Tell me about valve recession.
What causes it? Is it more likely after you have had a valve job? Does it result in the valve lash being less? How does it affect performance? When you get new valve seats are they a separate piece put in by the machine shop? With over size valve do you get new valve seats? If you use higher than stock spring pressures does this add to the likelyhood of valve recession? Does the valve material add to the possibility of valve recession? Is it more common on the front or rear valves? How about with/without headers?

I understand that the valve seats were originally hardended by induction heating and is only a few microns deep for the Un-leaded gasoline heads. What does that say about leaded gasoline heads which didn't have hardened seats? Prone to valve recession? Can you do multiple valve jobs without putting in new valve seats?

bwhitejr

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'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

Good question. Please see this thread.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I was re-lashing the valves and I noticed there were differences in the amount of space between the rocker arm and the pushrod. With the cylinder in question at it's firing position I get:
Intake Exhaust
#1 3/32" 1/16"
#2 1/8" 3/32"
#3 1/8" 1/16"
#4 3/32" 1/8"
#5 1/8" 3/32"
#6 1/8" 3/32"

The lash settings are 0.012 and 0.014 (cam card says 0.010 and 0.012). I couldn't go any looser because the rocker arm set screws get too loose also. This head has had two previous valve jobs and some porting.

Is this rocker arm to push rod spacing getting too small?
Should new seats be installed?
Could it be fixed by grinding the end of the valves off?
Could it be fixed by shortening the pushrods?
If new seats are in order, could I avoid putting in new seats by going to larger valves?

bwhitejr

_________________
'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head