CA/CB camshafts.

Tony Fearn · Post by **Tony Fearn** » Sat Feb 14, 2009 1:18 am

I have a couple of camshafts in the spares store that have attached to them little tickets.

One says CA camshaft, the other CB camshaft.

They both look exactly the same. Is this true? They have smaller cross-sections on all lobes than do the original pre-war ones I have.

Can either of them be used in a 1934 type pre-war engine?

Tony.

george garside · Post by **george garside** » Sat Feb 14, 2009 10:37 am

Hi Tony
I fitted a bradford camshaft to an '8' which definately improved the torque. Can't see any reason why it wont fit a '7' but try the suck & see method!. As far as I know CA & CB camshaft intercheangeable.

george

k. rogers · Post by **k. rogers** » Sat Feb 14, 2009 2:21 pm

I've used a Bradford cam in the 7 I'm restoring but I was told by Ian Priestley that it was necessary to also use the Bradford cam followers provided with it - not sure why but always assumed it was to do with the extra valve lift, apart from the fact they should be quieter; perhaps someone else can comment. They are certainly supposed to be interchangeable.

Keith Andrews · Post by **Keith Andrews** » Sat Feb 14, 2009 8:02 pm

If they are unused, it would be worthwhile taking them to a cam grinder
It would take a couple minutes each to spin them up and get a read out on the specs.
As far as I know, there are no acrrucate/detailed specs on jowett cams, to enable accruate reproduction to have made up in the future...
Or to use as a basis to modify to run on modern fuels, rather than the old British Pool fuel and pre war specs.
I do suspect that the differences where not made by the factory so much because of better preformance, but rather because the change in fuel specs in 1938/39 thru to about 1956.

They are both 'square' cams open close at TDC BDC when tappet clearance is taken into account. This ok for very fast burn low octane (6.5 to 7.2 octane) low compression engines 5:1 to 6:1 CR) but bad for modern high octane controled slower burn fuels.

Also if the cam lift and lifters are different then the valve spring rates and heights may also be different.

The Bradford man · Post by **The Bradford man** » Sun Feb 15, 2009 6:10 am

Dad used a CB cam shaft in his 8

Leo Bolter · Post by **Leo Bolter** » Sun Feb 15, 2009 11:39 am

As far as I know, there are no acrrucate/detailed specs on jowett cams, to enable accruate reproduction to have made up in the future...

Hi Keith,

We have here in Palmerston North, N.Z. a "pet" cam grinder who has/had (hopefully NOT had!) the grinding profiles for Javelin hydraulic tappet, solid tappet and also a "warm" solid tappet camshaft re-grind of a standard shaft (this reputed to be a Padman Special). I don't know if he has Bradford or other Jowett profiles in his collection.

Over the years I have had several re-ground by him for myself and JCC of NZ Spares. I have records of the specifications . . . lifts and duration of timing etc.

So all is not lost!

He was, when I last spoke to him, willing to make new camshafts as above, if required . . or to any shape your heart desires . . for a "small"

fee no doubt.

Cheers, Leo

Keith Andrews · Post by **Keith Andrews** » Sun Feb 15, 2009 7:21 pm

I have been using Franklin cams in Auckland here for my custom LPG grinds in the camarp.

k. rogers · Post by **k. rogers** » Wed Feb 25, 2009 7:07 pm

Further to my previous comment on this subject, I've spoken with Ian Priestley recently and he was of the opinion that Bradford followers needed to be used with a Bradford cam because of the narrower profile of the lobes, having said that he knows of at least one person who is using one with the original pre-war followers. As I have a set of Bradford cam followers I've decided to play safe and use them, but I do wonder how important this actually is. Does anyone know if there is any difference between the 8hp and Bradford cams, as we know that the '30s cams were definitely interchangeable?

george garside · Post by **george garside** » Wed Feb 25, 2009 10:05 pm

As far as I know the 7/8 hp camshaft was different from the bradford one although intercheangeable. I put a bradford shaft in a 1938 '8' with no other mods.

However the LATE 1939 '8' along with the 1940 '8' haad, I think, what may have become the CA bradford camshaft. The Autocar description of '39 models published 26.8.38 states taht the mechanical la;yout is identical to the previous years model. Yet the Autocar road test of a '39 '8' which was carried out 7.7.39 (i.e. only just before the announcementof the much revised 1940 model) states " the modifications recently made include the use of aluminium cylinder heads,providing an improved form of combustion space, whilst also the induction system has been revised, a high lift camshaft is used & double valve springs are fitted."

IN other words the CA bradford induction pipe , camshaft & valve springs were used in the normal in the normal 8hp crankcase. The 1940 models used these bu with a different crankshaft,flywheel borg & beck
clutch etc together with synchro box & enclosed bellhousing.

I have often wondered why the bradford effectively reverted to the 1939 set up rather than the 1940 one.

That the late '39 mods had some effect is beyond doubt although I have never seen any claim to increased BHP it must have at least had the Bradfords 19,( a 12% increase) & possibly more.

This is born out by road test results.

1938 1939 CC Bradford de lux (25bhp)

00 -30 15.4 10.9 10.4

00-50 -- 40.0 47.6

max 48.39mph 56.25 53.9

20-40 in top 36sec 21.1sec 20.8 sec

30-50 " " ----- 31.3sec 36.8

weight 17cwt 3lb 16cwt 2qr12lb 17cwt

make of it what you will!

george

Keith Andrews · Post by **Keith Andrews** » Wed Feb 25, 2009 10:36 pm

rather than the old British Pool fuel and pre war specs.
I do suspect that the differences where not made by the factory so much because of better preformance, but rather because the change in fuel specs in 1938/39 thru to about 1956.

1939 to 1956 is a very interesting period of changes in many vechiles due to the 'semi nationalised' fuel companies and the War and stds of the British Pool fuel stds.

Off subject...but the American jeep was resigned to run on it...then during the Italian campain the drivers found that the leaded American fuels, used for planes made them "go like the clappers". then after a week or so of this fuel all the jeeps 'clapped out" This created a huge problem in logistic of the campain and held up progress for several weeks.

I allude this this subject in an old thread reagarding octanes, redesigning compression ratios/cam profiles for use on modern fuels.

I have found that a 10% of A1+ avaiation fuel in 91 octance knocks the octane back to low 70s...increasing performance and economy in later model bradford.
Note:A1+ avaiation fuel is higher refined than kero, has lubrcants to stop washing bores, doesnt gum up under light loads.

The Bradford man · Post by **The Bradford man** » Thu Feb 26, 2009 2:50 am

My ex uncel used to run airforce engine parts cleaner in his bradford. he got it for free