Z Intake Plenum Constructoin

Mike Mackaman said:
Two thoughts on this:
1. Doesn't the fact that the 240 and 260 come factory with a velocity stack pretty much allow us to do whatever we want from the velocity stack standpoint as it is a replacement?
2. Playing around with a piece of string on the flow bench, what is more than 1-2 diameters in front of the openning doesn't even come into play. Several diameters to the side does however, even with a velocity stack. This may give you some direction to make sure you are ok.
Mike
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1. Not according to National Tech last time I asked ('course that was years ago). If you want to use stacks on a Z you need to use the entire stick backing plate according to them. Can't even cut out the stacks and use them, whole backing plate only.

2. True. You'd really want a big radius bell shape, not the tight radius sharp edge of the stock stacks.
 
FWIW, the K & N round filters will allow the stock velocity stacks to remain in place but they are a pain in the $%^ to fit and bolt on. :)

Factory backing plates/stacks are common on Ebay and on the z car sites. Expect to pay form $40-$75 on average with some going much higher.

The Pipercross filter with factory stacks and backing plate with a "modified air cleaner backing plate that has been extended and insulated" seems to be the ticket according to Katman. He even posted his up on here not too long ago IIRC.

I have all of the parts to make mine just haven't found the time. Hopefully by CMP it will be done.
 
Paul... Very cool. Nicely done.

When I first started I was told the same thing that Katman said, except I was told that you could only use velocity stacks if you used the stock part. I was not told that you have to have the entire unmodified stock air box backing plate. That seems to contradict the rule allowing you to modify the air cleaner box. If that is the case, mine is "non-compliant". I have a call in to Topeka. I'll let everyone know what I hear.
 
Ron Earp said:
What is that orange piece that all the stuff is attached to and has two pipes on it?
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That is the factory backing plate and stock stacks! :D

Steve, That is the picture Keith sent me. Mine will be similar but my fab skills aren't as good as what is in the photo's.

BTW, that is one of Katman's motor's Notice the cool oil pan!
 
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If anyone needs the stock backplates we have several layign around the shop you could have cheaper than from ebay (was going to ebay all but 1). I don't know if there were differences between the 240 and 260 backing plates though. Where can the pipercross filter be found???
 
The easiest way to tell the 240 and 260 apart is that the 240 air horns are round, the 260 are rectangular. Other than that they are both orange. not sure about size. The 260 also bolts on with three fasteners per carb.

Mike
 
OK... I got a response from Topeka yesterday. I sent an email to John Bauer, a tech assistant. The email had a photo of a stock air cleaner box backing plate, a modified backing plate that retains the stock air horns, some modified stock air horns, and some aftermarket replacement air horns. I gave a written review of the rule and arguments for/against each prep level based on the GCR.

After reviewing my submission he called me to discuss it. To put it in a nutshell, he said that his interpretation would be that the stock air cleaner may be modified, but if you want to run velocity stacks you have to use the stock ones. He didn't fell like the second sentence gave any wiggle room on that. He did say that he thought that it would be OK to cut the velocity stacks from the backing plate and use them with any air filter you choose.

Note that this is not a formal "rules clarification". So without that $250 piece of paper it would be up to the stewards interpretation if someone had heartburn with your setup and protested you. It's good enough for me. I'm comfortable with my modified air box and OEM velocity stacks.
 
Parrish57 said:
It's good enough for me. I'm comfortable with my modified air box and OEM velocity stacks.
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I am too, that is, I completely agree. You are using a stock piece and you are allowed to modify things in front of the carbs. You can certainly drill holes in the backing plate, right? You could snip off a piece of the backing plate to allow a hose to route around it, correct? Well then you've just snipped off the rest of the plate and left the stacks, seems like a good idea.

I need to find a plate for a 260Z so I can get to making my car all legal and make a new air box.

Anyone have a line on a stock piece for a 260Z?

Ron
 
"I need to find a plate for a 260Z so I can get to making my car all legal and make a new air box.

Anyone have a line on a stock piece for a 260Z?"



I'll check and see if we have one around. Inherited a warehouse with a ton of old datsun parts. Will get back to you this pm.
 
Ron,

I'm told we have a couple of 260z backplates though I haven't seen them with my own eyes. Email me at [email protected] if you would like one, and I'll be able to verify for sure by tonight that we actually have it.

chris
 
i gained the 4 hp with the foam type vs the twm with cone on the dyno. the cone was ducted to the openings in front by the radiator with a heat shield blocking heat from the radiator and directing air to the filter
not sure what the effects of air flow with the car moving are.Obviously the car was stationary on the dyno. I had the stacks on in both cases. The engine builder had said that the TWM unit created too much turbulence inside it.I had run it like that for anumber of years but decided to check it out while the car was on the dyno
 
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