A&Q about 350Z
Q:
the motor is a 350 bored 60 heads are shaved 40 the cam is a crane blue racer 302/302 .50. the only valves hitting are the intake exhaust are clearing just fine so i need to get a cam with smaller intake lobe but what would be the best cam any help would be appreciated
A:
hmmm the .040 heads could be a concern... are you running domed pistons? you may need the get them "fly cut" relieved for valve clearance. also if you are running longer than stock pushrods and a different ratio rocker arm you could have issues there
A:
Good post^^
Have you cc'd the heads to calculate a compression ratio?
Taking 40 off the heads may be a bit too much squeeze for those pistons you have, and the interference is just a warning sign.
Don't ruin the combination you have with a different cam. Notch the pistons, as noted above, or go for a different piston or look into a thicker head gasket if the comp ratio is really high.
A:
oh btw, stroker engines are great fun...i had one in an old '69 chevelle... man that thing would run... run hot... lol. watch out for overheating, especially at 60 over on the block.
A:
Chevys are pretty simple, but there are a dizzying array of piston relief/valve combos out there. I also agree that .040 off the heads is a touch aggressive. Some possible issues that I would check first:
-double and triple check that the cam is installed properly; dots lined up and all. Then degree the cam on every cylinder. Frustrating and time consuming, yes. But necessary. Its rare that a cam is ground incorrectly, but it happens.
-Re-do the math on the compression. I have a feeling you are sky high. If that's where you want to be, fine. But you can't go over about 10:1 and not expect at least some possible interference. On SBCs I check for valve clearance above 9.5:1 for a 5.7" rod and even a little more frequently on a 6" rod since the piston spends more time at TDC with the longer rod. Since 10:1 is pretty common on the street, many piston manufacturers will already know if there will be an interference problem with certain valve sizes, lifts, durations, etc, but I think we're past that.
-Lift isn't the problem. cams are at peak lift when the pistons are not at TDC, but duration can be a problem. that 302 advertised duration is mighty hefty. That plus the fact that the chambers are really small means you have gone way beyond bolt-together and are well into custom fly-cut pistons. This sounds like more than just a hot street engine. I think you're in for some machine work. Fun machine work, but work nonetheless.
Maybe someone here has more info on high CR chevy small blocks that can help with some combos that work. Post more info, like which heads, pistons, valve size, how the cam is installed and its LSA and ICL.
Sounds hairy. I like it
Can I drive it when you're done?
A:
Thanks for all the info and help on my little hickup with the stroker especially to curtis 73 we degreed the cam and it was off so we went last night and got new cam and had no troubles matter of fact was driving it this morning.
once again thanks to all who tried helping me on the problem