North American Turbocoupe Organization



Why to have your valves back cut
BogusSVO Offline
Member
#1
Back cutting valves for improved air flow


This is a procedure done to help flow the air charge across the back of the valve and smooth the transition into or out of the combustion chamber.
Normally don on valves that are not fully machined or swirl polished.


Once the valve has had the face re-ground. Most common is a 44* or 45*
The valve machine is reset, and another angle is ground onto the back side of the valve towards the stem, most common is 30*

[Image: DSCF3959.jpg]

The valve on the left has the basic face ground to mate back into the valve seat.
The valve on the right has had the basic seat inked,(black) and the added angle ground. (sliver)

Most OE valves are not fully symmetrical, so the width of the valve face to seat varies around the valve, the added angle will help correct this and smooth the transition of air flow across the back of the valve.
Owns more Turbo FORDS than the law should allow....and still getting more

85 TC going under the knife
84 Turbo ranger --($800.00 ebay) Redneck work truck
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dardave Offline
Junior Member
#2
How much power do you think this is worth on a TC?
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RC Martin Offline
Posting Freak
#3
I had a 3 angle cut done during my rebuild. Honestly didn't know why 3, have seen references to 5-angle, 3 is what the machine shop recommended and I didn't want to skimp since the rebuild cost an arm and a leg already
Thunderbird Turbo Coupe, Bright Canyon Red TuTone, Desert Tan Interior; 1 of 7 in this combo in 1984 according to Marti.  1 of 13,361 TCs in 84.
   Rebuilt, 3-Angle Valve Job, SYB37 "OE" Cam
   Full 3" Stinger Exhaust to Flowmaster 40, Gnari FMIC/Recirc/BPV, MBC @ 15psi, RF-E6 Manifold, Remote-Mount TFI, PC1 and Flowed 35# Injectors, Inline Walboro 255HP, Kirban AFPR
   Rebuilt Suspension -- KYB & Energy Suspension
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Harl Offline
Junior Member
#4
You get better fuel air mixture flow with a 3 angle valve grind. I put a 3 angle valve grind on all my rebuilds. 
Many performance engine builders recommended and use the 3 angle grind. I am not one btw.
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