25 replies to this topic

[72r1mini]

Hey guys,

Just looking for more information on my cam installed as there is little info on the net.

It's a British Leyland special tuning department 713 cam

[Spider]

I think you might mean a 731 cam?

 

They are well suited to the smaller bore, longer stroke engines, ie, the 997 Cooper and the 1100 engines.

 

They were factory fitted here in to the Clubman GT Highway Patrol Pursuit cars.

 

Very dated now days, you'd find something loads better than one of these.

[unburntfuelinthemorning]

731

 

Timing:                                 24-64-59-29 degrees

 

Duration:                              268/268 degrees

 

Lobe displacement Angle:   107.5 degrees

 

Valve lift standard rockers:  .320"/.320"

 

Valve lift 1.5 rockers:           .378"/.378"

[racingbob]

yes the mg metro cam lot better cam than the 731 out of intetest

[Cooperman]

Even 'back in the day' the 731 was not well liked. We used to jole that it lost you bottom end torque but added little at the top end.
The S 510 was a nice cam, with the 544 popular for rallying and the 649 for racing. Ideally the 544 needed a SCCR gearbox and a fairly low FDR such as a 3.76 or a 3.9

[72r1mini]

Thanks for the replies,

Unfortunately/fortunately this is the cam I have installed so I am stuck with it.

I recently took the time to adjust my rockers as the previous owner neglected to do so since the engine build in 2013. I found out my rocker gear is late model sintered type with good amount of wear.

My goal is to optimize my power but keep the car a nice driver.

When the engine was built the 998 block was pocketed and fitted with a 12G1316 head with the above mentioned cam.

The previous owner did all these engine modifications including a sportex exhaust but left the manifold restrictive.

I plane to run the stock airbox modified with the 6 holes, K&N, and removed air valve to keep it stock looking. It has a 1.5 SU that already has a upgraded stage 1 needle. Free flowing intake manifold already. I want to change the midget manifold to a header, change the carb pot spring to red, and replace the rockers to forged cooper s 1.3:1 rockers with upgraded shafted and bushes vice springs.

Should this set up optimize my power?

[unburntfuelinthemorning]

Why can't you change the cam?  Do you just not want to dismantle that much?

 

Not sure what a 12G1316 head is.

 

Your plans sound reasonable though but you'll likely need a different needle.  Get thee to a rolling road dyno after the mods are done.

[72r1mini]

I don't plan on removing my engine so I will be keeping the cam. Head is a 1275 midget head from what I gather.

[racingbob]

get some pressed steel rockers bit more lift. I put some 1.4 rockers bushes in mine

[72r1mini]

I was reading that high lift rockers for small bore were not effective? No issue with the 1.4?

[Spider]

Not what you want to hear, but IMO, it's not a great combination. You won't get much low down power and the Cam won't let you take advantage of the head (which is a smog version of the 12G940). I'm inclined to suggest at the least a head swap to something with smaller ports and valves, it will make it much more driveable and take little (if anything) away from the higher RPMs.

 

The alternative would be to fit some high lift rockers and try to make it a screamer, but you'd then want to change the final drive ratio too.

[DeadSquare]

I don't plan on removing my engine so I will be keeping the cam. Head is a 1275 midget head from what I gather.

 

It only takes a couple of hours to change a cam in situ, if you have a reasonable tool kit

[72r1mini]

The car runs pretty well now, just noisy rockers at the moment so I my intention was to optimize what I have without having to take the car off the road. I really don't think sourcing a head is an option(hard to find in canada) and new would be far to expensive.

So my options would be to go high lift rockers or a different cam?

[Retroman]

Got to agree a better more modern cam, some pressed steel rockers. I would also Vizard the HS4.

 

Cam choice MD266 MG metro SW5 or MS evolution001, all considerably better than the 731. Or even a piper 270.

 

You will also need a needle change and preferably a rolling road session to get the best from it.

 

As above its not too difficult to change a small bore or S cam with the engine in-situ.

 

 

 

I did a similar but slightly bigger engine [998 to 68mm] not long ago and it drives really well with a nice flat toque curve from 3 to 6k

 

The guy loves it, its twice the go and fun of a std 998.

[unburntfuelinthemorning]

I was reading that high lift rockers for small bore were not effective? No issue with the 1.4?

I think the problem with high lift rockers on small bore engines is if you exceed around .375" valve lift.  So on say a standard cam they could be advantageous but on a lot of more modern performance cams extra valve lift is built into the cam profile so using high lift rockers on these cams would overdo the valve lift.  Going by this - high lift rockers would work with a 731 but as the chaps are saying it's really not the best cam and if you can change to a better one with the engine in situ then that's probably the best option.