[abefromen]

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

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 used a new ATP 168 tooth flywheel for the '87 350 engine that accepts the bigger 11" clutch. (RAM 88764 with short TO bearing.) Same size flywheel that was on the '76 engine I pulled out.
I transferred everything else from the old engine to the new one, all OEM stock parts..........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. TO bearing is installed on the fork correctly with the clips inside the collar.
Correct short head flywheel bolts from ARP also used.

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 sbc 350 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", same measurement on the new 350 with the new 168 tooth ATP 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. The Chevy bell housing is all enclosed, no inspection hole/opening in the bottom to at least see the disc and try to turn it. Makes this prob tougher to figure out.

[Lemans64]

Not sure that flywheel will work on that engine? 1 piece rear main seal engine uses different flywheel. Info from another site.
In 1986 a crankshaft and flywheel change was made to the improved, once-piece seal design. 1986 and newer Chevy engines will not accept older flywheels due to the different crank flange and bolt pattern. Older bellhousings, however, will work on 1986 and newer engines.

[abefromen]

Originally Posted by Lemans64

Not sure that flywheel will work on that engine? 1 piece rear main seal engine uses different flywheel. Info from another site.
In 1986 a crankshaft and flywheel change was made to the improved, once-piece seal design. 1986 and newer Chevy engines will not accept older flywheels due to the different crank flange and bolt pattern. Older bellhousings, however, will work on 1986 and newer engines.

It's a correct flywheel for the one piece RMS engine. The older sbc flywheel won't even fit the hub of the crankshaft of the '87-up engine.

[Scott Thelander]

disc springs hitting flywheel bolt heads ???

[Lemans64]

Sorry read post wrong. Disc in backwards? Most have the spring stepped portion to the trans.

[HWYSTR455]

Did you test fit the clutch disc on the input shaft? Maybe it's getting hung on the shaft. Was it difficult to mate the trans to the bell?

You mentioned 11" setup, did you hold the disc up to the plate to make sure it fit? Possible stuff got mixed up from another box.

And just to ask, the 'flat' side of the disc is towards the flywheel?

You can drill an inspection hole in the bell too, if you need to.

If there's too much pedal throw, fingers/To might be able to hit the disc.

It's rare, but possible, the TO isn't centered on the fingers, or one side of the TO is under the fingers. You can try to peek in the hole the arm passes thru and make sure it's flat on the fingers.

Can't always trust the TO part listings either.

Just throwing stuff out there...


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[HWYSTR455]

Originally Posted by Lemans64

Sorry read post wrong. Disc in backwards? Most have the spring stepped portion to the trans.

Pretty sure the flat side of the disc usually goes towards the engine/flywheel.

EDIT: Ok, my turn to read post wrong!


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[abefromen]

Originally Posted by Scott Thelander

disc springs hitting flywheel bolt heads ???

Short head ARP bolts were used. No witness marks on anything. I test fit the disc to the flywheel beforehand and it fit flat no touching.

Originally Posted by Lemans64

Sorry read post wrong. Disc in backwards? Most have the spring stepped portion to the trans.

Definitely in correctly. If it was backwards it wouldn't sit flat and flush I tried it.

[abefromen]

Originally Posted by HWYSTR455

Did you test fit the clutch disc on the input shaft? Maybe it's getting hung on the shaft. Was it difficult to mate the trans to the bell?

Test fit to the input shaft before install. Smooth as silk. Trans went in no issue at all, practically by hand I could push it in

You mentioned 11" setup, did you hold the disc up to the plate to make sure it fit? Possible stuff got mixed up from another box.

Yes. Compared old disc to new, both identical. Only thing that was different was the fingers of the new RAM stock replacment PP were a little higher than the old plate that came out. (see pic) No idea if it's original or not but it does have corporate blue over spray on it. Could be OEM original idk. Has balance weights on it like I have never seen on replacements

And just to ask, the 'flat' side of the disc is towards the flywheel?

Yes

You can drill an inspection hole in the bell too, if you need to.

Could but would hate to do that. Why the hell does Chevy have a completely enclosed bell on this engine? No inspection plate like on a Pontiac. Stupid design.

If there's too much pedal throw, fingers/To might be able to hit the disc.

Something to check if I could actually see the PP in action.

It's rare, but possible, the TO isn't centered on the fingers, or one side of the TO is under the fingers. You can try to peek in the hole the arm passes thru and make sure it's flat on the fingers.

I'll look

Can't always trust the TO part listings either.

New TO exact same height as old one that came out.

Just throwing stuff out there...

Thanx for all suggestions, Getting more help here than other Chevy dedicated forums I belong to!


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[Lemans64]

Just another thought, are you putting throw out bearing on fork correctly, the spring on fork goes on the groove with fork, not behind bearing?
Sorry not trying to say you did it wrong, just throwing out idea's.

[HWYSTR455]

Well, guess it could be a defective plate, but not sure that would give the same results.

So when the fork is in the 'relaxed' position, with the fork free play slack taken up (just resting the TO on PP fingers), is the rod pad 90 degrees to the centerline of the drivetrain?

If it's not, and the pad is more towards the rear of the car, that could mean you're not getting enough pedal/linkage throw. To correct, it would require a different or adjustable pivot ball in the bell.


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[abefromen]

Originally Posted by HWYSTR455

Well, guess it could be a defective plate, but not sure that would give the same results.

Thia RAM clutch is the second i have tried. First was a LUK brand and it had a grinding noise when depressing the clutch pedal and I was unable to go in gear. Thought pressure plate was defective. Replaced with the RAM same result but it's smooth & quiet with a normal feeling pedal adjusted with the proper free play so the TO is not touching the fingers

So when the fork is in the 'relaxed' position, with the fork free play slack taken up (just resting the TO on PP fingers), is the rod pad 90 degrees to the centerline of the drivetrain?

If it's not, and the pad is more towards the rear of the car, that could mean you're not getting enough pedal/linkage throw. To correct, it would require a different or adjustable pivot ball in the bell.

what do you mean by rod pad? The round pocket end of the fork where the push rod sits in?
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Originally Posted by Lemans64

Just another thought, are you putting throw out bearing on fork correctly, the spring on fork goes on the groove with fork, not behind bearing?
Sorry not trying to say you did it wrong, just throwing out idea's.

yes i made sure it was. All suggestions appreciated. Since this is a stock set up it's really got me puzzled

[HWYSTR455]

Rod pad, correct, the pocket where the push rod meets the fork. It's 'flat' there where the divot is, and that flat spot angle should be 90 degrees to the centerline of the driveline.



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[abefromen]

Originally Posted by HWYSTR455

Rod pad, correct, the pocket where the push rod meets the fork. It's 'flat' there where the divot is, and that flat spot angle should be 90 degrees to the centerline of the driveline.



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I will check that out.
Also found this at the RAM website:

CHECKING CLUTCH FORK ANGLE AND MAKING APPROPRIATE ADJUSTMENTS
1960’s-70’s GM applications used several different fork pivot ball lengths and release
bearing lengths. Understanding fork angle will help you achieve the best release position for
the fork to minimize pedal effort and maximize bearing travel. For optimum operation, the
fork should have an angle to the front of the bellhousing exit window when the bearing is
just touching the fingers. If the fork is positioned in the middle or to the rear of the window,
travel and leverage is lost. To compensate for this, RAM offers two longer release bearings -
pn 488L is 1.560” overall and pn 495 is 1.810” overall.
You can pre-check the need for a longer bearing by sliding the transmission in and, before
proceeding with completion of the install, pulling the fork up manually to check and make
sure the fork is angled to the front of the exit window in the bellhousing when the bearing is
just touching the clutch finger

[abefromen]

First pic is clutch pedal at rest all the way up. Fork is at about mid window. According to the RAM instructions it should be more towards the front of the window opening.

Second pic if fully depressed.

Impossible to see inside the window without a bore scope to see how far fingers are down. But without a bottom inspection hole to see what the disc is doing looking in with a bore scope may not say much.

Old clutch with the flatter diaphragm fingers with same short TO bearing worked fine.......new PP with more raised fingers same short TO won't release disc. Makes no sense.

[HWYSTR455]

Ok, have to admit, not too familiar with the chebbie stuff, I can see the angle of the bell, and the bend on the fork, so maybe it needs to be at rest further forward, not sure.

It kinda looks like theres a witness mark on the bell fork opening, maybe it's reaching max travel?

It does look like you have more room to maybe go to the next height TO though, that might do it.


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[HWYSTR455]

I take that back, think the pivot ball needs to be longer, or an adjustable one so you can move it taller. That would make the fork go forward without it going at an angle, which would be the case if you went to the next height TO.

Is that bell cast aluminum? If it's steel or else, you can cut into it and not worry about it failing.

Think you're on the right track.

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[HWYSTR455]

That pic of the fork I posted has less of an arch to it, maybe because it's a Pontiac one.


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[HWYSTR455]

Yeah, more I look at that pic at-rest, more I think the next size up TO isn't going to help, it will probably put the fork at more of an angle and create an 'arch' path of travel, making it hard to initially push the pedal in.

Difference between the 2 TOs that the RAM website lists is a touch over a 1/4", that may make the end of the fork too close to the bell.

It's a toss up, you could try the next taller TO, but I think if you ever have to replace it again, the adjustable ball would be a better option.


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[abefromen]

Originally Posted by HWYSTR455

I take that back, think the pivot ball needs to be longer, or an adjustable one so you can move it taller. That would make the fork go forward without it going at an angle, which would be the case if you went to the next height TO.

Is that bell cast aluminum? If it's steel or else, you can cut into it and not worry about it failing.

Think you're on the right track.

aluminum

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Originally Posted by HWYSTR455

That pic of the fork I posted has less of an arch to it, maybe because it's a Pontiac one.

my Pontiac parts book shows that fork for 305 equipped F-bodys but also 76-77 ALL ENGINES and 78-79 X and F w/manual trans


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Originally Posted by HWYSTR455

Yeah, more I look at that pic at-rest, more I think the next size up TO isn't going to help, it will probably put the fork at more of an angle and create an 'arch' path of travel, making it hard to initially push the pedal in.

Difference between the 2 TOs that the RAM website lists is a touch over a 1/4", that may make the end of the fork too close to the bell.

It's a toss up, you could try the next taller TO, but I think if you ever have to replace it again, the adjustable ball would be a better option.


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next logical step would be adjustable fork ball I guess. Took some measurements and both old flywheel and new are 1 1/4" thick. But the flywheel on the newer '87 engine sits a bit closer to the block, .445 vs .510 on the old engine. Hard to believe such a small difference could cause this issue but who knows New flywheel is 87-96 Chevy truck it accepts the bigger 11" clutch