15 replies to this topic

[Ray Bell]

This was, I think, the first engine Cosworth built as one of their own with their own cylinder head.
My memory tells me it had:
* one overhead camshaft
* valves all in line
* Heron combustion chambers (ie. flat face on head, bowl in piston, a la Formula Ford etc)
* a capacity of just under 1000cc (998?)
That's what I think, but over in the 350-post strong 'Favourite Amon Stories' thread on the Nostalgia Forum my memory is being challenged. Not that I mind that, we all make mistakes and get our memories in a knot at times. But I'd like confirmation, one way or the other, that it had these features. Anyone interested can go look at the thread and Roger Clark's post that leads to this thread being posted.
It was, by the way, based on the usual Ford block, with the usual steel crank (to keep the block straight) and rods.

[Roger Clark]

I think you're spot on in every respect. My only disagreement was when you said it was a horrible little engine, or something similar. It was very successful in F2 and certainly had the beating of the BRM. It was only beaten when the Honda was working properly in 1966. I always liked the engine because with downdraft carbs and exhaust over the gearbox it looked, particularly in the Lotus 35 like a small Climax V8.

None of my posts Over There were intended to chhallenge your memory, only your opinion.

[desmo]

A little info I found on the SCA:




Cosworth SCA Formula Two Engine (Carburettor) 1964






Capacity 997 cc
Bore 81.0 mm
Stroke 48.36 mm
4 Cylinder
Compression Ratio
12.5:1
Gross Horse Power
115 bhp minimum @ 8700 rpm
Gross Torque
76 lb ft @ 6800 rpm
Specifications:
Cylinder Head
Cast Aluminium Alloy
Cylinders
Cast iron - Bored in block. Bore Dia. 3.1890 / 3.1895
Crankcase
Cast iron - monobloc type
Crankshaft
Forged-Nitrided-Steel End play .002 - .011" Thrust taken by two half washers.
Main Journad dia. 2.1255 / 2.1360" Conn-rod journal dia. 1.9370 / 1.9375"
Stroke 1.903 / 1.906"
Main Bearings
Shells - 'Vandervell' lead-indium, steel backed. Cosworth Part No. F0012
Main bearing caps are special steel, housing bored .015" o/s
Camshaft
Monikrom. Run in five bearings. Driven by a train of seven gears from the
crankshaft. Bearings - white metal shell type 'Vandervell'
Valve Mechanism
Inverted piston type tappets, running directly on the camshaft. Chill cast iron
Valve Timing
F1 - 102 deg Cosworth Camshaft
IO 58 deg BTDC
IC 82 deg ATDC

EO 82 deg BTDC
EC 58 deg ATDC

Valve Lift .400"
Ramp .010"

Connetcting Rods
Material EN.24 Length centre to centre 5.434" End Play .002 / .006 "
Bearings Trimetal (steel backed)
Valves Inlet
Material Austenitic steel. Head dia. 1.45 " Seat angle 45 deg Stem dia 9/32"
Exhaust
Material Austenitic steel. Head dia. 1.25 " Seat angle 45 deg Stem dia 9/32"
Valve Springs
Double springs, Outer variable-pitch wound. Rate 260 lb/in Free length 1.65"
Fitted length 1.29" (both measured on outer) Close coils to be fitted at head end
Pistons
Special Cosworth / Hepolite, forged in RR59, one compression, 1 oil control ring
Gudgeon Pins
Hollow taper bored. Ground o/d 13/16" dia nominal Clearance .0002 - .0005"
Retained by flat circlips
Compression Ring
Material Cast iron. Plain, high radial pressure Ring gap .019"
Oil Control Ring
Two seperate scrapers in single groove
Water Pump
Cosworth Driven from fron of jackshaft
Lubrication
See diagram Dry pump full pressure system. Main bearings - pressure fed
Connecting rods - pressure fed Gudeon pins - splach Cylinder wall
Camshaft bearingd - pressure fed Tappets - splash Timing gears - jet and
splash
Oil Pump
'Hobourn-Eaton' type, Cosworth designed, mounted on side of cylinder block
Oil Filter
Not supplied with engine Should be full flow with special felt cartridge, and
by-pass valve blanked off.
Distributor
Lucas 40731 10 deg - 1000 rpm. Rotation anti-clockwise, Firing order 1 3 4 2
Contact breaker arm spring tension 32 oz. Centrifugal advance 20 deg on crank
Contact breaker gap .010 / .012"
Carburation
Two 40 DCM2 Weber Choke size 32mm Jetted to suit engine whilst being tested
on dynomometer
Inlet Manifolds
Cast Aluminium alloy, machined to house 'O' rings for flexible mounting
Maintenance and Running Data
Oil Pressure
65 min psi 80 psi normal at running speeds
Tappet Clearance
.010 - .012" Inlet .010 - .011" exhaust (cold)
Contact Breaker Gap
.010 - .012"
Oil
Vegetable 30 Mineral 40/50 SAE. running at 90 - 100 deg C. Any oil starvation
will cause big ens shell failure.
Fuel
Normally Esso Golden Extra, but any equivalent should be satidfactory
Carburetters
Should hold settings, but main jet holders should be kept tightened right down
Carburetter Mounting
The nuts should not be tightened right down, but a gap between the manifold and
the Carburetter faces should be left to allow the rubber 'O' rings to take up vibration
Sparking Plugs
Lodge 10 RL 47
Bolt and Nut Tightness
Cylinder head
53 - 55 lb ft
Main Bearing Caps
55 - 60 lb ft
Cam Bearing Caps
14 - 16 lb ft
Big End
43 - 45 lb ft
Flywheel to Crank
45 - 50 lb ft

Head Tightening
Number bolts starting from front 1 - 5 on manifold side, 6 - 10 on distributor side
then order of tightening is 8, 3, 7, 4, 9, 2, 10, 1, 6, 5 There is also a long 1/4
UNC allen screw in the front cover tying the compound gear bearing housing to the
top idler bearing housing in the block. This should be removed first when removing
the head, and tightened last when replacing.
Rev. Limits
Safe Limit 9500 rpm. 9000 in first and second gears. Crack detect rods every
300 race miles
Assembly Information
Valve Timing
The timing was accurately set when the engine was assembled, and no vernier
etc. is fitted.
N.B. Owing to the very small clearance between the pistons and the valves, tuning
the engine with the timing over three degrees out will result in serious damage.
N.B. The camshaft is located lengthwise by shoulders at each and front camshaft
journal, matching the machined width of the front cam carrier housing. In order to
avoid damage to the flange and the fragile housing by the shell bearing retaining
tag slot, the camshaft must be removed carefully, raising it parallel to the can
carriers.
Before removing the
Cylinder Head
Removw carburetters from manifolds at 'O' ring joint. Remove sparking plugs.
Remove cam cover
Line up the timing mark on the face of the camshaft gear between the two marked
teeth on the larger of the compound gears, this maty take up to fourteen turns of
the crankshaft. In this position a mark on the joint between the gear cover and
cam cover should also be in line with the certre of of the root between the marked
teeth.
The can should for safety now be locked by loosening off No. 2 Bearing cap and
putting a strip of paper between journal and bearing and retightening. This setup
leaves the engine on TDC No. 1 and 4. Cylinder 1 firing, cylinder 4 cams rocking
Removing Head
Remove long allen screw in head front cover. Remove head nuts slackening
progressively from centre to outside. Pull head off studs. Remove old gaskets
and save .003" shim steel washer which surrounds the long 1/4" bolt in the gear
cover for re-use.
N.B. It will now bw seen that a mark on the adaptor plate is exactly in the middle
of the root between two teeth on the top idler gear in the block.
If the engine is turned, e.g. for stroke measurments, the engine should be rotated
to TDC 1 and 4, firing No. 1 on the distributor. This should be very carefully done
from the piston movement, and then the line on the adaptor plate should exactly be
in the root between two teeth on the idler gear. This will permit the head to be
dropped into place without the gear tips fouling and the timing will be correct. An
error of one tooth will mean that the valves hit the piston.
Alternatively the two teeth which are astride the mark on the adaptor plate may be
temporarily marked when the head is removed, and the engine turned until these
teeth are again in this position with No. 1 and 4 on TDC, distributor firing No. 1.
This may require twenty-seven crankshaft revolutions.
Camshaft Removal
Again it is advisable to line up the timing mark on the camshaft gear front face in
between the two marked teeth on the larger compound gear. This puts the No. 4
cams rocking.
Bearing caps 1, 3 and 5 can be completely removed tapping the caps to free the
dowel location. The cam can then be made to rise evenlt by progressively
loosening the remaining four cap securing nuts, and gently lifting the camshaft up
as necessary.
Gasket Notes:
The head gasket should be very lightly greased before fitting and it is also
necessary to trim the front edge straight, as standard it projects around the front
offside combind stud oil feed to the camshaft hole, and fouls on the alloy gear
cover gasket.
The gear cover gasket should be lightly painted with 'Wellseal' and the .003 shim
steel washer around the 1/4" allen screw hole is essential to ensure accurate gear
meshing.
Ignition Timing
This was aset on the dynamometer when the engine was tested; however, if the
distributor is disturbed, an approximate setting is 20 -23 BTDC points just breaking
on full retard.
In order to obtain a quick check a line has been scribed on the outside diameter of
the rear-most lengthwise location flange of the camshaft in line with the bearing
joint face.

[Ray Bell]

Thanks des, brought back things I'd long forgotten, like the downdraught carbies and all. But are the valves all in a line?[p][Edited by Ray Bell on 07-09-2000]

[Tigalola]

Ray,
In Desmo's excellent description of the engine it described the valve arrangement.

"Valve Mechanism
Inverted piston type tappets, running directly on the camshaft. Chill cast iron"

As the valves are running directly on the cam, I would assume they would have to be inline.

[Ray Bell]

Usually, yes, but they could have run offset followers... nor does it mention the essential difference, the Heron combustion chamber... with the flat head surface. Like a Rover 2000 or a Repco V8 of 66 or 67.

[desmo]

I would assume that the valves are inline given the desciption. If followers were employed, they probably would have been mentioned. Actually I think I remember mention of that in another article while I was digging that up.

I love some of the period details in there. The servicing instructions sound like contemporary shop manuals for British motorcycles I have read (and smudged with a carbon/dirty oil suspension).

[desmo]

Wasn't this thread over in the Nostalgia Forum? And didn't Maserati(?) make a Heron-head V-8 in the late 60s early 70s?

[Ray Bell]

By followers I mean buckets... and this question came up in the famous 'Amon' thread, but I brought it over here for clarification.
I don't recall any Masers with anything like the Heron head... Rover 2000, post-1967 British small Ford 4s, Repco V8 in the single-cam versions (I don't remember exactly the nomenclature... the -20 and -40 versions, with the preceding number denoting the size, from memory... 2.5, 3.0 and 4.4 litre, with 4.2 litre and 5.0 litre versions with the CAC block and twin cams being -60 and -80... the -20 had the exhausts to the outside, the -40s the bundle of snakes in the vee) and there must be some more... ignoring diesels, that is, which see this commonly in their designs to get the comp up a bit.
Come to think of it, I don't think I've ever heard of a Maser engine that wasn't twin-cam... even the one in the SM... lovely car that!

[desmo]

It might have been a Lamborghini engine I was thinking of, it was a long time ago. Italian, Im sure.

The Citroen (please excuse the lack of an umlaut, my keyboard is parochial that way) SM was a mighty interesting car. I lived a few blocks from one once and the sound was beautiful. And the turning headlights!

I'm curious Ray, how would you create a valve offset with bucket followers from a single cam?[p][Edited by desmo on 07-14-2000]

[desmo]

Yes it was the Lambo Urraco P250 V-8, turns out Heron-heads weren't amenable to US emission laws and the engine didn't fare well when forced to conform. This engine ran both cams off a single belt.

[Ray Bell]

I'm sure you know about cam followers and cam buckets being radius-ground on the face. This idea came to me when I reflected on what Frank Kleinig did with his Hudson engine, so settle in for a bit of a read.
Kleinig never ran a non-standard camshaft. He used these engines, the straight-eight side valve things, for front line competition in Australia from 1934 to 1954, and would probably have gone on another year or so before he was completely outclassed or forced to fit a Chevy... maybe.
To achieve different valve timing he would alter the radius of the grind on the followers. Standard was 3", he went as high as 6" to get more overlap. The 'flatter' follower being lifted by the camshaft earlier, lowered later, with the cam starting and ending it's work further from the centre.
The radius is, of course, there for a purpose. The cam is also ground at a slight angle... one, two, three degrees... I don't know, but this means that the cam isn't 'rubbing' on the follower's face, but rolling on it as it causes the follower to turn in its housing.
So, with a single overhead cam, one could go to lengths such as this and cant the valves over if one wished. What benefit it might be, I don't know. With a more pronounced radius and a greater angle on the cam, one could go a fair way with this (in relative terms... maybe up to five or six degrees, or am I wrong in saying that?) to produce a nice cant on the valves, but keep them in line with the axis of the engine.
Certainly, it wasn't done with the SCA, but a designer might do it to get a better spark plug placement or a hemispherical head with one cam and no rockers or more room for ports with a single cam or whatever.
Now cast your mind back to the Apfelbeck (is that the right spelling?) heads that were twin cam and four valve. These heads had the valves disposed radially (is that the right term?) so that the valve heads formed part of a true hemisphere (we're really not talking hemispheres her, parts of hemispheres would be more accurate), not a pent-roof arrangement or a hemisphere with valves distorting its shape.
These heads were used by the factory BMW F2 engines in the late sixties. I don't know how they achieved this goal, but the method I have postulated seems logical.
Do you have anything on these heads?

[Ray Bell]

And, seeing as how I brought Kleinig into this, here's a picture (taken from 8mm movie) of him at Bathurst in 1946. The chassis is from an MG Magna, the front axle and gearbox a Mathis, who knows where the huge brakes came from... and the engine and rear axle Hudson.. four Amal carburettors and water injection. Later it wore a Maserati body over an updated chassis with independent front suspension from a Peugeot 203, an offset rear axle and other improvements... it never raced like that. The engine is said to have pulled over 7000rpm once or twice... on splash feed big ends!

[desmo]

Sounds like the RFVC Honda motorcycle heads the've used since the 80s. On their single cylinder dirt bikes Honda splayed the four valves on both axes to form a more truly hemispherical head. If I remember these were run off a SOHC with rockers working on an axis that canted to avoid side-loading the valves.

[desmo]

Ray, I can't diagnose why your photo won't come up. If the URL is correct, then the photo didn't upload to the server properly.

On the BMW-Apfelbeck heads, I believe they ground the cam lobes conically to achieve the lateral splay of the valves. That was a long time ago... The point of contact on the cam must have been very small and it would impose a pretty stiff thrust load on the cams as well. I don't think I'd try these heads for endurance racing.

[Ray Bell]

They didn't use them for very long, I don't think, but they flew while they were there.
As for the pic, I put the right URL in, it just added the atlasf1 bit for itself!

Err... correcting that, I didn't put it in right... like always, as plain as the nose on your face... left off the 'http://'... fixed, anyway![p][Edited by Ray Bell on 07-15-2000]