that it's accurate. This procedure eliminates the need to heat the engine (sealing the gaskets), then take the valve covers off, make a mess, slacken the head bolts, angle torque them again, check the valve cover gaskets, etc, etc.... Just torque them down and you're done! A few shops over here use this technique - I've done it too using the updated pattern. I've never heard of any complaints or issues.
Good luck.
Travis