Everyday drivability of Triple carbs

[70 Cam Guy]

I just had a nice email conversation with Todd @ Wolf Creek Racing about a Mikuni PHH setup. Just want to say his good reputation on these message boards is well deserved.

On to my question and curiosity. I have spent the last couple days searching here and hybridZ for threads on the Mikuni's. They run the gambit but I failed to notice anyone talking about how our cars are to drive with a set of triple sidedrafts. I've seen threads about bogs and needing help but not many come back with a resolution and review.

When things are tuned and in good working order, what are these things like to drive? Say I want to to drive to work a couple days in mixed traffic. Will I be pulling my hair out in frustration for some reason that is car related? I am pretty aware that just stomping on the gas could (nearly) stall the engine. Do you triple owners have any major gripes? I would consider throttle response with my SU's to be very good, I hear throttle response is even better with triples?

I have driven my friend's race Mango (Corolla) and it runs like a top (and it's a monster) with the Weber 45's. No bogs, idles forever without issue, and pulls like no tomorrow. Other guys that frequent his shop drive their 18-RG and 2TG Corrola's/Celica's all the time with the Mikuni's. They don't complain but they are die hard old skool Japanese car fans. Are they just thick skinned and tolerant?

Cheers

[Zs-ondabrain]

Excellent question. When I had my triple Weber DCOE's on the 70', they were kick-arse after 2500 RPM. Awesome throttle responce, sucked air like a Hoover on Roids, and just sounded awesome. The car would idle, like you said, all day long and were adjusted to about 800 RPM.

However. Daily driving was a pain because my E88 head has bad valve guides, my block has bad rings on 2 pistons and Webers are a bitch to properly tune if the motor isn't up to par. If the motor was rebuilt and the N42 I have on the shelf was installed, and I had an O2 Sensor on the header with a proper meter, they would probably a lot easier to tune and more worth having for daily driving.

The problem with mine, on top of the bad motor, was between 1800 and 2500 RPM. Total flat spots, back-firing and low power. Those constant backfires filled my K&N filters with fuel, then the last time it ignited that fuel and scared the hell out of me with flames coming from the engine compartment. Beating the crap out of it with a towel then finally giving up and hitting the ignition sucked the flames back into the Webers and the fire was gone. That's when I decided to do the full polish and rebuild of the Original SU's and put the Webers on the shelf till the motor gets rebuilt, or I put them on the 260Z's rebuilt motor.

So in closing, the Webers are fricken awesome over 3000 RPM's, for me, but others will obviously have better or different results. Learn about them and how o properly tune them before considering them. They work great on 2.8's or bored out L24's and L26's.

By the way, when tuned right, I got over 27 MPG on the freeway.

Hope that helps,

Dave

Edited October 18, 2009 by Zs-ondabrain

[doradox]

My 40DCOEs were pretty well behaved. A little finicky below 2000 RPM ,couldn't snap the throttle wide open without a slight hesitation ,but perfectly driveable in Tucson weather. Idled well, got good mileage, stayed in tune. Keep in mind there is no choke but on a cold start a couple pumps of the throttle to get started and a minute or two warm up and all was good.

Steve

Edited October 18, 2009 by doradox

[conedodger]

Mine seem fine. I had them tuned on a dyno with EGT, CHT, and exhaust gas analyzer. Runs very nicely. With no chokes though, they can be a bit bitchy on cool mornings like today.

[jmortensen]

I ran triple 44's with a stock compression motor, a medium cam, a light flywheel, 2.5 exhaust and an ACT clutch and it was a *****cat in traffic. No problems at all. It did have less power off of idle, but that was a sacrifice I was willing to live with. I also drove basically the same setup (stock clutch though) with SU's and that worked great too. I think the car was faster at autox with the SU's because my gearing was too tall for the Mikunis, but I couldn't get myself to give up the top end power of the Mikunis. They made quite a bit more power on the top end.

[gnosez]

The only issue I have with my 44mm Mikunis is that I failed to have them modified to handle hard left hand turns. The bowls need a baffle to keep fuel from moving away from the pick-up.

For daily driving they are fine but a heat shield and coated or wrapped exhaust is required unless you want to boil off some gas.

A non-modified engine will not see much improvement over say a set of rebuilt SUs. Two inch bored out SUs on a slightly modded L series engine is a very good way to go also.

Mileage? From 25 to 8 mpg depending on my right foot. Average seems to be around 16 but then I drive my 3.2L hard.

ITBs with a good air/fuel computer would give me 20-40 more hp but at a cost of another $2-3K.

Triples aren't perfect but they are very very nice at what they do.

[jmortensen]

The only issue I have with my 44mm Mikunis is that I failed to have them modified to handle hard left hand turns. The bowls need a baffle to keep fuel from moving away from the pick-up.

You mean right handers, right? It's not a pickup issue, it's a sloshing over the jets issue. Tom Holt was nice enough to show pics of the simple solution here:

http://www.classiczcars.com/forums/showthread.php?t=18948

[Zs-ondabrain]

True, I've always Loved the INSTANT throttle responce when driving over 3K RPM, as aposed to the slower responce of the SU's. Those and a lightened flywheel would make for a neck breaking reaction to my right foot.

Dave

[gnosez]

Yeah, I got my right vs left screwed up (likely by being out here on the Left Coast for too long). I'll try the simple solution this winter (it snowed back home today in Boston).

[dimitri_zee]

Another thing though to keep in mind is not to skimp on the linkages. The people that say triples never run right usually are the ones that have cheap linkage setups that fall out of adjustment. Flatspots though are just acc pump adjustments and a good tuner can get rid of any. Just my 2c worth...

[Carl Beck]

Hi Andy:

I have ran triple Weber 40 DCOE's on my 72 since 1975. Once they were properly set up - I never had an issue with them again. You can hook up the chokes on the DCOE's, although I never actually needed them here in Florida. I'm pretty sure I have 36's for actual choke size inside the 40 DCOE's on my L28.

Want to enjoy driving your 240Z? Run the S.U.'s with electronic ignition.

Want a "wow" factor under the hood - triple carb's man.

Want to have a car that will start and run very well all the time - - get a modern Fuel Injection system.

In all three cases, the induction system has to be set up and tuned/programmed to perfection. A few dyno runs with someone that knows what they are doing is worth every penny.

Personally - today - I'd opt for a modern fuel injection system. If you want looks and performance perhaps fuel injection via the triple throttle bodies...

Just my opinion...

FWIW,

Carl B.

[70 Cam Guy]

Wow, I wasn't expecting this many responses! It gives me a fresh perspective and some more to think about

I actually have the SU's tuned in really well in my opinion. I have a ZX distributor and header/exhaust already. Before calling for a tow on my way to JCCS (voltage regulator went kaput) I was getting 25 mpg mostly highway. The car is definitely a lot of fun to drive and either way I want to get a Fidanza flywheel because I love a quick revving NA engine. Adding a moderate street cam has always been on my mind as well.

I like the idea of ITB fuel injection but I just don't realistically have the resources to support that idea. My friend's shop has a Dynapack 3000 (hub-mounted dyno). Tuning for max power would probably go fairly quickly but tuning for drivability takes a fair amount of time.

Aside from that, I have a seemingly irrational desire keep it old school. Being around what is probably an abnormal amount of classic Japanese cars with Mikuni's and Weber's, I love the look, I love the sound, and as shallow as it may sound, you can't beat the wow factor of all those carb's.

I've certainly had some biased influences

http://performanceoptions.net/Gallery.html

I assume the standard linkages from Wolf Creek are quality. The images Todd sent me look like very good quality actually. I do appreciate all the advice here as well. When little issues work together, you wind up with a big difficult-to-diagnose problem (as I experienced early on with a bum set of SU's). I will definitely also need a solution for the heat either homemade or other.

Thanks Jon, the 44's have actually been what I've been leaning towards. I still have my 4 speed so the gearing doesn't seem too tall to me. Is that me hearing what I want to hear?