Measuring HTOB to determine need for spacer? (Page 3/4)
fieroguru MAY 29, 09:57 PM
If the pressure plate clutch finger positions the HTOB in the right place, then pressing the pedal to the floor does not provide sufficient travel to over extend the bearing.... no pedal stop required. My F40 swap uses a very similar (if not the same HTOB) and the stock factory clutch master and I can press the clutch pedal to the floor w/o over extending the HTOB. If you do want to restrict the travel, loosen the bolts holding the clutch master to the firewall and add some spacers to shim it further away... but if you do it right, this step isn't needed at all.

The older style HTOB (92-94) did not have any snap ring to limit travel, so they would just come apart. The F23 and F40 versions do have a snap ring or some other means of keeping the HTOB from over extending itself w/o any significant pressure, but the ring is easily overcome by pressing on the pedal. I have been running various HTOB transmission in swapped Fieros since 2005.
FieroGT42 MAY 30, 06:11 PM

quote
Originally posted by joshua riedl:
I don't know if you got that far but autozone had a 12mm x1.0 coupler that I'm going to braze to the hydraulics to hook up the stock line.



Just FYI, I got my part today and it fits. I'll post something as soon as I get the photos from my phone.
FieroGT42 MAY 30, 07:45 PM
http://www.fiero.nl/forum/Forum2/HTML/128722.html
FieroNate MAY 31, 01:45 AM
I have dimensions as well if you need them. I'll see if they match FieroGURUs. But those look like what you need. I've found its easiest to visualize if you draw it. I can post a diagram of the side view if you want.
FieroGT42 MAY 31, 07:41 PM
After some sleep, confirming that the "straight" edge I loaned out was returned to me as a wavy edge, and re-evaluating everything, I changed my numbers. I think I'm very close to where I need to be already, and a .25" spacer would leave only 0.08" for clutch wear and air gap.

Like I said, I'm new to clutches so if anyone would like to go over the logic of my math and the calculations, that would be great. BTW, I'd have to dig through some papers to confirm, but I think I'm already using a pressure plate intended for a Cavalier but supposedly compatible with a stock Fiero.

[This message has been edited by FieroGT42 (edited 05-31-2013).]

joshua riedl JUN 01, 07:02 AM
It is still .200" shorter than the stock clutch, using the numbers posted in another thread. And leaves .410" for extension. My guess is it will work but I accept no responsibility for that statement. A .250" spacer should leave .115" for clutch wear.
mcguiver3 OCT 13, 07:16 PM
Just saw this thread and have a question.
Can a HTOB spacer be fabricated with the appropriate thickness of steel washer welded to a piece of appropriately sized pipe to center and hold it on the bearing?
fieroguru OCT 13, 07:32 PM

quote
Originally posted by mcguiver3:

Just saw this thread and have a question.
Can a HTOB spacer be fabricated with the appropriate thickness of steel washer welded to a piece of appropriately sized pipe to center and hold it on the bearing?



Before you measure for your spacer, make sure the bleeder assembly is installed on the HTOB. The HTOB has a built in check valve that will trap fluid and not give you the right fully retracted dimension.

The face needs to have a radius on it so that the edge of it does not make contact with the middle of the clutch release fingers once they break the transition from convex to concave. Besides that, there are lots of ways you can make one. Some people even use a junk HTOB assy and cut the cylinder part off so they can shim the base of the HTOB from the transmission (the HTOB has the input shaft seal). Here is a picture of the F40 HTOB removed.

[This message has been edited by fieroguru (edited 10-13-2014).]

mcguiver3 OCT 13, 07:58 PM
Great info.
I think I will try to fabricate the spacer.
It looks like I need something in the .275 range
Raydar JAN 18, 02:54 PM
Bumping this, since it's been buried for a while. Good info.