Clutch not disengaging properly

[1973GMC_1500]

The second 6.2 I put in my '87 starting knocking and losing power last week. I decided enough was enough and pulled it out. I dropped in a 307 Chevy for now, I might build a 350 later this summer. I used the 307 flywheel, but 6.2 pressure plate and clutch disc (shouldn't matter though- they all use a 12" clutch with a 4 speed). My truck also has a hydraulic clutch, which works fine.

When I press the clutch it won't disengage enough to get it into (or out of) gear. If I shut it off put in gear then start it with clutch depressed, it won't move but it makes a really loud grinding sound which goes away as soon as the clutch is released.

I was wondering if something happened to the throwout bearing- I pulled the boot off the fork but I can't see inside the bellhousing.

Any ideas let me know. I think I'm going to have to pull the engine back out but before I do I want to make sure the water pump fixes my coolant leak (I suspected head gaskets at first)

[billnorman]

Did you make sure the engine you put in had a pilot bearing? I have a friend here in Maryland with a 6.2 diesel he rebuilt 40K miles ago, and has all recalibrated and built pump and injectors that wants half a grand for it. It IS a long way from you, but it runs good, he's a good mech. Your T.O. brg may have died.

[1973GMC_1500]

Yeah, it had a pilot bearing. I could see the t.o. making noise, but don't get the fact it doesn't disengage.

[billnorman]

If you bent the clutch disc when installing, have rust or a groove on the tranny input shaft, have a bad pilot bearing, have a dragging centerspring on the disc, have a bad pressure plate, or have the adjustment wrong, of course, you'll not disengage properly. If the truck won't move in gear, the hub must be out of the clutch disc. Either that or the pressure plate is depressed, perhaps the TO brg is caught on the trans input shaft. Did you have any trouble installing the tranny, like, it didn't wanna go in? Is the bell housing too deep? I haven't had a stick Chev for so long, the last one I had had an 11 inch clutch. I once used a GMC truck clutch on a Pontiac 389 IN A '56 CHEV I slapped together, and it used a 12 incher. Wish I could be helpful, but I lack experience in this diesel engine arena.

[68 TT]

My 78 K20 was doing the exact same thing but I have a mechanical clutch. On mine one tab on the clutch fork broke and was allowing the throwout to pivot and not engage the clutch all the way.

With a hydraulic system you may have air in the system or a leaky hose that is not allowing the throwout to engage all the way. All the clutch parts may be fine and working right but are not disengaging due to the lack of proper throwout movement.

Bleed the slave cylinder and see if this helps.

[1973GMC_1500]

...If the truck won't move in gear...

The truck moves fine, the clutch isn't disengaging all the way. It will allow the truck to stop but you can't shift.
The engine slipped into the bellhousing fairly decently, they always put up a bit of a fight, this was about average.

The slave cylinder works fine, but that wouldn't explain the growling.

None of that is going to matter- the 307 either has cracked heads or bad head gaskets since it pressurizes the coolant and overheats even idling.

I bought a stock 350 out of a '83 K20 today. And the best part is it has the normal power steering brackets, not the goofy ones my 307 had. And It came with the right radiator, fan shroud, and brackets.

I'm pulling the 307 out tomorrow, and hopefully getting the 350 in if I don't run into any more issues.

[1973GMC_1500]

My throwout bearing was intact, but hung up and didn't spin very good.

I found the problem with the clutch- somebody () put the disc in backwards. I have done plenty of clutches, never had this happen to me. A sigh of relief knowing everything should work good with the new engine

I got a new t.o. and pilot bushing for the 350. I put the manifolds on and it's going in tomorrow.