My friend has a 88 mustang gt and he just rebuilt the motor last week and bought flat top pistons with 4 valve reliefs, and a pair of TFS track heat heads, his question was does he have to make the valve reliefs bigger, or will it be ok. ohh he has a F cam, and 1.7 rr.
thanx spchernandez
The TFS heads have a 'twisted' chamber (hence the twisted wedge name) -- the valves are in different locations than the stock reliefs. The stock reliefs only work for 1) valves that are small enough to fit inside them, and 2) heads that have the same chamber alignment as stock. The Trick Flow heads require valve reliefs in completely different areas of the piston.
The good news is that part of the benefit of twisting the chamber the way they do is that it moves the larger intake valve 'downhill' on the piston -- creating more margin for obtaining needed p to v clearance. Of course, that hurts you on the exhaust valve as it moves 'uphill' on the piston; but there's usually excess clearance on the exhaust side to play with.
Summary - your friend's piston reliefs don't match the valve configuration of those heads, so it don't matter. You have to mock it up anyway and check clearance.
I run stock piston with TFS/tw and a f-303... 1.6 RR and i have over .100 of clearance on both valves.... You should always check it... i used the modling clay method.
he should not have any trouble but that is one of those things you ALWAYS check when putting together and engine. Nothing like putting together a new engine just to bust up some valves when you start it.
You could pass it along to me at sn9550@frontiernet.net. I'm going to be installing my Camshaft Inovations cam this weekend. I don't mean to high jack your thread.