Hitchcocks Forum

The threads on three of the stud holes for the rocker boxes on my cylinder head have stripped. (Why is not clear to me).
What chance helicoiling them without removing the head?
'89 350.

Hi JOHN R ------------ every chance , as long as you can get to them from above.( the drill and applicator need to be at right angles to the aluminium face.). Try to have some compressed air to hand as this will effectively clear out the bottom of the blind holes. Which 3 are the "naughty rascals" then ??

The book quotes 1.5 ft lbs for the nuts. Seems a very small value but I've followed this without problem.

You can get 1/4" cycle nyloc-nuts these days but have to admit haven't tried them yet so don't know if there is enough thread showing on the standard stud for them to get a griP!!!!

With the front of the bike being 12 0'clock, the stripped ones are 6, 9 and 12 o'clock. This joint doesn't contain any real pressure, and with the torque values being so low, I might get away with just helicoiling two out of three. I must confess to tightening them to "one grunt with a 12" bar" previously, which may be the root of the problem.

Is there room to go up to 8mm?

I had to helicoil them all , once done all things will be cool , I had to do
my rocker block threads as well , the most important thing is making sure they are straight and use rags to catch the bits of alloy and if you can blow it clean with compressed air , it's a well known weak point of the head . My rocker covers never leak , and if you use the bike for life you will have to do many de-cokes unless you run on meth , I got caught out on the mini barrel stud ( push rod side ) that should be helicoiled as well . Indian alloy is a tad soft .

Got to disagree with you there Phil - Indian alloy isn't a TAD soft

Bloomin-eck!!--John, did I read that correctly ??--- A 12"(Twelve inch) bar ???? STREWTH, as Norm might say. Yep !! that WAS a tad overtight there me old china....But be of good cheer as last week I've stripped two rocker-block ones just AFTER fitting the head back on !!-BUMMER !!!!!!!!!

Alan,
I think I have heard that the Samrats are supposed to be tightened in inch pounds, something like 5 inch pounds. Could be way off the mark but I always just give them the slightest wrist nip, and I can't say I have seen them come loose at any stage