camshaft

[ampwhu]

is it possible to fit a better camshaft to a 948 engine? I already have a 1098 head going on the 948 block for some more power and was wondering whilst fitting the head, a better camshaft would be a straight fit.

[simmitc]

Anything is possible, but the standard 948 is a very sweet engine anyway. If you want more power then you should first uprate the brakes and possibly the gearbox and back axle. You might find it simplest to just purchase a 1098 engine, box and axle.

[ampwhu]

the car already has discs etc. gearbox and back axle are uprated as well. car is a 55 series 2.

I prefer the 948 engine as it, as you say, revs sweetly. I don't wont to fit a 1098 as I think they are a step backwards. the head going on has been skimmed to improve performance. I was just wondering if a better camshaft can be fitted to improve even further.

[philthehill]

It is quite easy to fit a better camshaft to a 948cc 'A' Series engine.
You do need to ensure that the camshaft oil pump drive is suitable. The 948cc engine has a pin drive from cam to oil pump. Later oil pump drives can be slot or star drive.
If changing the camshaft I would fit new cam followers as cam followers bed in to the particular cam lobe they work against.
The 948 has only one white metal bearing which is fitted to the front cam bearing, the other two bearings are just plain bearing surfaces machined into the block.
A camshaft that has high loading is not really suitable for the standard 'A' Series block and all three cam bearings should be fitted with white metal bearings.
The 'A' Series was originally fitted with 3/8" wide cam lobes and latterly 1/2" wide cam lobes. The wider lobes of the later camshafts are better.
The duplex timing chain assy should be fitted.
There may be a requirement to fit a different inlet/exhaust manifold(s) but is dependent upon the overlap of the valve timing.
The cam to be used will depend on the final spec of the engine.
The camshaft fitted to the 998cc Metro is a better camshaft than that fitted to the 948cc Minor engine with slightly longer opening degrees and better lift, has 1/2" wide lobes and is cheap and is easy to obtain.
I would change the oil pump whilst you are at it but that means the engine out.
What 1098cc cylinder head (casting number) are you fitting and more info as regards the build spec would be appreciated.
For further information - see the Calver engine technical section regarding camshaft selection.
https://www.calverst.com/technical-info/
Phil

[ampwhu]

thanks for an in-depth reply Phil.

I already have a duplex chain fitted. I understand about the oil pump as well.

the head I'm fitting is a 12g202 which I have had skimmed 0.060" as recommended on here in the past (along with several others I have spoken to). it has had all the unleaded parts fitted as well.

998c metro camshaft looks to be what i'm after I guess then. would I get the metro oil pump to match along with these bearings?

[philthehill]

The 12G202 head skimmed by 0.060" will be just right.
You will need the matching Metro oil pump as they are either star or slot drive.
As regards the camshaft bearings - the 998cc Metro (not MG Metro) camshaft is better and will not overload the plain camshaft bearings in the block or the valve train components, therefore the 998cc Metro camshaft can be fitted without having to resort to all white-metal camshaft bearings but of course it is always better to have all the camshaft running in three white metal camshaft bearings.
https://www.ebay.co.uk/itm/CLASSIC-ROVE ... 0033.m2042

Phil

[ampwhu]

I guess the standard exhaust and manifold will be ok still? I have the mini manifold with a 1.25" SU and servo take off.

[philthehill]

The Mini manifold will be just fine.

[ampwhu]

ive removed the camshaft bearings from the engine I'm building and am going to fit new ones.

do they need to be reamed? if so, how?

[philthehill]

The camshaft bearings need to be line bored.
Not a job for the home mechanic unfortunately.
See BMC Wksp Man Section AAA15 for details.

[liammonty]

I’ve lost track of whether it’s a 948 block - if so, it’s only the front bearing than can be replaced, as the cam simply runs in the block in the centre and rear ‘bearings’. Assuming the cam you’re planning on using is fairly tame, as Phil said, you should be OK running it in these bearings - you can of course replace the front one if it is past it. However, if you are planning to fit white metal bearings to the centre and rear, then yes, you’ll need to get the block align-bored to fit them. I did just that with my 948 when I rebuilt and modified it a few years back. It cost around £100.

[ampwhu]

sorry I didn't make it clear. ive decided to fit a 1098 now with other uogrades. the 948 is still in the car.

today I fitted new camshaft bearings to the 1098. this is a simple job. I used 2 old brake pistons. I drilled a hole in the middle of both of them and tapped one of them M12. a long M12 bolt and about 20 mins late, all 3 bearings were fitted. slotted the camshaft in and it turns lovely. all oil holes lined up and very happy.

on to the crankshaft bearings now...…...

[les]

Probably a good move now deciding to use 1098, it was a surprise hearing you say it was a backward step.
You now have to option to fit a 940 head.

[ampwhu]

yes I agree Les. I have 948 internals in my 803 box and a 4.2 diff.

covered on another thread, I have a HIF 38 carb with a marina manifold and custom built 40mm exhaust.

I'm looking forward to fitting all this at the end of the summer.

[philthehill]

ampwhu
Can you please enlarge on what brake pistons you used to fit the camshaft bearings.

I would consider that you are very lucky that the camshaft bearings did not require line boring.
I have never been able to just fit and forget as they have all required line boring.
When the bearings are fitted they have to be gripped by the block which results in a small amount of internal diameter shrinkage which for me at least has required the bearings to be line bored to suit the camshaft being fitted.
Could you also post a link to the camshaft bearings used?
Phil

[ampwhu]

surely it cant be beginners luck?

camshaft bearings were purchased from ESM. the camshaft fits nicely. if I put a spanner on the chain wheel end, I can turn the camshaft easily when its fitted in the block. very slight resistance (as you would expect).

to wind the bushes in, I used a pair of mg midget pistons. I drilled and tapped one piston with M12 threaded hole. on the other piston, slightly bigger. threaded piston on the bottom and using a M12 threaded rod, slowly wound the bearing into position. plenty of 20/50 oil covering both the block and bearings, making sure the oil holes line up. afterwards, blow through the oil holes with an airline.

if I knew how to post pictures I would.

[philthehill]

There should be absolutely no resistance to the camshaft turning when the camshaft is fitted into the block/camshaft bearings.
You should be able to turn the camshaft by hand without having to use the camshaft chain wheel or use a spanner on the nut.
Personally if there was any resistance to the camshaft turning however slight I would not run the engine as there is the possibility of the camshaft picking up and ruining the bearings and possibly the camshaft.
Line boring the camshaft bearings to spec as defined in the workshop manual is a must.
Phil

[ampwhu]

Not according to a couple of other owners who gave me the piston method.

[ampwhu]

When taking the camshaft out with the old bearings in the block, that had more resistance.

[philthehill]

http://www.morrisminorspares.com/engine ... cc-p830478

If you consider that the camshaft bearings are fine as they are all well and good but I would not accept resistance in turning the camshaft.
Only when the oil pump and/or the distributer drive is fitted should you encounter resistance to turning.

BMC/BL quote specific internal dimensions of the camshaft bearings (reamed after fitting)

Front...…………..1.6670" to 1.6675"

Centre...………..1.6245" to 1.62475"

Rear...……………1.3745" to 1.3750"

Those dimensions do need to be checked after fitting the camshaft bearings and/or after line boring the camshaft bearings.

If your camshaft bearings fall within the tolerances stated above then there should be no reason to query the turning resistance or not of the camshaft when fitted into the bearings.

Phil