L28 buildup advice

[Guest 280ZX_Classic]

I just had my '79 280ZX restored, and I decided to get some, but not all of the engine work done at the shop while it was in for body work. Right now all I have done is a new cam, pistons, rings, and the rest of the internals, the block and head were also cleaned and prepped. Nothing else in the engine bay has been touched though. Now that I have a fresh engine, my plan is to get the holley carb manifold, and run about a 350 to 400 cfm setup, with nitrous. I was wondering which nitrous setup to use for this application. I've seen the four barrel setups in JEGS and JC whitney, but they seemed to be geared for older V8 muscle cars. I figured it wouldn't matter since I am running the same carb setup though, but I am not sure. Here are the specifics. First, I live in Alabama, so smog laws aren't a problem for me, but I do want to keep things fairly clean. Second, I want to run around a 50 to 75 shot.

[Guest bastaad525]

Heheh just a warning... this is a long reply

 

I dont see why you couldn't run the type of nitrous system that has a plate that bolts in between the carb and the manifold.

 

 

Personally... I'd avoid this setup like the plague. First off, I would recommend against the 4bbl setup in general... most Z guys who are after performance agree that they are not the best choice for the L6... the problems are that a) they are notorious for running uneven mixtures across the six cylinders due to drastically different intake runner lengths, it will tend to run noticeably richer in the middle two cyls (3-4) and leaner on the outside cylinders (1-6), and inaccurate mixtures in general. The problem here is that the carb is a downdraft, and you're going to use it on a sidedraft head... air and fuel get sucked down hard, and are then expected to navigate a 90 degree bend, changing the direction of travel from down to horizontal to flow into the head. Keep in mind, 4bbl carbs dont atomize the fuel nearly as well as say, a high pressure efi system... it more or less just squirts it in there... big droplets. A lot of the fuel doesn't make it, and instead just slams down into the bottom of the manifold. Depending on the manifolds design, fuel can pool up in it directly under the carb. I have heard of instances where fuel kept pooling up in there... also causing a lean run condition, which in turn caused a backfire thru the intake, which in turn caused that pooled up fuel to ignite and KABOOM!!! there goes the carb and intake manifold, possibly the hood, and who knows what else. It's rare, but it has happened.

 

Now... those reasons should make it even more clear why you probably would not want to run nitrous on this setup. I dont know enough about how you tune a 4bbl to run richer when nitrous is present (or I guess you just need to run a wet system that supplies it's own extra fuel?) but you'd have to supply more fuel than usual for the nitrous just to make sure the outside cylinders dont run lean enough to be damaged. Secondly, with the fuel and nitrous going thru that 90 degree angle direction change, whos to say how well the stuff would mix or how much of what would be getting into what cylinders.

 

Of course, I have never done this personally... to be honest I dont think I've ever heard of anyone running nitrous and a 4bbl on an L6 before... so I can't say it would or couldn't work... I just would never try it myself especially on an engine I just had rebuilt or built up... just too many things that can go wrong, and too much chance of frying your new engine.

 

On the other hand there are quite a few guys who do run the 4bbl's on the L6 and many do like them... it seems to me that most guys that show up here asking about them can't be swayed no matter how many people will tell you it's not the best way to go. I can tell you now, you will not be gaining anything in performance by switching to a 4bbl carb.

 

If you really want to go nitrous, I say stick with the stock EFI, and run either individual foggers on the intake manifold in each cylinders runner, or run one fogger right before (or after, I'm not sure on this one) the throttle body. A bigger throttle body and ported manifold would help but isn't necessary. If you absolutely have to go carbed, look into SU's or even tripples. Nitrous installation would be the same as the EFI... individual foggers for each intake runner. I think any of these setups would be WAY safer for running nitrous than using a 4bbl... and probably perform better as well.

 

 

Or... last time I looked into it, the cheaper nitrous setups were running close to a grand (this may have been including installation but I dont remember, was a long time ago... so maybe it would be less if you were installing yourself... then again maybe prices have gone up?).... you might want to look into doing a turbo swap. A really cheap turbo swap could cost that much or less, I think a few guys on here have done a basic, stock turbo motor and efi swap for quite a bit less than a grand. Or since you've already rebuilt the motor, just look into getting the turbo itself and the manifold, and the turbo EFI system (or something like megasquirt or SDS would be even better... megasquirt costing only $200-400...). Then, just by upping the boost a couple psi you'd easily put down 50+ more hp than what you have now with your current motor. Actually, my built up, 2.9L (overbored, not stroked) 10:1 compression motor, with stock cam, high flowing intake and exhaust, and a few other little mods put down only 141rwhp (later, switching to SU's and a hot cam bumped me up to 170rwhp). A stock ZX motor would put down more like 120ish. My bone stock turbo motor with a VERY restrictive exhaust, and no mods other than a blow off valve and upping the boost 3psi, netted me 200rwhp... so a 59 hp increase, and it's there all the time... no bottle to refill. And of course the potential for more power down the road is huge with upgrades like an intercooler and more fuel... Just an idea.

[Guest 280ZX_Classic]

Thanks for all of the advice man. I can't go with a turbo setup, because I have the '79, and I would essentially have to swap motors, or at least the head and pistons, which will cost more than the motor would from a junkyard. I see what you're saying about the four barrel, so now I am either going to go with the stock Z carb setup, or maybe the Arizona Z Car's fuel injector setup, the high performance one, then I'll switch to a high performance fuel rail and pump. With that setup I should be able to run nitrous whenever I want without being too lean with my mixture.

[Guest bastaad525]

yeah as long as you're sticking with a form of fuel/air induction that was designed for the straight six Z, you should be fine with such a mild shot of nitrous.... Now the questions are wether to go with direct port with six foggers, or just one fogger at the throttle body if you stick with one throttle body, and wether to go dry or wet. I've always though one fogger with a dry system would be the best, easiest to install setup on a stock EFI system.

 

 

Anyways, I'm surprised dude!!! I was actually able to talk someone out of the 4bbl conversion for once! Well if I've saved the life of one Z motor then my job here is done