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I see all these guys running carbs more so than I do turbos lately, and so I inevitably have a question. Can I make more horsepower/torque running carbs (like triple webbers or triple mikunis or the ones that look like ITB's) than I would on my fuel injected l28e? Is there a conversion kit of some kind or an easy way to do this? Also, I heard that a carburreted engine has this kinda different growl to it. Is this true? I mean to tell you guys the truth, I know nothing about carburretors, I don't even know if I'm spelling it right, but I do know that the muscle cars of the 60's and 70's did have a different sound to them than the fuel injected cars of now, and I do know that the right carb will make power on some engines...

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I see all these guys running carbs more so than I do turbos lately, and so I inevitably have a question. Can I make more horsepower/torque running carbs (like triple webbers or triple mikunis or the ones that look like ITB's) than I would on my fuel injected l28e? Is there a conversion kit of some kind or an easy way to do this? Also, I heard that a carburreted engine has this kinda different growl to it. Is this true? I mean to tell you guys the truth, I know nothing about carburretors, I don't even know if I'm spelling it right, but I do know that the muscle cars of the 60's and 70's did have a different sound to them than the fuel injected cars of now, and I do know that the right carb will make power on some engines...

 

if you dont know much about carbs, i wouldnt run them, i would think a triple set up would require some tuning of the jets and etc. Then again i dont know much about carbs either......

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The stock injection is pretty bad as far as airflow goes. I think that AFM is a pretty big restriction and the TB might be a bit on the small side too. Plus the stock cam doesn't really give the L6 the rpm range it deserves.

 

Just slapping a set of triples on clears up all of those intake restrictions, but it isn't going to make your engine that much more powerful in and of itself. The triples breath well and make power at high rpms but you'll trade off some low rpm driveability. The cam as already stated isn't right to rev really high, so now you have an induction system that wants 7000 rpm and a cam that doesn't really want to go there. Plus you've now got to tune the carbs, which is not easy for some. The whole system works better when the engine and exhaust fit the triples. Triples work better on a car with higher compression, big cam, exhaust, etc.

 

Just slapping triples on may gain some peak hp, but it's going to take some time to tune, a lot of money for the carbs and manifold, and you will LOSE all the advantages of FI, low speed driveability, mileage, etc.

 

Here's a short clip to get an idea of the sound: http://album.hybridz.org/showphoto.php?photo=1562&cat=509&page=1

I LOVE the way they sound. You can really hear the engine open up and swallow air when you're at WOT. The engine I had in the car at the time of that video was 8.3:1 compression and medium cam. My Z has a LOT more bottom end now that I've upped the compression to 11:1 or so.

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...Plus you've now got to tune the carbs, which is not easy for some. The whole system works better when the engine and exhaust fit the triples. Triples work better on a car with higher compression, big cam, exhaust, etc.

 

Maybe it was just luck, but I had ZERO experience when I installed my triples, and I have to say it wasn't nearly as hard as some made it out to be. But like

John says, maybe that's because I had a large cam and good exhaust already too. For jetting, I used the formula in Honsowetz's book, and it was really close to start with.

 

...My Z has a LOT more bottom end now that I've upped the compression to 11:1 or so.

 

Same here, my motor has just about 12:1, and I couldn't beleive how much more torque it put out over the 9:1 one.

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Guest JustBurn

i was under the impression that stock SU carburetors won't fit. is that true? cause i'm about to pick up a 280Z and i don't feel like running the EFI...

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JustBurn,

 

Stock SUs (round tops, not the tuna can units) will work just fine as long as you have an intake manifold for them. If the car you are getting came stock with EFI and you are converting to SUs, you want to be aware that...EFI systems require higher fuel pressure than do carb systems, so you may need a different fuel pump and or fuel pressure regulator....or just install a stock datsun fuel pump, intended for SUs, on the engine.

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As long as you get the proper fuel pressure regulator to drop the pressure to the carburettors' range (3-4psi) then the stock EFI fuel system will provide plenty of flow and fuel for any carb setup.

You will get more HP and Torque on a stock motor with a set of Mikuinis (about 10% bump according to the Mikuini Literature of the day) as compared to a 22% jump over Mikuinis installed on an SU equipped car.

 

Now that is stock for stock, unaltered.

 

If you tinker with the stock EFI and simply get it in proper tune, you can generate decent numbers, and have excellent drivability with no downside. You want induction noise? Take the air cleaner off and install one of the ricer cold-air kits. It lets the intake growl nicely.

 

My stock EFI equipped L28 puts down 147HP to the wheels, the only modifications I have are a K&N Air Filter (in the stock housing), a TWM Big Throat Throttle Body (more for tip in feel than HP), and the MSA headpipe from the stock N42 exhaust manifold going to a press-bent 2.5" (I think) exhaust with two mufflers (pre muffler 36" glasspack and a Dynomax out back). The setup runs 15.30 in the 1/4 mile with my 330# butt in it, in a 1975 2+2, so the Dynojet ain't off by far I guess...

 

So EFI (stock) ain't all that bad, and if you add a cam (reasonable) along with maybe some porting and compression increases you can tweak that stock system to do quite a bit. But even stock (if you believe Mikuinis numbers) you stand to make 170 from the same car...

 

My car did seem to pull harder with the triple Webers on it (I took em off to install the stock EFI!) but that may have been the effects of the sound. It sure did attract more attention then...

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  • 9 years later...

Stock l28e efi systems are not designed for power. More for drivability. Not to say it's a bad system just not ideal for hp. Now if you get rid of the stock ecu and air flow meter. And swap to a mega squirt stand alone with MAF you will notice a considerable gain in response with out losing the drivability of low end torque. Now carbs on the other hand are not as efficient in the broad rpm range. But can still produce the same power as a n/a l28 efi system. Both systems require tuning to get the most out of them. A set of factory carbs from a l26 will out perform over a stock l28 efi system on the same engine due to the air flow difference. However if you want to make real power on a l28 go turbo with the efi. You will see much better hp difference per dollar.

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I'll try and post the video I just made yesterday of my triples. I like them and love the sound but I'm switching to efi myself just to try something new and possibly turbo down the line. Like they said you will need supporting mods to get the most out of them but I've never had any drivability issues or anything. I have a bone stock 2.6 with msa headers and MSD spark box. This video was made in 30 degree weather, no choke, a couple minutes after cranking and it had sat for a couple weeks with all the snow we've had I didn't rev it hard because it was kind of cold still but you can get the idea. I love my Z but it's all I know so my opinion is not nearly as informed as most here.

trim.70EBFF52-FCC3-484A-8B60-F22E494DBBFE.MOV

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