Again a cam question

[Vincent.vanGinneke]

Building my engine for the half WNG (see other thread http://forum.arielownersmcc.com/viewt ... &start=150 )
and I still have not decided on what type of cam to use...

It now has steel 350 flywheels and a late 1:7.5 piston on +30.
At the rally in Lowestoft I bought one of those club spares VCH camshafts.
I intent to put this VCH cam in this engine, but I am actually not sure....
I made a few pics and tracings to compare it to other cams I have (or used to have)

cardboard strip with tracings of different cams :

The tracing below shows 3 cam profiles into one;
HSMkIII with inside it the VCH profile and in red lining a standard fifties single lobe cam.
The HS MkIII cam and the VCH cam are the same height, only the VCH cam is 'slimmer' on the ramps.

The picture below shows a prewar twin lobe A7/642 1"base circle cam on top of the profile of a postwar single lobe.
Looks like the profile is the same .

Below all 3 together, which one should be a good choice for the engine ?
From 'THE DEFINITIVE ARTICLE' I learned that the prewar cam 'gives snappier acceleration' compared to the A6/664 cam (which I have but sits in Burney))
The standard single lobe is the safest choice, I know more or less what I get.
The VCH cam looks the same height as the HS MkIII cam but has rather straight ramps, but not flatter then the standard fifties single cam.
Perhaps I should just try them out.

Or does anyone of you use this VCH cam in a 350 ?

[Simon.Gardiner]

Vincent:

I used one of the post '50 twin-lobe cams in my '53 NH for a while and I reckon it was a bit more 'peppy' than it had been before with early single-lobe cam.

As you'll well know there's been a lot of discussion about cams in the forum, over the years - Pete Collings seems to have had some experience of that VCH profile - he's posted a few comments in these threads (which you may well have looked at already)
http://forum.arielownersmcc.com/viewt ... &hilit=vch
http://forum.arielownersmcc.com/viewt ... h&start=20

However, I think you'll probably have to try them all out for yourself - and then report back so we can add some more meat into the stew!

SG

[adrie.degraaff]

The VCH and HS cam willbe noisier and will need a full noise exhaust.
There is a silencer system wich is working silent in town and noisy on open road; take an old silencer, cut it open at the end, press discs with an edge and a hole in the middle the size of the tube, fix them with blind rivets every 50 to 70 mm apart in the silencer and close it again.
Now you can look streat through but the discs will work on low revs.

[david.anderson]

Vincent
Either the mk3 cam or the VCH cam will be a lot better cam on the road than the standard cams.
The VCH cam actually lifts .434” on the lobe and with a single lobe VH follower the lift ratio is .86 so the lift at the valve is .373” which is much more lift than the standard cams (A7/642 and 1750/54F) which only lift .317” at the valve. The VCH cam has a duration of 255 degrees whereas the std (single lobe) cam has a duration of 239 degrees both measured at .050”lift.
While I have not used either the mk3 or VCH cams in a 350, I have used the 1954mk1 cam which is hotter than the previous cams. The difference between the std cam and the mk1 cam (similar duration to the mk3 cam but more lift) is dramatic. There is a large increase in midrange power and hill climbing is dramatically improved, as is top speed.
A feature of the VCH and mk3 cams is that the ramping is very long and much longer than current cam design.
Attached find cam data graphs and a power comparison based on computer modelling.
David
For some reason I cannot post the standard single lobe cam graphs or power comparison as the file is corrupted? But they open on my computer? The computer modelling suggests about 2hp more with the VCH cam in a 500.

[Vincent.vanGinneke]

Thanks for the links to previous topics, I knew there has been a lot of talk about but most of the time I simply cannot retrace the topics.
Also thanks David and Adrie, I suppose the best way is to try out each cam (and not alter the rest in between) and see what happens.