mk1-forum.net

Hello, I'm about to have a mk1 998 cooper engine rebuilt. I've looked into the downton touring spec which I think used to utilise a coopers 510 cam. I'm after something period but with a slightly lumpy idle. The cars a stripped out period modded mk1 so looking for a cam to suit. Rest of engine will be built to suit the cam. I've looked into the 997 and 544. Any recommendations? Thanks in advance.

Looking into this myself recently, and was wanting to try the 997 cooper camshaft which looks better on paper than what was fitted to any other cooper or S. Think the Mg metro cam is a copy or version of the Downtown no1 touring cam.

The 510 Cam was what was fitted to the Cooper S when they went from the 163 head to the 940 head. It has 10 degrees longer exhaust duration to supposedly off-set for the reduced exhaust valve sizes but doesn't nearly make up for the difference in the Intake and Exhaust Ports, though, getting a little off the topic there.

The 544 maybe a little on the too wild side for regular street use, it has 288 / 288 timing! It will come down to personal choice and cylinder head mods, but I wouldn't go much beyond around the 275 / 275 mark for regular street use. To get any proper benefit from the longer duration cams, the head will really need to be able to breath in a big way (for a small bore), otherwise, you'll loose all the lower RPM Power and Gain little higher up. With a modded head, you'll still loose in the Lower RPMs, but reap the gains that a wilder cam can offer at higher Revs.

Innocenti used the 510 in the 998 Cooper, 60-65bhp ish as standard, nice engine spec

Spider wrote:The 510 Cam was what was fitted to the Cooper S when they went from the 163 head to the 940 head. It has 10 degrees longer exhaust duration to supposedly off-set for the reduced exhaust valve sizes but doesn't nearly make up for the difference in the Intake and Exhaust Ports, though, getting a little off the topic there.

Sorry, also meant to add here that the Cam 'one down' from the 510, the profile of AEG148 (and a few other Part nos.) was fitted to the 'standard' 1275's, MIKI Cooper S, 1100 Engines & 998 Cooper, it is a very tame cam.

I devoured vizards book...Tuning BLs A series looking for
answers and tips...
For my 997 i built a 998 using a 997 block, 12G295 head,
raised D crown pistons and a Piper 270 duration
cam with twin HS2s and M needles.
It has always had a slight lumpy idle but is sweet and
pulls well above 4000rpm on 98RON.
...if that helps.

If you're looking for a 'classic 60's BMC' cam but not as wild as the 643, then might be worth looking at the 731 profile. Has 268/268 opening with 107.5 LDA and lift at cam of about 260 thou.

The 731 does not have a great reputation, with comments like DV's 'lose bottom end power and don't gain much at the top' often quoted.

However take a look at AC Dodd's current RS+ profile and you will see this is 268/268 opening with 107.5 LDA but lift at cam of about 314 thou, and timed in about 5 degrees advanced compared to the 731.

The 997cc 252/252 degree cam was a good one,
the "731" at 268/268 did not get a warm reception...

However, the MG Metro cam, which is a hybrid of
the inlet lobe from the 997cc cam and the exhaust
lobe from the "731", ie, 252/268, worked very well.

I used this on a 998cc engine with a well-ported
12G295 head and a set of offset-bush rockers and it
went to over 7500rpm easily.

Oh-No-It-Didn't....
....Oh-yes-it did....

(I was there, the disbelievers weren't!)

For a "period" cam, I'd go with the 997cc profile.
If I was building another 998cc engine and was not
worried about originality, I'd go for the MG Metro one.

I also think that the 288/288 "643" cam would be
too much...

Ian

carbon wrote:If you're looking for a 'classic 60's BMC' cam but not as wild as the 643, then might be worth looking at the 731 profile. Has 268/268 opening with 107.5 LDA and lift at cam of about 260 thou.

The 731 does not have a great reputation, with comments like DV's 'lose bottom end power and don't gain much at the top' often quoted.

It's actually a bit of a shame that Vizzard gave the 731 the rap that he did. I'm not altogether sure why he made the comments that he did and he doesn't ever go in to any detail as to what he tried with this cam, but from my own experience, it is a good cam for the grind that it is, I found no noticeable loss at the bottom end and small gains up top, very very drivable street cam for the smaller engines for sure. While it would work in a 1275, with no negative effects, I don't think it would be worthwhile fitting one to these bigger engines as any gain would be almost academic.

Mitch,

To fulfil your design criteria you only have 2 real cam choices. The 997 (2A948 / 88G229) or the 544.

Both these cams were used by Downton in period, however, for a road conversion the 544 would in my opinion be "wild".

As I so often say, you can check back on original info using the main MK1 site.

There are a couple of great letters re cam choice on there, this is probably the best data sheet re cam choice. Read both sides, not just the first one.

http://mk1-performance-conversions.co.u ... m_data.pdf

997 cam in my 998 engine, you know it's got a cam in it but it's very drivable. Makes decent power with a full tilt build

Thanks for all the advise gents, very useful as always, did all downton 998 conversions use twin hs4's or were 1.25's also used?

Many thanks

Most Dtn conversions for the 998 used a single HS4 carb but conversions using twin HS2's were also available. Dtn didn't do any standard road going conversions that used twin H4's at all.

As always there are masses of original data sheets on the main MK1 site.

http://mk1-performance-conversions.co.u ... lubman.jpg