Techno Duck's LS1 conversion

Pulled the inspection cover and actuated the clutch with the car idling. Its clear the clutch is not fully disengaging. The driveshaft never stops spinning with the clutch depressed. The only time it does stop is by shifting it into gear.. the synchros are probably not to happy with me right now

Ugh..

Ive got two spare master cylinders, a .7 and a 7/8" bore. Ill throw one of these in to get the car drivable again. Will take the 3/4" bore apart and inspect the bore.

What a pain in the ass.. i am getting sick of swapping these things out  

This 3/4" bore didnt last long, it has around 7-800 miles on it. Of which easily 2-300 miles was highway done yesterday.

I am tempted to get a stock master cylinder and see if that works.

That sucks. I'm kinda in the same boat. I started with a 13/16 master which didn't give me sufficient release of the clutch disc like you're getting. I swapped to a 1" which made the pedal very heavy but things worked well. But lately I've noticed the friction point rising earlier in the pedal travel. Instead of about halfway down, the clutch doesn't bite until the last bit of releasing the pedal. I'm worried I'll start getting clutch slip soon.

Should I pull things apart and re-measure the need for a shim? Should I swap to a smaller sized master? Should I just leave it? And lastly, why has this changed? Any thoughts?

Rich

Is it a result of the bell housing design? It seems to be mostly the corvette owners getting the black fluid. And most of us are using the corvette bell housing.

Check this thread regarding the black fluid. I believe it is just a not so great throwout bearing design. The way i see it, the bell housing is well vented for us with the design of the oil pan (plenty of gaps on the side!). So i would think its getting plenty of ventilation.

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I made some good findings today, the root cause was definitely the master cylinder. Will report back later.

Yikes...knew the clutch dust problem was bad, but not that bad....and what a great tutorial:

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(opens full screen)

And this is showing a C6 slave...the C5 slave doesn't even have the green protection bellows (yup, under the dust, it's green).

"over pressure" venting through the filler cap seems important as well.

Gotta be a better way than changing the fluid every few weeks 

btw...at 2:40 I think he has the movement backwards...no big deal.

I looked into the angle of the master cylinder and sure enough it was off. The firewall has the angle built into it, the pictures explain it best...

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Now here is how the master cylinder was mounted, the angle was off quite a bit. I didnt notice this little detail on the many times i have swapped master cylinders.

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After some more trimming...

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And further modification to the mounting bracket to fit the recess on the firewall...

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I took the old master cylinder apart and the bore does have some very light marks in the bore. It is a little surprising because the marks are extremely faint (But noticeable) and do not feel rough, but you can feel the difference in smoothness in the bore. The plunger / piston is metal, i wonder if something like teflon would have been a better (though more expensive) choice so the aluminum bore isnt chewed up by misalignment.

No pictures of the bore, difficult to get anything with a camera.

The first few shifts were perfect, but after 6-7 miles the clutch is not disengaging again. I did have some trouble bleeding it, so i suspect there is still air in the system. Going to pressure bleed it tomorrow.

I am a little untrusting of this still. Before buying another .75" bore master i may just continue running the 7/8" for a few hundred miles and see if it lasts.

I dont think the clutch dust will cause anything other than premature failure of the throwout bearing. Then you have to wonder how many C5's and C6's are around where the owner is not flushing the clutch on a routine basis. Personally i do not think it will cause any difference in the throwout bearing travel, also the dust contaminated fluid will never see the master cylinder.

Rich, i noticed the same thing when i was trying to figure things out before the transmission was swapped out. Obviously that was the main reason for my shifting issue but i suspect i had a few other things going on also. One thing that i found that basically fixed your symptoms was adjusting the freeplay on the pedal. Previously i had set my pedal with basically zero freeplay. So as the car heated up i am guessing the throwout bearing was pressing on the pressure plate with some small amount of force constantly. I would bleed the clutch, problem would go away. Drive around maybe 20-30 miles and the pedal engagement moves again. After giving the pedal 1-2mm of freeplay (as it says in the factory workshop manual) i never had those problems again.

This worked for me atleast.

Honestly with all the things that went into this engine swap i did not think most of my issues would be shifting related!

Thanks. I'll look at the free play. Glad you're making progress. Agreed on the shifting. That's what ended a session of mine stranded on track recently, short shifter came disconnected.

Rich

Those little grooves cause havoc. During one race it got so bad that hydraulic fluid was squirting onto my shoe every time I depressed the clutch.

This is getting very frustrating. Rebled the system again today with the help of a friend. Shifting it in the driveway it felt perfect. After 1-2 miles i was having difficulty getting into reverse again. After 20 miles it is right back to where i started, difficult to engage 1st gear at a stop, even 2nd from a stop takes more force than normal.

Really unsure what it could be, going to check all the fittings tomorrow and make sure everything is tight. Maybe even pressure test the system overnight.

This is something i was thinking about a few days ago, the master cylinder cap i have has no vent in it, i was thinking perhaps the system is pulling a vacuum in the reservoir as a result, so it cant draw fluid out. Seems kind of far fetched, but i have seen master cylinder caps with tiny holes in the caps before. I think ill try drilling a very tiny hole in the cap and rebleeding the system (for the 100th time).

Torque tube misaligned? Check to see if any of the adapter bolts came loose. I had a problem when the bolts came loose and the shaft was binding on the pilot bearing causing shifting issues. Does the shaft spin freely by hand with the clutch depressed? When this happened to me I could barley spin the shaft by hand with the pedal depressed.

The input shaft does spin freely by hand. I will check the bolts though, probably wouldn't be a bad idea anyhow with the extra vibration / rhythmic shake at idle.

Unfortunately i won't have too much time to mess around with this until the weekend. Getting pretty annoyed too.. Wasting way too much time off on this car again.

My plan of attack is to check torque tube and adapter plate bolts, rebleed the clutch again and vent the master cylinder cap with a tiny drill bit. Then see how that goes. Next up putting the original linkage rod back in.

If those things don't help.. I am seriously considering a Tilton pedal box. Hope Thom remembers how he installed the one in Milkman's car    

Got a screw in my right rear last night also.. This car is a real bummer sometimes.

Different car, but when I was having issues shifting out of gear in my Audi it was a bad pilot bearing...

Rebled system and vented the cap. Before leaving i can go through all of the gears no problem at idle (reverse also). After 25 miles i came back home. 1st gear is a little harder to engage, cannot get it into reverse anymore. So venting the cap made no change.

I am going to let it cool off overnight and try to go through the gears again tomorrow. I wonder if its heat related.

Something ive noticed also but forgot to mention. Where i usually park in the driveway has a very slight incline. If sitting in neutral the car will roll back very slowly. Ive noticed i can put the car into say first gear (car running), clutch in and off the brake. Car will roll back very slowly. Now if i start to release the clutch, maybe 10% into its travel off the floor the car will stop rolling. Push it back to the floor, car rolls, release slowly to 10% car stops rolling. I can do this consistently at will. Even on flat ground though, the clutch does not fully engage until 80% or so travel, this is to be expected with the 7/8" master cylinder i am using. The car does the same on flat ground, you can just  barely feel the engine 'bog' a little. Its really extremely faint, this engine has so much torque even at idle it hardly flinches.

Another thing i noticed. After bleeding the clutch, i can easily go through the gears at idle. I pulled the rubber inspection cover off the transmission bell housing and recorded what the driveshaft coupler is doing at idle. Push clutch in, start car... driveshaft does not spin at all, or atleast hardly any. Release clutch, spins at idle speed. Release clutch, driveshaft slows down as expected. Now when the car is difficult to shift, i can do the same test. Instead when i start with the clutch in the driveshaft spins immediately up to speed.

I am really not sure what to think at this point. Not sure if the hydraulics are to blame or there is an issue somewhere with either the clutch assembly, pilot bearing or input shaft.

I think a good check would be to start it up with the bell housing inspection cover removed and see what the clutch does with it running... though i am a little hesitant to get under it with it running and the inspection cover off... like my face will be right next to spinning drivetrain!

Having the car tuned on friday but i am quickly loosing interest in this car again, just wasting too much time on it. Probably going to park it and leave it be for a while after the tuning is done.

Did you ever try swapping the HTOB?

Are you using a speedbleeder? I struggled to get a good bleed on my clutch with a pressure bleeder. A speedbleeder made it easier for me to get the air out.

Rich

Supes, have not done anything with the throwout bearing yet. If I remember right it was the Dorman made one, someone mentioned a while back they were the best made. I used the C5 vette type bearing also, brand new when installed.

Rich, I have a remote bleed line that has a speed bleeder on it. Lately I have been doing the two person technique though. When I am down at the shop tomorrow for tuning, going to have them vacuum bleed it for me to see if that makes any difference. Maybe just a bunch of air is still hung up.

Maybe. That's the only explanation I can come up for my situation too. Good luck with it. I'd hate to see you park it in frustration.

Rich

Strange, when i parked the car last night it was not possible to shift into reverse. 1st gear was also very difficult to get into.

Idled the car a little while ago in the driveway again, shifting is now fine again. So i guess it is something heat related.

Removed bell housing inspection cover. The two hoses for the throwout bearing look fine, nothing looks out of the ordinary. Travel of the throwout bearing looks fine aswell.

My best guesses are either air still trapped in the slave cylinder, or the clearances are changing as the car heats up. Possibly something involving the pilot bearing, or how the disc sits in relation to the flywheel and pressure plate with clutch fully depressed.

All bolts on the bell housing adapter and torque tube are tight as well.

Techno Duck wrote:something involving the pilot bearing, or how the disc sits in relation

+1

Verified also that the throwout bearing has plenty of travel. Had my buddy hold down the clutch and wiggled the clutch disc with a screw driver. Plenty of movement, so i also doubt the disc is getting hung up, even on a warm engine.

Going to swap the old shift linkage rod tomorrow before i head over to the shop for tuning. Other than vacuum bleeding, i am at a loss as to what else it can be.

Should have power #'s tomorrow night, any guesses? LS1, 226/230 cam, TPC long tubes into a single 4", ported throttle body, 36# injectors.

I am going to guess 380whp.

382whp / 348tq

Dont have the charts yet, hopefully will get a copy next week sometime. Throttle response is much improved. They did not do a baseline pull, so not sure what it was making with just the base tune. Quite a few tweaks were made before the first pull which was 371whp. The tuner thinks it was probably making in the area of 350whp with a very conservative tune with very little timing and very rich.

The basic engine specs...

5.7L LS1
LS6 intake manifold
TPC long tubes into a 4" single exhaust with Magnaflow muffler
Ported throttle body fed with a straight pipe from a C5 air filter
EPS 226/230 cam, 113LSA
36# injectors

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Talked a little to the shop regarding the shifting issues. At this point i am fairly certain the shim needs to be installed with the throwout bearing. The shop primarily works on LSx based cars so i trust their advice. They said every LS equipped car they have ever installed a Spec clutch in required the shim.

Now this got me thinking. Initially i thought the car did not require a shim, as i was getting engagement of the clutch very high up in pedal travel as i have noted previously. Basically the clutch was getting engagement anywhere from 40-80% pedal travel depending what master cylinder i have in the car.

But taking what i noticed regarding being able to stop the car from rolling backwards with the pedal at just 10% travel off the floor, i believe the clutch may be dragging on either the flywheel or pressure plate just enough to keep it spinning and at just 10% travel its dragging enough to stop the car from rolling. This could be caused by not enough travel from the throwout bearing or the disc being hung up on the splines.

I do not believe the splines are the issue though. I can wiggle the disc very easily with someone holding the clutch down using a screwdriver on the edge. Also the assembly was torn down once already, with no problems noted.

Now when the car is cold, the disc friction is minimal. So by shifting into gear its enough to stop the input shaft from spinning to engage a gear. But even with the car just warm, the friction is high enough that the trans cannot slow the input shaft enough to select a gear.

I am going to see if its possible to cut a slot in the shim so it can be slid around the input shaft. Unbolt the slave cylinder and see if the shim can be slid behind the throwout bearing to avoid having to drop the trans, slide back the torque tube..etc again.

Now with that said, it may be possible i can get away with the .7" master cylinder i was originally using. I bet that will move the engagement point higher up also, giving the benefit of a lighter pedal with enagement around 50-60% pedal travel.

Great power numbers. Right at the same as mine with a very similar setup.

Good luck getting the shim inserted. It'd be great to slip it in there without major disassembly. I agree that it does sound like you need it.

Rich

The shim needs to be measured for proper thickness. Someone here or on LS1.com measured three different slave cylinders and they were all different heights. Each would need a different thickness shim. Contact Spec and ask them what the AB difference should be. I went through all of that with Spec so I understand your frustration.