Heads from a 75 nova 350 block

[big dwag]

Look guys heres my problem, I just put a big cam in my 350, the valve adjustment is intake .022
exhaust .022
gross valve lift is intake .555
exhaust .555 the duration is at .015 tappet lift 306, the lobe separation is at 110.0,
now my question is if i take my heads off and have brass valve guides put in and have the studs pinned. do yall think the valves will hit the pistons????? now don't forget that this cam is a 306 with a .555 lift. let me know what you guys think.

[a1supersport]

I don't think the valves will hit the pistons. If the engine is still stock as far as the pistons and heads, it should clear. Remember these engines had dished pistons, and the valves would only be 1.94/1.50 at the most. If you're still using 1.5 rockers, you'll be fine. But with a cam like that on a stock engine, you may be disappointed with the performance. It may sound good, but by the time you get the rpm up to where the cam "kicks in", the engine will fall "flat". This cam was probably designed to put out it's best at around 4000-7000 rpm...a little high for a low compression mid-70's engine. When you run a cam this big, you'll need higher compression to go with it. A cam with this much duration and overlap will "bleed" off a lot of cylinder pressure. And if you don't have enough extra cylinder pressure to compensate for the bleed-off, you'll actually lose power. You may be better off investing in good heads and putting in a smaller cam around 270 duration and 450-460 lift. It'll still have a slightly lopey sound, and put the power where you need it...in the low-to-midrange rpm...or from idle to 6000. I've seen guys run Chevelles and Novas in the high 12's/low 13's with a small cam like this and good heads/intake/carb/headers...on a stock engine block. Good Luck.

[big dwag]

Sorry a1supersport i didn't give you all of the information, when i put the 306 cam in, i had forgot that the old heads that i had taking off had been shaved 20,000, and the valves did hit the pistons while they were on the motor because after i pulled them off, you could see where the valves were hitting.I also forgot to tell ya'll that the motor was bored out 40, a double chain and gears was installed 1.6 rocker arms & 1.7 valve springs with everything else that was wrote above. Now do ya'll still think it will work. the heads that are going on now will not be shaved this time. Give me some feed back. Thanks..

[a1supersport]

Hmmm, depending on how thick the head gaskets are, and if you still have deep valve reliefs in the .040 pistons, you might clear it. BUT...those 1.6 rockers may cause some piston/valve contact. Do you still have the "card" that came with the cam when you bought it? Usually the lift and duration numbers they give you are what you get when you use 1.5 rockers. If your card says something like "lobe lift .370", then .370x 1.5= .555. And if that's true, then .370x 1.6= .592 !!! WOW!!! Now that's "pushing" it. You might want to check and see if your springs can go down that far without coil bind, and also if the valve spring retainer will "bottom out" on the valve guide...especially if the valve guides weren't cut down to give you clearance. I'd try test fitting one head on. Put some clay or playdoh in the valve relief on the piston, torque the head down, set up the pushrods and adjust as recommended, then crank the motor over by hand to see if there's any binding. If that crankshaft stops turning or gets really hard to crank, stop. The valve may be hitting the piston, or the valve spring or retainer may be bottoming out. If you can crank it over a few times, pull the head off and check the clay/playdoh. It's written somewhere on how thick that clay is supposed to be for "proper clearance"...but I don't have it. But if that clay is really thin, I'd go back to 1.5 rockers, or a smaller cam...whichever is cheaper. Remember that there is some "flex" in the rotating parts, and as the engine heats up, these parts expand...and that thin clearance you had with the clay...will disappear. Sorry this reply is so long. Hope I helped, good luck .

[big dwag]

a1supersport, you were right the card did say 370 lobe lift. i picked up the heads today from the machine shop i'm going to put them on thursday morning, but i'm going to use the 1.5 rocker arms, a buddy of mine said that he had the same problem after building his motor, he couldn't use 1.6 rocker arms it gave him problems to. so i'll just use the 1.5 rocker arm and put the 1.6 on another motor that i'm going to build maybe a 383 stroker. Thanks for your input.i'll keep you posted on what happens.