Cosworth SCA, SCB, SCC engines

[Kevin Whittle]

How many Cosworth SCA engines were built?
Does any one know the split between carb and injection numbers built?

What was the bore stroke of the 1499cc SCB. It was claimed to deliver 175bhp. Was just one SCB engine built? and where is it now?

When the SCC was introduced, (to comply with USA class) was it a gear drive ohc, or was it chain drive
Or perhaps a mixture of gear drive to jackshaft then chain to sohc.

How many engines survive, I know that Cosworth has 2 engines, the one on display at 2004 Stoneleigh show was on carbs.
Why did they choose DCM over IDA Webers ?

So over to you experts please

Kevin Whittle

[Bryan Miller]

Kevin ,

The one only SCB is in Australia , came here in a BT21B Brabham built at the works by one of the employees , and came over at the end of , I think 1968.
Employee and builder was/is Neil Rear .

Car and engine are still together in Canberra .

Bryan.

[Bryan Miller]

Correction Neil Rear 2nd owner .
The man that was at Brabhams was / is Bob Illich of Western Australia.

Sorry about that Bryan.

[Ted Walker]

A pal of mine has an injected one.According to a very well known engine builder they only built a handfull of these as well.

[zefarelly]

the SCA was a bore of 80.96 (std Ford) . . .I have a set of genuine Cosworth pistons sitting in their tube on the shelf at home . . .beautiful things, but I can't quite bring myself to put them in a cortina engine !!!

[Kevin Whittle]

Hi Zefarelly,
what is the bore of your pistons, 80.96 ??

The SCA was 80.96 x 48.4mm = 997cc
The SCC was, I believe 85 x 48.4, ie same as 1098 FJ pushrod motor

But was the Only SCB 80.96 or 85 or ?? what bore x what stroke and was it injected.

It would seem to me that at 175bhp for a sohc 1498cc, it was getting close to the dohc FVA of 1600cc at I think around 210bhp ?

Bryan is the SCB now injected or on carbs ?

Kevin Whittle

[zefarelly]

SCA 1964 997cc 115-140 Bhp. Formula 2, first Cosworth designed head, aluminum, 116E block, 5 main bearings,
SCB 1964 1498cc 175 Bhp. Experimental only
SCC 1965 1098cc 135 Bhp. Bored out SCA for North American Sports Car racing, Many SCAs conveted to SCCs, chain drive cam

all of these would be 80.96, as are the set I have its the standard Ford bore they just changed the stroke and block height/rod length

in a similar way I've got a 1600 crossflow block, bored overbore with flat top pistons and the block skimmed so I run a 1700 precrossflow in my road MK1 Cortina . . .bit more oomph :-)

[Kevin Whittle]

I have most of an SCA, and am wondering if anyone knows the Cosworth numbering system
My front covers/backplate is stamped
743

19645

GP

BB48

S15


??? any one know
Re numbers produced in Jan 1964 Cosworth were reported in Autosport as planning to build 25-30 SCA that year.

Kevin Whittle

[PeterMorley]

When I had a Cosworth built twin-cam, Cosworth gave me the build details (e.g. type, spec. and first owner).

That had a 5 digit number that split as follows
type = 2 digits (e.g. 13 for the twin-cam)
number = 1 digit (e.g. 6 for the twin-cam, 6th one made - presumably this will go up to 2 digits as necessary)
year = 2 digits (e.g. 63 for the twin-cam)

The nearest number you have to that is 19645 which would suggest type 19, 6th one made but built in 1945 is unlikely. 5th one made in 1964 is a possibility?

I'm sure Cosworth should be able to help you, they still have the records.

[Bryan Miller]

Kevin,

The engine here is on down draft Webers , always has been.
As Peter advises , call Cosworth , very helpfull people.

Bryan.

[Kevin Whittle]

I have been calling Cosworth all this week not to much avail, but am keeping on at them.
It seems early pistons had a central dish and two very deep depressions for the valves, later pistons only had a central depression. The later heads had a angled inlet port to promote swirl, as well as smaller exhaust ports.
Re the dates, I assumed 19645 was a late 1964 engine?
It has a cam box with provision at the rear to drive the injection pump, as per Cosworth photos of the engine fitted into a Brabham and raced by Costin in the 1965 Senior Service 200 Race.
Talking to Mike Costin in Nov last year he said that the engine needed too much ign advance to be efficient.
Kevin Whittle

[rkshanahan]

If anyone is still interested, I have just purchased 4 SCA and SCC engines that have been apart since the 60's. I don't know a lot about this engine, but it seemed like a good hobby project for me to put them together and get them running over the next couple of years. I need one for my Lola T-60, as it is currently running a Twincam and the SCA was the original engine. Since here in the states I will still have to run with the Twincam powered cars with the SCA, I figure I will build up the first one as an SCB 1500 so I can be a little more competitive. Rules here are such that the SCB will still be legal.
Judging from my engines, the SCC had a bore of 83.5mm so it should have had a stroke of 51mm or so vs. 48.4 for the SCA. I will measure the stroke on these cranks and see what I get. Also, though I have read that the SCC was chain drive, all of my engines are gear drive.

Regards,

Rob

[rkshanahan]

So it turns out I have some cranks that are 48.4mm stroke and some that are 50.2mm stroke. The shorter stroke works out to 1000cc when paired with an 81mm bore, so I am guessing those are the SCA cranks. The 50.2mm cranks when paired with an 83.5mm bore gives 1100cc, so those must be the SCC cranks. The rod lengths are the same for both motors (5.434") and the pistons have different compression heights so that they both end up level with the top deck of the block. I am also in the process of making some new timing gears for cam drive to replace those that failed Magnaflux testing. New pistons and new cams are on order so this should get interesting pretty soon. I am also having new cam covers cast up as I do not have enough for all four engines and have not been able to find used ones.

[phoenix]

Hi Rob

What size inlet and exhaust valves do the SCA and SCC have? Just to satisfy my interest....

[rkshanahan]

Phoenix,

The SCA had 1.45" intake and 1.25" exhaust valves as standard. It appears that the SCB and SCC had the same, but I have seen a listing for an SCD engine, which was a 1500cc SCB engine with larger valves. The sizes listed are 1.55" intake and 1.30" exhaust. A couple of my cylinder heads have modified ports and larger valves but I am thinking this was done by the customer and not by Cosworth.

Regards,

Rob

[phoenix]

Thanks Rob

[rkshanahan]

All the cranks I have are marked "Laystall" and dated. The 1964 cranks appear to be modified MAE cranks, in that the snout is to SCA dimensions to mount the gear for the cam drive, but part of the keyway for the standard snout and pulley remains. The cranks that are dated 1965 do not have evidence of the keyway, so I assume they were purpose built for the SCA. By the way, the SCA has a rather unusual method of driving the crank gear. The gear itself floats on the snout on a bronze bushing and is connected to the crank via a small shaft that presses into the crank snout and the forward end of the crank gear. There are two pins sticking out the front of the crank that engage with slots in the rear edge of the gear. This setup allows the crank gear to rotate slightly as the shaft torques. I am guessing that this allows for absorbing some torsional shock and vibration in order to prolong the life of the geartrain for the cam drive. I am told the FVA used a similar arrangement but the DFV instead used a compound drive gear futher up the drivetrain that had similar shock absorption features. If anyone is interested in any of this I will see if I can take some photos and post them.

Rob

[Robyn Slater]

Interesting thread.

Yes i would like to see some photos.

[rkshanahan]

Robyn,

I have tried to attach some low res photos of the crank gear drive set up, as well as a shot of teh other gears in the cam drivetrain. You can see the short quill that presses into the nose of the crank and then gets the gear pressed onto it. In the last photo you can see the crank gear sitting in place on the snout with the two pins lined up in the slots in the gear. I am still trying to figure out how I am going to make sure it is all lined up before I press it together.

I should have some photos of the geartrain mocked up on the front of the engine next week, as I am going to have to figure out how to shim everything so that the backlash between all the gears is correct when I bolt the cylinder head on and install the cam. There are shims under the cam carrier to allow for adjustment there, but it is the head gasket thickness that will set the backlash for that particular pair of gears.

Rob

[phoenix]

I'd be interested to see some photo of the head too as I have never seen one. A shot of the combustion chambers/valves, one of the cam and valve operating arrangement, one of the inlet ports and one of the exhaust ports would be fantastic.

[rkshanahan]

Phoenix,

All four of my cylinder heads are at the cylinder head shop being rebuilt. I will have to pick up one next week in order to mock up the cam geartrain and see how the backlash is going to work out. The head will likely have no valve in it, but I can get some pictures then. It is kind of interesting because the ports and valves seem small for the claimed output, but my cylinder head guy said it is all about making it work with high velocity flow. As someone pointed out earlier in this thread, they actually reduced the exhaust port size in 1965 to improve performance.

In the meantime, I have attached a scan of the cutaway drawing from Autocar magazine 16 April 1965 edition. They did an article on the SCA that included some really good information and photos.

Regards,

Rob

[phoenix]

Thanks once again Rob.

That's really interesting.

I read that one of the final developments of the FJ engines was the XVII for which Cosworth converted the head to 'downdraught' from sidedraught by boring the head and brazing in more vertical replacement inlet ports. This was the first Cosworth to develop over 100 BHP/Litre and it looks like the SCA-C engines were a further development of the ideas explore with that engine.

Downdraughting the ports to the vertically installed inlet valve shallows the angle between the valve and the port and in doing so opens up the 'short side radius' which will improve flow through the port, delaying the onset of turbulence in the port and allowing higher inlet gas speeds to be achieved. The inlet valve size (1.45") in a sidedraught head would flow a maximum of about 128 BHP. In a 'hemi' style crossflow head the same sized valves would flow closer to 142 BHP due to the better port/valve angle and the better position of the valve exit relative to the cylinder wall. It would appear that on the SC engines the head can flow 5-8% more than the best side draught port arrangement could achieve.

I imagine the inlet port sizes are quite large due to peak torque being at 8000 rpm in the 997 cc engine. If this is the case it might have made it necessary to reduce the exhaust port diameter as a compromise in order to fit the large inlet ports into the space available. The plus side of this might have been improved scavenging; the peak torque of 76 lb/ft suggests a VE of around 114% was achieved, and that would not be possible without excellent inlet and exhaust manifold tuning.

[rkshanahan]

Phoenix,

The bottom of the cylinder head is completely flat, so the only combustion chamber is the dish on top of the piston. The picture below shows an SCA piston on the left and an SCC piston on the left. The Autocar article mentions that the '64 SCA pistons had the offset chamber like the one on the left and that the '65 SCA engines went to a shape more like the piston on the right. I assume that the SCC was a '65 engine and hence had the later chamber shape.

You seem to be keen on engine theory, so I would be interested in your opinion about the 1500cc SCB. I am currently building one of these engines as an SCB to fit in my Lola. Cosworth claimed to get 175hp, which would make it competitive against the Twincam powered cars I have to run against here. I have ordered a long stroke crank, shorter rods, and custom pistons. I have taken one of the large port heads and put in the biggest valves I can fit (1.60 in/1.35 ex). My cylinder head man is looking at things on the flowbench so I can get some data to select the cam profile, likely more lift and less duration than the original SCA cam. Do you think it is really possible to get 175hp out of such an engine? A friend of mine used to run against Brian Redman in F2 when he was using an SCB engine in '66 or '67 and he remembers Brian had more power than his Twincam but less than the FVAs. I assume that a Twincam probably made 150hp back in that time.

More later,

Rob

[phoenix]

Hi Rob

Remembering this is only theory I think the Cosworth figure is a bit optimistic, as I get 169 BHP as your likely maximum with 115 ft/lb of torque.

My bet is that the Cosworth A8 cam profile will be similar to what you end up with as optimum, though the A6 may be enough for this engine as it isn't going to be making the revs of the 997/1099 shorter stroke engines.

I don't think you could expect to match a twincam with 1.625" inlet valves which they seem to run over here now, but would be pretty close, maybe 7-9 BHP down, but back in '66-'67 the SCB might well have produced more power than the twincam.

Any details you can let me have of the original cam profile would be a great addition to my library of engine data....

Did the SCB use 4.825" rods like the 1500 116E and the twincam engine?

As for the pistons, the larger engine would need a slightly larger combustion chamber for the same CR ratio, wouldn't it?

Thanks

Martin

[phoenix]

Originally Posted by rkshanahan

I have taken one of the large port heads and put in the biggest valves I can fit (1.60 in/1.35 ex). My cylinder head man is looking at things on the flowbench so I can get some data to select the cam profile, likely more lift and less duration than the original SCA cam. Do you think it is really possible to get 175hp out of such an engine?

p.s. Let me know if your head man gets better than 166CFM @ 28"....