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rcb280z

Needing a 77 Throttle body complete.

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Looking for a throttle body and bcdd complete. A working bcdd. Long story short. I developed a vacuum leak at the bcdd that caused a 2500 rpm idle. After many attempts to repair, what I thought was wrong, I ended up installing a block off plate. Can't leave it that way, won't pass emissions. It has to be either a 77 or 78. These have 2 vacuum ports on the throttle body where 75-76 has one vacuum port. One port is for advance timing and the other is for the egr system. Hopefully someone has one. Here's a couple pics

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Edited by rcb280z

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Hmmm. Other things to consider...

In the later (latest?) years, 78 I think, they stopped putting the altitude correction nubbin at the bottom of the BCDD. Probably except for CA. So I don't know how detailed your visual inspection is, but you might need one from 77 or one from a CA 78 car. The final version still has an adjustment screw underneath, but doesn't have the bellows inside for altitude correction. Seems like the kind of thing that every state except CA would not have let them get rid of.

There's one of those stubbier BCDD throttle bodies sans altitude correction for sale right now in this thread:
https://www.classiczcars.com/forums/topic/61556-280z-oem-parts-fuel-ignition-door-stuff-grill-etc/

DSC03982.JPG

Other thoughts? Again, not knowing how rigorous your CA inspection is, but the energetic Z owner could be able to disable the BCDD internally and prevent any leaks while still having it appear externally as though it's fully functioning.  Not that I would encourage such behavior, but if it's a trade off of selling the car out of state or driving it...     :ph34r:

 

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The FSM says you should be fine with just replacing the BCDD.  No need to do the TB too.

image.png

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50 minutes ago, Zed Head said:

The FSM says you should be fine with just replacing the BCDD.  No need to do the TB too.

image.png

Yes long ago you could just remove the bcdd but due to age the gasket is extremely brittle and almost disintegrates when separating the two. I have tried on 2 others that's why my request. 

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6 hours ago, Captain Obvious said:

energetic Z owner could be able to disable the BCDD internally

This will increase Hydro Carbons and you could possibly fail emissions. 

The block off plate does the same thing with one other mod. Really simple. But I did this so I could still drive it. If I were testing emissions right now I would fail visual or HC's or quite possibly both.

Edited by rcb280z
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Looks like I have one coming, already! I thought it was going to be harder to find.

Our good friend Wayne (wal280z) is shipping one out to me for just postage! 

Will post results and may even, time permitted, open up the entire non working bcdd to see what I can find. And just for fun.

There is another thread on it but I want to open mine up to compare.

Edited by rcb280z
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51 minutes ago, rcb280z said:

This will increase Hydro Carbons and you could possibly fail emissions. 

The only time the BCDD does anything to decrease emissions (reduce HC) is when you are coasting and have a high intake manifold vacuum. So unless they measure the HC while they are decelerating driving the car, or blipping the throttle and seeing what the HC's do while the RPM's are coming back down to idle, then the BCDD won't make any difference to your emissions test. Under steady state conditions like idle or 30mph steady cruise, the BCDD doesn't do anything and has absolutely no effect on performance or emissions or anything at all. Under steady state conditions, it's just a closed valve.

However... Don't get me wrong. I'm a tree hugger at heart and am glad to hear that you are proceeding with a plan that keeps your BCDD intact. Just clearing up some of the technicalities about the operation.

Oh, and Wayne is the man.

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Yes CO that is what they do, measure while on the dyno. They spin the drive wheels at 15 mph and at 25 mph in the smog test. And I have a complete understanding of its, the bcdd, operations. Or at least I claim to. I appreciate your expertise for sure.

 

 

Edited by rcb280z

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I can just make out a raw fuel smell when coasting now. I didn't have this before. That extra air entering the intake is no longer there while coasting. I would have that with a working bcdd.

Edited by rcb280z

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6 hours ago, rossiz said:

PS: The SU’s are still performing beautifully...

I love the su's. Ran them on my 280 when I was in Nevada. Never had any issue with them.

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18 hours ago, rcb280z said:

I can just make out a raw fuel smell when coasting now. I didn't have this before. That extra air entering the intake is no longer there while coasting. I would have that with a working bcdd.

Yup. that's the exact situation where the BCDD is supposed to help, not steady state on a dyno. The BCDD will also help reduce the amount of oil pulled past the rings and valve seals when the cylinder vacuum goes up when you let off the gas and the intake manifold vacuum spikes. Especially on a worn engine.

On my first Z with it's worn out engine, I used to get a terrible eye-burning blast when I completely let off the gas at very high RPMs. I believe I have a much better understanding of the system now, and looking back, I don't think my BCDD was doing anything. That extra rich mixture (too rich to burn), combined with a whole bunch of oil getting pulled past worn surfaces produced a bird dropping cloud of unburned HC's.

I was a new work force entrant then just trying to get to work. Now I'm a tree hugger.

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29 minutes ago, Captain Obvious said:

I was a new work force entrant then just trying to get to work. Now I'm a tree hugger.

Exact reason why I'm replacing mine.

 

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