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Hey hows it going. I just picked up a 1981 280zx. Im really stoked. Ive been missing having a z car since my last one got stolen. My last z car was a 71 240 z with a 4 speed, high comp big valve fi head and dual round top su's. Any ways The 280z i just picked up is fuel injected. It runs but it seems to have a dead cylinder. I am familiar with fuel injection but id rather just convert to a 4 barrel set up instead of endlessly tinkering with the 23 year old fuel injection system. has anyone here converted their 280 to a 4 barrel? I was just wondering how the performance of a 4 barrel would compare to dual carbs? Thanks... Andy
 

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It will cost the same, about $600 to get a new manifold and a new Holley 390($280 manifold, $300 carb kit, $20 cable). It will cost about $600 to get new injectors, pump, FPR, hoses, etc to get the EFI all back up to new. Tinkering is now zero on my EFI system for the past 2 years.

Having done both, the EFI is smoother and got better mileage. I did not use a dyno but power seemed very close either way you go. The carb sounded better.

mark



Post Edited (Oct 4, 1:26pm)
 

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Discussion Starter · #3 ·
Yeah. the fuel injection is good stuff. I just like the intake roar of a carb set up. Another thing that has been floating around in my mind is how restricting the fuel injection afm and throttle body are. I hear this is the reason why 280zx's seem to run out of steam around 5500 rpm. I am also planning on intstalling a header, 2.5 inch exhaust and a cam. I am looking for a power band that goes out to about 6500Rpm. I think the carb set up would be better for me. Nothing beats a rough lopey idle.......
 

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I'd go with dual SU's rather than a 4bll.
 

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i wish you could hear and drive my 260Z . it has a built 83 engine in it with all the goodies. it also has the arizonazcar 4 barrel manifold with the holley 390 carb.
cam, lightened flywheel, MSD ignition and exhaust to go with it.
it revs and runs like mad!!
makes power to 7k .
i cant say enough ........im very happy with this set up .
 

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"Carbs are just a semi metered fuel leak. Stick with FI."

Yeah and FI is just an electically metered fuel leak.

If you want to make power in the 6500 rpm range then you will need a cam. The cam is the reason power drops at 5500 rpm, the intake system be it EFI or carbs are very capable of flowing the needed air.

The problem you will run into with the stock EFI is the factory fuel and spark tables are designed around the stock cam, they provide very little fuel over 5800 rpm. You as many have found would need to upgrade the EFI system to meet your goals. Carbs on the other hand are very adjustable and much eaiser for the common mechanic to adjust. I've yet to see at car shows, race tracks or people on this site running stock EFI and making power over 6000 rpm, and I'm talking about still building hp not simply "yeah it revs to 6000 real easy" I've also yet to see anyone actually tune a factory EFI computer, read some of JeffP's trials, even the programming from JWT is very hard to get and less than optimal.

The only real problem I see in converting a EFI car to carbs is future emmissions testing. I have 2 Z's that I'm going to have to unregister or swap EFI systems back into just so I can drive them legally.

Matt
 

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Actually the problem IS the stock EFI manifold. I went with SDS computer, turbo injectors, hot cam, high compression and still the engine felt weak at 6000+ and this was with a 60mm TB with the opening to the manifold ported. It would turn more, but like you said, wasn't making any real power up there. I then installed a custom large runner EFI intake and the difference in top end power was night and day. Now it runs at least as stong as a car with triple webers

I've replaced the stock EFI with SU's and the difference in top end power is substancial. Just look at the difference in runner size between the two. I wanted to keep EFI but in the long run it did turn out to be an expencive way to go.
 
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