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MG Midget and Sprite Technical - ASeries front camshaft bearing renewal. Easy&cheap

If you allow me to finish 7 posts sequentially, before any replies -- if anyone wants to -- it'll make it easier to follow later.


How to do an A-Series camshaft front bearing renewal, EASILY, QUICKLY, and CHEAPLY.

(I'm not sure if this would work in the same way for a 1500 Triumph engine. I haven't got one to test it on. But in principle, I can't see why not, other than perhaps you can't get the same type of bearing.)


Some of you may remember the oil sucking threads. Some of you may remember that about a year ago, in attempting to identify the exact cause (I failed), I did at least identify that my front camshaft bearing was knackered. I also confirmed that the other two camshaft bearings were barely worn at all. This is apparently quite common. So I decided to only replace the front camshaft bearing.

I removed the front bearing with the intention of having it replaced professionally. But as is my nature, I just couldn't bring myself, to pay someone else to install the new camshaft bearing, without first establishing that I couldn't do it myself.

The upshot is, that I did it myself. Not only VERY easily, but quickly, and VERY cheaply too. In fact it didn't cost me a penny to replace it, other than the cost of the new bearing of course.

Here's how.

I drifted the old knackered front camshaft bearing out, with a home made tool. It's just a short section of an ally scaffold tube, that I cut a slit in, to reduce the diameter, to enable it to slide through the empty front bearing hole in the block, as I drifted the bearing out. I used a bit of threaded stud and a couple of large washers, with a little help from a hammer. The bearing came out quite easily.

Here's my home made removal tool.

Part 2/7 follows.

Lawrence Slater

Type of bearings to buy.

Most (not all) people say that camshaft bearings have to be either reamed or scraped after they are installed. However, this only applies to split ring unfinished bearings. If you buy solid ring PRE-FINISHED bearings, they are advertised as not needing to be reamed. I can confirm that. They don't need to be reamed/scraped.

Here are the two types side by side.

Part 3/7 follows.

Lawrence Slater

Installation tool.

How do you install the new bearing in the engine block without a professional tool? You make your own. In fact, if replacing only the FRONT bearing, you don't even need to make a tool. You already have one. It's called a camshaft. It's quite likely that you're replacing your camshaft, if you are replacing a knackered camshaft bearing. Hence, you can use your old camshaft as the installation tool, with no worry about damaging it. But even if re-using the old camshaft, or only have a new one, you can use that too, because this doesn't damage or alter the camshaft.

First, install the camshaft sprocket onto the camshaft, BACKWARDS. Put on the retaining nut, but only tighten it to sit flush with the end of the camshaft.

This will give you a FRONT camshaft bearing installation tool, that because it runs through the existing two other bearings, exactly lines up the front bearing, as it's pushed into the block. What could be simpler, or cheaper? Maybe something, but I can't think of it. – Unless of course you already have, or have access to, the correct tool set.

Here's a picture of mine, assembled with my OLD bearing in place. The picture shows the OLD bearing on the camshaft, because I forgot to take a picture before I started to install the new bearing into the block. :-

Part 4/7 follows.

Lawrence Slater


I marked the block to show the exact position the bearing would need to go in at. I used the main oil feed to camshaft bearing, as my guide. The additional advantage of these Glyco bearings, is that in these bearings, the oil feed hole to the cylinder head, is larger than the hole in the engine block. This makes it much easier to get the main oil feed slot/hole, lined up exactly where you want it to be.

This is a picture showing my markings for the oil hole alignment. It's with the OLD bearing in place. The split was widened, to allow me to reduce the diameter, so I could slip it in and out by hand.

Part 5/7 follows.

Lawrence Slater


Oil the new front bearing, inside and out, the bearing retaining hole in the engine block, and the existing camshaft bearings in the engine block.

Slide the new bearing over the camshaft, and onto the front journal. Carefully slide the camshaft/sprocket/new bearing assembly into the block, paying close attention to the relative positions of the oil holes in the new front bearing, and the engine block.

The rear and centre journals, will just enter the rear and centre bearings (if you don't over tighten the sprocket nut), thus aligning the new front bearing perfectly. The new front bearing will be sitting at the face of the engine block, with the chamfer of the bearing, just inside the bearing retaining hole in the engine block.

It looks like it'll work to me. Famous last words?

Part 6/7 follows.

Lawrence Slater

Ready to go?

The reversed camshaft sprocket is a perfect surface to press against the lip of the new front camshaft bearing. The camshaft journal, prevents the chamfered lip of bearing folding in and being damaged.

Hit it with a hammer!

I could have welded, or drilled and tapped, some threaded stud to the rear of the camshaft, and pulled the new front bearing into place in the engine block. However, research online showed that many people simply drift them in without problems.
Because I like simplicity, that's what I did, and why I didn't need to alter/damage the camshaft. With a tad more care, I could easily have used my new camshaft, and would have done that, if I didn't have an old one. But I didn't need to.

With the block vertical, my 'camshaft bearing insertion tool' assembled and in the ready position, my oil feed holes lined up, and it all lubricated, I placed a bit of wood over the nose of the camshaft, and thumped it with a 4lb club hammer. It was very satisfying to see the new front bearing gradually, but easily, sink into the block.

I continued to drift the new bearing into the block, until the bearing reached a point where it was almost flush with the face of the block. I had to stop at the point. Because the reversed sprocket rim sits proud of the inner circle, I couldn't push the bearing in anymore with the sprocket. I could have made a packing washer to sit behind the sprocket, which would've allowed me to continue. But I couldn’t be bothered, since I already had a 'tool' that would complete the job.

Here's a picture showing the new bearing, a little over half way in.

Part 7/7 to follow.

Lawrence Slater

Tools to complete the job.

With the lip of the new front camshaft bearing, now almost flush with the face of the engine block, I removed the sprocket from the camshaft. I left the camshaft sitting in the bearings, to prevent damage to the lip of the front camshaft bearing, as I completed the job.

I then used an old brake calliper piston, that I had left over from a Girling 'type 14' calliper rebuild. It's the perfect diametrical size to sit over the threaded nose of the camshaft, and exactly on the lip of the front bearing. It's also EXACTLY the right depth, to be able to knock the bearing in flush, but NOT knock the camshaft rear lobe, into the inner face of the rear of the engine block. -- About a 1mm clearance.

Once the new camshaft bearing was in flush, I used my other 'tool'. This is the same tool I used to remove the old bearing. Again, leaving the camshaft in place to prevent damage to the lip of the bearing, I carefully drifted the lip of the camshaft bearing, just below the surface of the block face. I did this to maximise the oil feed to the front camshaft bearing/journal, from the main crankshaft bearing/journal, whilst still ensuring that the oil feed to cylinder head from the camshaft bearing wasn't obstructed at all.

Here are picture of the tools I used to complete the job.

And that's it. Done and dusted. A complete, quick, cheap, and easy job. Much easier than I expected in fact.

I'll now get on and build the engine.

Feel free to critique my efforts.

Lawrence Slater

I missed the cam bearing in the oilsucking thread Lawrence. Maybe I had to sleep lol!

But that's clever. Turning the camwheel around backwards is great.

If I ever have to do it on my 1500 I'll post what happens. I've printed your procedure for my geek folder.


Oilsucking threadZZZZZZZ grey. There were a FEW of them, and not at all short. You must have had a loooooooooooooooooooong sleep. lol.
Lawrence Slater

From memory (which is often wrong these days!) I don't think the 1500 uses replaceable camshaft bearings. I think it runs directly in the block.

Smart method Lawrence. Printed and saved for future reference!
Guy W

I had dreams (nightmares?) about how to do it Guy. But in the end, it was so simple. It really surprised me just how simple it was.

Shame if it can't be used on a 1500 then. Maybe a B-series?

And here, by the way, is my NEW camshaft.

It's a brand spanking new, BMC old stock item.

It was on sale on German Ebay, badly worded, and seemingly not noticed by anyone else.

I paid 50 quid for it plus 10 quid postage. However, because they failed to describe some very mild surface marks on the centre journal, I asked for and got, a 10 quid refund.

I polished out the surface marks with a non-scratch nylon pan scourer, and some liquid metal polish. Not a mark left on it.

Bit of a bargain I think, esp' for a spyder drive, which are getting a bit scarce.

Lawrence Slater

I think you're right Guy based on the two Spitfires I've done, but I have a dim memory of a version with a bush. Can't remember if it was early or late type or if it was another Triumph engine altogether. Possibly to do with thinking about the GT6 that now lives in The Shed. I'ts just a tickle in the back of my mind ATM. Bloody Ageing!

But I still think it's an inventive idea.

God told me how to do it, in a dream. Dream on! LOL.

You have a GT6, that you don't use Grey?
Lawrence Slater

You can get the Glyco bearings on ebay, circa 22 quid.

But Minispares still have them for
Lawrence Slater

Ah no. Forget it. I was confused. It was a conversation with the Brother I was thinking about maybe 30 years ago when he was kindly explaining the superiority of Minis over Spitties.

He had a tool based on a slide hammer that pulled and installed the bearings.

The Triumph reference came from someone who found a way to fix the crank-whip at high revs on 6 cyl Triumphs. Nothing to do with camshafts. Sorry I mis-spoke.

The GT6 lives in The Shed Lawrence, but it's not mine sadly. Belongs to a mate who has nowhere else to keep it, which is a subject for debate beween me and SWMBO.

I have always liked them.

He insisted on adding me to his insurance and I sometimes give it a little exercise. It's a sh***y job but someone has to do it!

I'll get some photos next time.

I've always liked them too. A bit like a mini E-type -- To a one eyed man ;). If I hadn't bought a Sprite, I'd have had a Spit, and either got a GT6, or put a GT6 in a Spit.
Lawrence Slater

TBH I didn't much like the Spittie. I thought it was too heavy for the engine. I did think it looked nice though. I saw one in Tarbert not too long ago.

I had a Mk2 GT6 in the early 80's. It was a total rot-fest and I blew it up thrashing it and scrapped it. My great regret is that I didn't save the O/D gearbox. I'd love to have that back for my Midget.

The one in the Shed is a Mk3. I've posted the pic before but here she is.

I think she needs a set of Minilites. What do you reckon?

I'm booked to do a top end rebuild this winter, side by side with the 1500. Should be fun, but ATM I'm flat out on a couple of fishing boat engines. BTW if anyone knows of a stash of bits for Gardner reduction boxes I'd be interested. I think maybe Noah's decendants might have something under the bench LOL.


Yup. Nice. And I agree, needs better looking wheels. Minilites fine too. How about slots?
Lawrence Slater

Well it looks like winner idea

But I think there are easier and less risky ways to save $20 at the local machine shop... maybe sweep there floor as a barter trade

Prop and the Blackhole Midget

Grey... to easy to common. Id look for some 70s era aftermarkets

Craiger SS, or some slots/mags would look sharp
Prop and the Blackhole Midget

You know what? Your American Racing wheels would be nice on this car. But it's not mine so I don't have spend any money on it.

Really nice to drive btw, but it'll be better when I sort the exhaust out so it doesn't ground so easy.

You have strange views sometime Prop.

"But I think there are easier and less risky ways to save $20 at the local machine shop... maybe sweep there floor as a barter trade"

What risk? How easier? Sweep someone's floor?

My "local" machine shop is 45 mins away, EACH WAY. He doesn't 'do it while you wait'. So even if I was willing to sweep his floor, I'd have to leave the block there, drive home, wait for him to email or phone me to tell me the job was done, drive back and collect it, and pay him, plus the petrol, significantly more than "$20".

Now contrast that with what actually happened.

10 min's to cut of a short length of ally tube, and slit it to make a removal tool for the front camshaft bearing.

Less than 5 min's to remove the front camshaft bearing from the block.

1 minute to fit my sprock on backwards on my old camshaft. Plus 5 seconds to slide the new bearing over the camshaft and onto the front journal.

1 min' to mark out the oil feed hole to line up the camshaft bearing.

1 min' to slide the camshaft assembly into the block, and rotate the bearing to coincide with the marks.

10 mins to drift the new camshaft bearing into place, and this includes using my finishing tool.

Total time, circa less than 35 mins. Cost ZERO. Risk, none. Ease of job, VERY.
Lawrence Slater

Lawrence, although l like the idea and would probably copy your method, l did wonder about the bearing alignment.

One aspect of reaming is to "line bore" the 3 bearings after installation to ensure the alignment of all 3 on the same axis. Well that's the theory. But assuming the block hasn't been damaged or warped in some way l can't really see how they would not align automatically when assembled by your method. And if there was any misalignment l guess you would feel the camshaft binding if it was inserted without the star drive, and turned by hand.

On balance, personally, l am sufficiently convinced but add this in case others are concerned and may have some other insight.
Guy W

Im certianly on the fense on this one as well,

I just assumed they had to be line bored and reamed cause thats what I was told but that always seemed like alot of work to me for know more then what it is

This is one of those areas where experiance is going to play a real part

Ive only done this one time, I remember looking back it wasnt cheap to do, but the fact that I dont recall and have had no issue with camshaft binding... probably says I made the right call ... for me, soneone else with more knowlege and experiance... probably not.

There is obviously a reason the machine shop does the work they do and not just bang those puppies in there and check mark the hit list
Prop and the Blackhole Midget

I think if the block was damaged or warped then those nice pre-sized main bearings that everyone expects off the shelf would be useless.
David Billington

If the block was warped or damaged, it would likely have happened when the previous camshaft bearing was in there, and you would have known about it because the camshaft would have already eaten into the bearings, and I guess vicky verky.

Plus, what David just said.

I'll repeat my 2nd post.

"Type of bearings to buy.

Most (not all) people say that camshaft bearings have to be either reamed or scraped after they are installed. However, this only applies to split ring unfinished bearings. If you buy solid ring PRE-FINISHED bearings, they are advertised as not needing to be reamed. I can confirm that. They don't need to be reamed/scraped.

Here are the two types side by side. "


They don't need reaming. That's the point. That's why I bought them. And why I wrote that I can confirm that they don't need reaming. The split ring type can indeed be installed slightly off square. But the solid ring type can't. Hence they are prefinished to the correct diametrical clearance.

I've checked that with my NEW camshaft in the block AFTER I installed the new front bearing. Spins freely.

So if your only reservation is that, and you enjoy doing things for yourself, and derive satisfaction from it, saving 20/30 quid, and time, then this is for you.

If you don't particularly enjoy those things, take the block to a machine shop.

Lawrence Slater

Plus, I'll repeat from my 3rd post.

"This will give you a FRONT camshaft bearing installation tool, that because it runs through the existing two other bearings, exactly lines up the front bearing, as it's pushed into the block."

Lawrence Slater

If any of you still have doubts, and don't trust a 'rank amateur' like me, then maybe you'll trust this.

"At 09:14 PM 11/8/98 -0600, David H. Cole wrote:
> I had my machine shop put in new cam bearings I purchased from VB. The machinist said he didn't like split bearing design, but that he didn't have too much trouble installing them.

Smart fellow, I don't like them either. The stock cam bearings are made from flat stock rolled up to make a ring, three bearings, three different diameters, not very good tolerances, so they are intentionally a tad undersize and need to be reamed after installation. If you just ask the engine shop to install cam bearings they will order seamless bearings that are pre-finished (precision made) and can be installed without reaming. They may even charge you less for the parts than you pay VB. There is nothing unusual about the parts. They are used in a lot of different engines (just don't ask me which). They are Federal Mogul #1307M for the three piece cam bearing set to fit any Austin B-series engine."

So if you have a B-series, this could well work for you too, assuming the bearings are available.

But for an A-series, no problem. I'll repeat it.

"Minispares still have them for £12.28 inc vat, plus postage.

Just double check with them, that they are GLYCO solid ring pre-finished bearings."

Lawrence Slater

You reminded me of something I read years ago Lawrence, to the effect that it is the front bearing that wears more in general, owing to the radial load on the camshaft from the drive gear.

That said it described an engine that had a belt-driven cam. Maybe a Ford(?). I'd imagine the chain drive of an A series would be less severe than a belt in tension.

However, the thing I remembered about the split bearing needing reamed was it was said to offer the opportunity to ream it a lttle undersize, so as to compensate for wear on the journal. But that the seamless bearings you talked about were recommended where the journal was still in spec.

Does that sound reasonable?

BTW I didn't doubt you for an instant. I think it's a clever solution.

Nice write up Lawrence, the only suggestion I can make is that bearings will always go in more easily, if you freeze them, and heat up the component into which they are about to go. Don't know if that's practical in this case.
If you cannot get the bearing into a freezer for some reason, freeze release is a good substitute.

Dave Barrow

"You reminded me of something I read years ago Lawrence, to the effect that it is the front bearing that wears more"

The 948cc A35 engine - and possibly the early Sprite 948 - had only one cam bearing, the front one. The other journals ran directly in the block.
Dave O'Neill 2

From the Moss website:

BEARING SET, camshaft, 3 bearings

(e) 9C, 948cc BHM1210
Doug Plumb

It's probably not possible to buy a single bearing, these days.

This from

"The front cam bearing is the same as later blocks that have 3 bearings. If you need to replace it you will most likely have to buy the 3 bearing kit. Then you can decide to either use just the front bearing or have the block bored for the other 2. If you have access to a lathe you can make a bearing removal/installation tool. If not, a machine shop could either make the tool, or install the bearing for you. I had this work done on a few 950 blocks back in the 70s when I raced a Bugeye. "
Dave O'Neill 2

Dave Barrow.
I didn't mention it, but I did actually think of turning the blow torch on my block, prior to the deed.

But I forgot. :-

It makes sense though. I reckon you could almost push them in, if the block was hot and the bearing cold.

In the event though, it was easy anyway.

Precisely. Each time I've had my engines apart over the years, and when I'd had the cam bearings replaced back in the 80's, I could see that it was only the front that showed any real sign of wear. That's why I only replaced the front on this engine this time. I really only replaced it, because it had a deep score in it, and because I was looking for the elusive cure to oil sucking.

I'll know when I put it back together if the oil sucking's been cured. I doubt it though, so I drilled the block for an additional breather where the mech/petrol pump blank is, in anticipation.

Lawrence Slater


Lawrence Slater

Technical's dying, so I thought I'd just say hello, until another thread comes along :).

It's a little known thing, but if all the threads drop off, the server has to be rebooted or the bbs dies completely. :-
Lawrence Slater

It does seem a bit slow over here.

I wonder what controls the number of threads in each section and when they disappear.

If you take a look at the "MG 1100 and 1300 Sports Sedans" section, there are four threads. The most recent is from November last year, while the oldest was posted by a Mr Slater in Kent in 2012.
Dave O'Neill 2

Lol. Never got a reply, and I still have them.

Maybe I should drop the price.
Lawrence Slater

This thread was discussed between 19/12/2015 and 01/01/2016

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