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Overheating and combustion chamber seal

From: Keith Clements
Category: Technical
Remote Name:
Date: 05 Jan 2002
Time: 19:24:43


You might like to discuss ‘my theory’ that the blocks stretch so not allowing the correct pressure to be applied to the head gasket thus causing leaks and overheating.

I was at Spero’s mending his Jup yesterday and did my usual set up of the liners by bolting down without a gasket to 20ft/lb(no more or you will crack the block!) and then checking for 8thou all the way around. Usually even if the liners were set correctly originally they will sink or part of the block will stretch particularly around the bottom centre studs. I have even found over a week the gaps close signalling a creaping crack or necking of the bock or bolt. Note it is VERY important to torque in the correct sequence and in 5 lbft stages or you will notice the head not going on square. Try it, feeler gauging at each stage.

Most of the gaskets I see from people with heating problems have the gasket in the top outside corners of the combustion chambers blackened while the rest is clean alu or cooper. This is caused, I think, by incorrect liner pinch.

Note I stick the shims on the head face of the liner and check without gasket at 20lbft before finally taking the liners out to fit permanently.

Note the Jowett Service bulletins (75,90,113)and manual say 8-12 thou and 40lbft final torque if you do go to these limits you need a really good block which really should have been strengthened with weld. Even metal gets fatigue and old age!

Note I have also reused gaskets for years since they are already compressed which helps when you do not have the luxury of being able to retoque after 200 and then 1000 miles. Note if the nuts turn when retorqueing you may have a neck or crack problem. Make a note of which ones do!

Doug Rath asked how to get a reliable Jowett. The answer is good engineering patience. You have to look hard and check everything. You cannot just fit components to Jowetts.

Keith Clements

-----Original Message----- From: bill lock [] Sent: 04 January 2002 10:52 To: Subject: Re: jowett contacts in Australia

keith Thanks for your recent message. Mike is coming to my house with Ted Cockerell on Wednesday 9th January at 12.30 pm to discuss engines crankcases and visit my store. you are welcome to join us .He is also going to the NEC AUTOJUMBLE next Sunday 6th.The only contact number I have is 01275 392782. Might you be interested in attending our Midland Section Annual Lunch at Ullesthorpe near Lutterworth on Sunday 3 February? If so please let me know. Best wishes Bill Best

Last changed: November 19, 2008