Keeble

iTrader: (3)

I was thinking about making a tubular intake manifold for my mazda scince i don't have the money for a nice RB intake. I've never seen one on a rotary engine, but i was wondering if anybody had done this and if anybody had any pics.

lfb1

Have you made any progress on this? I've been thinking about the same thing. I figured I would make the top interchangeable between and a Holley and the stock carb. I planned on using exhaust u-bends and welding them to a plate
cut to match the intake gasket. My only concern is that the material may be to
thin and allow the fuel/air charge to get to hot.

Keeble

iTrader: (3)

ya something along the lines of what i was thinking, but we cuold use small tubing and possibly a conduit bender to acheive thee bends. and as far as heat is concered you could always make a heat shield between the header and the intake.

warwickben

iTrader: (1)

lol. i just got this idea too, then i came on the site and found this.

i am a welder, and tubing/pipe bender by trade so i figure i could make some thing up.
right now i am and a friend are making a new upper intake manifold to the stock 2 piece on a ford 2.3.

my idea is pretty simple. I'm more or less going to be making some thing like a inline 4 turbo manifold.nice simple L shape.

the thing i can not figure out is the tube's meeting the carb. for a 4 port motor, should the pipes feeding the port's get air and fuel from all barrels . i know what to do on a 2 side draft setup but not sure about a 4 barrel setup

orion84gsl

iTrader: (5)

There are primary and secondary ports on the engine and on the carb. Match them up the same as the stock intake mani.

PercentSevenC

That has been a matter of some debate. Jeff20B has some interesting threads on the subject of separate runners versus channels between the primaries and secondaries. It's also been suggested (I want to say by 84stock, but I could be mistaken) to connect the primary runners together with a channel, but leave them separate from the secondaries. Generally it's not considered a good idea to have all four runners open to all four barrels (i.e. open plenum). The best thing to do would be to make a bunch of spacers and try different combinations.

Jeff20B

iTrader: (13)

I will eventually try an Edelbrock 600 on a stock '74 intake manifold which has seperate runners. The carb adaptor has a channel connecting both primaries only. I have a four hole Holley gasket and an open plenum Edelbrock gasket to try. Engine is a streetported 4 port 13B.

Keeble

iTrader: (3)

hey warwick, why not make the manifold 4 seperate runners, and the play around with some 1" carb spacers to see which works best? It simplifies the whole guessing process, and would let you change it out fairly easily.

warwickben

iTrader: (1)

i dont really know to much about carb's, but i have a idea about how they work. i mean i dont know how to tune them or what size cfm a 12a would need and jets and so on. if some one could draw some thing up showing how the flow path should be from the carb to the port's . ie should i make the primary's on the carb go to the center iron's or the end iron's. should both runners have a channel cut in them to share the air ect ect.

orion84gsl

iTrader: (5)

A 12A will flow a max of about 365 CFM. No more without forced induction. On the stock manifold the primary venturi runners go to the centre ports and the secondary runners to the outboard ports. No reason to do anything different. A good manifold would help since the stocker is said to be a bottleneck. I believe the reason for the channel in the stock manifold is to aid in idle quality, but I can't say for sure. Just have a look at your stock manifold and copy that with some larger ID tubing.

Keeble

iTrader: (3)

i'll take a look at the stock manifold laying in my garage, and try and figure out tube size, but what wall thickness should it be? i'm thinking something like 14gauge would work good. i'll try and pick up parts this week

perfect_circle

it has been done, but it was a weber as i recal.. i think the dudes name was like coldy13 or something similar to that.

warwickben

iTrader: (1)

Jeff20B your the man in the know. what size 4 barlle carb would you say i should go with for a stock na 12a and a 12a turbo motor(thats my plan down the road) id rather have a na 4 rotor 12a but i couldnt make one my self.