Does anyone know if the valve seats in Dart Iron Eagle heads can be milled deeper without problems? I have a set of 215 intake 49 cc heads. We were doing some measuring on them today and may need to cut the seats deeper. Thanks

oops.. spring pockets may need to be deeper, not valve seats.

why would you need to sink the spring seat?

If you go to the Dart Machinery web site you should be able to pull up a spec sheet on your heads. It has all the info you would need.

http://www.dartheads.com/csbhiron.htm

You should find your answer there.

I have looked at that web site and I can't find anything but an application chart. Honestly I don't understand why I might need deeper spring pockets. The cam card calls for a certian closed spring pressure at a specific spring height. I already have the longer valves and the spring height is still shorter than what is recomended on the cam card. It would seem to me as long as you have the correct closed and open spring pressure and no binding it would work fine. Why would the spring length matter??

If you click on your head on the Dart web site it will give you the follwing details. I do not know which exact head you have but, here is the specs on a set os 215 Iron Eagles. I did notice even on my Pro 1's that they only recommend cutting the spring seat .030" deeper MAX!! Double check to see if this applies to your head as well (it does to the Iron Eagle listed below)


Material: Superior iron alloy
Comb Chambers: 64cc & 72cc
Intake Valve Dia: 2.05” & 2.08”
Intake Port Volume: 215cc
Intake Port Dim: 2.150” x 1.190”
Int Port Location: Stock
Intake Gasket: Fel-Pro# 1206
Exh Valve Dia.: 1.600” or 1.625”
Exh Port Volume: 75cc
Exhaust Port Dim: 1.375” x 1.325” w
Exh Port Location: Stock location & bolt pattern
Exhaust Gasket: Fel-Pro# 1404 or 1405
Flow, Intake: 268cfm @ .600” lift / 28”
Flow, Exhaust: 175cfm @ .600” lift / 28”
Head Bolts: Stock bolts can be used. We recommend ARP# 134-3601
Head Studs: ARP# 134-4001 or 234-4301 (12pt)
Manifold: Alum Single Plane Dart (opening - 1.100”x 2.000”) 5.500” tall
Milling: Min. 58cc = .060” (.0065” = 1cc) Flat Mill Angle mill .125” safely / .200” = 49cc 1.5º (carefully)
Pistons: Most 23º aftermarket pistons.
Push Rod Length: Stock thru +.100” Should always measure (Stock length = 7.800”)
Push Rod Guide Plate: Must use Comp Cam # 4808 (flat)
Retainers: Steel (10º) / 1.250” ( 7º)
Spark Plug: Angle or straight, .460” reach, tapered seat, Champion V59C / V59YC
Spring Pockets: 1.550” OD (.030” deeper max)
Springs: Our Assembly: 1.250S = 110# @ 1.700” / .520” max Comp 981
1.437D = 130# @ 1.800” / .620” max Comp 987
1.550D = 195# @ 1.900” / .690” max Comp 954
Stud Girdle: Use any standard girdle
Valve Length: Std 4.890” w/ 1.250 & 1.437 / 5.015” (+.100) w/ 1.550
Valve Stem Dia: .3415” - 11/32”
Valve Train: Std SBC 3/8” or 7/16” stud mount
Valve Guides: 1/2” OD Int = Mag-bronze Exh = Phos-bronze (.002” press)
Valve Guide Length: 1.950”
Valve Guide Clearance: .0014” - .002” (with our .3415 dia. valve stem)
Valve Guide Spacing: 1.890” moved .030” from stock
Valve Seats: Exh = Hardened Ductile Iron, .006” press
Valve Seat Dim: Exh - 1.650” x 1.350” x .350”
Valve Seat Angles: Int = 32º - 45º - 60º - 70º Exh = 37º - 45º - radius
Torque: Head Bolts = 70 ft/lb; Rocker Studs = 45 ft/lb; Manifold = 35 ft/lb
Block Use: Any SBC Iron or Aluminum
Weight: 52 lbs

WR,
"I already have the longer valves and the spring height is still shorter than what is recomended on the cam card."
You answered your own question ... if the installed hgy is shorter than the cam card calls for, then you spring pressures will not be correct. The answer is not sinking the valve but changing springs, or retainers, or maybe using +.050 locks. I always tell my customers to have the heads in hand before ordering valve springs. That way you can see what installed hgt you have to work with and get a spring that will work.

My motor builder decided he wanted to try changing springs like BillK suggested. Springs got sent back today. My cam is calling for a 160 lb seat pressure. The recommended springs at my spring height were making 210 lbs. Even at the recomended height on the cam card the springs were over 200 lbs. That 160 sounds a little low to my builder for a solid roller cam. Sure hope it wasn't a typo. Maybe I better double check.
Thanks for the help.

I agree 160lbs on the seat it not much for a solid roller. It of sourse depends on the cam. How aggressive is it? Is it a "street" roller?

I also agree with swapping springs over cutting the heads.

Cam is a crane cam #118251. Big lift but smaller duration for a roller. I double checked:
http://www.cranecams.com/index.php?show=browseParts&action=partSpec&partNumber=118251&lvl=2&prt=5
The seat pressure is 160. I had the same springs listed by on that link. They measured WAY more than what it says they should. We were wondering if someone put the wrong springs in the box. K-motion springs are on the way.