Which cam for a 948

Post by **hamford14** » Wed Nov 11, 2009 1:18 am

I was just wondering what cam would work best in a 948,
I am planing to do the following mods,

12g295 head skimmed
better exhaust
1 1/2" SU
bore out 40 or 60 thou
maybe something with the distributor

i was thinking about one of the kent cams, maybe 256 or 266

Any help would be much appreciated
Thanks Todd

Post by **Peetee** » Wed Nov 11, 2009 7:56 am

Try it with the standard cam. I did all the additions you list (with the exception of the overbore) and ended up with a very tractable, smooth and revvy engine that was a huge improvement on a standard 1098.

Post by **PSL184** » Wed Nov 11, 2009 8:09 am

Consider using a 12g940 head - these don't need skimming (just check you have valve clearance). I use a 266 cam in my 1275 and an MG Metro cam in my 948. Both are fairly similar in terms of delivery in the power band. The 948 pulls well upto 6500rpm....
I found the best carb for the 948 engine was an HIF38 on an MG Metro intake and I use an LCB from Birmingham Morris Minor Centre which I took of my 1275 set up untill I can get hold of another one.

Post by **Kevin** » Wed Nov 11, 2009 3:46 pm

Hi Todd if you decide to change the cam my preference is for the Swiftune SW5 as having had a kent cam in another engine it was always a bit lumpy low down but the Swiftune is smooth at all speeds.

Post by **bmcecosse** » Wed Nov 11, 2009 8:06 pm

Problem with the 948 engine is that it doesn't have proper cam journals in the ecntre and rear bearings - they just run directly in the block! Therefore - you must be quite careful to NOT run too extreme a cam, certainly not with high valve lift - and even more careful to NOT use strong valve springs. Unless of course you line bore the journals - and fit bearings, and exercise l;ikely to cost upwards of £100 or so! So - for simple basic mods as you suggest - the AEA 630 cam from a 1098 engine will be ideal - giving a usefull power increase without excessive revs. Next up would be the 2A948 cam - from the 997 Copper engine. I would say using an MG Metro cam in a block with no cam bearings is 'unwise' - although provided standard valve springs are used it will be ok. Similarly - you should NOT run the double valve springs in the 295 head - just use singles - to prevent excessive cam/block wear.
Best solution of course is to use a 1098 block - which HAS the cam journals installed - and fit standard 998 Mini pistons in that block with your 948 crank - thus getting a 998 in-line engine - which can happily run an MG Metr cam with double springs - or even up to a 544 cam for a 'full race' engine. The 940 head is also a great choice for that engine - but the exhaust valves need recessing by 40 thou to use with a standard lift cam - any more than 0.250 cam lift would be better served by cutting 'pockets' in the block.

Post by **PSL184** » Fri Nov 13, 2009 4:59 pm

bmcecosse wrote:I would say using an MG Metro cam in a block with no cam bearings is 'unwise' - although provided standard valve springs are used it will be ok.

Can you expand a little on this statement Roy. You say it is unwise and then say it is OK in the same sentence. The MG cam has the same lift as standard cam, I think, so is it OK to run an MG cam in the 948 block or not. I'm running one at the moment (with 940 head) but I don't want to screw it up.....

Post by **bmcecosse** » Fri Nov 13, 2009 5:07 pm

Weeeellllll - I would say it's certainly unwise IF using double valve springs, but I suppose it will be 'ok' - just a bit 'unwise'! It's certainly at the top limit of what should be run in that block - without bearings - and certainly NOT with strong or double valve springs - or daft 'high ratio' rockers!

Post by **PSL184** » Fri Nov 13, 2009 5:26 pm

Not running any silly rockers - Just standard and single valve springs.... I might look out for a 1098 block though and build a 998 bottom end as you described above....

Post by **bmcecosse** » Fri Nov 13, 2009 5:33 pm

That would be a MUCH better motor - but you need a 1098 block, 948 crank - and a set of 998 Mini pistons and rods!

Post by **PSL184** » Fri Nov 13, 2009 5:39 pm

I have all the above except a 1098 block (which I gave one away in the summer

)
What kind of bhp could I expect....
1098 block, 948 crank, 998 pistons, MG Metro cam 940 head, HIF38 carb, MG Metro inlet, LCB and 1.5" system....?

Post by **bmcecosse** » Fri Nov 13, 2009 7:50 pm

Could be good for 60/65 bhp - at highish revs ? Marginal for the 1.5" carb - may need larger HIF44 to get full power. If you had the large valve version of the 940 head - and say a BMC 544 cam - could get up to 75/80 bhp! But -it would be a 'screamer' with not much power below 4500 revs - and would probably break the crank - eventually. You would be revving it to ~ 7000 rpm - maybe even higher! Obviously - a crank damper should be fitted - a lightened flywheel would be useful - and the rotating assembly nicely balanced would help. Lightened/balanced pistons and rods would be a good idea too....... and a centre main strengthening bar.
I ran a Mini 998 engine to more or less that spec - it had a genuine S head fitted (so large inlets and exhausts) - which had been flowed quite extensively. With home made long twin SU manifold (Weber like - no balance pipe) and much modified 1.5" SU carbs - running on open exhaust after an lcb - it was beating fancy 999S Minis - to the dismay of the owners who had spent a small fortune at Downton and others....
I tried it with a 649 cam, but felt I gained nothing at the top end - and lost a LOT low down. So it was back to the 544 after just one event. I think that was the secret - the engine was more flexible than the fancy 999S engines which were all on 649 or Sprint cams.

Post by **PSL184** » Sat Nov 14, 2009 12:18 am

I don't think I'll go for a screamer as it is just for normal road use but I'd be happy with around 65 bhp anyway so sounds good, thanks.

Post by **bmcecosse** » Sat Nov 14, 2009 9:45 am

The 'screamer' engine is very definitely not for everyday road use! Week-end warrior maybe ! It will just break the crank anyway after a short time - unless you can find one of the very rare works 'red' cranks!

Post by **Kevin** » Sun Nov 15, 2009 1:43 am

PSL184 wrote:I don't think I'll go for a screamer as it is just for normal road use but I'd be happy with around 65 bhp anyway so sounds good, thanks.

Might be easier to just fit a 1275 with 65bhp in the first place perhaps.

Post by **PSL184** » Sun Nov 15, 2009 10:55 am

Kevin wrote:
PSL184 wrote:I don't think I'll go for a screamer as it is just for normal road use but I'd be happy with around 65 bhp anyway so sounds good, thanks.
Might be easier to just fit a 1275 with 65bhp in the first place perhaps.

I've got a 1275 in the black Traveller and it is noticeably"rougher" than the 948. I wanted to attempt to maintain the smoothness of the 948 with the power of a 1275 (and because I'd have nothing to do in the garage over the winter)

Post by **bmcecosse** » Sun Nov 15, 2009 11:14 am

The short stroke 948/998 engine is very nice - but won't ever have the 'lugging' power of a 1275

Post by **PSL184** » Sun Nov 15, 2009 11:41 am

Aye true but I think it will be a fun engine to build with a nice smooth power delivery and none of the harshness you get with the 1275.... We'll see. I just need to find a decent 1098 block locally and I'll get started. I could probably do with a 1098 gearbox too

Post by **Peetee** » Sun Nov 15, 2009 11:47 am

Aye true but I think it will be a fun engine to build with a nice smooth power delivery and none of the harshness you get with the 1275.... We'll see

Having experienced both I know which I prefer. If I had a 'everyday' Minor, on the premise that a bit more power is never enough, a modified 948 would be my engine of choice.

Post by **bmcecosse** » Sun Nov 15, 2009 1:45 pm

I'm still looking for an 848......