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MG MGA - Camshaft and Bushes

Excuse my ignorance on camshaft replacements. Part of motor engineering that I have little knowledge and never had cause to play around with. When replacing a camshaft for a new one (performance purposes rather than wear and tear) is it necessary to replace the bushes or can it be as simple as one out and one in?

Nothing untoward. My motor is fine. I was just reading some emails I got from Moss a while back about which supercharger I would need in my 1800 MGA. They also mentioned for best performance to put in a specific camshaft for which they gave the part number.

Steve Gyles

If you have kept oil clean, and no catastrophic failure of the engine, camshaft bearings might last forever. All of the camshaft and crankshaft bearings in my current engine are very close to 200,000 miles n doing fine. If it ain't broke don't fix it.

most people I have spoken to on this subject advised me that the standard camshaft works just great with a Moss supercharger. So you could probably stick with what you have,

I had a 3-bearing MGB motor with a Piper 270 camshaft and a higher compression ported fast road cylinder head.
I was advised that I would need a lower compression ratio head, a cam designed for use with a supercharger and that my 3-bearing head was probably not a good candidate for being supercharged.

In the end it was more cost effective for me to fit a 1950cc motor with a Weber 45 DCOE instead of going the supercharger route. Which was a little disappointing as I have always loved the idea of supercharging an MGA.

I used a Newman PH1 Cam in my engine which has an amazing power band stretching from 1500 rpm up to 6000.

Maybe Dominic is the best person to ask about camshafts and supercharging?


Colyn Firth

I defer to Mr Burgess, Prince of Tuning

I have just fitted my new 1622 SC spec engine, which has a PB SC head and Dr. Betson underpinnings. According to the spec sheet it has a Piper 456@110 cam.

But I am sure Peter will be able to give much more solidly fact-based info than my sample of 1.

According to the date on the spec sheet the engine has been hanging around in either Peter's, Chris' or my workshop for five years, so I am glad to get it installed.

On the SC front (once it's run in on the standard carbs) it's getting the SU HIF44 modded Judson. Timing is to be managed with a clever box of tricks that manages timing advance not only according to revs but also to vacuum or pressure in the plenum between the body of the SC and the head.
see here for more:

This will be programmed to allow adequate boost but no pre-detonation (which is what kills most SC engines).

Spec sheet attached for interest

Dominic Clancy

Thanks guys. I think mentioning about the supercharger was a red herring. It was the engineering aspects of changing a camshaft that I was actually interested in. Judging from Barney's comments I gather that it should be a straight one for one without any need for new bushes and reaming.

Steve Gyles

Hi Steve, I had my camshaft bearings replaced when I did the motor in my 2000cc coupe about 4 years ago - following recent failure of the cam and followers (a long story), cam bearing were still okay! You will see pretty much when looking at them if they are worn. It is easier to let an engine shop do the work for you as you need the right puller/pusher gear - care must be taken to line up the oil holes correctly. There are two types of cam bearings available - the split type (one split in the cylinder) or the non split type - I was advised to use the non split type. Also you will need to check/adjust cam end float - you may need a need thrust bearing also.
Mike Ellsmore

Hi Steve,

way back in the days of my restoration of the car (around 12 years ago), when the engine was out of the car I did an engine rebuild. I had replaced many parts from inside the engine, one of which was the camshaft. After doing some measuring of the bushes it was discovered that hardly any wear was present. Inserted the new shaft very carefully inside the bushes, and it went in sweetly with a press fit. Only finger pressure was used. Replaced the end thrust washer and fittied the cam sprocket. No problems encountered since then.

F. Camilleri

The only way you can tell if the cam bearings need to be changed is to look at them - if they are scored then change them, if not then they will be fine.

The 456 cam in Dominic's engine is a special grind by Piper to suit to overall spec of the engine.


That engine was dropped off to you in the trusty yellow van on the 20th April 2012 - so definitely your garage! 8-)
Chris at Octarine Services

Many thanks to subsequent posters. That's what I was hoping, not that I have any immediate plans. Funds for this Spring are going on a Spitfire trip! Something I have always wanted.

Back in 1977 I tried to organise a posting to RAF Coningsby on F4s where the Battle of Britain Memorial flight was and still is based. My plan was to 'ease' my way into to the flight and fly the aircraft. The powers that be changed my posting at the 13th hour and sent me to Scotland instead as my experience was urgently needed on 43 Sqn at RAF Leuchars - chance gone! I paid them back by ejecting from a 43 Sqn F4 after 3 sorties up there and then being off flying for 4 months with multiple spinal fractures. They carried on quite happily without my 'experience'.

Steve Gyles

Hi Guys from Down Under,
I wonder if anyone has had sufficient cam shaft experience to kindly comment on this one?
I bought an Austin 1800 MK 2 saloon--dismantled it--sold off heaps of parts and kept the valuable engine to go into a Californian MG A Coupe rebuild. The rebuilt Coupe' has run for 20,000 exciting miles.
The Austin's cam shaft has timing slightly different to an MG B's.
The Austin's Inlet valves are aparantly the same timing, as an MG B's.
However, the Austin's exhaust valves open at 40* rather than 51*
and the Exhaust valves close at 10* as compared to the MG's at 21*.
The question is-- The 11* difference on both sides of the exhaust operation---Would the Austin's timing impare the engines performance as compared to an MG B's shaft.
The engine is out of the car at the moment--this would be the opportunity to make a swap, should the MG B's shaft offer better performance.
Also, an Aussie reader might offer a suggestion on a local supplier for a slightly warmer cam .
The engine is fuel injected.
Looking forward to comments.
Ian Cowen Gold Coast Australia.
I.W. Cowen.

I did the Spitfire flight out of Biggin Hill. Can't rate the outfit there any higher, they offered the best total experience compared to others, plus, it was a far more appropriate airfield to fly out from.


Colin Manley

Colin, Great photo!
Doug Wallace

Hi Steve
hope your cam bearing question has been answered.

We had an MGA run out to Coningsby a couple of summers ago and it was a fantastic place to visit.
The 3/4 hour guided trip around the hanger was superb.
The guide was brilliant, he really knew his Spitfires, Hurricanes and Lancaster Bombers and loved his subject.
So with a little encouragement from me, the tour lasted about an hour only being interupted by the glorious sounds of the V12 Merlin engine and the Typhoon engine on re-heat.

I cant recommend it enough.


Colyn Firth

I'm doing it with one of my old colleagues and ex BBMF pilot, Cliff Spink. He was on Lightnings during my time on them back in the late 60s. If you watched the prog of Guy Martin helping rebuild the Spitfire it was Cliff who flew him.

Steve Gyles

Hi Chris

Hope you are well. It's really good to see you are still watching over us in the background.

That was the first time. As you know the engine did a return trip to the UK in the interim, and turned up the second time in the white van after the yellow one went to the great scrapyard in the sky. I reckon that accounts for 18 months, the rest must be down to my other distractions!

I had a twinkie and a long line of other jobs in all last winter which blocked me from getting to this again. This year the "others" have all had to wait while I do the stuff I want on my car! It now runs a treat, and I'll hopefully be finishing the install and other jobs on the weekend (if Moss delivers in time).

I'm in Asia for the last 3 weeks of March, but looking forward to welcoming you soon in Zürich. You will of course be invited to take a spin on the way to dinner!

Dominic Clancy


In Asia... are you planning a Bali visit? Please contact me, here in Bali until 12 April before Adelaide..


Doug Wallace

This thread was discussed between 15/02/2017 and 17/02/2017

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