Switch from Cannon to Harada Triple Manifold

[Mike W]

So I have never been particularly happy with my Cannon manifold for the triple Webers that I run.  As many of you know, the alignment of the rod ends that are tapped into the manifold and not particularly accurate and as a result it has been necessary to remove the middle rod end so as to minimize binding of the throttle rod.  I have always had issues with this setup in terms of "return to idle" and this misalignment exacerbated the whole setup.  I have also had to use external return springs which just add more clutter to the engine bay as well.  So the primary motivation I had for this upgrade was to achieve a smooth return to idle regardless of whether I was successful in eliminating the return springs or not.

 

For some time I had been contemplating an upgrade to a beefier throttle rod with the existing Cannon manifold, but this would have also required larger tapped holes in the manifold due to the necessity of having to use larger rod ends as well.  Also was never clear if doing this would potentially eliminate the external return springs that I was using. 

 

In the end, I opted for a brand new Harada manifold that I purchased on eBay from a seller in Japan.  It received very good reviews and I know that a few folks on this forum have used them as well.  The transaction was flawless and the shipping from Japan was like lightening.  I received this unit faster than some things that I have purchased domestically!!

 

In any case, I thought that I would share my install and the results that I have achieved.

 

First a few notes about the Harada. 

 

The throttle rod "arms" are actually built into the manifold as opposed to the threaded approach with rod ends that the Cannon took.  There are only 2 arms and so the alignment by definition is perfect.  The manifold does provide for a "middle" arm but I chose not to use it as it interfered with one of my throttle arms to the middle carb.  Also, given that the Harada uses a 10mm throttle rod (which I actually replaced with a high strength stainless steel version that I purchased from McMaster) the rod is definitely beefy enough that you can do without the middle support arm.

 

In addition, the Harada includes a built in return spring that I was hoping would be beefy enough so as to eliminate the external ones that I had been using with the Cannon. 

 

Finally, the Harada is about an inch shorter than the Cannon and although I definitely welcomed the increased room it gave me in the engine bay, I did not anticipate the improvement in engine performance that I ultimately achieved.  More on that later.

 

Upon receipt, I noticed that the casting on the manifold was a little rough (although significantly better than the Cannon) and so I proceeded to clean up all of the casting marks and also did my best to polish up the runners as well.  Once this was complete I had the manifold powder coated in a gun metal grey which really complimented the rest of my engine bay.

 

Now for the install itself.

 

On my old Cannon setup, I used the front or forward facing throttle mechanisms on the carbs themselves, but given the layout of the Harada and the positioning of the arms and return spring, I was forced to move to the rear most throttle mechanisms on each carb.  This was actually an easy swap and worked out well with no interference.  I also had to fabricate a new bracket to hold my throttle cable mechanism to as to avoid any interference with the new positioning of the throttle arms.  Everything worked out perfectly.  While I was at it I also rebuilt each of the Webers with new gaskets, needle valves, etc., and upgraded to the heavier internal return springs so as to increase my chances of being able to remove the external return springs.

 

I kept all of my jetting the same based on the belief at the time that the small change in manifold size would not really make that much of a difference.  For reference, my primary jetting specs were as follows:

 

Choke - 32mm

Idle jet - Keith Franck / Hypojet equivalent of 60F9

Main jet - 130

Emulsion tube - Keith Franck equivalent of F11

 

Car started right up but was running a little rough and seemed very rich.  Went through a complete balance as well as setup of the idle mixture, but car still ran very rich at this point.  However, I had no stumbling issues or the dreaded off idle stumble and the car ran great especially at higher RPM's with the exception of the richness.

 

So I ended up backing off on my idle jets to a 55F9 and also increased my choke size to 34mm.  I had tried the 34's with the Cannon setup in the past and could never get it to run properly no matter what I did to the jetting. 

 

Well the Harada was a whole new experience.  Once I finally got everything in sync and I properly adjusted my idle mixture, the overall performance of the car was like never before.  Acceleration is smooth with no signs of an off idle stumble.  No coughing, no backfiring, just smooth acceleration and great pulling power.  And best of all a perfect return to idle without having to use the external return springs!!

 

For good measure I also did add some longer velocity stacks that had a more rounded lip than the stock ones that came with the Webers.  They do look cool and I also believe the design of them helps quite a bit with the air flow into the carb bodies.

 

I have not messed with my ignition timing yet but so far have no pinging even under the most severe loads.  I suspect that I may be able to add a little more advance and see if I can eek out a little more power as well.  It's very easy to do with the 123 Igniton system I have so I will probably be tweaking that this week.  Other than that and the possibility of going to a slightly smaller main jet, I am very happy with the upgrade.  This is definitely a cut above the old Cannon manifold both in terms of performance as well as drivability.  Wish I had made the change years ago.

 

I've attached a few pictures so you can see the install progress.

 

Mike.

 

                   

[grannyknot]

Mike, very nice work as always. The new intake looks like a solid unit and the velocity stacks are stunning!

I had a hard time getting my trumpets centered on the the intake hole of the carb so took a piece of ABS plumbing pipe and tapered it down and inserted it into the trumpet with the nuts loose, then tightened.

It probably doesn't make much difference but makes me feel I have done everything to allow a perfect laminar flow of air.

Chris

[Patcon]

How did you go about purchasing this manifold exactly? I have tried looking some in Japan but the language is quite the barrier for me. Also where did you source the airhorns and filters? I like those too. The setup looks great and very clean. I like all the braided hose.

[Mike W]

Chris,

 

Thanks for the compliments.  I am very happy with how everything turned out and even got some unexpected positive surprises at the end.

 

Charles,

 

I purchased the manifold from eBay.  The seller I purchased from is selling an exact replica right now.  You can find it here:

 

http://www.ebay.com/itm/Datsun-240Z-260z-280z-Harada-Intake-manifold-for-triple-Mikuni-Webers-/281695592902?hash=item41965da1c6&vxp=mtr

 

He was great on communication as I had some questions for him before I pulled the trigger and his shipping was as if the item was across the street.  I think from payment to arrival at my door was about 4 days.  Japan to Texas!!

 

The air horns were hard to find and were not inexpensive but they are works of art.  I was trying to get them originally from Techno Toy Tuning but they did not have stock and it was going to be a few months before they completed another run.  Instead I went with Borla Induction (formally TWM Induction) and they were great to work with.

 

The filters come from Bills B Racing.  He made the ones I used on my old horns and knew exactly what I needed for the Borla trumpets.  In fact it was Bill who steered me to a specific person at Borla who ultimately helped me out with my order.  You can find Bill's site here:

 

http://www.bbrfilters.com/

 

I've gotten a lot of flak about running these filters and the potential wear on my engine.  I've run these now for about 3 years (and perhaps 6000 + miles) and completed a recent inspection of my cam, etc and it all looked perfect.  I don't know if I would use these on a dirt track, but for normal street driving that I do they work great and look really nice as well.

 

Hope this helps.  Let me know if you need anything else.

 

Mike.

[Patcon]

Mike,

Thanks for the links. I would buy the intake today if I had the extra cash. I saved the listing. You would think if the filters were suspect the two guys with GT40's wouldn't be running them...

[Reverend]

Wow that looks sweet, and it comes with all the hardware as well? Damnation... i think i have to get one.

[Mike W]

Yes it is a complete kit. although I did not use the supplied linkage as I have a custom made billet set of arms and actuators.  It does come with the complete linkage assembly, mounting plates and gaskets, studs, nuts, and washers for the carb mounting, and even a new intake / exhaust manifold gasket. 

 

It is a little on the expensive side but frankly no more than what you would pay for a new Cannon setup and in my opinion this is a cut above the Cannon system.

 

Hope that helps.  I can supply more pictures of the Harada system if anyone needs them.

 

Mike.

[LeonV]

My biggest problem with the Cannon manifold besides the misaligned holes for the heims was that it has a big balance tube built into it. I think that's one of the major contributors to lazy idle syndrome seen on many Zs. I've since installed a TWM intake on mine but have yet to test out that hypothesis.

[madkaw]

Beautiful set up Mike!

[Reverend]

There is no balance tube in my Lynx manifold and idle is lazy anyway.

[LeonV]

There is no balance tube in my Lynx manifold and idle is lazy anyway.

 

Like I said, it's a contributor but certainly not the only factor...

[Mark Maras]

Please excuse my ignorance but what is the symptom of "lazy idle". I haven't heard the term used before now. It seems to be related to triples in this thread. The only triple setup I ever worked on was a 65 Pontiac GTO.