Swapping Cams

Hey all - I have a pair of piper cams ready to fit and have a few questions, but I guess the general process is this?

 

- rocker off

- slacken chain tensioner a little

- secure chain to pullies

- secure pullies

- unbolt pullies from cams

- remove cams

- refit new cams

- bolt pullies to cams

- tighten tensioner

- rocker on again

 

What parts require replacing at this point? Gaskets etc. I know the chains are on the list but I plan to do those over winter along with balance shaft delete etc. In and out is key here for the last trackday of 2019 in a couple of weeks.

 

using this as a basis seems I need pulley bolts and an intake cam seal? Do I really need the locking tool?

 

https://www.verboom....cams/index.html

Edited by paul_mck, 23 October 2019 - 01:17 PM.

You don't need new sprocket bolts or a locking tool. Tie wraps to lock the chain to sprocket positions, that's all. Make sure you oil the cam bearing as they go in.

 

A new cam cover gasket is handy as they can leak a little if the cam cover hasn't been off in a while (make sure you tighten it down in the correct sequence to prevent leakage)

Your procedure could work but it would be too risky for me without taking the timing cover off to check the chain hasn't jumped a tooth on the crank sprocket. Maybe with some bungy chord to keep the cam sprockets under upwards tension when removed it could work but I'd still want to practice that with the cover off before recommending it. The cam "locking" tool isn't much use for locking anything but it would help confirm timing is good if you did get brave with this procedure 👍

A new seal is really a "while you're there" thing.

I was going to place a bar of some sort across the tops of the pullies and cable tie the chain to the pullies then the pullies to the bar so they are being pulled up and away from each other. seems like it might work?

do yous bother removing the tensioner?

I think I would remove the tensioner and when refitting it do so in the activated state, not deactivated like it says in the TIS workshop manual. It will make it more difficult to screw it back in but the procedure for activating it in situ doesn't always work. I match mark the start of the thread so I know where to press against the spring pressure to get it in.

For the record I recommend you don't do any of this and wait to do the cams when you change the chain.

Hi Paul - yes you will need to remove the tensioner.

The above will work, but as said you need to keep tension in the chain or it may slip a tooth on the crank pulley.


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well all done in a couple of hours last night. wasnt too bad in the end although I made the mistake of doing both cams at once where it would have been much easier to manage the pullies and chain if I did one at a time.

 

car feels peppier up the revs now, so glad I done it. Will get an updated map asap but it felt 100% on my odbtuner map.

 

The only reason I did them now and not the chains too was that Ive a trackday next weekend and I want to see how they performed. I want to make a decision then on whether to SC it or not. If its going well I may just leave it NA and maybe do a LW flywheel or something.

 

Either way it will be getting some love over winter inc new chains and balancer delete so would rather not rush it.

final Q - they sound a little "clackier" than the oem ones - is that expected with the higher lift?

 

will pop the top again and retorque the cap bolts just in case but they were all torqued up ok

final Q - they sound a little "clackier" than the oem ones - is that expected with the higher lift?
 
will pop the top again and retorque the cap bolts just in case but they were all torqued up ok

 
I was told that was fairly normal for different cams - something to do with the lash adjusters

Great to hear they are going to good use!!!
Now you’ve got better cams you could consider the Itb route as an alternative to SC...
Two very different options...


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On Peters advice I just need to do an injector test to make sure they aren’t maxing out. He sent me a new map so I’ll get that on.

I really toyed with ITBs but it’s hard to look past a blower for pure bang for buck and ease of installation. In truth it’s a K20 that really calls me. But I’m afraid to cost it up.

On Peters advice I just need to do an injector test to make sure they aren’t maxing out. He sent me a new map so I’ll get that on.


I really toyed with ITBs but it’s hard to look past a blower for pure bang for buck and ease of installation. In truth it’s a K20 that really calls me. But I’m afraid to cost it up.

Bhp per pound sc is the way to go, but ITBs are an amazing and engaging driving experience - for a road car I think it gives a better outcome. But for track, sc would be my choice...


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final Q - they sound a little "clackier" than the oem ones - is that expected with the higher lift?

will pop the top again and retorque the cap bolts just in case but they were all torqued up ok

If they're regrinds the base circle is reduced which means the hydraulic lifters have a harder time taking up the lash.

Don't go crazy with the cap bolts - it would be quite easy to strip the thread on the soft alloy head. I think its 10Nm with reasonable a 1/4" drive torque wrench.

Yeah I torqued them up ok so I’ll just leave them as it sounds like it’s normal.

I still can’t understand how cams can be reground to give more lift.

The lift and profile of the cam lobe is given by the material that is above the base circle.
If you reduce the base circle, you have more meat to shape the lobe...

Yep - the lift is the difference between the min and max distance from the centre line. Reduce the minimum and the difference increases.


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