I have been through this!!!
OK, the older TFS heads had cast iron guides that have wear problems. Trick Flow will replace the guides and perform a valve job for free. You just pay the shipping.
Mine were also used heads that made no noise at start-up, but after driving a while they would tick. It was the guides. Look for plugs that are burning a little oil, or you can check them fairly easily yourself.
Remove the valve covers and remove all the rocker arms. fill a cylinder with about 100 psi from an air compressor. Remove the valvespring. Release the air from the cylinder, but still hol the valve stem. Dont let it drop. If you can feel any wiggle at all the guides are worn.
I had my TW's repaired and they still tick a little when warm. I have 2 friends with these heads as well and they also periodically tick a little.
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1988 Mustang GT
11.8 @ 123 (7/14/01)
11.5 @ 120 (9/14/01)
1992 BadAzz Wrangler
1993 Explorer
See my car at:
www.mustangworks.com/cgi-bin/moi-display.cgi?179