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Triple carbs for stroker motor


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I am in a bit of a quandry.  I have a set of Mikuni PHH 44 carbs on a Mikuni manifold AND a set of Weber 40 carbs on a Cannon manifold.  Either set will need to be refurbished.  I'm trying to decide which ones to put on my stroker motor.  I'm not going to ever race the car but I do intend to drive it in a spirited manner every now and then.

Years ago, I talked with John Coffey about this choice and he gave me his advice as a racer who spends hours near redline - which is something I shall very rarely, if ever, do.  His advice was to use the 44s, but, then again, he was a racer.

I know quite a few members have carbed strokers.  So what have you guys experienced?  And, if I do go with the Webers, what manifold do you recommend to replace the Cannon?

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What makes you think the Canon is insufficient?

I think I would do some volumetric calculations to see what the engine might want based on final displacement.

I would also contact whomever is now supporting mikunis II don't remember if Wolf still does it) and somebody for the webers (Redline maybe) and see what their thoughts are on the respective carbs for the proposed engine.

The 40s should perform better down low but that's not an absolute

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Patcon:  It isn't that I think the Cannon manifold is insufficient.  Heaven knows enough guys have used them over the years.  It's just that it may be too long for me to also fit an air box onto the carbs.  It's 252 mm from the manifold/head surface to the outside carb flange where an airbox would be mounted for the Cannon/Webers whereas it's 190 mm for the Mikuni/Mikuni combo.

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jitenshakun: What a sweet calculator you've identified.  And, as one might suspect, it tells me 40 DCOE for flexibility and 45 DCOE for power.

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20 minutes ago, Patcon said:

I would also contact whomever is now supporting mikunis II don't remember if Wolf still does it)

Todd Walrich, owner of Wolf Creek Racing, passed away in 2015. The business was taken over by FutoFab, but a quick search of their website does not show anything about Mikunis. I suppose one would have to contact them.

Edited by crayZlair
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I had been talking to Todd prior to his passing and have always wondered who might take up the Mikuni support baton in the U.S.  I've dealt with FutoFab in the past so it seems what my next step needs to be.  Thanks.

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I had been talking to Todd prior to his passing and have always wondered who might take up the Mikuni support baton in the U.S.  I've dealt with FutoFab in the past so it seems what my next step needs to be.  Thanks.
Kyusha House is the premier Mikuni support right now.
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2 hours ago, jitenshakun said:

There's a handy online calculator for DCOEs that's built by input from users and suppliers. It splits between 40s and 45s on a 2.8L on conservative or spirited driving. Extrapolating, I'd say pick up a bit extra for the 3.1L.

https://www.carbparts.eu/calc
 

@Mike

Could a page be made to house some of these really helpful links?

Tire calculators

Engine calculators

Zcar registries

Atlantic z car links

Etc

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2 hours ago, Patcon said:

I have always found Dave Patton to be very helpful

I've used futofab for parts simply because of the shipping prices. I live closer to the East coast so he saves me a good bit. But he has been very helpful as far as a gentleman that owns a business. 

I give him 5 stars! Would buy from him again.

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Thanks for the replies, folks.  Here's another related question for you then: I know it's very important to "port match" the intake manifold to the head as one would obviously want an unrestricted, predominantly laminar flow of mixture going into the head.

However, what about the other end of the manifold?  What I mean is, for instance, suppose one has 40 mm carbs and puts them on a 44 mm intake manifold?  Clearly, there will be no flow restrictions but there might be eddy currents or turbulence generated by the instantaneous change in diameter.  Might there actually be an opportunity for the fuel to condense somewhat in the manifold if there is, in fact, a pressure drop from such a mis-match?  Similar to the contrails seen off the rear wings of F1 cars in humid conditions?

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In reality, I'm thinking of mounting Weber 40 DCOE carbs on a Mikuni 44 manifold.  I put a carb and spacer on the near end of each one to illustrate differences.  I roughly measure the distance from the tabletop to the highest point of an air horn as 295 mm for the Cannon and 240 mm for the Mikuni.  That gives me almost 2 inches to play with for installing an air box.  However, it also brings the carbs that much closer to the headers.  But, putting in a heat shield is not an issue for me.

20210927_144152[1].jpg

 

 

 

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I certainly did not know that.  Are there any equations for making a determination of the effect?  Or, do you just have to put different configurations on a dyno?

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I think that there are too many factors involved to come up with a simple equation. The dyno tells all!
Yup, based on you application. Where you want to make power, what your cam is doing, etc.

Port match, run a reasonable velocity stack, a good air filter and call it job done.
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41 minutes ago, jitenshakun said:


Port match, run a reasonable velocity stack, a good air filter and call it job done.

Air filters ? We don't need no stinking air filters ! (Autocross only) 😁

Length from head to end of velocity stack is approx. 300mm (11.75 ")

 

DSC01537.JPG

Edited by crayZlair
added more for clarity
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