948 tuning

[philthehill]

I would suggest that you read the Vizard 'A' Series tuning book as most of what you require especially the camshaft details are printed in there.
All 'A' series camshafts have three bearings.

[Fentuz]

All 'A' series camshafts have three bearings.

I miss explained myself; I thought the early one had 3 bearings with 1 shell in the block while the 2 other seat on the block while the later ones have 3 shells

[Fentuz]

All 'A' series camshafts have three bearings.

I miss explained myself; I thought the early one had 3 bearings with 1 shell in the block while the 2 other seat on the block while the later ones have 3 shells

[philthehill]

The 948cc has only the single white metal bearing directly behind the camshaft drive sprocket as that is where the most loading takes place. The other two bearings are machined direct into the block and therefore are plain cast iron.
The 1098cc and 1275cc engines have three white metal camshaft bearings fitted because the loading on the camshaft journals is higher.
If a high loading camshaft is installed in a 948cc engine all three camshaft bearings should be converted to have white metal bearings. If the bearings are not converted there is a good chance that the camshaft will pick up and seize in the two plain cast iron bearings.

[Fentuz]

Were the 997 single white metal or triple?
If the earlier then, it works for me as I don t want to strip everything and machine the block...
Hence my earlier question on specs.

[liammonty]

""

[philthehill]

The 997cc Cooper had three white metal bearings.

For what it is worth I would not fit a 997cc Cooper or performance cam without having the 948cc Block fitted with a full set of white metal bearings.

Here is the 997cc valve timings.

Inlet valve opens 16 degrees BTDC. Closes 56 degrees ABDC.

Exhaust valve opens 51 degrees BBDC. Closes 21 degrees ATDC.

Valve spring pressure with valves open 90 lb.
Valve spring pressure with valves closed 55 lb.

[Fentuz]

For what it is worth I would not fit a 997cc Cooper or performance cam without having the 948cc Block fitted with a full set of white metal bearings.

That's the sort of thing I was after. I want to put the car together and do things once while it's opened but I don't want to add loads on extra work... Swapping the cam while the head and radiator are off is one relatively easy thing. taking everything apart and effectively rebuilding the engine is another thing (I might do on a spare block).

[Fentuz]

reading the abingdon tuning manual, it seems they used to fit the 88G229 on 9C engine (single white metal bearing) and 9CG (Triple white metal bearing.
Were there issue reported with that and corrected or was it an accepted issue that people took?

M'Odel Sprite H/ANS, H/AN6 & MIDGET G/ANl
Engine Type Prefixes 9C & 9CG Sheet B - 1 Issue 5

NB: most the engine parts can be fitted to any B. M. C. 948cc engine if care is taken in the selection of parts in conjunction with the Mechanical Parts List.
Detailed tuning information for 9C engines is described in Tuning Booklet C-AKD 1021 most of which also applies to 9CG engines. The following parts are still available , but before carrying out any tuning of this nature , ensure that the engine is in good condition.

High compression piston (9· 3: 1)
(Std. , +· 010", +· 020", +.030" & +·040" sizes) C-2A 946
Oil pump, large capacity 12G793
Camshaft tuning ( 2A 948) 88G229
Distributor, for tuning camshaft C-27H7766
Rocker cover joint - F .J. type C-AEA511
Valve spring - inner 9C ONLY AEA401
Bottom collar for inner spring 9C ONLY C-AEA432
Valve spring - · outer 9C ONLY C-2A950
Top cup, for double springs 9C ONLY AEA402
Valve spring, inner 9CG ONLY
Bottom Collar for spring 9CG ONLY
Top cup for springs 9CG ONLY

Competition exhaust system, comprising:
Manifold (includes clips AHA 5450)
Pipe
Silencer
Joint - manifold

[philthehill]

I have never come across an 'A' series engine other than the 803cc, 848cc (MINI) and 948cc engines that were fitted with a single white metal camshaft bearing.
I have the various BMC Special tuning booklets and I will big out the booklet quoted above and have a read of what it says.

[Fentuz]

I found various data a cross referenced them.

[Fentuz]

I did further researches. It seems the 1098cc (AEA630) and 997cc (88g229) could go in 9C engine however if going further, 9CG was required.

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[philthehill]

It should be noted from the attached notes that the AEA311 standard single valve springs should be used with the 997cc camshaft when using a 950 block without full white metal bearings. It also notes that stronger springs put an higher loading on the valve train and cam lobes - which is then transferred to the camshaft bearings in the block.
By all means put a 997cc camshaft into a 950cc block which does not have all three white metal bearings, then add stronger dual springs - but it comes at a risk of the camshaft galling and seizing in the block.

[Fentuz]

Ok so that's what I am trying to understand.

The problem come from the accumulation of increased lift and the load from the double spring. So does this mean that it is ok to either use
-std cam with double spring
-997 cam with single spring.

now why do double spring get fitted? is it to avoid valve buns at high rpm?

looking at the somerford site:
std 998cc, 997cc cooper used AEA311
998cc cooper uses both AEA311 and AEA401

[philthehill]

The double springs are fitted to control/reduce or eliminate the possibility of valve bounce at high revs.

Having the two springs allows the spring(s) to be tuned to suit the engine revs. With twin springs one is a strong spring (main) and the other is a much lighter (secondary) spring. There is no need to have excessively strong springs as compressing the springs uses energy/bhp that you are trying to generate. The correct fitting of valve springs is an art in itself.

[Fentuz]

Humm, it seems the old head was fitted with double springs...
This engine keeps being a mystery.

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[Fentuz]

As I said earlier... this engine is a mystery...
It appears the the twin hs2 carb are fitted with 2 different types of needles.... so I will get 2 new one so that they balance better.
Now on a ported head with cooper size valves on a 998cc flatop, what would you put. i read a su manual and it clear as mud... if it was a std 948, I would go for the std. the cooper 998 seems a good start but as it is ported, it should draw more fluid. In injection car, this makes the mix leaner as the fuel is controlled by the injector.
For carbs, isn’t it drawing the air fuel mix i.e. it doesn t matter if the sucked volume is greater as concentration of fuel is the same? Or is it like injection...

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[ampwhu]

above chart is showing incorrect info. I've a 1963 A35 van with a 1098 engine in. The chart says it was a 948cc engine in 65/66. Austin started using the 1098 (from the MM) in 1963 in the A35 van.

wonder what else is wrong on that list?

[Fentuz]

As I said before, looking at the old cracked head, I noticed the double valve springs which are supposed to be on 9cg, 10cc and 10cg engine but not on the 9c... so l looked at the a little further... and with the head casting is a 948cc 9c, it has been the valve trains was converted to 10cc spec, inlet valve are 29.3 mm and exhaust are 25.4. The combustion chambers and the ports were not reworked other than the unleaded insert...
so, we shall measure how much cam lift there is as there are several evidence that this engine was and “hybrid” 948/1098.... if it goes with .22”, its a 948 cc, if its .25”, it can be a 1098cc or a 997cc... if the later, I m not sure how easy it would be to ckeck the actual duration value. Having said that, we can compare the inlet and exhaust, if inlet is shorter that exhaust, it will be a 1098, if it s the same, it a 997...

I have to admit that I had never suspected that as it was not shifting much passed 3.5krpm... May be it was due to the poorly fitted small minor exhaust manifold???
Other thing that was found is the needle.... Although it was fitted with twin hs2, it seems that when the previous owner removed the weber 45 and long 321 exhaust, he raided the parts bin and fitted 2 different type of dash pot, on with fixed needle and on with bias needle... so I am going to fit the same type with new needle and a mini spare rebuild kit...


Steep learning curve.... and still waiting for the DV book...

[philthehill]

This is how I measure the lift of a camshaft:

Put the camshaft in a couple of 'V' blocks, fit a digital Vernier to the camshaft lobe with a support at the tail end of the Vernier, fit a rubber band around the internal measurement jaws, turn the camshaft clockwise and the digital Vernier will indicate how much lift there is.
The difference between the MAX and MIN measurements indicate the camshaft lift.
The rubber bands make sure that the jaws of the Vernier follow the profile of the cam lobe.

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