The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Hyd throwout bearing ... and clutch pedal effort, in general

markeb01 · 01-16-2011, 05:19 PM

I had a factory hydraulic throwout bearing on our 1986 S10. When it failed, it wiped out the clutch and cost $750.00 in repairs (I was going through a divorce at the time and didn’t have any place to work on it myself). That experience deterred me from wanting hydraulic fluid inside the bellhousing when I put the 4 speed in my 60.

Since a hydraulic clutch is normally designed with a one-to-one ratio between the master and slave cylinder (both being the same size), theoretically the only reduction in pedal effort should come from the elimination of friction in the mechanical linkage. However when I was researching what to do on mine, I met a guy with a 33 Dodge sedan with a hydraulic throwout and he offered to let me operate his clutch, which I could easily cycle with hand pressure. So perhaps there are other dynamics in play.

I decided to go with a Novak slave cylinder designed for a Chevy V8/Jeep conversion combined with a Wilwood master cylinder. After a bad experience with the Master Power Brake clutch master cylinder setup, I designed my own firewall reinforcement plate and mounted the master cylinder directly in front of the factory pushrod lever. Installing the clutch master cylinder at the same height on the firewall as the original master cylinder, maintains the correct pedal ratio and piston travel. The Master Power Brake bracket mounts the cylinder too low, requiring some type of Z shaped link to connect it at the factory height on the clutch pedal, or the pedal ratio will be off and/or risk blowing out the master cylinder from bottoming out.

Here’s what my setup looks like:

Quite by accident I used a ¾” master cylinder connected to a 7/8” slave cylinder. This decreases pedal pressure at the expense of travel, in effect providing a “power” clutch. This arrangement releases completely, so I’ve never bothered to correct it. If I were to change the slave cylinder to ¾”, I could lower the pedal closer to the floor for convenience, but this would also increase pedal pressure. Since it works perfectly I’m leaving it as is as I prefer the easier clutch operation.

For the slave cylinder I purchased a Novak kit designed to install a Chevy V8 in a Jeep:

http://www.novak-adapt.com/catalog/kit_hcrc.htm

It’s relatively expensive, but works perfectly and is easily adjustable.

The Wilwood master cylinder can be seen here:

http://www.summitracing.com/parts/WIL-260-1304/

For a clutch set I chose the Centerforce 1 to keep the pedal pressure low, while retaining excellent clamping force. Unfortunately the pressure plate suffers from “weight rattle” during shifting, and I would not recommend this product for a street driven vehicle. I find the rattle very annoying.

01-16-2011, 05:19 PM	#2
markeb01 Senior Enthusiast Join Date: Feb 2007 Location: Spokane Valley, WA Posts: 8,356	Re: Hyd throwout bearing ... and clutch pedal effort, in general I had a factory hydraulic throwout bearing on our 1986 S10. When it failed, it wiped out the clutch and cost $750.00 in repairs (I was going through a divorce at the time and didn’t have any place to work on it myself). That experience deterred me from wanting hydraulic fluid inside the bellhousing when I put the 4 speed in my 60. Since a hydraulic clutch is normally designed with a one-to-one ratio between the master and slave cylinder (both being the same size), theoretically the only reduction in pedal effort should come from the elimination of friction in the mechanical linkage. However when I was researching what to do on mine, I met a guy with a 33 Dodge sedan with a hydraulic throwout and he offered to let me operate his clutch, which I could easily cycle with hand pressure. So perhaps there are other dynamics in play. I decided to go with a Novak slave cylinder designed for a Chevy V8/Jeep conversion combined with a Wilwood master cylinder. After a bad experience with the Master Power Brake clutch master cylinder setup, I designed my own firewall reinforcement plate and mounted the master cylinder directly in front of the factory pushrod lever. Installing the clutch master cylinder at the same height on the firewall as the original master cylinder, maintains the correct pedal ratio and piston travel. The Master Power Brake bracket mounts the cylinder too low, requiring some type of Z shaped link to connect it at the factory height on the clutch pedal, or the pedal ratio will be off and/or risk blowing out the master cylinder from bottoming out. Here’s what my setup looks like: Quite by accident I used a ¾” master cylinder connected to a 7/8” slave cylinder. This decreases pedal pressure at the expense of travel, in effect providing a “power” clutch. This arrangement releases completely, so I’ve never bothered to correct it. If I were to change the slave cylinder to ¾”, I could lower the pedal closer to the floor for convenience, but this would also increase pedal pressure. Since it works perfectly I’m leaving it as is as I prefer the easier clutch operation. For the slave cylinder I purchased a Novak kit designed to install a Chevy V8 in a Jeep: http://www.novak-adapt.com/catalog/kit_hcrc.htm It’s relatively expensive, but works perfectly and is easily adjustable. The Wilwood master cylinder can be seen here: http://www.summitracing.com/parts/WIL-260-1304/ For a clutch set I chose the Centerforce 1 to keep the pedal pressure low, while retaining excellent clamping force. Unfortunately the pressure plate suffers from “weight rattle” during shifting, and I would not recommend this product for a street driven vehicle. I find the rattle very annoying.