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Old 29-10-2008   #1
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Fast Road Cam (pipercross) - need some help

Im going to buy a piperX Fast Road Cam from the NeedForSpeed website (FIAX19BP270-E). They are going to machine the existing part, I think! and send it back to me.

What I'd really like to know is if you just replace the new Cam without needing to tweak or adjust anything else. The car has a CSC exhaust and KnN already so I'm guessing that the fast road cam is preferable over the Road/Rally version. I don't really understand much about timing and the mechanical side so if anyone knows if this is a suitable replacement (hhmmm Jimbro) it would me much appreciated.

Thanks
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Old 29-10-2008   #2
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Re: Fast Road Cam (pipercross) - need some help

OK - bad news first

You are looking at what is called a regrind cam - the profile should be good (early cams from the UK were worthless but a modern one should be better) but the base circle of the cam lobes (the smallest radius) will be reduced in order to create the extra lift (difference between the two radii). The end result is that the valve shims will be completely wrong - you need to find a good source of replacements in order to get the valve clearance correct.

I suggest you start by getting in touch with the supplier and finding out how much they are going to take off the base circle. If it is more than a few thou' then you may have a problem as the valve shims have to be so thick that you can't get hold of them from any supplier.

The alternative is to have the camcarrier skimmed to reduce the gain in clearance between the cam and the valves - you still need to reshimm the valves, there is no escaping this but at least the shim sizes will be closer to the normal selection. The downside to this approach is that you will need a vernier pulley to get the cam timing right - you will probably need one anyway as the timing can be changed by the regrind as well.

You are going to need a tool for depressing the valves to lift the shims out, you can't reliably shim everything up with the camcarrier removed.

For reference the shims come with the thickness stamped on the underside, do not trust the figure, measure them with a micrometer first. Second hand shims will have worn down so while they are still usable they won't give the expected results.

Make sure you put the shims in the right way up when you replace them.

You *can* get away with not changing anything else but there is no guarantee it will give the results you desire.

The real minimum you should look at is a session on a rolling road to rejet the carburettor.

As for being a good choice - a race or rally cam is a bad idea without significant engine modifications, you will either break something or find it gives less power than standard (or get lucky and get an all round improvement).

A fast road cam is just a mild upgrade on standard. In this particular case I would suggest taking the car to a rolling road first and getting a tune up first - and a power run graph so you know what you have to start with. Once the new cam is fitted, provided you go back to the same rolling road you can make a comparison and see where and how much the new cam gives you.

Personally I would try to obtain a second stock camshaft, camcarrier and pulley just in case you ever want to go back to standard.

As you can see this is not the sort of thing you undertake idly - it takes a fair bit of effort to get right.
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Old 30-10-2008   #3
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Re: Fast Road Cam (pipercross) - need some help

[quote=jimbro1000;1790291]OK - bad news first

You are looking at what is called a regrind cam - the profile should be good (early cams from the UK were worthless but a modern one should be better) but the base circle of the cam lobes (the smallest radius) will be reduced in order to create the extra lift (difference between the two radii). The end result is that the valve shims will be completely wrong - you need to find a good source of replacements in order to get the valve clearance correct.

I suggest you start by getting in touch with the supplier and finding out how much they are going to take off the base circle. If it is more than a few thou' then you may have a problem as the valve shims have to be so thick that you can't get hold of them from any supplier.


Hi jimbro, thanks, i told you I'm not much of a mechanic (but willing to learn). my dad who is helping me with the car will be able to understand the finer details of what you wrote.

I've had a response from NEEDFORSPEED, here is what they wrote:

"i have just spoken to piper and the exchange cam will need larger shims.
but if you go for the outright blank camshaft the cam lobes will be to standard spec.
the price for this is 250.38 inc vat and delivery."

Does the "outright blank camshaft" they mention overcome the problems you mentioned whilst giving a performance gain??

I've also got the following info to hand if its useful:

lift - 9.8
duration - 280 degrees
overlap - 66
cam timing - 107
profile - 270
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