L28 with a 4V

[alsil]

My son and I have been talking about what kind of car we're going to build him for his first car, and he's pretty sure he wants a Z! But I don't want his first car to be a scary fire breating 12 second V8 car. I was planning on finding a good L28 and rebuilding it with just upgraded stock components. I was wondering 2 things, have any of you guys used a 4V carb with one? I figured that it would be the easiest and most reliable way to do it (plus I already have a 500CFM Edelbrock he can use), but was wondering how good it works. I have seen the intake MSA sells, I know either Carter or someone made one also, had anyone had any experience with it?

About 10 years ago my friend came across a NAPCO motor from Japan that had the single 2V version of the Z intake, and I rebuilt the carb and ran it, it ran great, and was easy to adjust. Anyone have one of those (FAT CHANCE, but what the hell?). Just trying to make him a reliable car. I of course will upgrade his brakes, suspension, steering, driveline (5-speed and R200). Just want the motor to be solid.

Any thoughts would be appreciated.

 

Thanks

AL

[Guest Anonymous]

Al,

 

I think the opinions are usually pretty much against the single four barrel. All sorts of reasons are mentioned, the inside cylinders running rich, the outside lean, supposed fuel having to make a 90 into the intake and dragging on the bottom of the intake runners (works on a Chevy, I donno, although the runners are slightly angled and shorter).

As I said, those are the reasons I've heard explained. That said, there are domestic inline six engines all over the country that run extremely low times using a single four barrel on like Clifford Engineering manifolds. Why the Z should be any different is beyond me. Outside of the OHC and shorter stroke its not that much different from a Chevy or Ford six in that its not a flow through design. Granted the inside cylinders might run slightly richer and the ends a bit leaner but it shouldn't be a concern for a street driven car that is generally tuned a bit rich anyway. I'd look at a 390 CFM Holley, or the 450 cfm edelbrock if I were going this route.

 

Another option is I think one that Victoria British (I believe it was them anyway) has is that twin 2300 Holley setup. These are progressive 2 bbl (primary and secondary) carbs used on lots of applications, it comes with the stub manifolds and all linkage and stuff.

 

Oh well, thats my .02, I'm sure others will chime in.

 

Lone

[Drax240z]

Al I can't really speak from experience, but from the posts I've seen from people that did the before/after comparison between a 4 barrel and dual SU's, every single one has said that the stock dual su's make more power, and the car just plain runs better.

 

If you look at the manifold design of the 4 barrel intake, you'll see why... the runners get progressivly longer as you get furthur away from the center of the engine, #1 & #6 will be much longer than #3 & #4 runners... pretty darn hard to tune.

 

Generally downdraft carbs on a side draft engine don't work... I'm sure you can find more testimony from someone here that has run both. If not, talk to Tyson at zcar.com. He did a before/after comparison.

[alsil]

Well, I knew about the lean/rich condition - had a FEW old Ford 6's. The MSA manifold looks OK, seems to even it out a bit. Anyone use that one? I know the Clifford one doesn't try and equal length the runners like the MSA one.

I saw one once from Carter that bolted onto the stock maifolds (where the carbs bolted on), so you would figure that would be as even as the stock config.

I don't really want to use a dual-carb setup, just because of complexity. I know I could get it to work, but my son is just learning.

 

Al

[Guest John Adkins]

A lot of people in the "purist" (nobody here at Hybrid Z!)Z community have an extremely anti-American attitude and according to them any American part that is bolted on a Z (like a Holley or Carter carb for instance)will not work as well as the "superior" foreign engineering.

Like Lone mentioned, there are many domestic inline 6's running downdraft carbs that run great. My dad had a Pontiac OHC 6 (almost like a domestic version of the Z's engine) with stock factory 4bbl and that car ran great. As long as the manifold design is good (even distribution,correct runner size), and the down draft carb is properly sized, an L28 should run just as well

quote:

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Originally posted by lonehdrider:

As I said, those are the reasons I've heard explained. That said, there are domestic inline six engines all over the country that run extremely low times using a single four barrel on like Clifford Engineering manifolds. Why the Z should be any different is beyond me. Outside of the OHC and shorter stroke its not that much different from a Chevy or Ford six in that its not a flow through design

---

 

[ May 22, 2001: Message edited by: John Adkins ]

[DavyZ]

Al, my 260Z had dual downdraft Webers--do NOT go this route. The SUs work better IMO and they don't end up with pools of gas in the "pea trap" part of the manifold!!! Z-Therapy apparently does some serious work on SUs. It may be $$$, but they're supposed to be the cat's meow. Al, what about a detuned Ford or Chevy V8 like a 305 carbed Chevy V8--stock with no mods. Only 190hp! C'mon, you're ready for another project!

 

David

[alsil]

Nah, no V8's for this! I want to keep this as clean and easy as possible. Plus, for a first car, there shouldn't be a bunch of engineering going in. He needs to learn why things work the way they do, what better than a stock car? That way he can see how things fit together and learn how to put them together before learning how to MAKE them fit. He's seen me cuss and swear at my car, I doubt he wants to do that on his first car. I know I didn't!

anyway, I also have a bunch of stock 6cyl parts left over from my car, so I could save him some money in the process. See, I'm matching him dollar for dollar, and helping him build it. So the more money I can save him, the easier it will be for him to build it. I mean, it's tough for a kid 14 or 15 to make decent money, why make it hard on him?

Anyway, any others try out the manifolds?

 

AL

[alsil]

By the way - a detuned Ford or Chevy with 190hp will be good for 14's in the 1/4. A little fast for a first car!!!!

 

Al

[Guest Tom Scala]

I had a 230" OHC-6 67 Tempest with a factory 750 cfm q-jet and it ran perfectly. Pontiac actually copied the valve train design from Mercedes 5 years before Dastun did. No rich running/lean running cyliders,high 15 sec. 1/4 mile ET's with a 4 speed & 3.90 gear, and 22 MPG on the open road. I posted this once on zcar and was met with the usual anti-American nonsense and intolerance that site is known for. I suspect most people who have had poor running 4 barrel engines never spent the time to properly tune & jet them. They then replace a poorly tuned 4 barrel set up with a well tuned Su set up and voila! What a difference. The trouble with the SU's is in cold start drivability and the constant fiddling to keep them tuned properly. All that said the SU's probably would run somewhat better than a 4 barrel, but a 390 Holley would be a set it & forget it proposition and with an electric choke very easy to get along with in any climate. Just think how nicely a nitrous plate would fit under that carb. Just for when you drive it of course.

[Guest Anonymous]

Haha, parental lockout on the nitrous bottle.. thats funny...

 

 

Lone

[alsil]

Yea, that's kinda what I was thinking. a Holley 390 or an Edelbrock 500. easy enough to tune. I wanted to have the stock motor, but with more reliablity. If I was that worried about efficiency, I would just do an EFI conversion and drop off the extra stuff (smog pump, hoses, etc.). But the carb will be cheaper, easier, and simpler to diagnose. That and we could use the stock fuel pump, exhaust, ignition, etc, except I would put a Pertronix module in the distributor (simple!). Thanks for the info!

By the way, which manifold do you guys think would be the best for this application? any opinions on the MSA one? Know anyone with one?

 

AL

[Guest Anonymous]

I would think the one that bolts onto the existing SU manifolds would work the best if you can find one. I saw a picture of one on ebay a few weeks ago and compared to the full 4 barrel manifolds I've seen, this looks like a better design (all things considered). I would think that this one would avoid the fuel starvation problem the best. I could be completely wrong of course. If you decide to go this route, look around for em on ebay I think it closed for about 100 bucks.

[alsil]

Do you happen to know what the title was of that post? Can't find it. I'd like to take a look at that, haven't seen one in about 10 years.

 

Thanks,

AL

[Guest John Adkins]

quote:

---

Originally posted by jeromio:

It runs great on the highway, but must be driven

on the highway

during those first, crucial 5 minutes of warm up. Otherwise at least one plug will end up fouling.

 

SUs + cold = sucky.

---

 

 

The SU intake manifolds are engine-coolant heated, but this doesn't help until the engine coolant warms up

On Most domestic inline 6s, the bottom of the intake manifold, usually right below the carb, is joined to the exhaust manifold to allow exhaust heat to warm the intake manifold. This really helps with drivability when the engine is cold and I believe it also helps in everyday driving around town and in traffic.

I know my old mopar slant 6 with a 1 bbl downdraft carb with a properly operating automatic choke and exhaust-heated manifold would always start and idle well even in extremely cold temperatures, even when other cars wouldn't start.

 

I built an intake manifold from exhaust tubing that allowed me to run a holley 2bbl with the stock SU intake manifolds on the L24 in my 240Z. My intake manifold design is far from perfect because I used exhaust tubing that matched the diameter of the SU throttle bores (too large). Because of this, it doesn't have a lot of power down low, but once the throttle is wide open it really hauls. When cold, the intake I built would get water condensation on the outside due to the lack of heating. It idled well when warm & started better when cold or hot than the old SUs. If I had I had to do it over again, I would use smaller diameter tubing for the intake runners and add some sort of heating for the carburetor.

 

[ May 24, 2001: Message edited by: John Adkins ]

[Guest Anonymous]

I am running an unknown 6 into two header with a 2.25" pipe to a turbo muffler. sounds pretty nice. I hated it a first cause I thought I made it sound like a civic but I soon realize that it has a sound all its own.

 

I am running a 75 elec. dist. with MSD boxz and wires also... making a custom cable as we speak cause my old one well apart....very pro looking!

 

Jake

[jeromio]

The SU's are obviously great, performance-wise, but for a daily driver, my experience has been very poor.

 

My carbs are very likely not tuned as they should be (though I've tried ). It runs great on the highway, but must be driven on the highway during those first, crucial 5 minutes of warm up. Otherwise at least one plug will end up fouling.

 

SUs + cold = sucky.

[Guest Anonymous]

I am currently running a bob sharp four barrel intake with a ford two barrle cab and adapter plate. It hauls serious but compared to my dual wbers and I have a 7200 rpm redline. I love it.....I hate multo carbs...oh yeah....i am running the original 2.4 but it hangs in with a lot of cars. I recently was playing with a fellow Z driver adn he was quite surpised cause he was driving a high compression 2.8 and he couldn't loose me on the freeway. Off the line it is just okay but damn i get get around 20-25 mpg in town when i am not all over it.......usually get closer to 17. but that is a huge improvement over my duals.

 

I will be putting a V8 i asap by the way. Not suer how sson you want to do your buildup by if you want i will let you know when i do so you can buyu my header and intake setup cheap.

 

 

Jake

[alsil]

Yea, let me know when you do your swap, can you send a pic of the setup? Like to check it out. What exhaust do you have on it right now? Let me know!

 

Thanks

AL

[Guest Anonymous]

Alsil,

 

I can't remember the post offhand, may have it in my email at home, a friend sent the link to me. I checked the closed auctions and can't pull it up. It was pretty simple designwise, just a straight tube with 90 degree bends right before the part that bolts onto the stock intake, and a carb sitting in the middle of the whole thing.

 

Re: SU's+cold=sucky, If you're having problems with your SU's you should seriously also look at the ignition system, that makes a huge difference if it's not working very good, totally turned around my SU's. Granted I put an optically triggered points replacement in and an MSD 6A but it definitely helped on the cold starts.

 

[ May 24, 2001: Message edited by: Z3bra ]

[pparaska]

I'll tell you what made SU+cold=sucks for me - low compression! The head gasket was leaking and trying to start that POS in the cold was incredible. I even engineered a tube to squirt starter fluid into to crank that beatch in the Winter when it was my daily driver.