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Reptoid Overlords

Intake manifold interchangeability.

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For a great price(a few beers)I have acquired this intake manifold from my friends '76 280z. It was in use before he changed to carbs. He says he bought it from a guy who said he got it from California Datsun. Who knows.

 

What I like about it is it is perfect for deleting all of the rats nest items I plan on deleting along with my engine build.

 

Will the fact that this manifold has capacity to move a higher volume of air affect anything when installing to my P79? I will be using my stock ECM along with stock cam and all EFI componets. 8b1212ccdd9203ee50a9be6216d85dac.jpg

 

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If you do anything to improve air flow and volume, you will need a new ecu...
But that is a great way to improve performance. Especially if you add a Borla TWM throttle body and port match the head and intake.
f8baa0997505da7871c50ab89ea866fe.jpg

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49 minutes ago, Reptoid Overlords said:

Will the fact that this manifold has capacity to move a higher volume of air affect anything when installing to my P79? I will be using my stock ECM along with stock cam and all EFI componets. 

Are you assuming that the larger plenum will flow more air?

Your throttle body will not fit if it comes from a 280ZX intake manifold.  They're different, the ZX TB's and manifold opening are smaller.

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I guess I'm not expecting to gain better performance, more like avoid unwanted, adverse affects.  I'm mainly interested in cleaning up the engine bay.  Looks like it's a moot point though, as I do have a ZX TB.  Haven't attempted to fit one on it..it does still have the TB from the previous owner's '76 280 though.. 

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The 76 throttle body is still pretty puny. If you’re looking to gain air flow and performance you will not be able to run the stock ecu...

Negative effects of the ZX intake? Not tracking.

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Careful folks. Consider carefully before changing major EFI components without having any control over the stock ECU to adjust fuel and AFM response curves to match. Larger throttle bodies without other corresponding changes will do little but reduce air velocity into the AFM. That flap that gets pushed around responds to air velocity....  

Edited by zKars
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I've been musing about the same thing. I will hopefully have a F54/P79 combo in my car sometime in the not too distant future and I've been thinking about how I will dress the motor when it's in there.

I could redress it as a 77 using just the block and head. That would use my original throttle body, intake manifold, and ECU.
Or I could bring over the entire system from 83 including the ECU. The biggest thing there is that I would need to incorporate an O2 sensor.
Or I could do something hybrid like use some of the 83 parts (like the intake manifold) but keep the original 77 ECU and wiring.

As far as interchangeability goes for the intake manifold... I compared 77 and 83 intake manifolds and throttle bodies, and I believe they are interchangeable. Mounting holes are in the same spots and the diameters of the airflow ports are the same. The throttle butterfly plate is the same diameter and all that, so I don't think there would be any problem mixing and matching them. I don't think the ECUs would know the difference between any of them.

The BCDD for 83 does not reside on the throttle body, but is separate and located on the underside of the manifold. So if you're mixing and matching, you would need to pick one. The only other complication I could find was that the inlet side of the throttle body where the ducting connects is a little smaller. It's the same ID so there's no functional change, but the OD is a little smaller. Not the end of the world, but something you would need to address.

I don't know about other years, but that's what I found when comparing 83 to 77.

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My mistake on the TB fitting.  It must have been the hoses between the AFM and the TB that I was thinking of.  The ZX hose and TB inlet is smaller.  I thought that there was a bolt pattern issue but apparently not.  p.s. edit - although I do also vaguely remember a throttle linkage problem.  Worth double-checking, but kind of pointless if you have the other parts.

Just like when swapping any of the EFI parts there's always a way to make it work.  It's a crude system.   The engines all have about the same power from 75-83.  

Edited by Zed Head
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I would stick with the 76 throttle body. The ZX butterfly is smaller and will restrict flow a little.

Years ago there was a modification with a 60mm throttle body and the AFM from a toyota cressida. You had to solder the 280Z electronics into the toyota unit. A resistor in the temp sensor wire allowed you to, all be it little, adjust the ECU to compensate for the extra air flow.

Tip: If you do these changes to a running engine. Check the performance before making the changes.

The way I do it is this.

- Pick a quiet road where you can safely drive up to 70 mph.

- Drive in 4th or 5th gear at 25mph and accelerate to 60 or 70 mph. Don't change gear.

- Have someone video the speedo and tacho while you do it and plot the values against time (seconds) in excel.

That will give you a performance curve you can refer to after you do the mods.

 

 

Edited by EuroDat
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19 hours ago, EuroDat said:

The ZX butterfly is smaller and will restrict flow a little.

I measured them yesterday and I do not believe this is incorrect. I believe they are the same size.

I'll check again if I get the chance today to confirm for positive sure.

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@Reptoid Overlords, do you have all the ZX parts including the wiring harness and ECU? Or just the mechanical stuff?

I wouldn't assume that the ZX intake manifold "has capacity to move a higher volume of air". In fact, might be a fallacy, but I would like to believe that the years of additional research, testing, and development would result in improvements in the overall design. Other than the lack of EGR, what is it about the 76 intake manifold that piqued your interest?

My car is a 77, and the ZX system I have is from 83. A whole lot happened in the world of technology in those six years. Might be wishful thinking, but I would hope that the 83 system is "better"? Possibly? Maybe?

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So I double checked my measurements on the 77 and 83 throttle bodies, and they're the same ID. They are both 2 in. ID.

77 throttle body:
P1150483.JPG

83 throttle body:
P1150482.JPG

The only significant difference I could find was the OD of the input side. 77 OD on the inlet is 2.35 inches OD and the 83 OD on the inlet side is 2.20 inches OD. So the original 77 ducting would be too big, but the inside diameter is the same.

I also re-checked the mounting holes, and they are in the same spots. No difference there.

And I didn't take any measurements on the location of the throttle linkages, but to the naked eye, they look the same. 77 on left, 83 on right:
P1150492.JPG

 

 

 

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Put them on the manifold and check functionality.

I wonder if there are different versions of the ZX TB's.  I spent some time looking at this same type of project and remember finding more reasons it might not work.  My TB came a from a 1981 280ZX 2+2.  I was using a 78 TB to compare.

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[mention=31744]Reptoid Overlords[/mention], do you have all the ZX parts including the wiring harness and ECU? Or just the mechanical stuff? I wouldn't assume that the ZX intake manifold "has capacity to move a higher volume of air". In fact, might be a fallacy, but I would like to believe that the years of additional research, testing, and development would result in improvements in the overall design. Other than the lack of EGR, what is it about the 76 intake manifold that piqued your interest?

My car is a 77, and the ZX system I have is from 83. A whole lot happened in the world of technology in those six years. Might be wishful thinking, but I would hope that the 83 system is "better"? Possibly? Maybe?

 

I have all of the equipment, both electrical and mechanical, to direct transfer all items from my completely intact 1980 manifold over to the 1982 P90/F54. Minus the ECU. Budgetary constraints prevent the purchase of standalone EFI. In other words, I'm using my original 1980 ECU.  

I liked the idea of the earlier manifold because it does not have all of the connections and lines and EGR equipment, so cleaning that area up seemed easier and more tidy with that manifold. Aft of the throttle body, the cavity that runs forward to aft along with the car, is wider than the 1980 manifold. Meaning more air must go in there before moving through the 6 individual passageways to the intake ports on the head. Perhaps this means nothing.

 

My concern is that this will cause problems I can't foresee, such as the ECU leaning or richening it out, or something to that effect.

 

I can transfer everything over directly and know it'll work, or clean it up for looks and maybe end up with some poor running condition.

 

Or I can just clean up and delete things from my 80 manifold.

 

 Edit: I don't have the 1982 ECU. Just my original 1980 ECU.

 

 

 

 

 

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Gotcha. Well I don't have any idea if the two manifolds flow the same, but I "try" to believe that the later manifolds are the same or better than the earlier ones. One thing to think about is that by the time you get to the rear part of the manifold, you're only feeding one cylinder, so maybe the fact that the ZX version tapers down at the rear doesn't have much impact.

Or... Maybe it just makes the bean counters happy because it lowers the car's weight ant takes less aluminum to produce. Maybe that's why it's "better".

Not being an expert at all in the field, my gut tells me that you won't notice any change one way or the other. My non-expert advice is to use the one you think looks better. At the performance level of these engines, I doubt there's much performance impact.

So does your 80 ECU use an oxygen sensor? That hadn't been incorporated yet, had it?

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Mine was built in November of 1979, a few months before the O2 sensor got Incorporated. I plan on getting some headers from MSA, and welding the O2 bung closed.

I appreciate the replies on this. I have a few months to decide what I'll do. All the big things add up, but the little things like head bolts and hoses and exhaust manifold studs and injector holders and seals all add up quick.

I need a second job to feed the sickness haha.

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Don't weld anything shut. Just use a threaded plug. You never know if you'll want that O2 bung some time in the future.

Yeah, all the bits and pieces add up. Good luck with the project!

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I would want the O2 even if it was to just feed a gauge. Makes diagnosis much easier

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2 hours ago, Captain Obvious said:

Don't weld anything shut. Just use a threaded plug. You never know if you'll want that O2 bung some time in the future.

Yeah, all the bits and pieces add up. Good luck with the project!

To be specific - Use a threaded plug with a good coating of anti-seize. Otherwise, it's likely that you are still welding up the O2 bung.

I'm pretty sure I used anti-seize on the bung for my headers, and I still had a bear of a time removing the plug.

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