Recommendations for race cam - 998

[850RS]

Hello friends,

As the title suggests, I’m looking for a little more power out of my 998. The obvious choice is to scrap the 998 and just go full race 1275. But that’s not in the budget at the moment, so looking for any reasonably cheap gains I can find. I have the 998 with .040 over pistons and a well worked 202 head. Oversized rimflow valves with 1.3 ratio rockers. Aldon red dizzy. Dcoe 40 carb. Currently I have a Kent 544 cam. It’s nice as it pulls really well from down low and I have a standard ratio gearbox. My winter plans are to build a close ratio straight cut gearbox to put under the 998 which could be transferred to a 1275 in the future.

I was looking at the swiftune cams and I think the sw23 is just too much for the 998. What’s a good option for running 5k-7k rpm range with the current setup I have?

I do have a slightly used 997 cam sitting on the shelf, are they any better than the 544?

[mk1]

In short, the 544 is about as radical as you can go on the spec you already have. An SW23 is WAY too much for it. The 997 Cooper is a road cam that is hugely milder than the 544 you are already using.

[850RS]

Hey Mark,

Appreciate your advice and I know you are well versed in the motorsport world.

I thought the sw23 was way too much as well. When I reached out to Swiftune and told them the spec of motor I have and they told me sw23 was the cam to go with I thought they were crazy.

I’ll stick with the 544 and work on fine tuning what I have.

Cheers

[Oneball]

I tried a SW22 (the predecessor) in my 998 race car. It lost torque everywhere up to 7k compared with the MED cam I was running. With a lot of development and wilder and wilder cams I got over 100bhp out of my 998 but it actually ended up slower as it lost too much torque in the mid range. Cheapest way to gain more everywhere is to increase compression ratio. Do you know what yours is at the moment?

[NZmember]

https://www.theminiforum.co.uk/forums/t ... 7-engines/
MG Metro cam. Seems incredible but scroll down and see OzOAP dyno results.

[OzOAP]

544 with std Rockers is 0.390 lift.
I doubt your 202 head will benefit from that much lift.
940 head on 998 is the way to go, but valve lift is still restricted by block pocket depth depending on top ring height.
Flat top pistons are a must then you run deeper chamber in head.

[850RS]

I tried a SW22 (the predecessor) in my 998 race car. It lost torque everywhere up to 7k compared with the MED cam I was running. With a lot of development and wilder and wilder cams I got over 100bhp out of my 998 but it actually ended up slower as it lost too much torque in the mid range. Cheapest way to gain more everywhere is to increase compression ratio. Do you know what yours is at the moment?

Currently I have an 11:1 compression ratio. I’m at 5k’ in elevation so as I understand it that lowers the effective compression to about 10:1. I could stand to increase my compression a bit, but prefer not to get too crazy with it as I would prefer not to switch to race fuel if at all possible. I spent $40 on 91 octane (ethanol free) fuel for a full weekend of racing. A friend who runs race fuel spent nearly $200 on 100 octane race fuel for the same weekend. I know trying to race while being on a budget is always going to come with compromises.

[850RS]

544 with std Rockers is 0.390 lift.
I doubt your 202 head will benefit from that much lift.
940 head on 998 is the way to go, but valve lift is still restricted by block pocket depth depending on top ring height.
Flat top pistons are a must then you run deeper chamber in head.

Thanks Oz for the info! I do have some flat top .020+ pistons in there at the moment. I’ll start researching the 940 head conversion. What kind of compression ratio are you shooting for with the 940 head swap?

I see you run the CAM6648 in the 7 class. Is the Kent MD256 the equivalent?

https://www.theminiforum.co.uk/forums/t ... 7-engines/
MG Metro cam. Seems incredible but scroll down and see OzOAP dyno results.

Thanks for the link. Lots of great info there.

[OzOAP]

544 with std Rockers is 0.390 lift.
I doubt your 202 head will benefit from that much lift.
940 head on 998 is the way to go, but valve lift is still restricted by block pocket depth depending on top ring height.
Flat top pistons are a must then you run deeper chamber in head.

Thanks Oz for the info! I do have some flat top .020+ pistons in there at the moment. I’ll start researching the 940 head conversion. What kind of compression ratio are you shooting for with the 940 head swap?

Depends on the chosen cam.
Cam choice is also critical to final drive ratio as well.