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60 Posts
would like to ask about head bolts. what is the limit of power on them. I mean OEM. price is very different than ARP bolts so I don't know what to use on powered engine. One group of people say that oem is also good and I don't need for arp. I am preparing for 500hp

1,421 Posts
One reason to go with ARP is so you can reuse them. Especially on a 500 hp build theres a decent chance you'll end up pulling the head again and can just reuse/retorque the head bolts and just throw a new gasket on. I'd imagine head lift with the stock bolts isn't a problem at that power level.

237 Posts
Been doing a bunch of head reading, and would love to see the photos in the original post if anyones got a way to scour them off a interweb history or somethin....

47 Posts
Discussion Starter · #24 ·
Apologies for the loss of photos and graphs in this thread, primarily the fault of Photobucket when they decided to throw their long term userbase under the bus.
Been many years since I came this way.
Unfortunately some of the graphs are lost, however its possible theyre still on my old laptop, so will have to see if theyre recoverable.

Ive re-instated the photos I could find and added a bit more info on this post.

This was all calculated stuff regarding port velocities and measurements etc.
Intake valve seat insert counterbore stock=32.45mm
Exhaust valve seat insert counterbore stock= 27.50mm
Shim under hardened spring seat =0.62mm
spring seat thickness=0.93mm
1.55mm total under spring.
ex insert height stock=6.60mm
in insert height 7.30mm
Intake valve diameter-32mm.
Seat angle 45 degree.
Lower angle 75 degree.
Throat diameter=26.90mm.
Port width of controlling section at the splitter=24.50mm.
Total width of port at splitter= 49.12mm.
Port height at splitter =31.24mm.
Port entry width= 44.7mm.
Port entry height= approx 31mm.
Valve angle-24 degrees.
Coil bind at 12.0mm lift (inner/outer springs).
Intake guide oem depth 10mm (from spring seat machined platform).
Inner spring free length-34.00mm
Outer spring free length-40.00mm
Inner spring compressed height-29.70mm (approx due to valve fitted height)
Outer spring compressed height-31.00mm (approx due to valve fitted height)
Shim under hardened spring seat =0.62mm
spring seat thickness= 0.93mm
1.55mm total under spring.
Seat pressure-Inner spring 20psi
Outer spring 45psi
Total 65psi seat pressure per valve.
Max psi at 12mm lift 130 psi outer.
Max psi at 12mm lift 60 psi inner.

Component weights.
Valve- 49 gr.
Cap- 19 gr.
Collets-2 gr.
Hydro tappet-70 gr.
Inner spring-14 gr.
Outer spring-24 gr.

VVVVV might need revision VVVVV

Inlet Valve Speed of Sound (MACH) Index

Your bore size is 3.2 inches with a stroke of 3.4 inches and has 2 inlet valves with a diameter of 1.259 inches. Running a Mean Valve Flow Coefficient of .490 inches at 7000 RPM, the inlet valve mach index is 0.363 . The mach index for maximum volumetric efficiency is .6 . Beyond .6 the volumetric efficiency falls off. As the mach index rises beyond .6 the volumetric efficiency can be increased by later inlet valve closings (60 to 90 degrees ABDC).

Feet Per Second: 467.69 feet per second at your 1.0 inch lift and 228 CFM .

Discharge Coefficient:
Curtain Area: CD is 0.855.
Curtain Area is 1.451.

CID is 136.7 Head CFM is 194
Intake Flow Ratio is 138.57
Intake Valve to Bore Ratio is 0.40
Bore to Stroke ratio is 0.94 Rod to Stroke ratio is 1.66735294118
Mean Piston Speed Angle is 74.52 degrees after TDC

Your Limiting Port Velocity computed from your Cross Sectional Area of 2.34 sq. in.
and Bore of 3.2 in. and Stroke of 3.4 in. and Peak RPM of 7000 is 367.65 fps.

Curtain area.
pi X D= 32 X3.142=100.54 X lift @10mm= 1005.44 square mm (per valve)
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