Triumph Repair: Herald 1200 main bearing size?, main bearings, thrust washers

Question
QUESTION: Hi Jim

I know you don't specialise in Heralds but i thought i'd ask a question anyway in the hope that you might be able to help (spitfire has similar parts i understand)

I have recently had a problem with the thrust washers dropping into the sump, and so i'm changing the main bearings (they are very worn) and am going to drop in some new thrust washers (perhaps oversized ones to avoid this happening again)

However i bought some new main bearings and am having trouble slotting the upper halves over the crankshaft, i haven't yet tried turning the engine to help slot them in but i was worried because the old main bearings seem awfully thin in comparison to the new ones which are 2mm thick.  Do you happen to know the standard thickness of the Herald 1200 main bearings?

Kind regards

ANSWER: Rob,

Yes, it's true that the Herald 1200 is basically the same as the Spitfire MkI/II 1147 engine (ok, in reality the Spitfire "borrowed" the engine from the Herald ;) so you're not off base with this question.

2mm sounds about right for a new bearing shell.   Actually I'd have said closer to 3mm, but without measuring one myself it's just an estimate.  Currently I'm away from the workshop, so a measurement would need to wait.

I have some questions myself.   

What size bearings were in place currently?   They're typically marked on the back with the undersize (.010, .020, etc).   Are you replacing like for like?

How do the main journals look? Heavily grooved?  Or still basically smooth?

And have you checked the new bearing shells for any burrs, etc?

It is possible to change the bearings with the engine in the car in a pinch but it's not really a good practice.  It'd be better to pull the block and have it properly checked by a machine shop.


Cheers,

Jim

---------- FOLLOW-UP ----------

QUESTION: I could not find a relevant number on the back of the old bearing, I just found two numbers 140111 and 4921, I'm not sure if you can make any sense of these?  I was hoping to replace like for like so I bought what I thought were standard sized herald 1200 main bearings, they were original stock from ebay (so I'm just hoping really) but as I said it's very difficult to tell how thick the original ones were because they're so knackered.

The main journals still look smooth.

I haven't yet checked the new shells for burrs, but now you mention it that's something I should do to avoid scratching.

Ideally I'd take the block out but in all honesty I'm on a very low budget at the moment (I'm a student) and I'm just trying my best to fix the problem.  Taking the block out is something i'd consider doing in the summer when it's a little warmer!

Thanks for your help it's appreciated

Rob

Answer
Rob,

What brand replacement bearings did you pick up?   And part number?   And did you try to look up the part # to see if it's correct for the 1147?

And do you have all the main caps slightly loose?  Or are you just trying one at a time?   A few thousands of an inch in clearance can make all the difference in getting the bearing to slide in smoothly.


Cheers,

Jim