404/504/505 camshaft timing

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davemcbean

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I've just been puting together some camshaft details for a friend and I thought I'd post some of what I said here:

The details of my 504's camshaft:

Wade grind number 112
Maximum lift at cam follower: 0.285" (7.2mm)
Lift at TDC on number 1 inlet follower: 0.039"
inlet opens 22 degrees before TDC
inlet closes 63.5 degrees after BDC
exhaust opens 63 degrees before BDC
exhaust closes 23.5 degrees after TDC
So by common cam timing terminology this cam would be called a 22/63.5 63/23.5
the inlet duration would be 265.5 degrees (22+180+63.5)
the exhaust duration would be 266.5 degrees (63+180+23.5)
the valve overlap would be 45.5 degrees (22+23.5)

this is not very wild by comparison with:
the 505 STI and GTI have a 20/60 60/20 cam
BMW 2002 Tii 18/66 66/18
the 2 litre Cortina 18/70 64/24
the 1.6 GT Cortina 27/65 65/27
the Renault 12TS/GL 22/62 65/25
the Renault 16TS 21/59 59/21
the Renault 17TL 24/68 68/24
the Renault 17TS 40/72 72/40 (quite wild)
Alfa Romeo Alfetta 1.8 litre 41/60 62/25
Michael Loney's hot 404 44/74 74/44 (very wild, 88 degrees of overlap!)
Michael Loney's cam had about 0.300" of lift, which isn't large, but it is probably as much as is practicable in a 504 engine. The rocker ratios on the 504 engine are somewhere around 1.1:1 or 1.2:1 (does anyone know which it actually is?), which isn't large, so the most lift possible at the valve is somewhere around 0.355" (9mm). On other engines it isn't uncommon to have performance cams with valve lifts as high as 12mm.

There are a number of 504 TI cams, but the 504 timing is difficult to compare with the above cams because it is measured from the time the valve is 0.7mm (0.028") from the seat, until it reaches that point again, whereas the 505GTI is measured at 0.35mm of lift (and I think most cams are measured at something similar to 0.35mm -can anyone confirm this?). Because of this 0.7mm reading, these official 504 TI cam figures look tamer than they actually are:
1.5/36 35.5/9
2.5/42 36/7
0/44.5 33.5/9.5
Their actual timing may be as much as 16 degrees more on each figure,
which is something like:
17/52 52/25
18/58 52/23
16/60 49/25,
The 1.8 litre injected 504 has a maximum lift at the cam follower of around 6.82mm (0.272"). This is an average figure (It's actually 6.79mm inlets, 6.86mm exhaust). I'm not sure about the lift of the 2 litre TI cams.

The 404 and 1.8 504 cams have a maximum lift of around 6.18mm (0.247")
Their timing is officially 0.5/35 35.5/10, but it may actually be as much as 16/51 51/26
The early (round port) 2 litre carb 504 has this timing 1/36 33/5.5,
but again it may actually be as much as 17/52 49/21

I'm not sure of the timing of the later square port carburettored engines.
There was a variety of other tamer and more restrictive cams fitted to anti-pollution
carby 504s in the US (e.g. -4/34 34/-4). I think the restrictive cam timing and low compression are the main things which hold the 504 engine back, but I guess they're ideal for abusive environments like Africa and the Middle East.

Using the 8.8:1 pistons and 0.5mm shaved off the head (which is typical for old heads which have been shaved a few times) gives a compression ratio of around 9.2:1 (same as 505 STI). So basically every half millimetre adds about 0.4 of a ratio point to the compression of a 504. Shaving anymore than 1 millimetre off the head may necessitate shortening of the pushrods, to allow for valve adjustment and to avoid the rockers hitting the rocker cover.

Here's the phone number and address for Wade Camshafts:

Wade Camshafts Pty. Ltd.
113 Dryburgh St
North Melbourne
VIC 3051
Ph: 9328 4001
FAX: 9329 8318

Regards,
Dave
 
Hi Guys,

That list is amazing, I wonder how 'wild' the cam is in the old Cit CX2400's. Mine definatly comes 'onto cam' at around 4000rpm, and with a low restriction exhaust 'pops' a lot on the overrun (in fact you think it'll blow the exhaust off when you back off hard at about 200km/h, er, elledgedly)...

by the way low restriction exhaust == the rear resonator has shit itself and has no bottom in it
smile.gif


seeya,

Shane L
 
Shane,

I think the old Citroen cams must be measured in the same way as old Pug cams, because this is what is listed in the Boyce's tune up and service specs book:

ID 19 0.5/42.5 38.5/4.5
DS 21 0.5/42.5 38.5/4.5
D Special 0.5/42.5 38.5/4.5
DS 23 0.5/42.5 38.5/4.5
CX2200 0.5/42.5 38.5/4.5

It's interesting that they're all the same. If they are measured with a similar calibrating valve clearance of 0.7mm as the old Peugeots are, then I think the actual figures would probably be atleast 10 degrees more and possibly as much as 15 degrees more.
So the real figures are probably atleast:
10/52 48/14
but probably not more than about:
16/58 54/20

It would be nice to find someone who could tell us for sure what the actual figures are in "plain English", rather than these useless high valve clearance measurements, which are difficult to compare with common measurements of valve timing. It's a bit like measuring speed in Furlongs per Fortnight rather than Kilometers per Hour.

Regards,
Dave
 
Unfortunately these type of numbers are only a rough guide unless you quote the lift at those figures.
ie 20/60 at 0.050" lift is a lot wilder than 20/60 at 0.010". Most manufacturers don't quote this so it's almost impossible to compare grinds. Quoting the inlet lift at TDC helps to give a better indication of how "big" the cam will be, but only once all valve clearances and ramps are taken up can you compare grinds. Thus 0.050" gives the best comparison. A
 
Exactly! Alot of them tend to be quoted at about 0.015" of lift (give or take a few thou) and the cam grinders seem to do likewise, but for some reason Peugeot used to use 0.028" which is really unusual and impossible to compare with others, and makes the cams look alot tamer than they are.

Obviously there's alot more to cam grinds like lobe centre spacing, rate of lift, etc, so technically it is very difficult to accurately compare any cam grind with any other, even if they are measured at the same lift and ground at the same place. It really takes alot of Dyno and other measurement work to accurately assess the potential of any particular cam grind and this is what separates a good cam grinding business from a bad one. Most people would agree that Wade Camshafts is a good cam grinder that knows their stuff and so often a Wade 20/60 grind can have a better power potential than someone else's 30/70. Bert Jones, in Sydney, is another guy who knows his stuff, but unfortunately he doesn't do cam grinding for the general public anymore. Alot of the best cams for 2 litre Cortinas only have timing of around 25/65, but they have very high lift (0.500"), but the lift at TDC is low (because that is what those engines like) and then the subsequent rate of lift is very high. Different engines and port designs require different cam characteristics, which is another reason why it is difficult to compare a cam from one engine with a cam from another. It's easy to see why there is such a huge difference between different cam grinding firms.

Dave
 
Peter,

I agree with what you said:

<font face="Verdana, Arial" size="2">Originally posted by PeterT:
Quoting the inlet lift at TDC helps to give a better indication of how "big" the cam will be, but only once all valve clearances and ramps are taken up can you compare grinds. Thus 0.050" gives the best comparison. A[/B]
Click to expand...

It would be nicer and more useful to see a comparison of cams done at 0.050" lift, as you said, although it would still only be an indication of their potential rather than an accurate comparison.

Dave
 
Most of US cam grinders use the 0.050" reference which makes them more comparable in a very competitive market. Everyone has their favourite grinder, mine was Bert. He wouldn't sell you a cam unless you could tell him how much cylinder pressure you had (or expected to have!)

I know Owen Wuillemin has an absolute cracker grind planned for his Mi16 powered 205. As if it isn't quick enough already! I'm waiting for the opportunity to add them to my 405.
 
Yeah, I was looking in a book of mine on modifying Mustangs yesterday and in the camshaft section I noticed that they quoted everything at 0.050" lift. Makes alot of sense.

A few years ago I went to a talk given by Bert Jones and his son Wayne. Very interesting indeed. At the time they were doing alot of work for Tony Longhurst's V8 Commodore race car.

Dave
 
I believe Wayne works from home now. He can alter the mixtures on a race car in Perth from his laptop at home.
 
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