I know this is a 3rd gen board but this involves an '87 IROC L98 350 swapped into a second gen firebird.

Have an '81 Firebird that was a factory 305 car with 4 speed BW ST10 trans. Bought it with a '76 350 swapped in at some point.
Engine was wiped out so I rebuilt and put in the '87 L98......... One piece RMS engine.

I used a new 168 tooth flywheel for the L98 one piece RMS engine that accepts the bigger 11" clutch. (RAM 88764 with short TO bearing.) on the new L98. Same size flywheel that was on the '76 engine I pulled out.
I transferred everything else from the old engine to the new one..........bell housing with the short pivot ball (PN 3729000). Also used a new NOS fork PN 14066235. It's a replacement for the original fork. It's beefier but the geometry is the same looks to me.
Correct short head flywheel bolts from ARP.

So the issue is the clutch will not release. Pedal feels perfect and everything is adjusted properly. The first clutch I used was from LUK but it had a grinding noise coming from it when depressing the clutch pedal with the engine not even running. It wouldn't go into gear when I had it running so I thought the pressure plate was bad. Swapped in the new RAM clutch, same problem.
I double and triple checked everything before I installed the new RAM clutch and everything seemed in order. All linkage good, no binding or hanging up. Pedal is smooth as butter and I can feel it depressing the PP properly..........but it wont' release the disc.
I wouldn't think so but does the newer L98 engine with the one piece RMS need the longer pivot ball for the fork? Is the bigger flywheel an issue? I measured the height of the flywheel from the back of the block to the face of the flywheel on the old '76 engine I took out and it was 2 5/8" if I recall correctly, same measurement on the new L98 with the new 168 tooth flywheel.

I am open to any suggestions as what to do next because this doesn't make sense unless I am missing something obvious. I have done many clutch jobs before but I am a bit stumped.

 

Start here.



It's nothing about 11", 76, 2-xx", or any of the rest of that. All that stuff is all the exact same. Not the problem.

 

The TO bearing is installed correct.

 

Since that's the only thing that can cause what you describe, I don't believe you.

Show us a pic.

 

Assuming it's all together properly, You may need an adjustable pivot ball. You maybe just aren't getting enough travel to release it fully. Also, does your z bar have multiple holes on the linkage arms?

 

I agree that it seems like it's not getting enough travel but what is odd is that everything is bone stock and put together exactly like it was before. The only changes are the new clutch assembly, the new ATP flywheel which is the same thickness as the old one and the replacement NOS fork.

No additional holes on any linkage.'
One thing I did notice when comparing the old worn out PP to the new RAM pressure plate was that the diaphragm fingers were higher than than the old one. The old one looks to be more low profile but maybe the fingers are just lower from being a high mile worn out part, idk.
This is an odd problem for sure especially since everything is stock and working ok before the engine replacement with the new clutch/flywheel added.

As I mentioned the replacement fork is a heavy duty unit with "ears" near where the bearing sits and a thicker wider arm than the old one but laying them side by side and looking at it from different angles, the geometry looks the same. The correct part number is even stamped on it and it jives with the number in the factory parts book for my application. It's a fork that is common to many different engines, Chevy, Pontiac, etc etc.

 

I have a ram clutch, when I bought it they strongly recommended an adjustable pivot ball. I ended up w a hydraulic setup so I didn't need one. If the diaphragm fingers stick out more then the pivot ball me be your answer. There are ideal angles for the release fork you can check but if it won't release you kind of know there's and issue. The option you don't want to hear is a hydraulic setup will work better but the process of swapping is a pain in the ***. Part of why I bring it up is to do the pivot ball the trans needs to come out either way.

 

I'd think with the RAM clutch fingers being a little higher I'd actually have more travel and the diaphragm would be pushed further since there would be less room for the bearing to move before contacting the fingers of the plate old vs. new.

 

I think it depends on the leverage ratio of the diaphragm fingers. It's worth contacting ram tech support, they were really helpful with my setup and pretty spot on. There's only 1-2 millimeters of space between the disk and its mating surfaces when the pedal is pressed in so it doesn't take much for it to not disengage. That's why the adjustable pivot ball is so useful.
you can also use a scope and look in the bell while someone actuated the clutch to see how things are moving.

 

You don't need an adjustable pivot ball. The clutch itself is almost certainly fine, nothing wrong with it. I've used PLENTY of Ram clutches over the last 40 years or so, and they're as reliable as any in this regard.

Show us a photo of how you put the TOB onto the fork. 99.99999% likely, that's what's wrong with it. It's pretty much the only thing that can cause that.

See my signature for a helpful mental discipline that is pretty damn reliable even if it's unpleasant to admit to sometimes.

 

So after pulling the trans for the third time I was able to take a look at the PP in action.

Had someone push down on the clutch pedal and the disc dropped. It is releasing as it should be. But with the trans installed and engine running it will not go into gear. As soon as I shut the engine down I can shift into any gear.

When I had the trans out on the bench a while back I took the shift cover off to change the gasket. Reinstalled the shift cover and bench shifted it thru all gears. Also had the tail shaft housing off too to change the rear bushing. Nothing in the main case was taken apart.

I'm ruling out a trans issue because it shifts fine when engine is off and when I had it on the bench.

Trans was not hard to install either. Went right in practically by hand. Didn't draw it into the bell with bolts.

Still searching for an answer.

 

If the clutch releases but the engine & trans are still partially coupled together, it's a pilot bushing/bearing problem. That's the only other point of contact.

Which did you use; a bushing, or a bearing? If a bushing, how hard was it to drive in? What did you use to do that? Any possibility it's mushroomed into the bore? Did you grease it?

 

Sofaking has the right idea, but ^That^ doesn't sound like a tight pilot. Can you start the car w/it already in gear, and when doing that, does it want to "creep" on you?

When doing ^That^, how far off the floor does the clutch pedal go before you can feel it start to engage/load the engine and/or move the car?

I'm guessing that it will only grind, if you try for reverse with it running? Can you start in reverse, Pop it out of reverse and in doing so, "Feel" the load on the input shaft? If not, can you pop it out of reverse and then back in quick, to ascertain how quickly the disk/input shaft speeds up? I'd guess it speeds up virtually instantly, if you can't get it into the other gears...

These aren't solutions...they're ways to get a better feel for what is actually happening, IMO.

 

Just to update:
Problem turned out to literally be pilot error. I thought the pilot bushing was driven in as far as it could go but that was not the case. I drove it in until it was flush with the hole in the crank and felt solid when I hit it but it still had a little way go. Just past flush it needed to be. Strange because the the trans went right in and did not need to be drawn in with the bolts but upon closer more careful inspection it was not quite touching the bell after shoving it in.
The input was obviously riding on the bushing just a touch causing it to turn when clutch was disengaged.
All better now thanx for the suggestions.

 

See, I'm not as dumb as I give myself credit for. I'm even dumber.