MilesA Posted April 13, 2015 Report Share Posted April 13, 2015 At the weekend I decided to catch up on a number of outstanding jobs on the car including the relatively straightforward one of replacing two weeping gaskets - one on the thermostat housing the other between the housing and the block.. However, when I attempted to bolt the housing back onto the block I could not get any real purchase with the bolts. Looking at the bolts the threads seemed a bit deformed but not stripped. Using new, replacement bolts had the same result. The housing seemed reasonably secure even if I couldn’t ‘lock’ the bolts down. Ran the car statically for about 20 minutes (I was testing other work) and the head / housing gasket did not leak, but I am not convinced as the car was not being run in anger. Looking at the original bolts, I noticed some sort of crud on the threads so I suspect a PO has had a similar problem and used some substance to secure the bolts. The original gasket had been fine for about 5 years but was pretty degraded when I removed the housing. So I do not think head / housing gasket was weeping because of the housing not being bolted down, as some (but not excessive) force was required to free the bolts. So, is there a fix that I can employ or is this one for the professional engineers? Many thanks. Miles Quote Link to post Share on other sites
RogerH Posted April 13, 2015 Report Share Posted April 13, 2015 Hi Miles it sounds like the thread in the block is wearing out. Ideally you need to get the thread sorted - 5/16 unc helicoil. If it is not as tight as you would like then simply apply the torque figure for it (is it in the WS manual) . If it pops before that figure then the choice is made. Helicoil into the block is fairly straight forward and upmost precision is not required here - try and keep the tapping drill as square as possible. Roger Quote Link to post Share on other sites
mleadbeater Posted April 13, 2015 Report Share Posted April 13, 2015 Hi , a tip for drilling square when fitting helicoils is to drill on a pillar drill, (ie square,) a hole in a block of hardwood or better still metal, of the od of the tap, then use this block over the hole to be drilled and tapped, as a drill and tap guide. Cheers Mike ps another solution is to make some oversize stepped studs, say 3/8'' Whitworth at one end and 5/16" unf at the top end, again tapping the block with the oversize thread using the above method. Quote Link to post Share on other sites
RogerH Posted April 13, 2015 Report Share Posted April 13, 2015 Hi Mike, good idea about using a makeshift drilling guide - it will help. As for 3/8 whithworth - which planet are these from - helicoil back to standard everytime. Roger Quote Link to post Share on other sites
AlanT Posted April 13, 2015 Report Share Posted April 13, 2015 A 3/8 Whitworth is to all practical purpose identical to a 3/8 UNC. I have UNC Helicoils here if you need. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted April 13, 2015 Report Share Posted April 13, 2015 Tap right through with the original 5/16 unc then use new longer threaded bolts that will grip in all the thread. Vertical studs to hold the t/stat housing on are a nuisance on the TR2-3B model as you need to slip the housing rearwards to disconnect the top hose. Peter W Quote Link to post Share on other sites
MilesA Posted April 14, 2015 Author Report Share Posted April 14, 2015 Gentlemen Thank you as ever for all the practical guidance. A choice between helicoil and Peter's suggestion of tapping all the way through the shelf on the block I think. In fact the existing threaded area on the block has a smaller hole drilled right through. I think Peter's solution has the added benefit that if the block thread gets damaged again, I could secure the bolts with nuts (and an appropriately shaped spacer). Miles Quote Link to post Share on other sites
RogerH Posted April 14, 2015 Report Share Posted April 14, 2015 Hi Miles, you Ludite What is wrong with a Techno-Whizzo- superduper- whistles and bells- helicoil. They are the flavour of the month. Good luck with the drilling. Roger PS- if it goes wrong don;t use nuts - remember the helicoil Quote Link to post Share on other sites
mleadbeater Posted April 14, 2015 Report Share Posted April 14, 2015 Roger, nowt wrong wi Whitworth threads, invented by a Yorkshireman you know, good enough f't Rocket then good enough fer TR's. Bettter than this UNC yankee rubbish. Seroiously though, the main point is to use coarse threads in castings, Whit, UNC, Metric coarse or whatever. Mike Quote Link to post Share on other sites
BlueTR3A-5EKT Posted April 14, 2015 Report Share Posted April 14, 2015 Roger, nowt wrong wi Whitworth threads, invented by a Yorkshireman you know, good enough f't Rocket then good enough fer TR's. Bettter than this UNC yankee rubbish. Seroiously though, the main point is to use coarse threads in castings, Whit, UNC, Metric coarse or whatever. Mike You want a good read then have a look at this. http://books.google.co.uk/books/about/Sir_Joseph_Whitworth.html?id=ZENSAAAAMAAJ Peter W Quote Link to post Share on other sites
mleadbeater Posted April 14, 2015 Report Share Posted April 14, 2015 thanks Peter, will try to find copy, this guy IS the standard. Mike Quote Link to post Share on other sites
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