Big Ends

[AlanBartlett]

I think i may be on to some quite serious engine damage, while manovering the car in and out the garage, the throttle return spring came adrift from its mount on the floor board as I was putting pressure on the pedal to give it the last umph up the drop kerb into the garage. I felt the pressure release on the pedal, it quickly for revved higher than id ever heard it before, i got to the ignition as quick as could to turn it off. Now when i start and run it i have this knocking sound metallic dull knock as described in another post when I rev the engine. . Which answering my own statement is the big ends, which also means engine out again. Though oil pressure has always been betwen the 30 limit, and never dropped below 20 so possibly not enough pressure to the big ends causing the damage. Will investigate tomorrow when I get the engine out.

[george garside]

Alan, you can remove the con rods without removing the engine. It might be woth trying to ascertain which big end (if thats what it is) is effected by shorting out each plug in turn - it should be the side that goes quiet i.e. does not knock when shorted out..

[AlanBartlett]

Ive got the engine out, and the pots off, and the con rods out, it was the drivers side which had caught, you can see in the metal its moved about, as there is small rough patch in the smooth ness of the bearing, it has several scores in the metal itself, but does not seem really deep, but Im sure its probably not helping matters. Ive gotten quite used to the engine coming out, have got it down to a fine art, about and hour to take out, hopefully not too long before I can put it back together again.

[AlanBartlett]

On further removal of the engine internals I think. well i know Ive found the source of the ominous knocking. It turned out to be the rear main bearing, its locator slot has sheared and the bearing is free to move from side to side inside the rear main housing. I do have spare so now im in the midst of finding a place to machine it to the right size.

[Tony Fearn]

Alan,

Is it not possible to press out the bearing, turn it 90 degrees or so having milled-out another locator slot, and then re-produce the oilway in the different position.

Just a thought... don't know much about engineering, but you'd still be able to use the original.

Tony,

[george garside]

Tony's idea seems quite reasonable provided the white metal bearing surface is OK as the crankshaft win't know which way round the bearing housing is anyway! It is my understanding that if a different bearing is used it will need to be line bored which I am not sure would work well on a used bearing off another engine . Other than using Tony's method it may well be better ,since the engine is out and dismantled to fit remetled front & rear mains & line bore them in situ.
This also raises the matter of measuring crankshaft ovality & wear on mains & big ends etc etc

george

[AlanBartlett]

On further inspection, the rear main, has obviously picked up something in an oil way, and has scored the inside of the rear main heavily. Although I do have a spare which I intend to have bored out to the right size, The front bearing also has deep scoring in it too, are these bearing matched? I know they are line bored straight through, but are they the same front and rear? As part numbers in the book 2011x?? both have a 1 and 2 next to them? As i do have a second spare rear wondering if it was possible to fit in the front, just a suggestion bearing in mind im no engineer. Not unless JCS, do new ones which I'd ideally like to do.

[george garside]

Alan,its not so much a question of a 'new' one but of having a pair( front & rear) remettled then line bored in situ as a pair. I'm sure Ian Priestley will have arrangements on behalf of JCS to have remetaling done or to put you in touchwith the right outfit to do the job. There may well be others on this forum who have appropriate contacts as well so all you willneed is a front and rear bearing casting in good condition.

george

[AlanBartlett]

Thats what I was unsure of, if it is possible to remetal/repair them, and get them re bored to match my crank. I know they do this with big ends but wasnt sure if they could do it with the mains.

[george garside]

if rplacing mains it makes sense to look at big ends as well with view to having conrods remettled if necessary. Before dicideing what to do check the crankshaft ( mains & big end journals for both overall size and ovality) as it is a waste of time putting new big ends on an oval shaft. Talk to Ian about costs etc.

[AlanBartlett]

Having looked at my spare mains, its unlikely to be able to be used again, so am going down the new route. and rebore them to match the crank, the big ends were done only a year ago, and at this time the engineer also checked out the mains to be fine, also double checked tolerances with GW, the big ends have had just over 250 miles use out them. So fairly happy that they are going to be ok, Am just going to start from scratch again, and go through everything to make sure its going to last more than 250miles this time

[Tony Fearn]

Hello Alan.

Years ago I added a second much lighter spring to the accelerator rod on both pre-wars, just in case a scenario as you opened this post with occurred.

Tony.

[Forumadmin]

Very wise to start again and check everything. Bent con rods, ovality, line boring, ... you name it , anything can cause premature failure. It may be worth assembling and then dismantling to see what might be rubbing, or even running for a few miles and then dismantling.

[Tony Fearn]

Alan,

This is on eBay, but I don't know whether they'll be suitable. Perhaps someone will advise.

http://www.ebay.co.uk/itm/Jowett-Bradfo ... 3cc3e303df

Tony.