bigend/mains knock knock

[shuey]

hi peeps need to pick some brains again my tr6 has developed a bigend/mains knock more mains at the mo I was hoping to do a complete engine rebuild next winter not just at the mo firstly i want to use it and more to the point I can`t afford it at the mo.

 

is it worth droping the sump and just doing the shells as a quick fix will they last

 

ifso can you get enough movement on the crank to flick them out with engine still in car

 

would it be worth while setting a bit more oil presure to help things for timebeing

 

any other ideas would be greatfuly received

 

I KNOW WHAT I`VE GOT TO REALLY DO IN THE END

[mikew]

Mains bearing failure tends to rumble more than knock.

 

Big ends knock and if left untreated will make the end caps oval, so even after a crank grind and new shells the problem returns quickly and you have wasted the rebuild money.

 

Drop the sump and investigate.

 

Pure wear in the shells - revealed usually by seeing copper emerge through the white metal amy be fixable (on a temporary basis) by replacing the shells.

 

However crank journals that are scored need regrinding - anything else is a waste

 

Raising oil pressure won't fix anything.

 

If money is short how about a cheap second hand engine - seen running - drop it in and sell it later after fixing your own you'll recover most of your money this way. I think flying englishman on ebay has one for sale - smokes abit but no knocks - should run for the summer

 

mike

[Richard Crawley]

Yes you can change the mains/end shells & thrust washers by dropping the sump, it's not a particularly nice place to work though & if you haven’t got a ramp; you need to get the car up off the ground a fair bit to give enough room to work in. Changing the shells will almost certainly make a difference but for how long rather depends on how knackered the journals are! Don't try & increase the oil pressure as it will not make a lot of difference & will cause all sorts of other problems; are you absolutely sure it’s the bottom end? if it’s really rattling badly, I would plan on a rebuild sooner rather than later!

[shuey]

thanks very much chaps for advice

faily sure it`s bottom end nasty knock on staring for the first couple of turns good oil presure when cold but fades away when hot and coasting down to about 25 psi not much of a knock when warm but you can feel it if you put your hand on the engine I`ve backed the timing of to try and releive a bit of presure on the crank

I know there`s only one true cure but I`m just trying to nurse her along at the mo