Im stumped...
 

I put compcams grind for tbi 350 in my friends 92 350 half ton c1500 pickup (auto, TBI). put it all back together and im sure i did everything right. But when i told him to bump the starter so i could put the distributor in the crank doesnt move, the front accessories spin but the pistons dont reciprocate. is there like a clutch that engages the crank? i dont understand it, i pulled off the converter cover and the flexplate spins when the starter turns and so do the front accessories but no recipracating??? if the flex plate is connected to the crank there is no way this could happen without the pistons moving. My only thought is there is a clutch or sumthing that has to engage the crank on this newer small block.

ok, theres a few things that i really dont understand, i'll state a few facts first then i'll ask some questions to try to figure out what your actual problem is....
first off, if the front accesories move, then the crank is moving, since the starter turns the fleplate, which turns the crank which turns the crank pulley and then the front accesories.
Second...What makes you think that the pistons arent moving? I assume the heads are on. Therefore the only way to tell if the pistons are moving is to use a compression tester or remove a sparkplug and put your finger over the hole and check for compression as you turn the crank. As long as you didnt unbolt the rod caps, the pistons ARE moving.

OK now i'll try to help you solve this.. i'll try to briefly explain the main steps of a basic cam swap, starting at the installation of the new cam...
Install new cam,
bolt up cam retainer plate,
align timing mark on crank timing gear(top) and cam gear(bottom),
Install timing chain making sure gears still line up,
Install timing cover,
reinstall lifters,
reinstall pushrods,
reinstall rocker arms,
reinstall valve covers, intake manifold, water pump and front accesories,
move crank balancer to TDC(comp. stroke -when piston is up in cylinder1)
install distributor - make sure the rotor points to #1 cly. wire on the cap,
reconnect plug wires according to firing order

If you did all that right, you need to explain you problem more.
Bumping the starter will turn the crank, there is no "crank clutch".
If you are having trouble dropping the distributor in, it will only go fully in 2 ways, one way is 180 degrees out. post back so i can get a better idea of whats going on.

Well its all installed right. I had him bump the starter with my thumb over #1. nothing, no compresion and it sounds like the pistons arent moving, but the front accessories turn. the distributor is out because i was having him bump to tdc on #1 when this happened. im stumped

well if you just bump the starter, like 1 sec at a time, you will not feel any compression really. You basically have to let it go at least 3 seconds or so. if the piston is on down stroke when you bump it, youll need to at least make the crank turn almost a full turn, tapping/bumping the starter will only move it a little. If the engine ran before you did the came swap and you didnt open up the bottom end, dont worry the pistons are moving correctly.
To fix it, you can still try to have a friend turn the key more than bumping it, while you feel for compression and do it that way, OR if you still cant get it, just put the balancer to 0 degree on the timing mark, it will either be on the exhaust or compression stroke(TDC) Then drop in the distributor. You'll have a 50/50 shot at getting it right. If it doesnt start or sounds like its popping in the intake manifold. the distributot is 180' out, if that happens...turn the crank so the rotor points at #1 wire terminal again, then pull the distribuot back out, turn the crank 360'(one full revoloution back to 0'timing mark) with that done, drop the distributor back in the exact same way you just pulled it out, then it should be correct.

maybe you feel nothing because the valves are adjusted too tight thus hanging open and the compression is escaping? How did you set the valve lash?

That's what I was thinking. We went through this when we built the 305 for my Monte. Filled the lifters with oil, but they bled down and we had the valve lash set too tight.

It's got to be the valves, there is no way the flexplate and crank pulley can turn and you aren't having rotation on the rotating assembly, it just isn't possible. You're valves are probably mis-adjusted.

it was the valves lol. how tight should they be?

If you decide to do it while the motor is running, you should listen to each one individually. As it's tapping, start to tighten the rocker arm. Once it's quiet, go 1/4 turn past that point. Repeat 16 times. :)

Didnt trucks still run flat-tappet cams? or is it a hydrualic roller? If its a flat tappet I wouldnt even consider attempting to set the lash while the motor is first running (since you must break in the cam)... A motor running at 2500RPM would be pretty hard to set the lash on. To adjust the valve lash on a motor while its not running pull out all the spark plugs or get a long breaker bar and turn the motor over slowly by hand at the crank, watch the valve springs...

Adjust the Intake valve lash when the EXHAUST valve begins to open and adjust the Exhaust valve when the INTAKE valve has just closes. Tighten it down slowly while wiggling the pushrod up and down. Once there is JUST all the slack taken out of the pushrod, tighten it a 1/2 turn more. Remember, just tighten it slightly then take the wrench off because its weight may screw up the adjustment, then wiggle the pushrod, repeat. You may not even want to go the extra 1/2 turn because more than likely your first time doing this you'll tighten them a little too tight

What SlowZ said....

I would stick with 1/4 turn instead of 1/2 though. It all depends on what cam, lifters, and springs you have, but 1/4 to 1/2 would be ok, as long as you are careful.

You may also want to pull that cam out if you have been trying to start it to make sure that you haven't rounded off a cam lobe. That could really tear up the rest of that engine.

- Justin