Clutch pedal travel issues

[VKannan]

Hi all,

The good news is I did the first start of my engine last weekend and it fired right up! A very cool milestone to hit.

The bad news is, even with the clutch fully depressed the driveshaft kept spinning, so the clutch wasn’t engaging. I toyed around with it a bit and found that I needed to adjust the clevis in order to give more pedal travel so that the hydraulic throw out bearing could go farther. The problem is that I had to back the bolt out so much from the clevis that there are very few threads engaged at this point. I must’ve cut the bolt too much when I mistakenly fitted everything to where it looked aesthetically correct, aligned with the rest of the pedals. After a lot of back-and-forth I found the maximum amount of thread engagement I can get while still disengaging the clutch is 4 1/2 turns of the master cylinder bolt into the clevis. That means the bolt is only about halfway through the clevis itself, possibly less. Is this enough engagement, or do I need to buy a whole new master cylinder, or is there some other fix?

The first picture shows how much thread engagement there is, and the second picture shows how much closer to the driver the clutch pedal is relative to the others.

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[Jacob McCrea]

I won't say for certain if that's enough thread engagement, but since there is a jamb nut I think you are probably OK. If you are uncomfortable the plunger rods can be swapped out without too much aggravation. There is a circlip behind the rubber boot which retains the rod and a few other things. You could try to buy a new rod from Wilwood. Someone here may have one sitting around. I will see if I do.

Edit: I seem to remember that as my clutch components wore together, I needed less pedal travel to disengage the clutch. So, you may find you can screw the plunger rod into the clevis a bit more as the moving parts get to know each other.

[Hoooper]

Doesnt look like much engagement. While youre at this very open stage and replacing the rod is pretty easy I would go ahead and replace the rod. On a side note, it also looks like your brake pedal is out of position.

What size master for the clutch do you have? I found that the wilwood "13/16" master I bought which does not have ANY size markings on it moved far less fluid and was much smaller in physical size than the 1/16" larger Tilton I replaced it with. I wasnt able to get enough stroke with the Wilwood to replace the clutch, but with the 7/8 Tilton I needed a clutch stop about 3" off the back of the pedal box. So a 15% increase in piston volume somehow resulted in about 2x fluid volume, very suspicious.

[edwardb]

X2 to not enough engagement. You can get a Wilwood MC rebuild kit that includes a new pushrod. Much cheaper than the whole MC. < $30 last time I bought one. It's easy to do with just a snap ring to take things apart. But assuming your pedal is maybe at the wrong location (I would say it is based on your picture) you should consider going up one size for the MC as already mentioned. That's assuming you have the clutch end adjusted properly. With an external setup, you should get full clutch release with just over 1" of travel.

[KippRacing]

Is it possible that there is air in the line also? Just a thought....

[MB750]

What size MC, and what size SC? (master cylinder and slave cylinder)

[VKannan]

Hi all, I have this :

https://www.amazon.com/gp/aw/d/B002G30G7G?psc=1&ref=ppx_pop_mob_b_asin_title

It’s 3/4” bore and 1.12” stroke, paired with a hydraulic throwout bearing from Ram that said it should work with those specs. But I am still worried about how far I am going to have to push the clutch pedal to get proper disengagement, it’s going to be quite a workout. Do I need to change the bore or the stroke or both in order to reduce that? And do I need to make them bigger or smaller?

[scrubs]

Is it possible that there is air in the line also? Just a thought....

This. I had same issue and was air.

[VKannan]

I’ll try bleeding it again just to be safe, thanks!

[edwardb]

Assuming you have no air in the system and you have the hydraulic throwout bearing set up properly (very important!) you need a larger MC to get more throw with less pedal travel. As I mentioned in my previous post. FWIW, my Coupe has a Tilton hydraulic throwout bearing and I have a Wilwood 260-10373 13/16 inch MC. Throw is perfect. Aligned with the brake pedal (which I prefer) and clutch is fully disengaged with the pedal on the floor. Your RAM bearing may require something different than my Tilton. But mine came with very specific instructions for which MC to use with different driveline setups. Their recommendation was spot on.

[MB750]

As mentioned, larger MC means more throw in the SC

What's the specs on your slave cylinder (or hydraulic throwout bearing)? I can back out the math to see if you're getting enough volume transfer to fully actuate the bearing. From what you've described, you don't (assuming you don't have air in the lines).

FWIW, I used to have the 3/4" MC in my hydraulic clutch setup, but I'm using an external slave cylinder with a normal throwout bearing. I had BARELY enough pedal sweep to fully release the clutch and I had to preload the hell out of the throwout bearing. I went up to a 1-1/8" MC and now I've got plenty of pedal clearance. Almost half my pedal sweep is air, but the friction zone is pretty tight and it's a beast of a press with my leg.

Edit: I just checked the RAM website and they don't show a stroke volume equivalent for that throwout bearing. I'd send them an email and ask. Telling me a "minimum of 3/4 inch MC" doesn't sit well with me, they have no idea how much stroke I can get on the MC with my pedal setup.

[CraigS]

I agree I'd like to see more thread engagement. But I have no problem w/ the pedal position. I always set mine up so the clutch is higher than the brake. I feel like the brake is going to move about 2 inches. The clutch may need 4 inches. So I like to start w/ the clutch pedal higher. As Jacob said, "Edit: I seem to remember that as my clutch components wore together, I needed less pedal travel to disengage the clutch. So, you may find you can screw the plunger rod into the clevis a bit more as the moving parts get to know each other." Back in the 70s brother and I had a 2 man import car shop. We often found that replacement clutches would not fully disengage. We fixed that often by some extra clutch slipping on a test drive. Kind of a forced quicker wear-in process.

[Hoooper]

Just a heads up, the reason I said it looks like the brake pedal position isn't right is the relation to the accelerator pedal height, not the relation to the clutch pedal