Measuring HTOB to determine need for spacer? (Page 2/4)
FieroGT42 MAY 29, 11:56 AM
That's very generous of you, thanks! I'll have to measure my PP to the flywheel to see if it works for me. I'll let you know.
trotterlg MAY 29, 01:07 PM
I can bolt it down to a FW with a disc in it to get a measurement, just not sure where to measure to, fingers to the flywheel surface? Larry
FieroGT42 MAY 29, 01:21 PM
Yeah, I measured from the transmission side of the fingers to flywheel surface.
trotterlg MAY 29, 05:23 PM
OK, with a clutch disc in it that measures .275 thick, the height from the flywheel face that the pressure plate bolts on to the top of the clutch fingers that the throwout bearing runs on ranges between 1.960 to 2.005. I laid a file across the fingers to measure at the edge where I could get to the flywheel face. Hope this works, would be really nice to find a pressure plate that would eleminate shims on this project. Larry

[This message has been edited by trotterlg (edited 05-29-2013).]

joshua riedl MAY 29, 05:27 PM
That seems pretty close to the measurements I was getting. I just ordered the spacer and the salesman said he only saw one part number and it happened to be .250", so I didn't say anything but I imagine any different thicknesses would take a conversation with more than a salesman.
fieroaddicted MAY 29, 06:27 PM


I am at this stage as well, so i am very interested. I will check later on tonight to see if i can come up with some #'s myself. I don't have my "new" HTOB yet, but the old one should do for some measuring. I'll see if i can figure it out. Although i am not 100% sure how you are coming up with a couple of the measurements. Maybe it will be clear when i look at it

EDIT: Opps i just re read the first post and realized it was being installed to a 2.8, not a 3800....guess my measurements would be different anyways.

[This message has been edited by fieroaddicted (edited 05-29-2013).]

fieroguru MAY 29, 06:35 PM
If my memory is correct, the Spec pressure plate for the 3800/F40 combo had the pressure plate fingers designed to extend past the pressure plate by some amount when the clutch was engaged. They were trying to make up the extra 1" of depth within the F40 by using the thicker camaro flywheel (un cut) and this pressure plate with extended fingers. The initial mockup didn't release the excess fluid in the HTOB and was off by 1/4" so spec made the spacer for that application, but it has been used numerous times on the F23 as well.

The pressure plate for the 3800/F40 combo might be the ticket for use w/o a spacer, but it might not clear the differential bulge or the fingers could be extended too far.
FieroGT42 MAY 29, 07:26 PM
My brain has fallen out and I'm wondering if my math is correct. I know the measurements are good though.

What stops the HTOB from over extending and blowing out if I don't have a pedal stop and happen to put my foot down too far?

And how do I measure for the pedal stop? Do I have to connect everything and carefully hit the pedal while I measure the HTOB?

[This message has been edited by FieroGT42 (edited 05-29-2013).]

trotterlg MAY 29, 07:36 PM
Never seen the system, but I would guess there is a clip that will not let the piston fly out of the system. Larry
FieroGT42 MAY 29, 07:41 PM
I haven't seen it apart, but then why are people blowing the piston seals all the time? Too much pressure because the master cyl is allowed to compress too far past the point when the slave (HTOB) is fully extended?

That leads me to the question of how much is acceptable, or too much, and still how far down to place a pedal stop. :/