MOPAROFFICIAL
If it has tits, it's a liabilititty.
TDC, sacrificial valve, cut and sharpen a notch... power drill. Finesse the reliefs w a diegrinder. Ooooor buy the tool or take them in.
piston valve reliefs, how to
- Thread starter Rapid Robert
- Start date
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TT5.9mag
Two atmospheres are better than one
Just have to make sure the sacrificial valve is large enough to give radial clearance to whatever size valve you’re using.
MOPAROFFICIAL
If it has tits, it's a liabilititty.
I saw your post after I posted. lol
Great minds think alike.
Dave999
Well-Known Member
check it first with the cam dialed in. don't assume necessity until you have tried to work out a solution that avoids machine work.
only need 1 piston in the block to get an idea
if it turns out to be very close put more pistons in and check that the rest are not closer...
you will be able to see already if the valves are all of equal installed height all seats on a level plane. if they all start in the same place etc none can protrude further than the rest
if retarding the cam slightly allowed me to avoid digging holes in my pistons, i'd probably do that, will bring the torque in a little later and avoid machine work.
that in my mind is a better outcome. you purchased a nice flat top piston.... they are supposed to be flat.
only do this If the application for the engine and your gearing allows for a slight move of the torque curve up the rpm range.
look at 25 30 40 thou gaskets as well... with a mind to impact on CR
slightly lower static CR and the cam back straight-up well your are probably back where you started and the piston is still flat
retarded cam timing as well. again you never know till you check
if none of this is suitable the 4th thing in the list would be start digging clearance holes in the crown
its a case of which compromise suits ... and that is potentially linked to the shape of the chamber as well
any cut needs the edges knocked off, sharp edges act as a glowing beacon for detonation and corners act as a magnet for carbon build up which can eventually act as... you get the picture.
A mate built a 318 with some god awful flat top pistons with 4 clearance pockets WHY? they only go in 1 way...no idea where they came from.
it was a hand grenade in respect to detonation...he never revealed why, coulda been cam could have been CR, curve and poor tuning.... the motor in that configuration was never spoken about again....... I've always had my suspicion though, about that "special" set of pistons.
Dave
only need 1 piston in the block to get an idea
if it turns out to be very close put more pistons in and check that the rest are not closer...
you will be able to see already if the valves are all of equal installed height all seats on a level plane. if they all start in the same place etc none can protrude further than the rest
if retarding the cam slightly allowed me to avoid digging holes in my pistons, i'd probably do that, will bring the torque in a little later and avoid machine work.
that in my mind is a better outcome. you purchased a nice flat top piston.... they are supposed to be flat.
only do this If the application for the engine and your gearing allows for a slight move of the torque curve up the rpm range.
look at 25 30 40 thou gaskets as well... with a mind to impact on CR
slightly lower static CR and the cam back straight-up well your are probably back where you started and the piston is still flat
retarded cam timing as well. again you never know till you check
if none of this is suitable the 4th thing in the list would be start digging clearance holes in the crown
its a case of which compromise suits ... and that is potentially linked to the shape of the chamber as well
any cut needs the edges knocked off, sharp edges act as a glowing beacon for detonation and corners act as a magnet for carbon build up which can eventually act as... you get the picture.
A mate built a 318 with some god awful flat top pistons with 4 clearance pockets WHY? they only go in 1 way...no idea where they came from.
it was a hand grenade in respect to detonation...he never revealed why, coulda been cam could have been CR, curve and poor tuning.... the motor in that configuration was never spoken about again....... I've always had my suspicion though, about that "special" set of pistons.
Dave
Last edited:
Rapid Robert
Well-Known Member
excellent comprehensive info! and very much appreciated. thanks a bunch guys. RR
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