Captain Obvious

In my experience, your expectation is not valid. If that thing was completely open, your idle would be at 4000 RPM. That opening you've got on that one should be plenty to raise the idle to a high "cold idle" level. The important part is that it completely closes when hot, or the idle will stay high. Mine went intermittent. Sometimes the idle would slowly creep up to cold idle level even after the engine was warm. And then it would slowly drop back down as connection was made.

Thanks for the link. I'm hoping that I don't need any adhesive at all since the bushings are slip fits on the shaft, but I'm just not sure what's going to happen as things heat up, age, wear, and get dirty from being on the road. I consider the glue "insurance". I did put those adhesive grooves in the bushings and also roughened up the surface with sandpaper before final install. Trying to give the JB weld something to bite onto.

I just had a headergasm.

A while ago, I was looking into an issue where my idle would hang a little because the throttle body butterfly would not always return to fully closed. The puzzling part is that it always closed just fine with the engine off and it only got sticky when manifold vacuum was present with the engine running. Reference old thread about it, but that old thread never really got to the bottom of it: http://www.classiczcars.com/topic/45152-sticky-throttle-body-hanging-idle/#comment-409180 My solution at the time was to simply add an extra turn to the throttle body return spring and that extra spring force overcame whatever was causing the stick. Worked, but not really the right way to fix it and I always wanted something better. So this off-season, I pulled the throttle body off again to do some more investigation. I believe I have traced the sticking issue to worn through chrome plating on the throttle shaft exposing the softer steel beneath, and that softer steel doesn't slide as well against the pressed in bushings pressed of the throttle body. Even though everything seems to move just fine with the engine off, I believe the friction between the worn shaft and the bushings is amplified when the two of them are forced together by manifold vacuum causing the hanging idle. After considering several different approaches to fixing the issye, I decided to try replacing the original steel throttle body bushings with Delrin. The thinking was that Delrin is a naturally slippery material and the hope is that it won't stick to the exposed steel of the shaft. Also, while I was in there, something else I wanted to improve is that with the original design - The only thing locating the throttle butterfly plate within the throttle body bore is the butterfly plate itself (just like the carbs). In other words, when the throttle is closed, the butterfly plate should self center within the throat because the walls of the throttle body bore will contact the brass butterfly and move it into the center. But when the butterfly is opened, the plate is free to move back and forth a little within the bore. This results in scraping against the internal walls and wear on the walls and butterfly. I was thinking that I might be able to come up with a way to incorporate shaft locating into a new bushing design. So with all that as background... I started with this: I ran a tap into the original bushings and pulled them out: Here's the original steel bushing and the new Delrin bushing for the side where the throttle linkage attaches. The larger diameter lip section keeps the throttle butterfly from moving too far in one direction: Here's the linkage side in place. You can see how the lip is sandwiched between the linkage and the body casting to take up the side-to-side slop and acting as a thrust washer in the inward direction. The other end will address the play from the TPS direction, but this is half the battle won: And here's the concept I came up with for the TPS side. I turned a groove on the throttle shaft to accept a spring clip, and made a stainless steel "D" holed thrust washer to run against the outside of the bushing. These features are what prevent the throttle shaft from moving in from this direction. With the combination of the two limiting features, the throttle plate is now locked centered in the middle of the throttle body throat bore. This side was more of a PITA because there is very little room to work with since everything has to be hidden behind the TPS: This is what the TPS side looks like when installed. Spring clip limits motion in the inward direction: Here's the two new bushings on the throttle shaft to show how they work: A little epoxy to keep the bushings from spinning in the throttle body casting (that's what the grooves are for). Not much sticks to Delrin (including epoxy), but it doesn't need to stick well. Just enough to make sure the shaft spins withing the bushing instead of the bushing spinning within the body: And a little blue thread lock on the butterfly screws: It's all put back together and back on the car and I'll post the final results after the salt is off the roads!

Too late now, but forgot to mention it before... I was in HD and Lowes this past weekend and both of them have plenty of muriatic acid on the shelves. I thought of you when I saw it. NJ may not have it, but you can still come across the bridge to get it.

Haha!!! I like it! A friend of mine suggested that I get my wife a new milling machine for Valentine's Day.

Cool. So they moved that hole. Wonder why. Anyway, glad you're back on the road. I've got a couple months to go yet before they stop salting the roads up here.

And before I forget... I'm planning to cut another vent passage into my aluminum spacer as close to 6:00 as I can. I just rebuilt my booster and even remade some of the internal parts out of stainless, but I don't want that thing to ever suck brake fluid again. Getting that thing apart and together again is not something I plan to make a habit out of!

Yup. Just the tip. As for the o-clock positioning of the vent, I was remembering incorrectly and talking earlier as though the vent passage was in the aluminum spacer, and it's not. My vent passage is not in the aluminum spacer, but is stamped into the booster clamshell. Mine points right at the vacuum hose connection which is in the same place as the one in your pic (mine's a 77). So the bottom line is that my vent hole is at maybe 4:00?

I haven't messed with any of that stuff so I don't have any experience, but I agree that seems a little hokey. With a little web searching, however, it does seem that's the "accepted" solution, and I didn't see any records of failures. Do you know if the Timeserts hardened? Other than the obvious (and expensive) solutions of boring and rethreading or sleeving the entire hole, one other idea instead of epoxy would be to turn (and maybe even thread) some aluminum spacers to take up the gap? Loctite to hold them in place in the upper portion of the recess?

Hmmm... Maybe Klingon? SoHvaD Hija Ha'DIbaH. Qapbej maj.

Yup. I got it. I didn't pay attention to the polarity at the time so I don't know if I got it right, but here's what the reluctor output waveform looks like:

I wouldn't be surprised if the cutter is carbide (which is brittle).

My thoughts on the subject... First, I would be careful with lithium grease on the master cylinder output shaft. A very little bit right on the very tip would probably be OK, but you don't want any of that stuff to come in contact with the vacuum seal that rides on that shaft. I wouldn't want to assume that rubber seal is compatible with that grease. I think a better choice would be silicone based brake grease. Something safe for rubber seals. As for sealant on either of the seams between the parts... I don't think sealant is necessary on either of those seams, but a little sealant between the M/C and the backing plate won't hurt anything. And some sealant between the backing plate and the front side of the M/C clamshell won't hurt anything either as long as you don't block the vent passageway. My read on that vent passage is that it does two things: First, it allows for the change in volume in that (otherwise sealed) cavity when the brakes are depressed. If not for that vent, when the volume inside that cavity were to change, the pressure would change as well. That vent keeps everything at atmospheric. Second, that vent acts as a drain for brake fluid out the hole in the event of a rear M/C seal failure. It would be best if it drains before that fluid ends up inside the master cylinder, but clearly from the amount of fluid inside my failed booster, that's not always the case. One last thought... If that vent is to act as a drain, it would be pointed down, not up. I don't know if it's the original position or not, but mine was pointed at the 5:00 position, not the 11:00 position. Do you think yours was stock original position at 11:00?

Wow. Well that really sucks. I've seen your skill in the other work you have done, so I know it's not an ability issue. Thanks for the warning, and thanks for taking the leap so the rest of us didn't have to.

I don't think any 260 used points. I believe all the 260s (both early and late) used the electronic ignition with the reluctor pickup. If you can't find a proper distributor, you should be able to bypass the TIU and connect the points directly up to the coil like they did for 70-73. Another option? I haven't tried it or researched it, but I bet anything from 74-78 would work (as they're all reluctor pickup). The advance curves might not be "right", but I bet they would "work".

I love the look. It's a view of a Z that I've never seen before. Have you considered clear coat only and do the DeLorean thing? Couple (real) questions: 1) Would the paint guys consider the clean metal surfaces "ready to paint" or would there be additional clean-up that would need to be done? Just a wipe down with solvent, or something more labor intensive? 2) How long do you think you have to get paint on there before things start rusting? I know that in my garage it only takes a day or two for surface rust to start on completely clean surfaces. I'm guessing that the pickling solution in the third tank applied a rust preventative coating of sorts? 3) Do you really think the solder melted? Do you think the bath(s) were that hot?

It's true. So this coming Saturday is going to be mid-sixties and mostly sunny. Great Z weather...

I'm probably the last person on the planet to figure this out, but I was thinking some more about the geometry of the plastigage and what happens when you crush it. As you decrease the thickness and extrude that material into additional width, the change in width is non-linear. The amount that the width changes will go up faster as the thickness decreases: You can see this phenomenon in the reference stripes on the plastigage package. I'm sure you already knew this, but for example, that's why the width change between .003 and .002 is much smaller than the width change between .0015 and .001. I do have a point though, and that point is that you are much closer to .0015 than you are to .002. Still within spec though, so the binding is curious. Of course, the whole spec is only applicable to a crank that is perfectly round, a rod that is perfectly round, and bearings that are perfect consistent thickness in every location. Any high spot or oval anomaly anywhere could miss the gage, but cause the bind. It's too bad they haven't come up with a plastigage that allows you to spin the crank WHILE the plastic is in there and still get an accurate reading. There's a product idea for you. Not that it matters now, but I assume you tried that rod in other locations and the issue followed the rod? I also assume you tried swapping the rod bearings around and same thing. Didn't follow the bearing, but followed the rods? About a torque spec for the force required to spin the crank, I'm not aware of anything.

Cool. Thanks. I don't know how it hooks into the temp lever yet as my non-AC control head doesn't seem to have provisions for attachment, but I'll figure something out. So they used that device to regulate the evaporator temperature by turning the compressor on and off? So what are you going to do about your vacuum test results? You going to replace the compressor front seal and see what happens?

I agree with the assessment about the plastigage. How far out were those two rod ends? Couldn't have been much! So how was it when you turned the crank with (almost) all of the pistons in there moving up and down? The hiss of the new tight rings sliding across fresh sharp crosshatch? Exhilarating? Give you chills? All this talk about bore measurement and the like... Reminded me of this old guy resting in the bottom seldom used recesses of the toolbox. I don't know when was the last time he was pulled out for any reason other than to just admire him:

Here's my evaporator from the 74. I assume the thermostat you were talking about is the device on the lower left of the pic? I assume this is the thermostat you were talking about:

Haven't put it in yet (obviously), but... Normal position with button pushed down (switch closed and the pump will run): Give it a knock on the palm of the hand, and popped (button up):

They look great. Did you put heaters in? I took pics of one of my seats earlier today. I'm guessing you figured out which side was which and don't need pics anymore?

That's fricken awesome!!! Can I bring you my car???