valve clearances
- Thread starter tomwest
- Start date
frank
Club Member
about 10 deg either side of tdc on overlap eh craig.
where the piston is at a standstill for about 20 deg, and the exh valve is almost shut, and the inlet valve is starting to open
frank
Club Member
aye, the piston is 2/3rds the way down when the valve is fully open (so lift has nothing to do with p2v clearance eh)Cheers budI guess it will always bear near TDC and the plasticine test will tell you if you need to pocket or not - did you just leave your 1l pistons flat topped then?
and yes, stock 1.0 pistons
frank
Club Member
my 1.0 piston 260/10mm setup had about 2mm mate, you probably would,nt need pockets till about 290 deg4mm
frank
Club Member
that block looks decked dave ?Aye, no problems with 'fast road' cams.
You'll only have to worry about PTV contact if you build something exotic, which only a few are mad enough to do
Here's our pocketed pistons in our CGA lump....
Just a nat's #### to ensure a good surface Frank. Both myself and my engine builder consider decking in the general sense a no-no.
frank
Club Member
not enough to warrant removing 2 links from the lower chain then dave
i hope those pistons dont hit the quenchsteps ! (slightly proud aint they)
not enough to warrant removing 2 links from the lower chain then dave
Just the shadows from the flash....
Aye, no problems with 'fast road' cams.
You'll only have to worry about PTV contact if you build something exotic, which only a few are mad enough to do
Here's our pocketed pistons in our CGA lump....
Waa, the pic doesn't work for me
They Matt Humphris pistons?
Waa, the pic doesn't work for me
They Matt Humphris pistons?
-- Link Fixed --
No, they're custom. Matt's pistons didn't give us what we needed compression wise for the cam profile we're running. It was less risk and less cost to spec up a piston that we knew would do the job instead of trying to fudge something already available.
Not secret no. I don't have the spec sheet to hand to get any specific data from though.
They are on an absolute minimum overbore, as block strength is paramount over outright CC. They're pocketed as you can see and are intruder type design to give additional compression to put us into the right range for the cam while effectively managing PTV clearance.
Haven't asked the price of them yet. They were made by CP pistons and yes open deck, as that's all there is with a CGA.
Cheers Dave, top quality pistons indeed.
