if you want a better manifold for your hitachi carb then you should search out a rare manifold from the US that was fitted to some rx5 and maybe some REPU
this manifold is reversed
you read correctly
the engine fitted with this manifold originally came as 4 large , same sized ports
the carb fitted to the manifold is spun around ( intentionally from mazda )
so that the primary ports take the long runners to the endplates
and so the secondaries take the short runners directly to the engine middle plate
Could be achieved easily with a holley and RB holley manifold because they are square bore, all 4 holes are the same space from each other and from the 4 mounting posts so it would be easy to mount a holley with the primaries feeding the end plates and the secondaries feeding the centre plate. Might have to try it some time.
craig has tried an original rb manifold and 650 dp holley yes car ran ok no secondaries though revving up to 7000 on primarys
didnt feel like any better accelaration and idle was good
i run a 12a with secondary bridgy and run out of fuel at the race track due to the following
1 pick up in fuel tank in series 2 rx7 - result will make a group c 80 litre tank tyo go in my series 2
now big question 10mm or just use 8mm fuel lines ??
2 float levels almost touching the roof of my nikki carby - result currently modify my carby to what onerios does have drilled jets and air tubes nicely primary - 90 air - 120 , secondary - 140 - air now at 220 .
3 replaced mazda fuel pump which gives you a static unloaded fuel run into coke bottle of 450mls
- now have carter u.s. 30 gallons model - which gives me 1700mls tested for 60 seconds
4 car does run a little better can get some racing out of it goes to half a tank and does splutter on some bends when cornering.
so after i decide to make a bigger tank with 2 pick ups for fuel at the back corners OR DO I MAKE ONE PICK UP IN MIDDLE with small box sectoin at back 50mm lower 100 to 150mm box area for fuel to fall into thus never running out , theory!!
willing to try 1 or 2 things simple and easy on my budget
anyone else having as much fun as me!!!!
and as for a holley 450 4 barrel good luck finding one under the $$450 mark
so i soon may have a first gen rb 12a manifold for sale if i can't figure this nikki carb thing
good luck fellow mazdas ........craig