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Intake/Air Filter for Triple Mikunis?


Doc Hawk

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I have a 240z with triple Mikuni carbs and velocity stacks. Does anyone know of a source for an air filter box / intake system that will work with my carbs? I didn't receive anything with the vehicle, just the naked velocity stacks.

 

Any advice appreciated.

 

Thanks,

David

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If you use a filter with a chrome cap on the end like the K&N's you have to watch that the velocity stack isn't too close to the cap. If you use an ITG or similar where the air can go straight down the carb throat the stack length is less critical, and you get the stack much closer to the end of the filter without really hurting flow.

 

Stock Mikuni manifolds are short, and the stacks are long. So you need a fairly deep filter. Also keep clearance to the fender in mind as that can be a problem for some setups.

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I did not like the cheesy chrome K&N style filters so I got these.

http://www.cbperformance.com/catalog.asp?ProductID=557

 

aoc11.jpg

 

You will need to cut the throttle arm mount off of the base on 2 of them because of how close together they are but it was easy with a die grinder and took maybe 15min to smooth them out.

These may not work with weber style velocity stacks that lock the aux venturi in place because the base is about 1/4 inch thick.

You could still use them but you would need to make sure that you use a set screw to lock down the venturi so they don't slide out during use.

I am using them with delorto's that have the velocity stacks bolted to the base plate.

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Superdan, I like those a lot. What part # did you buy? I have written them for info; I'd like to see a diagram that shows the mounting points so I can figure out if they would bolt up to my Mikunis, behind the horns. It seems like a 6" assembly would clear my fender well, and provide plenty of headspace for the stacks.

 

Thanks for the link!

David

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Superdan, I like those a lot. What part # did you buy? I have written them for info; I'd like to see a diagram that shows the mounting points so I can figure out if they would bolt up to my Mikunis, behind the horns. It seems like a 6" assembly would clear my fender well, and provide plenty of headspace for the stacks.

 

Thanks for the link!

David

Or, since you are also in SD if you want you can drop by my house and bring one of your carbs and we will see if they will bolt up.

Send me a PM if you are interested.

 

Dan

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You could get one of these

 

DSC00823.JPG

 

I supply them (I own the molds and a collegue/friend makes them) to guys in the UK.

 

Full carbon fibre (or glass if required) colours possible.

comes with 6 x stainless over centre clips and lip seal

Can be connected direct to 80mm cold air feed or cone filter.

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That looks pretty trick, SKiddell. It would probably be spendy to ship it over to the Left Coast USA. Also, it wouldn't accomodate my velocity stacks. Still looks nice. How efficient is the CF at blocking engine bay (esp. header) heat? Also, I'd like to see what the back side of the intake looks like, where it mounts.

 

How much do you charge for them?

 

PM sent, Dan. Thanks for the invite.

 

- David

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You cannot fit "stock" mikuni velocity stacks under individual filters without cutting away some of the stack. I went round and round trying to solve this problem. I ended up making a sandwich with two stainless sheet metal plates and two Lamborghini Countach K&N air filters. These were the only filters I could find that clear the stacks.

8254Engine_Small.JPG

 

If I had it to do over again, I would metal form the ss to make a lip for the filter and build a spacer so that only one filter was needed.

 

Sam

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I run 65 mm carbon fibre stacks under the airbox, clearance is fine. The carbon fibre air box does a good job at keeping incoming air temps down (around a max of +15 degrees whilst driving but more often lower) due to being connected to a cold air feed that goes through the rad support panel to a drum type ITG foam filter.

 

The CF backplate is cut out (6 x 50mm or 2" holesaw) to sit between the stacks and the carb bodys (ITB's in my setup) the stacks then hold the backplate in position, stainless overcentre clips then hold the airbox onto the backplate.

Its been on the car for 2 years with no issues, doing around 150 drag passes, several really hard track days and umpteen thousands of miles on the road.There are a number of cars in the UK using the same solution in either glass or CF.

 

I'll try and post some "install" pictures

 

I sell these units at cost (materials+labour) although the high dollar to £ at the moment would propably make the whole thing impractical.

Good for me buying stuff at the moment though:mrgreen:

We started making these after a very VERY bad incident with a $300 aftermarket, black, non flowcoated, fibreglass unit spat a rivet into number six inlet and nearly trashed my engine:fmad: the rivet pulled trough the thin glass and trapped itself under the inlet valve, the valve stuck open (partially) and the lash pad popped off its seat, the rocker broke, the seat was mashed and the valve bent.

They shouldnt have used rivets unless supported correctly and riveted the right way round

The makers didnt want to know about a replacement so we set about a redesign.

 

I won't mention who they are as thats bad form.

 

PM me for any other details

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wouldn't happen to have the initials T W M in it now would it? :D

 

On that note, can you elaborate on how you are securing the clips for the airbox to the base? Mine have a tendency to open up due to engine vibrations. They are held very loosely and really should have had some kind of lip to keep them in place. Instead, they are relying on pure friction, which is marginal at best and changes with temperature and vibrations.

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wouldn't happen to have the initials T W M in it now would it? :-D

 

Couldnt possibly say either way:mrgreen:

 

On the back plate we included a reversed lip that the clip "hooks" into.

The clips are secured into the main box by securing plates and nylok nuts....I then use aluminium foil race tape over the top, once bitten and all that.

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Couldnt possibly say either way:mrgreen:

 

On the back plate we included a reversed lip that the clip "hooks" into.

The clips are secured into the main box by securing plates and nylok nuts....I then use aluminium foil race tape over the top, once bitten and all that.

 

Sounds like something similar to what I was planning to do. There is a real problem with this design for securing the clips. Both in the way they use the rivets and how the spring clip stays secured. Since the recess molded into the base doesn’t have a lip, these clips are prone to just pop off. Each time I came back from a drive, I found at least 1 or 2 loose. I too contacted [insert name here] company about this issue and after several email exchanges, was basically brushed off with the notion that we haven’t really seen this problem and don’t think it’s a problem; therefore there isn’t a problem attitude.

 

I was also rather disappointed in the lack of a finish layer on the outside. The black gelcoat inside is fine, but the outer layer could have used a nice finish coat to make keeping it clean a little easier and dress up the appearance a little. Now that I have it all apart, I’m somewhat inclined to just go ahead and finish that aspect myself.

 

As far as the latches go, I’m going to have a go at these…McMaster Carr p/n 1889A34 (see attached drawing). The retainer portion needs to have the ends cut off and new holes drilled to fit in the molded recess, but this should work. I will re-use the backing plates for the new rivets, but will be using blind pop rivets instead. I suppose there is a slight chance the mandrel could potentially fall into the intake track at some point, but that is fairly remote in my experience. Perhaps a little application of some racer tape might be a good insurance policy.

 

If our USD wasn’t so weak at the moment, I’d be inclined to pickup one of yours. Looks like you’ve addressed all of the issues that [insert name here] company refuses to acknowledge.

mcm_1889A340L_thumb.jpg

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My uncle's solution on his roadster racer was to simply fab a sheetmetal base plate that attached to the carbs underneath the velocity stacks, like the base plate of the CF unit above, get an oval shaped filter tall enough to cover the stacks, and fab a solid sheetmetal top plate. The two plates were simply held together with carriage bolts and wingnuts; but more inventive types of clipping etc could be done.. and if enough care were taken in fabbing the two plates, it could look plenty clean.

 

You could even get some sort of "quick-n-dirty" clips to clamp the plates together, and have a pair (or more) of security screws that run through the affair hold it together safely.. IE, when installing the fliter, set it all together, clip it. The clips hold in loosely in place enough to free your hands to install the two bolts that REALLY hold it together.

 

my .02

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Added a picture of them installed to my above post.

aoc11.jpg

 

I do not care if I live to be 120 years old and see the day where all automobiles left are powered by Mr. Fusion.. that image will ALWAYS mean "horsepower" to me.

 

 

A thing of beauty is a Joy, Forever.

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I do not care if I live to be 120 years old and see the day where all automobiles left are powered by Mr. Fusion.. that image will ALWAYS mean "horsepower" to me.

 

 

A thing of beauty is a Joy, Forever.

 

agreed

 

this is a great thread; i'm glad to see so much coming out about [insert company name here]'s CAI box, as i was considering getting one. guess i'll have to wait until the USD heads back up before i think about the CF one, though :)

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