13 replies to this topic

[087dave]

Hi all

I have replaced the cam bearings on my mg metro engine with a tool

But when I tried to put the camshaft back in it is very tight

Does anyone know why this is?

Tks

[Fast Ivan]

they will need finishing to suit the cam, see here

 

http://www.theminifo...shaft-bearings/

[087dave]

Thanks rob

But I can't even get the camshaft into the bearings it's very tight

[ACDodd]

of the ones I fit, 2 or 3 sets out of 10 will require the front bearing scraping all the way through. This is why DIY fitting of cam bearings is not always a straight forward operation. If you don't know how to do this I would suggest taking it to a suitable engine establishment to have them ease the fit for you.

 

AC

[Spider]

All Cam bearings I've ever bought were finished to size right out of the box, though I do acknowledge that they do show Cam Bearing Reaming Tools in the Factory Workshop Manual.

 

How did you actually fit the bearings?

 

For starters as well, turn the cam back to front and see if the front journal fits in to the front bearing. You should also be able to do the same with the rear one.

 

Pretty rare, but I have had maybe one of two bearings that needed a small scrap, but that was from tunnel misalignment rather than being undersized.

[Guess-Works.com]

I suspect an edge has been "bumped" during installation, I'm not a fan of tools which use a hammer action to install cam bearings, much prefer a "wind in" approach. I'm currently awaiting the delivery of an new tool for installing cam bearings.

[mini13]

yep as above, as long as you pull the bearings in gently without them going on the piss, or there being any marks in the block they should fit the cam fine...

 

bit if they dont yoey will need easing wit a bearing scraper.

[Turbo Phil]

My Dad made a tool for pulling in cam bearings as part of his apprenticeship. That pullers now over 45 years old and has done a fair few sets of bearings in its life.

Phil.

[087dave]

I have looked again and there's a high spot alright where the bearing joins

Would it be ok to rub this high spot with a needle file or wet/dry paper? After all a cam scraper is a 3 sided file

[ACDodd]

Do not use abrasive paper, a small needle file is ok, as long as it has not got hard material already imbedded in the teeth. Any material in the file is easily embedded in the soft bearing material. That's why they are scraped.

Drifting bearings in is fine, as long as you chamfer the driven face with a bearing scraper before you drive them home. In virtually all cases, the bearings need tweaking as mentioned above, around the join and sometimes the front one comes up small, all the way through, this has nothing to do with the method of insertion, it's purely toleranceing. In some cases the block is too large for a new bearing and new oversize replacement has to be made to fit. I once had a rear oil pump liner tunnel that was 0.010" oval and 0.003" tapered. No off the shelf bearing could correct that. I had to make an oillite bush fit and then scrape the bore to fit the cam. A pain to do, but it saved another block going to the scrap yard!

AC

Edited by ACDodd, 22 March 2015 - 10:44 AM.

[087dave]

Thank AC

The camshaft is in now and it's turning with the help of a spanner

Should it also turn by hand?

[ACDodd]

It needs to turn by hand.

AC

[mini13]

yeah, needs to turn easy with thumb and index finger.

 

if youve got  bench grinder you can convert a three sided file to a bearing scraper, just grind the seratioons off... the grind stone wil give a slightly convex face so it scrapes. try not to get it too hot or it'll lose its hardness, but if you do re heat it and quench it, then give it a final quich sharpen.

 

slide the cam in rotate it and take it out and look for polished areas, scrape these.

[Fast Ivan]

You might find that grinding the teeth off a file will make it impossible re harden as some files are only case hardened. Also you will want to do some tempering after hardening steels.