11 replies to this topic

[Someone called James]

Hello Guys and Girls,

 

I'm relatively new to The Mini Forum so I apologise if I've posted this in the wrong section.

 

Anyway, I should be taking the engine out of my 1989 Racing Flame 998cc in the summer to replace the piston rings, seals, gaskets, etc and fix a minor oil leak. I'm wanting to change the camshaft to either a Kent 256 or Piper 255 to give it a bit more 'get up and go'. It's currently running completely standard with a single HS4 carb but planning on fitting twin HS2 carbs, K&N filters, 12g295 head and Maniflow Freeflow exhaust manifold and Maniflow 1.75 single box, centre exit exhaust in the future. 

 

These are the specs for each cam, taken from Kent Cams and Piper Cams websites respectively:

 

Kent 256:

Duration Inlet - 254°

Duration Exhaust - 254°

Valve Lift Inlet - 8.12mm

Valve Lift Exhaust - 8.12mm

Full Lift Inlet ATDC - 106°

Power Band - 1000-6500 RPM

 

Piper 255:

Duration Inlet - 270°

Duration Exhaust - 252°

Valve Lift Inlet - 10.29mm

Valve Lift Exhaust - 9.88mm

Full Lift Inlet ATDC - 108°

Power Band - 1000-6000 RPM

 

What are people's opinions on these cams and which one would be better? I'm not looking for top speed, just better acceleration.

 

Ta very much,

James. 

 

[carbon]

For a fast road 998 I think the Kent 256 may be a better option.

 

The Piper will likely give more power, but not be as flexible as the Kent. But I have not tried either, so just a guess.

[Someone called James]

For a fast road 998 I think the Kent 256 may be a better option.

 

The Piper will likely give more power, but not be as flexible as the Kent. But I have not tried either, so just a guess.

 

Thanks carbon.

 

I was originally thinking the Kent 256 but just seeing what people think of the Piper.

 

James 

[minidaves]

new age cams like sw5 or acdodds range of cams :)

[Cooperman]

The first question is what are you going to do about the cylinder head? To get improved engine performance from an A+ unit the first thing is to fit an improved head. Ideally for a 998 the head to fit is a 12G295 Cooper 998 head, suitably gas-flowed and with the compression ratio set to around 10:1. For this head to work best it needs flat-top pistons in order that there is not a need to skim too much from the head face when setting the C.R.

A different cam can only work if the head can flow the additional mixture in and get the exhaust gases out.

It can be that changing the cam without significantly improving the head's ability to flow more mixture will actually reduce power as it will lose some bottom-end, but be unable to improve the top end.

Consider an up-graded engine to be an engineering exercise with matched parts working together rather than just trying to gain power by bolting bits on.

[Someone called James]

The first question is what are you going to do about the cylinder head? To get improved engine performance from an A+ unit the first thing is to fit an improved head. Ideally for a 998 the head to fit is a 12G295 Cooper 998 head, suitably gas-flowed and with the compression ratio set to around 10:1. For this head to work best it needs flat-top pistons in order that there is not a need to skim too much from the head face when setting the C.R.

A different cam can only work if the head can flow the additional mixture in and get the exhaust gases out.

It can be that changing the cam without significantly improving the head's ability to flow more mixture will actually reduce power as it will lose some bottom-end, but be unable to improve the top end.

Consider an up-graded engine to be an engineering exercise with matched parts working together rather than just trying to gain power by bolting bits on.

 

Hi Cooperman,

 

I'm looking at getting a 12g295 head but I was going to fit the cam first so I don't need to take the engine out twice. I'm going to try and get a 12g295 head for when I actually take the engine out so I can swap it then but I'm not taking it out until the summer so still got some time. 

 

Ta very much for your help.

James.

[Someone called James]

Has anyone else used either of these cams in the past or using them currently and what are your opinions?

 

James.

[fwdracer]

Brother had 255 Piper cam in his 1000cc unit (Original unit in his GTM). Lively and driveable, didn't have a 12G295 head. Ran with flowed standard head and single box exhaust. Went well.

[Cooperman]

To be honest you might as well wait until you get a properly flowed head before changing the cam.
Then do the job properly with the engine on the bench.
Just changing to a more aggressive cam whilst leaving the head standard will achieve virtually nothing.

[Someone called James]

Brother had 255 Piper cam in his 1000cc unit (Original unit in his GTM). Lively and driveable, didn't have a 12G295 head. Ran with flowed standard head and single box exhaust. Went well.

 

OK, cheers. 

 

Do you know how well it ran in terms of revs? Your brother's spec seems similar to what I want to do so should perform about the same.

 

James

[fwdracer]

It ran a 3.65 (100cc Metro Diff) and was revved to 5.5-6K regurlarly. It was a bit busy on the motorway but had good torque and was fun on A-B roads.

 

I'd advocate Cooperman's advice, change the cam and head at the same time and get the new unit set up properly on the rollers. Budget for eighty-to-a-hundred quid setting the thing up, as it is money really well spent.

 

If you want a recommendation - Try Ralph Saunders at Pitstop in Brize Norton. An hour away from you and great drive to get the car warm and then enjoy the difference on the way home....

[Someone called James]

It ran a 3.65 (100cc Metro Diff) and was revved to 5.5-6K regurlarly. It was a bit busy on the motorway but had good torque and was fun on A-B roads.

 

I'd advocate Cooperman's advice, change the cam and head at the same time and get the new unit set up properly on the rollers. Budget for eighty-to-a-hundred quid setting the thing up, as it is money really well spent.

 

If you want a recommendation - Try Ralph Saunders at Pitstop in Brize Norton. An hour away from you and great drive to get the car warm and then enjoy the difference on the way home....

 

 

I'm going to get the done at the same time as it's pretty pointless to bolt the standard head back on, only to take it off again. And as Cooperman said, just changing the cam and not the head wouldn't make any difference to the performance. 

 

Thanks for the recommendation, I'll check it out at some point.

 

Ta,

James.