Thread: valve clearance

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I have my 79 350 with 416 heads. I have a cam with .470 lift. I adjusted the preload on #1 and turned it to goto the next cylinder. Then the motor stopped turning and I could feel the bolt turning inside. so instead of pushing the issue I stopped and loosed the rockers again. I turned it over with the starter and it turns easily now. I have the spark plugs out so it's not the compression. Was I making constact with the pistions with .470 lift?

anyone have idea what the maximum lift I can run with flat top pistons with valve reliefs with a 1.84 intake valve?

"I could feel the bolt turning inside"

I have no idea what you mean by this. Please explain.

There are several areas of concern that could lock the motor up on the valvetrain:
1. rocker binding up on the stud
2. valve to piston interference
3. retainer contacting the top of the guide/valve seal
4. coil bind (spring stacking solid)

Nobody can tell you how much lift your motor can tolerate before any of these things take place because every motor is different. Nobody knows how much the decks have been cut, or how much the heads have been cut, or the valve seat position relative to the surface of the head or the actual compression height of the pistons or the length of the valves or the actual rocker arm ratio or the number of coils on the springs or the wire diameter of the springs or the clearance on the rockers at the studs or the clearance from the bottom of the retainer to the top of the valve guide. This is one area of engine building that you have to check yourself.

The motor stopped turning, but I could feel the crankshaft bolt turning inside the crank without turning the motor. I'm going to check for contact between the retainer and valve guide when I get home today. I have the stock rockers. I believe that they're 1.5. I don't think the coil was binding. It didn't looking like they were stacked, and as far as I know the block or the heads have never been machined. This'll suck if I have to get a different cam, but at least I found it out now without having everything put back together.

It's very unlikely the lift you have will be an issue with valve to piston clearance. I always adjust my valves with the sparkplugs out. Makes for much easier turning of the motor. My motor gets pretty tight when I'm adjusting valves and the harmonic balancer bolt with twist tighter some.

i had the plugs out. I just adjusted all the lifter preload's without any problem. Got a good bit done today. Wish I had the time and a garage to get it all done at once, but hey it gives me something to look forward to at work.