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cracks in saloon block?

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nkh763
Posts: 24
Joined: Mon Feb 15, 2016 4:01 am

cracks in saloon block?

Post by nkh763 »

Hi there.

A spare engine has been stripped down for assessment and, although the heads are fine, there are fine cracks from three of the bolt holes towards the cylinders.
Is this a common issue or solely related to over-tightening of the head bolts? I had a search through old and new forums and couldn't pin down a relevent thread. I am assuming sourcing a new block the best course of action?

Cheers,

Nigel

Christopher Storey
Helpful Person
Helpful Person
Posts: 404
Joined: Wed Mar 16, 2016 6:40 pm
Location: Cheshire

Re: cracks in saloon block?

Post by Christopher Storey »

I had this on my V8, with hairline cracks from the waterjacket at the corner of the block . It was fairly easily repaired using nickel screws drilled and tapped into the cracks . You need an experienced machinist to do it for you . I also had the ubiquitous cracks between cylinders on a Jaguar 4.2 engine repaired in the same way

tjt77
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Posts: 525
Joined: Wed Mar 23, 2016 7:01 pm

Re: cracks in saloon block?

Post by tjt77 »

Just faced the self same issue with a jaguar 3.8 block that had been 'rebuilt' but was very tight to turn.. after it pulled apart I discovered there were cracks between the intermediate liners.. I repaired it by drilling and tapping the cracks to 1/4" NF... and screwing in some bolts coated in red locktite..then chopped of heads of bolts with die grinder. This bridged the cracks perfectly . I then sent the block out for a line bore of main bearing housings.. and to have the top face of block and timing chain cover milled flat.. re-fitted the crank this am and its now spins beautifully .. all ring gaps and piston to bore clearances measure up perfectly, so I'll get back on the rest of assembly Monday..
Issues of 'cause and effect' :- I have some light timing chain noise on the current 3.8 Mk2 jag and suspect that the real issue is that the top idler wheel that tensions the chain is not getting oil (its a plain bearing, drip fed from a hole in the timing wheel holder..car had sat for about 20yrs and has some internal crud build up).. I can get the chain quiet.. but it seems to be WAY too tight when adjusted for no noise.. one notch backed off and there is noise that sounds like the chain wheel vibrating just above idle speed.. same noise as one gets from a lucas heater motor with dry bearings.. it will probably run just fine 'as is'..but i want it to be 'right' so a major engine dismantle is on the cards to do so..

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