Switch from Cannon to Harada Triple Manifold

[LeonV]

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.

 

Another way of saying the engine doesn't like coming back down to idle, or is very slow to do so.

[Mark Maras]

Thanks, I'll add that to my list of descriptions.

Edited May 22, 2015 by Mark Maras

[madkaw]

I'm not sure I buy into the balance tube= lazy idle. If you remember my set up ,I had/have a separate vacuum log with all the associated hoses and my throttle response and idle was like a motorcycle. Never had an issue with a 'lazy idle', but have a Mikuni intake tapped at all the runners.

[LeonV]

I'm not sure I buy into the balance tube= lazy idle. If you remember my set up ,I had/have a separate vacuum log with all the associated hoses and my throttle response and idle was like a motorcycle. Never had an issue with a 'lazy idle', but have a Mikuni intake tapped at all the runners.

 

Did you sync the carbs with the balance tube disconnected? You can't disconnect the Cannon balance tube...

[madkaw]

Leon,

I know you have read pages of archives regarding syncing carbs. You know that is one of Tony's pet peeves about making sure that you can seperate the carbs for balancing, but there has been many arguements the other way. If you think about it, does anyone disconnect the balance tubes on SU's when they balance? Does your engine operate with all the time with the balance tube disconnected? No.

I would try and mechanically set the butterflies equal before doing anything and I would try and sync seperately, but in the end the carbs will be all tied to each other.

[LeonV]

Leon,

I know you have read pages of archives regarding syncing carbs. You know that is one of Tony's pet peeves about making sure that you can seperate the carbs for balancing, but there has been many arguements the other way. If you think about it, does anyone disconnect the balance tubes on SU's when they balance? Does your engine operate with all the time with the balance tube disconnected? No.

I would try and mechanically set the butterflies equal before doing anything and I would try and sync seperately, but in the end the carbs will be all tied to each other.

 

SUs are a completely different animal in the way they are arranged and in their function, and not comparable to triples.

I don't want to have a balance tube, period! So yes, my engine operates all the time without a balance tube. Firing pulses overlap each other during the inline-6 engine cycle and cause all sorts of disturbances in flow through the carb venturi. If you must have a balance tube, a smaller diameter one is preferable to at least somewhat restrict the effect. Cannon's balance tube is relatively large. FWIW...

[LeonV]

Anyway, sorry to derail your thread, Mike. Your setup looks fantastic!

[240260280z]

FYI Passini does not like the unwanted effects of balance tubes on intakes. "The small advantage a balance passage between the barrels of a DCOE carburettor might give at idling speed is more than offset by disadvantages at other times."

[Rio24]

I know this is a long shot since this post is from 2015. Mike I'm also having a return to idle problem what triple Weber's in a cannon intake do my shoes only happening when it's really hot outside and the engine temperature engine bay temperature goes way up do you remember if you were having the same issue or was it always?

[Zup]

@Mike W

[Rio24]

Thank you @Zup

[Mike W]

@Rio24

Yes I had a rather severe return to idle issue with my old Cannon manifold and it certainly contributed to the problem, but the manifold itself was not the only issue.

The main issue with the Cannon wrt this problem is that the 3 heim joints do not line up and I found on my setup that this misalignment caused excessive friction and a very slow return to idle.  I had to use rather heave return springs which really impacted the drivability of the car and so I needed to find a better solution.

I ended up eliminating the center joint but doing this made the main throttle rod less stable and so I ended up going with larger heim joints and a heftier throttle rod.  This change definitely helped the return to idle but did not eliminate it completely.  

The final solution to this, at least in my situation, was to replace the old worn OEM throttle linkage with a throttle cable.  I used a universal throttle cable from Lokar and in the end this solved the return to idle problem.  I was also able to change the return springs to something lighter and this really helped with the drivability.  

When I went to the Harada, I was able to eliminate all of the return springs except for the one that was integrated into the Harada.  It really cleaned up the engine bay and also helped with drivability.  You can also adjust the spring rate on the Harada and dial it in so it works in your setup.

I would say that the biggest change to this problem was going away from the OEM stock linkage and replacing it with the throttle cable.  I fought the OEM linkage for years and wish I had made the change to the cable long before I did.

In any case, I hope that helps.  If you have any other questions just let me know.

Mike.