Engine Quest Heads Lift

From what I've seen it's the head, it has be machined.
 
Just found this

OUTSIDE DIAMETER
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Most V8 engine valve springs have an outside diameter of about 1.50″. The spring’s specific outside diameter is machined into the cylinder head to create the valve’s spring seat. This is usually prevalent in two closely related engines: the 1967-92/93 A-engine (small block) and the 1992/93-2003 Magnum (small block).

The A-engine springs have a 1.50″ OD while the Magnum uses 1.42″ OD.
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A-engine springs do not fit on the Magnum engine family. Machining the spring seats to the larger diameter is one solution to resolve this situation. This operation is commonly done for racing engines, but it’s expensive for a street engine and for just a cam change.

The best solution is to use a specially designed HP Magnum valve spring like P5249464 and use retainers P4452032 (no special machining required). This is good for valve lifts up to .525″ lift. If you need more lift capacity, then use P4876062 spring (with the “032“ retainer) for up to .600″ valve lift.
 
Hughes Engines makes a Magnum spring retainer and valve springs that are good up to at least .550" lift. I used them in my engine, measured out around .560" I think from bottom of retainer to top of valve stem seal. My heads weren't machined either.
 
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