I'm having Ford Performance 1.94/1.54 stainless valves installed in "G" heads. Is a 3-angle/5-angle valve job recommended. Should it include cutting the seats and back-cutting the valves? Recommended angle? Without attempting to extract every cfm, are there any obvious obstructions to flow that should be addressed? At what point does valve shrouding become an issue? Joe, I would particularly appreciate your input. 

Yes, you need at least three angles on the intake valve seat, more is better.  You only put a back cut on the intake valve, leave the exhaust valve with a complete 45* face.  The exhaust seat may have a radius with only a 45* seat, but I still prefer multiple angles on the seats.  This is for a no nonsense street/strip valve job.  If you were trying to extract every cfm of flow, then I would have suggested a bit larger exhaust valve in iron heads.  I have found the 1.940-1.960" intake valve works better in iron heads due to unshrouding the combustion chamber wall.  I use 15/30/45/60/75* on the intake seats, and 30/45/60/75* on the exhaust seats. I mainly use the 15* to get rid of any ridges left from the 30* angle cut.  Joe-JDC

JDC

Very helpful, thanks. 

At what point would shrouding become an issue if milling the heads? Valve lift minus lash = 0.485. Notching the cylinders necessary?

Seems to be around .525" with the 2.020" intake, but it all depends on how much the heads have been cut, the valve seats been cut.  I have one engine with a .512" lift with 1.6 rockers and no issues.  Shrouding does not come into play unless you use the larger intake valve.  I have ported G heads with 1.940 intake valves that flow as well as the larger 2.020" valves up to .450" lift.  Joe-JDC

JDC

Great! Thanks, again. 

I plan to use flat tops/w no valve reliefs, zero deck, and non-posted heads milled .021-.025. Although it's been said that non-posted heads can be safely cut .025, should the heads be posted if increasing the static compression ratio? I would rather be safe than sorry. The DCR should be less than 8:1. 

On my 303 EMC engine, the compression ratio was 10.4:1 and it showed a bit of stress around some of the water holes when we changed heads.  Those heads were milled to 70ccs(about .032" if I remember correctly).  I don't think there would be a problem with less than 10:1 compression.  That is just my opinion.  Joe-JDC

JDC

When measuring blocks/pads to determine if the heads have been milled, should they measure 1.00 or 1.10? When you're talking about thousandths of an inch, how exact were they when they left the factory?

Measure the two center ones.  They should be ~1.010" if stock.  Clean any paint off before measuring.   If the heads have been milled any prior, the end pads will be slightly different if the machinist was not careful.   I would CC the two end combustion chambers in each head and see if they are close to the same.  That will give you a better idea of how much needs to be milled or if they need to be milled more on one end than the other.  This is where a competent machinist is needed.  Joe-JDC


JDC

I cc'd one end chamber, using a syringe, not a burrette, and an acrylic plate/w one larger hole at the high point/w 3 smaller holes to allow air bubbles to escape. Even then, air bubbles were a problem. Tilting the head caused alcohol to leak out of the holes. It took multiple tries just to do the one chamber, which measured 70cc. Accuracy? I know they're "nominally" 69cc. At this point, I have to decide to mill them .021-.025, or post them and go as much as .035. I'm aiming for a 9.5 static (stock stroke 292 + .060 bore).