I am about to shell out for a new set of Roush 200 heads with the 2.02 I and 1.94 E valves and 64cc chambers for my 351w and as I was reading some info on another site, I had an ugly thought. My short block is all stock with stock pistons. It was built just a couple of years ago, runs A-1, and only has 8,000 miles on it, so I don't want to pull it down. It suddenly occurred to me that with the valve reliefs in the pistons sized for stock valves, I may end up with valve to piston clearance problems with the larger valves if I run much of a cam at all. I won't be milling or otherwise modifying the heads. Out of the box onto the engine. I haven't decided what to use for a cam yet. I figured that I'd send all my specs to Crane and let them pick one for me. I'll be using 6:1 roller rockers and my emphasis will be on lots of low to mid RPM torque rather than big horsepower numbers on the top. I've never ran aftermarket heads with big valves before, so this is relatively uncharted territory for me. Of course, I will be checking the clearances as the engine is assembled, but I don't want any surprises and end up stuck with parts that I can't use or have to change pistons to make them work. Any comments are appreciated! Thanks!

 

Best thing would be to check with the head and cam manufacturer. I am installing the 180's on my 302 and am using a cam with .462 and .474 gross lift on 1.6:1 roller rockers. World told me the pistons won't even come close on this set-up. I'm still going to check for my own piece of mind tho.

Randy

 

Thanks for the post. I'm almost afraid to ask World what they think at this point and the same goes for the cam makers. The first thing that either will want to know is what cam I want to run. I know that to size the cam, they are going to want to know vehicle weight and tire diameter - two critical points in their calculations that I do not know at this point. The weight could be guessed pretty close (the truck is scattered over a shop and 2 storage buildings in two counties right now and the finished project will be nowhere close to stock configuration), but I have no clue what skins will be on this when I'm done. I guess that maybe I could ask World what they recommend as the limits on duration and lift.

 

Rage, I hope this is a rumor, but I'm pretty sure that the only heads with 2.02" intake valves that will work with stock pistons are the Trick Flow Twisted Wedge heads. The Roush 180's will work though, I've got a set of those on my 302 right now, the brand new one (Ford Motorsport short block). A problem with running those is that their chambers are 58cc, which will jack your compression up. World's tech dept. is pretty useless, you really have to drag information out of them, but if you're persistent, they'll tell you what you want to hear. Good luck! TK