Timing A New Piper 285 Camshaft - Vernier Pulley ?

[hoodygoodwood 71 3 Cars]

I have fitted my new Piper 285 cam to my head and fully rebuilt 1905 cc 8v engine , I have used the standard original cam pulley first to see if I can avoid having to buy a vernier .

Have set up a plastic timing disc on the crank pulley and rigged up a pointer which I have set to TDC ( 0 degrees ), the Piper spec sheet says full lift on the inlet lobe should be at 106 degrees ATDC , I have full lift at 102 or 103 degrees ATDC . Not having done this before I have to assume that 3 or 4 degrees out is a significant amount and that it would be worth buying a vernier pulley so I can get it spot on .Any recommendations on a pulley , some of those I have seen have got very flimsy looking locking bolts .

[pug_ham 244 3 Cars]

Miles, to get the best from the cam you'll definitely want a vernier pulley so it's timed spot on, I've been running a Piper vernier on mine without any problem.

 

BakerBM do them now iirc, as do Catcams, Kent & Piper but you can also use one from a TU engine or later 16v turned down to suit, I did this on a friends car a few years ago.

 

I think I still have one somewhere if you wanted a cheaper option & I could get it turned down to suit.

 

g

[petert 588]

If correct, 102 is way too advanced for that cam. Using the lobe centre line (LCL) method on fatter cams can be inaccurate due to the dwell at full lift, if you're not experienced. You should verify your position by measuring 30 deg either side and compare the lift. There are plenty of videos on YouTube if you're unsure. You can also verify by using a lift @ TDC measurement. Piper should be able to supply you with lift @ TDC number which corresponds to a 106 LCL.

 

Whilst the later 16V pulley can be reduced in thickness, ideally you need to add a 1.5-2.0mm shim between the end of the cam and the pulley to centralise the belt on the pulley correctly.

[hoodygoodwood 71 3 Cars]

Thanks , I set TDC by checking 10 degrees either side to make sure as it is a little vague around TDC because of dwell as you say .Must be more straightforward on an engine with a central spark plug , the angled plug hole on an 8v made it a little awkward , will be making up a longer tip for my Baty DTI .I do have the other specs on the Piper data sheet and will check them later .

Thanks for the offer of the pulley but I think I will buy one new , just need to find one that I like the look of - 3 bolts to lock it off does not look enough to me !

[petert 588]

Doesn't sound like you're doing it correctly. The only reason you need access to plug hole is to verify that your external TDC marker is correct. Once established, use the external marker to check 30 deg either side of LCL. Ten degrees isn't enough.

 

If using the lift @ TDC method, don't forget to subtract your inlet valve clearance.

[welshpug 1,661]

i make a degree wheel using the pin hole as datum as that always pins an xu mid stroke, add a pointer under one of the bolt heads, i used ss welding wire.

[petert 588]

Flywheel and original timing marker is my favourite.

 

http://www.taylor-eng.com/xu9j4/finding_tdc.html