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

[Guest Stoker3.0Z]

OK guys, I need your very skilled opinion. I am building a 3.0 Stroker out of my L28 engine. I really like the way the triple carbs look but have heard some horror stories of finding jets, sycronizing the carbs, and differant things downgrading this setup. Saying that they are hard to keep tuned and stuff like that and that the way to go was with the Holley 4 Barrel 390 CFM Carb. What do you guys think. Maybe some posts from folks who have done one or both who can give hints and ideas. Please Please help!!

 

Mike

[GrayZee]

I used to be a big carb advocate, however now I think that fuel injection is the way to go.. Especially with a z31 ecu, I hate that door flapper AFM in the 280's

[JMortensen]

I'd sooner go with a set of hogged out SU's from ZTherapy than a 4 barrel. As for triples, Webers are still being produced and parts are easy to find. Mikunis aren't made any more and parts are still available but starting to become more scarce, but you can get them through Mikuni dealers like Rebello, Nissan Motorsports, and others. In my experience I can say that the Mikunis are easy to tune and don't need to be adjusted often. With a stroker I'd go 44's or 45's, not 40's.

[Guest bastaad525]

When I used to have a built 2.9L N/A motor, this question was on my mind almost 24/7, and I spent a LOT of time asking questions and reading everything I could find on the two options, I'll try to summarize what I learned here:

 

Tripples are not as bad as many people make them out to be, but are not the most awesome carbs on earth, either, as some people make them out to be. They can be a PAIN IN THE BUTT to tune initially, and costly yes, but once tuned are usually pretty problem free, and don't need to be messed with much, no more than SU's should need (retuning for changing seasons, etc.). Tripples are more suited to a motor that likes to rev high and make good high RPM power. They also work very well on heavy breathing 3.0L motors. They tend to make less low end torque SU's, so are not as 'street friendly', but they are livable. They tend to get worse mileage than SU's. If you've got a 3.0L, fully worked head, and hot cam, tripples will be a great match for your setup, and should definately be worth more hp than *STOCK* SU's.

 

Conversely, SU's are about the easiest carbs to tune on earth. They seem to make great down low power and be better and more responsive than tripples at low rpm, and are great in daily street driving , but can be restrictive in stock form to heavier breathing and/or higher revving motors. My built motor with hot cam and stock SU's still didn't make good power past 5500rpm (cam was supposed to be good to 6000rpm). With some mods however they can be made to be high rpm 'screamers' as well. Norm 'the 12 second SU dude' has proven that. There is a lot of potential locked up in them.

 

I have heard GREAT things rom the few people that have tried the big bore SU's. They seem to be the true 'best of both worlds' in all respects, able to keep up with a high revving motor while still maintaining the low RPM 'oomph'. I only wish I'd gotten around to buying a set for my old motor.

 

I kinda agree that if you really want the best of ALL worlds EFI is the best way to go, but if I were going to do another carbed, built N/A L28, I'm 99% sure I'd go with those big bore SU's.

[datsunlover]

I'm not well versed in triples, but I have had good expiriance with my su's and they really are the simpilest carbs known to man. I 'slapped' them on last year to my tired l28 (FI was failing) and was very impressed.. but now I'm noticing some issues with high RPM power though. I had the motor rebuilt and added a .510/280* cam, as well as a slight bump in c/r. The cam is suposed to make power from 3000 to 6500 (and after 3K rpm it SCREAMS) but anything over 5500 feels.. weak. As it is, it's a little rich on the low end, but seams to lean out up top.. I'm gona try to mess with the needles a bit, but I'm thinking of shipping off the spare set I have for a core/rebuild and getting some big bores, or maybe even try it myself (I'm a 3rd year machinest apprentice, I SHOULD be able to do it.. )

 

I'm really liking the power after 3K and I'd like to keep it going to get to the full potential of this cam. I've thought about going with triples.. but personaly, I would like to stick with the SU's as I am familiar with them now, and they are quite simle to set up. Even with the drastic change's I made to my engine, I simply bolted the SU's back on, ritchened them a bit, and the car ran.

[Guest bastaad525]

One key to getting SU's running the best that they can and a big step towards getting them to keep up with a higher RPM motor/cam, is the needles. Rather, getting CUSTOM needles. There are a couple different common needles out there that people use and recommend, most commonly I see the SM needles recommended, and these will work, but they are not the OPTIMUM solution by a long shot.

 

Rebello will custom grind needles if you can provide them with some basic information, and I think if you really want to squeez good performance out of your setup this should be considered mandatory.

[Guest tony78_280z]

Granted I've never touched a triple carb set up before, but in my opinion that would just be three things to keep tuned and thrice the potential for something to be wrong or break. Since I've learned so much about Holleys carbs, I'd love to put a 4 barrel 390 on a Z's L28. But what do I know?

[4everDATSUN]

dont do it, keep away from american perfomance parts

[Guest tony78_280z]

dont do it, keep away from american perfomance parts

It's a little late for that don't you think? Check out my signature. Doh!!

[SuperDan]

dont do it, keep away from american perfomance parts

 

You are well on your way to being escorted out of here.... just thought you should know.

[Guest nikko74z]

Quote:

Originally Posted by 4everDATSUN

dont do it, keep away from american perfomance parts

 

tony78_280z, your response was classic. I needed that laugh!

[tsheldon]

Stroker,

 

Before anyone can answer a question like that we need a little more info about your setup and useage.. Cam timing, Compression Ratio Gear ratio's and most importantly a realistic appraisal of the vehcle intended rev range and end useage are critical factors in building a balanced combination which will make power where you need it... Stroker motors tend to be torquers making their power in the low to upper midrange revs so it makes no sense to cam and carb for 7k rpm if the motor will never see those revs... It has to be a balanced package....

 

That being said I have run all of the mentioned choices on a high strung free reving L28 p 90 setup and each has it's plusses and minuses....

 

For track useage I have a set of tripple 44's that are awesome.... do I like driving them on the street? ... no ..they have no bottom end and in my setup cost me 5-7 mpg over my Z therapy SU's on a portrd E36

 

Z therapy SU's are a Great Street and autocross choice..... make tons of torque great driveability great mileage, but they do fall off above 7 K RPM

 

Holley 390 would be my last rtesort as getiing the same A/F to each cylinder becomes more of a chore than either of the others..

 

I have jusst helped a friend set up a Mega squirt Injection system ( search Archives for Moby) and I will probably have My SU's and 44's up for sale soon as a result.... what a sweet package.... If you aren't afraid of electonics and tuning via a laptop it seems like the best of all worlds and certainly a lot cheaper alternative as well..

 

Hope this helps

[datsunlover]

I don't think I would have even given that warning Dan... I came back to this topic to post a thought I'd had after my last response. I saw that coment and actually laughed out loud.. I'm suprised his post count here has got as high as it is considering the mind set evident in that reply..

 

I had thought about maybe going to a 4 barrel carb/intake setup as it might flow more fuel than the su's and wouldn't have to deal with 'syncronising issues' of twin or tripple carbs. Only reason I havnt is that like I said, I have working knowlege of SUs now, and figure I'll go as far as I can with them rather than start freash on adifferent carb(s) setup. I say go with wat you know... if you're versed in holly/domestic carberation, go that route... unless you WANT to try something new of course..

[Guest bastaad525]

Stroker' date='

 

For track useage I have a set of tripple 44's that are awesome.... do I like driving them on the street? ... no ..they have no bottom end and in my setup cost me 5-7 mpg over my Z therapy SU's on a portrd E36

 

Z therapy SU's are a Great Street and autocross choice..... make tons of torque great driveability great mileage, but they do fall off above 7 K RPM

 

Holley 390 would be my last rtesort as getiing the same A/F to each cylinder becomes more of a chore than either of the others..

[/quote']

 

See there's a first hand account basically confirming what I said above. Tripples are great for racing on a high revving motor but aren't that great on the street. SU's are perfect for the street with great low end torque but fall off at high rpm. And I agree with the Holley comment as well... I've never seen how a single, centered carb on a long inline six engine is the optimum choice for performance.

 

If you're not racing on the track and building a motor that's gonna make good power at 6000rpm + SU's are your best bet and make a great all-around setup... for a street driven car they are probably the best choice, and on a 3 liter motor I would definately take a good look at those big bore SU's.

[Guest tony78_280z]

And I agree with the Holley comment as well... I've never seen how a single, centered carb on a long inline six engine is the optimum choice for performance.

With the same length runners it would flow equally. Think about it in three demensions. It is possible.

 

And these people seem pleased with the set up. In this Thread. Has anyone compared performace with every thing else being equal? I'd like to put this myth to rest.

[JMortensen]

Putting the myth to rest was talked about at length with Dave from AZC, who seemed to only be able to say that his intake won a car show, and point to customers who liked their new carb setup. See here: http://forums.hybridz.org/showthread.php?t=92930

 

The problem is that putting a new 4 barrel on a car with worn out SU's and listening to the reaction of the owner isn't a good test of the performance of the 4 barrel. It IS a good test of what is most likely going to happen to people who buy a 4 barrel intake since all of these people are buying the intake to FIX A PROBLEM. FWIW, see if you can find some posts from guys who just put the Ztherapy rebuilt SU's on their car. Here is one from another board: http://www.classiczcars.com/forums/showthread.php?t=17363&highlight=Ztherapy The owner is just as emphatic about the huge power increase they get. He claims it "feels like he gained 25 hp". Testing new to new would be the only way to resolve the issue.

 

My major issue with the 4 barrel is that it is a down draft carburetor. I am sure the carb flows 390 cfm on a V engine, not so sure that it would on a Z, because there is a hood clearance issue and the turn below the carb is very sharp. How the intake can make that sharp turn and maintain the full 390 cfm is the issue for me. I would bet dollars to donuts that new Ztherapy carbs would be at least the equivalent of a new 4 barrel, and the bored SU's would be a big improvement over the 4 barrel. The bored SU's flow 350 cfm and it doesn't have to make that sharp turn. The mixture issue remains unanswered also, but I remain convinced that it isn't a "performance upgrade" from a new set of SU's.

 

Maybe we should talk about AZC's bitchin oil pan so I can tell everyone how much I like it. Feel like I'm always the naysayer for Dave. Nothing personal Dave...

[SHO-Z]

I have to agree with the last post. The only real way to compare all of the carb options is to test each on the same engine, properly set up, and see how they perform. I have reservations on the 4 BRL carb set up never seen a 4 BRL on an inline race engine, but that is my personal opinion. If I could design my own set up I would probably use triple SUs like the old E type Jag had. I have a set of triple SK racing, weber clones, on my bench and will see how they perform some time this summer. The DGV Webers on my car now are ok but I would have been better to pick up a set of round top SUs.

 

I think a lot of it is how you use your car and what you expect out of it.

[Tony D]

I posted a reply on a similar thread earlier. Our Bonneville car had a Clifford 4BBl manifold for it's first record. Soon thereafter it was swapped out for triple DCOE Webers.

When we got off ElMirage and went to Bonneville for the second time for the serious records we were running Tec2 with EFI and 45mm TWM itb's. The engine made 40HP more than the Webers at 8250rpm, and was over 300Hp to the rear wheels.

 

BUT....

 

There was a guy posting at ZC.C under the screen name Andrei who built a stroker, and spent a lot of money for HKS 45mm ITB's, as well as an SDS setup (which I bought off him later) only to be disappointed with his performance. He "only" made 30 more HP than he did when he had a 4BBL manifold on it (252 or so vs 220 or so with the 4bbl) at a power peak of 6250rpm. For a street car, the 4bbl will work, you just have to play with it. Dave at AZZ talked around it, but wouldn't come out and say his setup is NOT the hot ticket for all out performance, he would only say "12 second 1/4 mile times are not applicable to the discussion, or not what this was designed for"

 

So in other words, you WILL be donw on power with a 4bbl compared to triples, and the can of worms exists if you will be up or even on power compared to a set of SU's.

 

Thusfar nobody has tested the setup. I hgave tested the Clifford, and the Cannon (Cannon, was hideous, we actually threw it in the TRASH!) But reading spark plugs for mixture distribution is stone age compared to aircraft instrumentation and EGT monitoring during a dyno pull---and with even the Clifford there were cylinder to cylinder variances.... I would be interested to instrument another engine and do the pulls to see just how much of Dave's sales pitch is hype and how much is B.S.

 

For a stroker where the power level will be reached below 6500rpms, I would say for as street car, the $ bbl would perform decently, but you would be down on power starting around 4500rpms (if our testing with the Clifford holds true to the AZZ intake as well)

 

BTW, we ended up running an 1100cfm Predator off a 500CID 11-second Cadillac V-8 on that manifold because the 390CFM unit was simply WAAAAAY undersized for our needs! Calculators say one thing, but actual real world dyno pulls say another!

[Guest norm[T12SDSUD]]

I might be considered a biased source...cough.... cough... but I say go with the SU's. I was able to hit 12's even with the stock bore SU's. They are good reliable carbs that need very little attention.

 

Later,Norm

[hellraiser]

i say roll with the tripples, still i agree with the members that stated it depends on ur set up , but tested or not tested how can two single throat su's compare to 3 double throat makuni's (webbers being garbage). a 4 barrel holley,on a z come on really ?