Picture Request: Hydro Clutch Pedal Assembly installed

[Snoozer]

I've been chipping away at a SM465 swap when I have a spare hour here and there. I've got the Hydro pedal assembly in, but I'm afraid that my clutch pedal sits too high. When I go to push the clutch pedal down, my knee nearly hits my steering wheel.

I have a few theories behind why this is. But before I go into that, I'd like to see some pics of how your clutch pedal assembly looks in your truck. I've searched and found tons of pics and videos that show these pedals, but not "on purpose". But I CAN see that everyone's clutch pedal seems to "rest" higher than the brake pedal does. As a matter of fact, all 3 pedals (gas, brake, clutch) seem to do a progressive height increase; gas being lowest, then brake, then clutch.

Anyway, can someone please try to replicate these pictures on their truck for me so I can compare?

Thanks!

Taken from the Passenger side, camera sitting on the floor hump, pointed straight at the clutch pedal.

Driver side (obviously)

This is how the pedal sits with the Master installed on firewall, rod hooked to pedal. However.... there is no fluid in the system yet (master is still capped).

 

[dyeager535]

Unfortunately I cannot because I don't get home until it's dark.

But that does appear to be too high.

IIRC there is a rubber bumper that contacts the front edge of the clutch pedal "shaft" that would act as a stop, is that in place? Only piece I can really think of, although my first aftermarket master cylinder had an adjustable (threaded) shaft that might have affected pedal height.

 

[Snoozer]

an adjustable (threaded) shaft that might have affected pedal height.

Really? Hmmm. That just might be an option.

Here's the deal: Since my truck is a '76, it didn't have the dimples in the firewall to drill the holes for the master. But there was an existing hole already in the firewall that had an electrical junction that passed through the firewall. It just so happened that the hole was the correct diameter for the master to go through, and it was really close to placing the master in the same spot that I'd seen in other pics. So after mocking up the master in that existing hole; connecting the master rod to the pedal, and seeing that the rod looked to be centered and angled correctly, I ran with it. I only had to drill 2 small holes for the support rod studs to come through.

I met a fellow CK5 member this weekend, and he let me borrow a firewall template that someone else had cut off of a hydro truck. I overlayed it on my firewall yesterday, and here are my findings. I was CLOSE! But you know what they say about where "close" counts.

Now before someone points out that the upper-left grommet hole doesn't match up with the template's, I think this is proof that not all GM truck firewalls are the same from '73-up. Because if you look at the bottom-right corner of the template (just below where my screwdriver is pointing), you'll notice the corner edge of a contour that rests on the corner of the wiring junction box. I lined that corner up exactly, and also lined up the upper "shelf" contour above (really hard to see in the pic). There was also a screw hole near that corner that the screw that holds the junction box to the firewall from inside the cab. I lined that up too.

I then used a screwdriver to scribe where the template's holes are compared to mine. Here, I've circled those scribes for the mounting holes per the template. And I've labeled everything else. You can plainly see where the template wants the position for the master to be.

 

[nvrenuf]

Here's a pic of mine. All factory hydro parts in a '91 K5 (original auto truck) using the factory dimples.

 

[Snoozer]

John, thank you! You da man!

 

[Larry]

You might want to double check the master you are using. The first master I got from Napa (part number 39732) for an 85-91 truck did the same thing. The only thing I could figure was the rod was too long as the pedal would bottom out before it was even with the brake pedal. Sure enough, I took the m/c back and got another and the rod was considerably shorter and both were Napa pn 39732. Must have been misbuilt or missboxed. Double check the rod length. I’ll try to measure mine today for you to give you an idea of the correct rod length.

First master cylinder

Second master cylinder

Interior view of the master cylinder mounting. The support rods that fasten to the pedal box on one end house the studs for the master cylinder to fasten to on the other end.

 

[Snoozer]

Hey Larry!!

That's interesting about the Master pushrod length. And I too bought mine at Napa. I'll be sure to pay them a visit to see about different lengths.

Your pedal height in your 1st pic looks similar to mine. And yes, my pedal bottoms out too (hits the end of the master cylinder's stroke) before the actual pedal "shaft/leg" hits the rubber bump stop on the pedal assembly bracket.

I know about the support rods going through the firewall and fastening the master. Based on where I cut my firewall holes, I actually had to cut my support rods down by about 1/4" (and sleeve them), to correct the length.

I know.......










They wouldn't go through the firewall otherwise, because my master sits "too high" on the firewall by about 3/4".

 

[Snoozer]

...I’ll try to measure mine today for you to give you an idea of the correct rod length...

Larry, I would really appreciate that. I'll measure mine tonight when I get home, and I'll post it up.

 

[kyle.rj133]

Hey I recently just did this in my 76 but with a nv4500. I can also take pictures if you need/want. If I remember correctly my rod was also too long but it was threaded so I was able to adjust it.

 

[Snoozer]

That would be great! Yes, I would appreciate any pics you're willing to share.

Where do some of you guys find these master cylinders with adjustable pushrods?

 

[dyeager535]

Mine probably came from schucks (oreillys) back in the day. The replacement I bought since then isn't. It was apparently a random thing, I've never seen one advertised as being adjustable.

As Rockauto often shows pictures of their products from the various manufacturers, you might get lucky looking there.

 

[Snoozer]

I've beat Rock Auto to death looking at their pics. I've tried all kinds of combos of 85-91 trucks, K5s, and Burbs with different options to see if the part numbers change. No luck.

I'm either going to get lucky and find one with a shorter pushrod (as Larry stated), or someday I will patch the firewall and relocate the master cylinder where its supposed to be, or...... I'll live with a high pedal.


Kicking myself for not being more precise with locating the master. I even took tons of pics of Larry's Blue truck and his Polar Bear Burb in person when I went down there to pick up my SM465 from him this summer. Lo and behold, when I found the existing hole in my firewall (the electrical junction shown in Larry's pics, but mine's about 3" higher up), I ran with it. I did everything except make a template from a donor truck. From what I could see in every pic I could find, I determined that at best, I'd only be about 3/4" higher, which should only effect the support rods, right?? Wrong! Turns out, it makes the clutch pedal sit higher too. It makes sense when you think about it. I changed the geometry of the pedal when I effectively raised the mounting point of the support rods and master on the firewall. The actual master pushrod length doesn't change, so the result is that it pushes the pedal out more, because there's an angle involved between the master and the pedal.

 

[78SWB]

I'm a little late to the post but I just did this swap in my 78. I'll tell you I never want to do it again, that's how much fun it was. If I remember right mine kinda looked like yours and was sitting way out like that and after I started driving it, it became normal.

Here's mine as of now.

 

[78SWB]

Another

 

[dyeager535]

You checked the S10's and the '88+ C/K's? No idea what the firewall/pedal situation is, but it never hurts to look, and they are probably stocked locally so you can get your hands on them to compare.

 

[Snoozer]

Wow. This is more common than I thought it'd be. Lots of good recommendations from you guys, thanks! I'm going to compare some different master cylinders at some different parts stores (thanks Larry), and if I don't get lucky, I'm just going to run with how it is for now.

78SWB, I did have a thought that maybe the pedal would settle down a bit once there was clutch fluid in the system.

Yeah, this swap has been pain. Lots of cramped areas and tough-to-reach bolts, cut knuckles. I've heard others say that swapping the pedal assembly is the toughest part. We'll see about the rest. I have Larry's old SM465 sitting on standby right now. And I rebuilt and SYE'd a NP241. I just need an open 3-day weekend to git-r-done.

Thanks again for all the pics and recommendations, guys!


By the way, here's a shot of the existing "electrical-junction-firewall-hole" that I used. I still haven't figured out what those wires go to. I unplugged it and have since driven the truck and everything seems still seems to work.

Behind that corrugated wire loom hanging in the way, you can see where my speedometer cable passes through the firewall. If you look at Larry's post from inside his cab, you can see that his is actually located much lower compared to mine.

 

[Snoozer]

Thanks 78SWB. See, your clutch and brake pedals look almost level with each other. So strange to me there are so many variations.

You checked the S10's and the '88+ C/K's? No idea what the firewall/pedal situation is, but it never hurts to look, and they are probably stocked locally so you can get your hands on them to compare.

Actually no, I hadn't thought of that. That's another good idea.

 

[dyeager535]

Camaro's might be another one.

I kind of thought S10 or C/K when I got that "adjustable" one. Only thing I could come up with as to why the more expensive threaded portion was maybe some manufacturer trying to have one master that fit multiple applications, where all GM did was change the pushrod length. It wouldn't surprise me if GM used the same body, with just a different pushrod. It would have cut down on cost quite a bit.

 

[78SWB]

When I did mine, I just looked at tons of pictures of the master cylinders mounted and basically set the pedal assy up there and make some markings and drilled. Not the best way or 100% correct, but it worked.

I know for a fact my clutch pedal was out further than my brake pedal before I started driving it and now it seems normal. My pedal rod is not adjustable either. I got it from Napa.

 

[readymix]

I have the firewall from my truck on the side of my garage with nothing mounted to it if anyone needs photos, measurements, our a section cut out if it.