Pre-detonation or Big-end nock.

[68vitesse]

Blew the head gasket between five and six in my 2L Mk1 engine and noticed a knock on acceleration only afterwards and was wondering if hot gasses from the adjacent cylinder could cause pre-detonation,or have I damaged a big end. I don't have a two inch micrometer to check the crankpin diameter and don't want to go to the trouble of removing the crankshaft unless I have to.

Currently have a spare engine fitted so no rush to refit.

Regards

Paul.

[Pete Lewis]

i cant see a HG failure causing any journal problems its not related unless you emptied the coolant in the sump and drove for miles on 

a nasty mix of oil and antifreeze in an overheated uncooled engine 

but knocking from the cross flow between 5 &6 will do a variety of knocks ,bangs and whistles 

 

[johny]

Not too difficult to check the big end shells in situ anyway if you are worried. You'll know from the shell if theres a problem and then have to measure the crank...

[68vitesse]

Thanks for the replies, didn't lose any coolant, engine temperature normal,  and oil was not contaminated so hopefully just a head gasket problem.

Regards

Paul.

[NonMember]

My Mk1 Vitesse went through a few years of blowing head gaskets between cylinders. It makes a godawful racket of knocks, like Pete says. Partly it's down to the combustion on one of those cylinders happening while the other has an open valve.

[Pete Lewis]

so remove studs clean the faces   die the threads on the studs fit HD nuts and Hard washers  or if its a 3/8 stud use flange faced head  nuts from minispares 

bet the old washers have deformed  this looses torque the head pants and pop goes the gasket

Pete