To use triple carbs or not..that is the question!!

[Guest norm[T12SDSUD]]

Norm what dealership do you work at? And what track have you ran your car at?

 

Hey Sparks I worked at a number of dealers for the last 13 years and was at Bush in Lenoir off and on for the last 5 years but I quit the car biz last summer.

 

I run at Wilkesboro, Farmington, Shadyside, Mooresvillle and Rockingham in that order of frequency. I like Wilkesboro the best as I can get LOTS of runs!! I once ran 44 times in ONE night at Wilkesboro! It isn't the fastest track, but it's the best for having fun!

 

Later,Norm

[Sparks280zt]

Wait a sec Norm! I think we have met in person, does your hatch say "Jesus Saves" on it? I dont know if you can remember or not, but I had the yellow 77 that sat on 321 and was for sale a couple years back, you talked to me about it at the gas station in hudson and I ran into one day at Wendys in hudson and we talked about Charles Yelton and all his junk cars, anyways hope you are the same guy cause if you arent I feel like an idiot............

[Tony D]

Ill be the first to use it.

 

 

LOL! Priceless!

 

And very "on topic" given the debate that never ends, yes it goes on and on my firends, someone started it...not knowing what it was, and it keeps on going just because....

 

LOL

[Guest norm[T12SDSUD]]

Wait a sec Norm! I think we have met in person, does your hatch say "Jesus Saves" on it? I dont know if you can remember or not, but I had the yellow 77 that sat on 321 and was for sale a couple years back, you talked to me about it at the gas station in hudson and I ran into one day at Wendys in hudson and we talked about Charles Yelton and all his junk cars, anyways hope you are the same guy cause if you arent I feel like an idiot............

 

Yup I remember that meeting, that was me! BTW,that was a good looking 280Z!

 

Later,Norm

[texasz]

.....So if you want a screaming L6 monster then go with the triples. If you want easy to opperate, go with the 4barrel. I still agree with my previous post. I'd go with the 4 barrel.

 

And you'll go slower, generate less power, and your engine won't run right (the #1 and #6 will be way lean, and your #3 and #4 will be way rich). These cars were just not designed to run on a single carb and it's been shown over and over again that the 4bbl is a poor set up for these cars.

 

Yes, many proclaim this the be then end all beat all performance carb set up but show us some hard results to support this. Now your next request may be for me to do the same showing how bad it is...well I can not recall where all I've seen the proof but one was a show where they took two 240Z cars and put a 4bbl on and ran it down the drag strip and it didn't do well (I wish I could remember the name of the show but someone here will likely know what I'm talking about and post the name). You can also talk to any long time Z mechanic who is very knowledgable in these cars and they will tell you too.

 

Don't waste your bucks on a 4bbl, if you want to increase performance without going to triples get the ZT SUs, if you can affort it go with tripples.

[SuperDan]

And you'll go slower, generate less power, and your engine won't run right (the #1 and #6 will be way lean, and your #3 and #4 will be way rich). These cars were just not designed to run on a single carb and it's been shown over and over again that the 4bbl is a poor set up for these cars.

 

Can you please provide some more information on this? I have been doing my own searching and have not come up with anything so far... links?

 

 

I remember a post a while back on Chevytalk and DougF who works for Holley and is the resident EFI guru over there posted some information about central mounted carbs on V8 engines. They have a new tool that they are using that uses 8 WB O2 sensors located on each exhaust port.

 

He was blown away by the different A/F ratio's between them, worst case was something like 10.5 - 14.1. And this was tuned by one of there Holley gurus and the engine was running perfect!

 

I wish I could find that post again, very informative.

 

I emailed him back then and he said they tried allot of different combinations of manifolds and carburetion / EFI.

 

The results were all over the map, some good, some bad.

 

In the final analysis the type of air-fuel mixing device (they tested there own Holley carbs, Edelbrock carbs and the Commander 950 TBI) was not a factor in fuel distribution… it really came down to manifold design.

 

Obviously MPI was a completely different story, they were able to tune down to a .5 A/F between cylinders.

 

So, some of the members on this forum are just waiting there life’s away with their current career paths. The ability to look at a manifold / Air-Fuel Mixer and determine it’s ability to evenly distribute this between cylinders is a god given gift, you need to stop what you are doing a go to work for a auto manufacturer.

 

I know I am coming off a little harsh but understand I am just playing devil’s advocate here.

 

I really want to see some data on this. It does not even need to be a Nissan L6 motor, any inline 6 will do where someone has tested the A/F variances per cylinder for different types of manifold / carb designs using a setup similar to what Doug was talking about.

 

Do I believe there is an issue with fuel distribution on 4bbl intake manifold? I sure do.

 

Do I believe there is a fuel distribution with the SU setup using stock manifolds? Sure do.

 

What I would like to know is how much and what cylinders are affected and is the variance that large.

 

Yes, many proclaim this the be then end all beat all performance carb set up but show us some hard results to support this.

 

Yes, hard data would be nice. Not a couple of knobs on SpeedVision racing 2 different cars against each other.

[johnc]

Do I believe there is an issue with fuel distribution on 4bbl intake manifold? I sure do.

 

Do I believe there is a fuel distribution with the SU setup using stock manifolds? Sure do.

 

Agreed. Having looked at dyno runs using 6 EGT probes on an SU equipped L6 I can verify the mixture issues and a big factor in the problem is the exhaust ports on the L6 head! Surprise! Just when you think you "know" the intake and carburation is where you should focus your energy...

[SuperDan]

Agreed. Having looked at dyno runs using 6 EGT probes on an SU equipped L6 I can verify the mixture issues and a big factor in the problem is the exhaust ports on the L6 head! Surprise! Just when you think you "know" the intake and carburation is where you should focus your energy...

 

Interesting.

Doug had mentioned that the put their new Stealth Ram injection on one off the test motors, tuned it using a single WB O2 and were seeing a ~15% A/F ratio variance between cylinders at varied rmps. He did not elaborate on what was the cause.

 

Thinking back to it, I think the point of his post was to point out that even though you may have a setup that should have an even distribution of Air and Fuel that there are a lot of other factors that can also have a big influence on this, as you pointed out John.

 

Without some kind of EGT, WBO2 etc test equipment how would you ever really now you are getting the most out of your engine? Lots and lots and lots of trial and error and speculation I suspect.

[Guest DoTheDrew888]

The show you were talking about was "Full Throttle" I think and it was on the History Channel.

[Guest bastaad525]

The show you were talking about was "Full Throttle" I think and it was on the History Channel.

 

 

yeah gawd that show SUCKED!!!

 

They put the 4 bbl's on two classic 240's (in addition to a hot cam and full headers/exhaust) and then took them to the dragstrip where they ran way SLOWER than stock... that was so freakin sad. I don't blame the 4bbl carbs for that one though... EVERY time I've seen that show they build these fantastic cars and really build them UP... highly modified... and I think "wow that's going to be a 10-11-12 second car" and they take them out and run like 16-17's. They built up two Buick GNX's for example, with upgraded turbo's and such... expected about 400hp, and I think they ran like a 15+ in them. Then last night they built up these classic old Caddy's... new heads, intake, cams, exhaust on some big block V8 motor and then a big shot of nitrous (one team ran 150hp, the other ran 250hp shot)... they were estimating about 400hp on those motors WITHOUT the nitrous. On the second run the 250 shot team blew their motor which was funny and not at all surprising... and out of three runs the best they managed in the 1/4 was a low 16. That show is retarded, the 'turbo twins' are retarded, and they are giving classic cars a bad rap.

 

I shudder to think some ricer kids are watching this show and thinking that these times those boneheads run in these built up cars are what cars like that are REALLY capable of... "Wow they put 150 shot of nitrous on a 400hp Caddy and it still ran slower than my Civic... my **** must be fast yo!" *shudder*

[Guest bastaad525]

The show you were talking about was "Full Throttle" I think and it was on the History Channel.

 

 

yeah gawd that show SUCKED!!!

 

They put the 4 bbl's on two classic 240's (in addition to a hot cam and full headers/exhaust) and then took them to the dragstrip where they ran way SLOWER than stock... that was so freakin sad. I don't blame the 4bbl carbs for that one though... EVERY time I've seen that show they build these fantastic cars and really build them UP... highly modified... and I think "wow that's going to be a 10-11-12 second car" and they take them out and run like 16-17's. They built up two Buick GNX's for example, with upgraded turbo's and such... expected about 400hp, and I think they ran like a 15+ in them. Then last night they built up these classic old Caddy's... new heads, intake, cams, exhaust on some big block V8 motor and then a big shot of nitrous (one team ran 150hp, the other ran 250hp shot)... they were estimating about 400hp on those motors WITHOUT the nitrous. On the second run the 250 shot team blew their motor which was funny and not at all surprising... and out of three runs the best they managed in the 1/4 was a low 16. That show is retarded, the 'turbo twins' are retarded, and they are giving classic cars a bad rap.

 

I shudder to think some ricer kids are watching this show and thinking that these times those boneheads run in these built up cars are what cars like that are REALLY capable of... "Wow they put 150 shot of nitrous on a 400hp Caddy and it still ran slower than my Civic... my **** must be fast yo!" *shudder*

[Corzette]

Ill chime in here. I had a L28 bored to L29 Mikuni 40s to start and headers, MSD etc.. I know that compared to the SUs, the triples were a major upgrade power wise. I could feel the difference by seat of the pants. I then upgraded to the 44s and did even better. Mikuni also had a 50mm carb setup but was alot harder to tune and keep tuned. The 44s were easy to tune and didnt need alot of adjusting. My mechanic Japanese guy at the time would put a piece of fuel line in his ear and the other end in the carb horn and tune it by ear. They also sold an air meter gauge thingy that you could put over the horn to tune that way. Either way, I never had any problems with them except that you should have a return fuel flow system. The triples will flow over from the bowl out your air horns if you put too much fuel pressure to them. The pressure is really low like 3 to 5 PSI if memory serves me right. You can start a fire really easy on a hot set of headers and raw gas pouring on to them. Webers come in a 45mm setup I think and would be my second choice.

 

The four barrel setup did not work as well from a few people Ive known in the past. Probably because of the way it sits in the compartment and angle in induction etc...just my two cents worth.

[Tony D]

 

Can you please provide some more information on this? I have been doing my own searching and have not come up with anything so far... links?

 

 

I remember a post a while back on Chevytalk and DougF who works for Holley and is the resident EFI guru over there posted some information about central mounted carbs on V8 engines. They have a new tool that they are using that uses 8 WB O2 sensors located on each exhaust port.

 

He was blown away by the different A/F ratio's between them' date=' worst case was something like 10.5 - 14.1. And this was tuned by one of there Holley gurus and the engine was running perfect![/font']

 

I wish I could find that post again, very informative.

 

I emailed him back then and he said they tried allot of different combinations of manifolds and carburetion / EFI.

 

The results were all over the map, some good, some bad.

 

In the final analysis the type of air-fuel mixing device (they tested there own Holley carbs, Edelbrock carbs and the Commander 950 TBI) was not a factor in fuel distribution… it really came down to manifold design.

 

Obviously MPI was a completely different story, they were able to tune down to a .5 A/F between cylinders.

 

So, some of the members on this forum are just waiting there life’s away with their current career paths. The ability to look at a manifold / Air-Fuel Mixer and determine it’s ability to evenly distribute this between cylinders is a god given gift, you need to stop what you are doing a go to work for a auto manufacturer.

 

I know I am coming off a little harsh but understand I am just playing devil’s advocate here.

 

I really want to see some data on this. It does not even need to be a Nissan L6 motor, any inline 6 will do where someone has tested the A/F variances per cylinder for different types of manifold / carb designs using a setup similar to what Doug was talking about.

 

Do I believe there is an issue with fuel distribution on 4bbl intake manifold? I sure do.

 

Do I believe there is a fuel distribution with the SU setup using stock manifolds? Sure do.

 

What I would like to know is how much and what cylinders are affected and is the variance that large.

 

 

 

Yes, hard data would be nice. Not a couple of knobs on SpeedVision racing 2 different cars against each other.

 

BAH! I've been drawn in again! Where's that Horse .gif?

 

When Andy Flagg and I were doing testing on the Bonneville car, we didn't have individual AF Ratio Sensors in each header tube, but DID have a six channel EGT out of a Cessna for datalogging and comparisons.

 

Much like you mention about HOlley finding 10 to 14:1 in different cylinders, our testing of the different Cylinders on the Z Six with three different 4 BBL manifolds showed well over 100 degrees difference between individual cylinders. This is unacceptable. On Triples our differential was less than 25 degrees at almost all times. At partial throttle the differences were staggering.

 

I don't know if it's was a function of the carb just doing a terrible job at atomization, or not, but I suspect insufficient thought towards the manifold design.

 

If you look at factory inline six manifolds (most notably the Mercedes Benz) you will find it's a DUAL PLANE design. You have one primary and one secondary feeding two sets of three cylinders. NOBODY in the Z Aftermarket has a manifold like this, they ALL dump to a common plenum, and then suck the fogged mix down runners (usually of UNEQUAL LENGTH)...

 

Mixture distribution can not HELP but be disturbed! ACtually the way to solve it would be to decrease the cross sectional area of the plenum and runners to keep veocity up, drawing the mix equally down each runner to each cylinder. To get our Clifford manifold to get below 100 degrees between cylinders at full throttle, (I almost hate to admit this) we put a BIG pad of JB WELD in the center of the plenum with depressed "runners" going to each individual cylinder runner.

This got mixture distribution as revealed by EGT to less than 100 degrees, but NOWHERE near where the Webers were, which were within 25 degrees OUT OF THE BOX! The only thing we did on the webers was adjust jetting to get the EGTs' up where we wanted them and for what got us the terminal power we desired.

 

If someone was to take a Mercedes Benz Manifold, and somehow copy the design to the L-Engine (perhaps weld an L-Flange onto the MB Pleunm and Runners) I would be VERY interested to see how it worked out in terms of cylinder to cylinder variation.

But remember even MB put a redline limit on peak HP production well below 6000 rpms with this setup. The plenum design and carburettor are almost mutually exclusive for High RPM operation. At least IMO.

 

I really wish I had kept the notepads from those dyno sessions. It has been over 6 years ago now, we only ran the 4bbl one season, before going to the Webers. And the Webers for a season before going to the Triple TWM 45mm setup.

 

The differences in HP production and idle characteristics were significant, also.

The 4bbl idled at 2200rpm (similar to my old Full Race Ice Racing Corvair from the 80's), the Webers at 1700 rpm, and the TWM with port EFI at ridiculous numbers: it would idle tickover as low as 400rpm! On a 39*F morning at ElMirage, the TWM / TEC2 setup would fire off first crank, idle at 1500 and then step down on the warmup circuit to an 850 rpm idle.

 

On a cam with BIG lobes. Big enough for a terminal figure of 315HP to the rear wheels at 8250rpm, on a non-stroked .040" Bored L-28...

 

The Webers power peak was around 7500, and the TWM was up on them by 40HP at 8250, and somewhere around 20HP at 7500.

 

The 4BBL was around 13-20HP lower at a power peak around 7200, and similar to that at 7500 compared to the Webers. If I recall the power peak of the Webers was 286 at 7500, and the 4bbl on the Clifford Manifold was 246 at 7200 or 256.... It was a while ago.

 

Annyway, putting that EGT Datalogger with variable alarm parameters is a VALUABLE tool for someone running on a dyno. They are only about $1200 from Aircraft Spruce. Neat Gadget, people will always ask "what's that?"

Unless they are a pilot, then they make a comment like "Why the hell do you have THAT in your car?"

 

LOL

[SuperDan]

Ok, fair enough.

But.

If you look at factory inline six manifolds (most notably the Mercedes Benz) you will find it's a DUAL PLANE design. You have one primary and one secondary feeding two sets of three cylinders. NOBODY in the Z Aftermarket has a manifold like this, they ALL dump to a common plenum, and then suck the fogged mix down runners (usually of UNEQUAL LENGTH)...

 

The ArizonaZ manifold is a dual plane manifold.

 

When Andy Flagg and I were doing testing on the Bonneville car, we didn't have individual AF Ratio Sensors in each header tube, but DID have a six channel EGT out of a Cessna for datalogging and comparisons.

 

 

My understanding has been (and I am in no way an expert) that useing EGT sensors are a stone-age way of measuring A/F ratio. I mean what does a 100 deg variation translate into?

[Tony D]

Thanks for the AZ Z manifold. I was informed incorrectly then. it was told it had a simple plenum.

The MB manifold is separated longitudinally along the centerline of the car, but function should be similar. I wondered why the holley was mounted crossways (floatbowls left and right) instead of fore-and-aft. That makes more sense.

 

I would be interested to hook up the EGT and see what differences there were.

While EGT may be "stone age" in people with an unlimited R&D Budget, stationary engine operators routinely use EGT as the standard for monitoring engines. Anything more than a 25 degree separation is unacceptable, and sounds an alarm for attention. It is very accurate when it comes to diagnosing misfires, which are important for different reasons than AFR. If you have EGT and a single AFR monitor (five gas monitor is even better) you will learn a LOT about what your engine is doing during your run. During full throttle runs, the Clifford (the best one we tested) had 100 degree differences, and during partial throttle the differences was greater than 200 degrees! No matter how you look at it, that is waaay too rich. At least by the Single AFR probe we had in the tailpipe (so the misfires were diagnosed as rich misfires, jetting seemed to have little effect... So on to increasing velocity to stop dropout. That seemed to work)

 

We were more interested in finding if we could equalized temps and we did using the method mentioned. The manifold that bolted onto the original SU Manifolds was hideous in distribution! We didn't have the EGT setup when we tested the SU's, but that bolt-on-to-the-SU 4bbl manifold was down on power compared to the SU's from 3500 on up. As such we poopcanned the thing early on in testing and concentrated on the Clifford unit since it was $40, and the AZ Z was a bit more pricey.

 

As far as I know, Andy and I were the only people who have actually come forward with the results from tests we ran. Our conclusion was that the Clifford unit was able to be made to work, but only for a mild street engine below 6500rpms. Above that, the loss in HP was simply unacceptable.

 

Perhaps a larger engine would keep velocities up and draw the mix better, but it would have flow problems before the 6500 mark anyway...

 

In any case, I have never said the AZ Z manifold was tested by us, and I reserved judgement on it till I had one to test. I know it will be down on power compared to Webers or Mikuinis, or port EFI for that matter.

 

But now seeing the design in that photo and far more equal length runners drawing in a separated manifold gives me hope that it will perform at mid and lower throttle ranges far better than the previous offerings. Like in the other post, there are a lot of enthusiastic converts, but none of them have done any empirical testing. I probably don't blame them with the cost of gas and dyno time just to win some sort of argument. Really, Dave from AZ Z should step up and define the market for the manifold by showing testing he did. Anecdotal evidence is usless to anyone but salesmen. I would be swayed by hard dyno numbers, or even a "comparative curve" of performance gained by his system, similar to what Mikuini had for all their setups.

 

I believe the costs for a business would be a write-off as advertising expense. He could take a set to the MSA show one year and on that saturday run on the dyno in front of a crowd and by word of mouth alone pick up converts and shoot down us skeptics.

 

Testing is testing, marketing is marketing, many times the two rearely coincide with facts and figures.

[Tony D]

What I was trying to say about the misfires being more important than AFR is that when you are misfiring on one cylinder, you loose that fraction of HP.

While AFR may contribute to the misfire, if the cylinder is firing then the AFR is only loosing a fraction of the HP loss a misfire would.

 

Does that make sense? With a singe AFR channel on the tail pipe, and EGT on all cylinders you can tell once tuned if you are up or down on power simply by monitoring the alarm status on the EGT monitor.

 

In a small aircraft, being down 17% on power because of a single plug misfire may mean the difference between making it over the pass, and becoming part of the pass!

 

In Bonneville Competition seeing your cylinder temps come up to peak during the run means you are on full boil. We also have a simple AFR monitor, that we run in the "green"... If it changes, we lift. A cylinder going dead may not warrant a lift, but if it's preceeded by an AFR dip, may mean we lost an injector...

 

I digress...

LOLO

[Nismo280zEd]

Good information here.

I run triple webers and didn't know the EGT was just as usefull as afr if not more.

-Ed

[Tony D]

they go hand-in-hand.

The EGT is telling you when you have misfires.

If your AFR is right, and you are having misfires, then suspect the ignition.

If your AFR is wrong, you will see the EGT take a characteristic temperature.

 

On long full power runs like Bonneville, you will see a problem with your EGT almost immediately if you have a bad ignition wire, or plug, while the single AFR will let you know if your selection of jets was correct at 4700 feet altitude (with sometimes a density of 6000+ feet!)

 

Yeah, EFI is the way to go. I would skip carbs altogether if at all possible. With Megasquirt available, there really is no reason to fight a metered air leak to supply the engine with combustible mix...

[arizonazcar]

I'll post a couple more reactions to my unworkable intake:

 

"Hi my name is Robert Remlinger I recently purchased the aluminum intake manifold from Arizona Z Car for a 1974 260Z 2+2. The car was bought new in '74 by my father and has been very well cared for over the years, since 1980 the same mechanic has worked on it. I now own the Z and was excited to see your product on the web, once I got the part in the mechanics hands it was count down time to performance. He had seen a similar manifold set up but he thought it was flawed because of the low height of the carb, he thought your part had addresed this issue. After a few days in the shop my father and I went to pick up the Z, Dave the mechanic had a grin, one look and I knew why. The part looked AWESOME on the Z! It did not stop there Dad and I took "MY Z " for a spin, it performed flawlessly, what performance! I have now been driving with the manifold for a few weeks and its still thrilling. I show it off when ever I get a chance. Anyway, thank you very much, I highly recommend the manifold and I can't wait to order disc brakes from you for my next upgrade."

 

Here's another one:

 

Dave,

First let me say that it works beautifully and I am very happy. There were some issues that had to be addressed with a grinder,vise grips and a small hammer. The header I have is 6 into 2 from MSA. The manifold actually made contact with the #2 pipe. I had to work the header a little to gain about 1/4" of clearance. The linkage kit I found has a steel braided appearance and works fine. I did have to bend the gas pedal to better align the end with the existing hole in the firewall, and grind the end to allow smooth operation of the cable. When I installed the Holley and turned on the ignition fuel began to flow out of the carb, come to find out Holley forgot to install a few gaskets. There were other issues with the carb and I ended up returning it and getting a new one (checker auto argued with me and said I had to deal with Holley, they ended up giving in). With the second carb on and a new ignition switch (another story) the car started right away and the only adjustments needed were,idle speed,float level and double check the timing. The manifold and carb work great.. It starts easier than with the injection and idles smoother. The engine pulls harder ,and with the cam is a lot of fun between four and six thousand RPM's. I want to thank your for your commitment to quality products that attribute a smile every time the clutch (purchased from you) is let out!

 

P.S. I hope this email doesn't have a negative tone. I am very satisfied and I realize that when after market parts are purchased from different vendors that one might have to customize a little. The end result is what really matters and like I said earlier, I am happy with the performance.

 

Thank you,

Mark Shepard

 

I still find it interesting to read the negative posts from those that have never used the product.

Dave

 

http://www.arizonazcar.com

ARIZONA Z CAR

2043 E. QUARTZ ST.

MESA AZ 85213

Phone 480-844-9677

E-mail dave@arizonazcar.com

[arizonazcar]

Here's a quote from the previous thread.

By:

plainswolf

Member

 

Join Date: Apr 2002

Location: Western Nebraska

Posts: 133

 

 

--------------------------------------------------------------------------------

 

Wow this sure turned into an interesting thread!

 

But I must admit Dave does make a very valid point.. there are alot of guys out there just like me who have a Z and either just want to keep the thing up an running as well as possible, or want to see exactly what they can change on it to make it even better.

 

For less than 600.00 total(shipping included), I was able to get not just a rebuilt intake system, but a brand new one.

 

I compared the costs of a rebuilt S.U. system to Dave's Holley setup. But that was not my only reason.

It was the simplicity of his system (the engine compartment is SO much less cluttered up now)

the reliability of it(based on 2 years experience now),

combined with parts availability(I can get the parts quickly at almost any autoparts outlet in the country).

and it's potential for further power upgrades. (this intake can take alot more cam and head flow than stock).

And lastly, he's not kidding when he says driveability.(When it's a -20 degree winter morning this thing starts without fiddling with anything)

To be honest, I kinda though he was full of crap when he told me about the 'as good or better gas mileage' with this sytem, but I have to admit, he was quite correct.

 

But this is just my opinion based on my 2 years experience running this sytem.