I have a 69 Camaro with a 396. I built it pretty much stock. It has a solid cam, open chamber heads, Edelbrock Performer RPM, 800 Holley, Hooker headers. The bottom end is balanced, steel crank, recon. rods, line bored, with stock replacement forged domed pistons, the 325-350 hp replacement. I have a set of 290 castings, which are closed chamber. I am having them redone, with one size bigger valves-2.19"/1.88". They are way ported. The guy I bought them from had about 80 hours port work time. I am wanting to run these on my engine along with a Comp 306 solid Magnum cam. The lift is .629"/.629" both on intake and exh. I was wondering with this combo, if I would have enough piston to valve clearance. The rep at Comp Cams helpline said I probably would, but I would hate to buy a new camshaft and install it, and find out I don't have the piston to valve clearance, and then be stuck with the cam, because it had already been installed. Also, if my budget allows, I would maybe like to run the 308 Comp Solid roller with .652"/.652", but there again who knows on piston to valve clearance. I was wondering if there were anyone out there that has this sort of combo, and how much piston to valve clearance do they have? Any info would greatly be appreciated.

69man,

First of all read this link VERY carefully:
http://www.centuryperformance.com/piston2valve.htm

I have a 396 with RPM Performer heads and a VERY small TRW forged dome piston and with .610 lift on the exhaust side, I have about .120 clearance (.100 is min.). I verfified this by using the CLAY method (see link for more details) UNLESS those dome pistons have very deep valve reliefs cut in them, I think your valve clearance is going to have to be checked VERY carefully. There are alot of factors that affect this: head gasket thickness, deck height of piston in relation to the top of the block, depth of valve reliefs, whether or not the heads have been milled down etc. etc.

The best person to ask would be the piston manufacturer and your machine shop guy.



[This message has been edited by sr71bb (edited 03-25-2001).]

SR71BB is right. Don't take anybodys word for it, measure during assy. preferably befor balancing. Somebody elses combo, evean tho same parts, may not have the same clearances as your combo. It is not a big deal to have the pistons "cut" for valve clearance.

I don't know if they deepened the valve reliefs in the pistons when they made the forged copy of the fac. cast piston but I would be nervous about that much lift. I don't know the actual cam specs but it would have to be very mild for the valves not to hit. If you try it make sure you use the clay method to check it is impossible to do it wrong.