did you realize that the intermediate housing and the intake gasket match, but the manifold port seems to be about 20% smaller. why this restriction and could a person enlarge the ports on the intake to match the ports?

 

I asked peejay that, and he said if it was port matched it would cause turbelance, and you will LOSE HP.... I think that is what he said.... better clarify that people's..... LATERZ

 

i thoght that was polishing.

 

Polishing gets rid of some turbulence, which can be a bad thing. Expanding your manifold might bring your velocity down, but I've never heard of it creating turbulence in the runner.

 

but the restriction is only one little spot, like a kink in the garden hose.

 

ok.... polishing will make it collect carbon deposite, or somtin like that.... polishing is bad.... port matching the primary intake runner is bad..... that is what I was told from people who has experience.... I coulda miss read, but not likely...... LATERZ.......

 

Matching Port Sizes should not be any problem, if the size remains the same thoughout.

Enlarging all ports will slow velocity. This is why you can't make 3 inch pipe headers, the "push" will literally get lost in all that pipe.

If it has "kink" as you say, then remove it, and match ports. I did that with my Jet Ski, and matched intake and exhaust ports, the difference was amazing.

The way I match ports...

Lipstick on the large end, then Kiss Em together.
It will leave clear marks as to what needs to be removed.

 

No need for that in this case. You simply use the gasket as a template.

 

Awwww. Iddendat cute!

 

why would mazda mis match this so poorly. possible emmissions?

 

True, but sometimes even the gasket needs to be enlarged.

 

Cause you loose HP......

 

You don't lose hp. You may lose a bit of velocity and low down torque but in high power applications most people port match the manifold for better flow.

When I was running the modified Nikki on my ported 12A I gained 5hp by porting and port-matching the intake manifold. This was verified by before and after dyon runs.

 

He meant that Mazda mismatched the ports so that the engine would lose high end horsepower and gain low end torque.

 

How?
For the stock (STOCK) Nikki carb, the manifold is just fine. Exceptionally fine. The Carb is the bottle neck. Mazda did'nt purposely "detune" their intake manifold. If anything, they made it better by keeping the cross section small. The velocity is better...FOR A STOCK NIKKI CARB.

Now get rid of the choke, take a die grinder to the housing of the carb, enlarge the venturis, and slap in some bigger fuel jets and air bleeds, and suddenly...
....Yer STOCK MANIFOLD sucks!!

A couple things to remember;
We know from experience that the (stock 12A) is capable of 165 HP. It needs to breathe perfectly both in and out for this, but it is possible.
We also know that the Nikki carb that came with it was made to conform to emissions regulations all over the world. Squeeze it a little more for economy.
Then they stuck on an exhaust sytem that had to meet like requirements.
Then, they probably had to go back and revamp the whole thing to insure that it all worked perfectly together, and that it would last.
By the time they were done, they had lost a potential 60 HP.

But the manifold itself is just a sand casting. Castings shrink anyway. This was not a very precision made piece.
It never HAD to be!

Better attention is paid to other manifolds nowadays. But for a production "slapper-onner" where the manifold was'nt the weakest part of the car; Well...what do ya expect?