hey guys im new to your forum but i must say this site has been so much help to me and has answered many of my questions ive had about my 12a turbo but i need your help once more



The setup consists with ,a holley blue fuel pump and nikki 4 barrel the motor has street port side plates but standard exhuast porting , runs a turbo from 88 rx7 that has been rebuilt with t04 internals and flowed front cover the nikki has pressurized floats to fuel for boost my questions are:



:How much hp and boost will the 4 barrel support before i go to lean the last owner said hes opened up the jets ect.



:is this a sufficient way fuel for boost if not any other suggestions i want to keep the nikki as moneys tight



:my dizzy is locked what timing should i have it set to at idle so i dont deternate later in the revs



thanx so much for any input you can give me it is greatly appreciated

 

Hey mate I set up a customer car a while back running a street port 12a, stock s4 turbo with external wastegate, electronic dizzy locked at 15deg btdc no retard, a stock nikki carb (standard chokes but larger jets), holley blue pump, s4 intercooler(front mounted) and 2 1/2in exhaust. It made 241rwkw (325rwhp) on 13psi boost.

 

thats awsome mate cheers for that info ive been told by heaps of people that the 4barrel will not cope with over 10psi boost and will leak ... obviously they were wrong



did you guys pressurize the floats like in my pic or a diffrent method , im not going to intercool this setup as the to4 internals should have that boost resonbly cold

 

Cool setup.



You should definately intercool that thing. Just go to the salvage yard and pick one up from another car.

 

Yes all nikkis leak when blowing through them, its just something you put up with. 10psi should be plenty with a to4, I wouldn't exceed 12psi. The float bowls don't need to be externally pressurised as shown as they are connected to the air horn via passages, this means they will be pressurized anyway when blowing thru the carb. Just make sure the floats are solid (I'm fairly sure they all are anyway), if they're hollow they'll collapse under boost pressure.



Or you could save yourself a lot of trouble and inject it. Blow thru nikkis are very time consuming to set up and tune and will always leak fuel around the gaskets. By the way you need a rising rate fuel reg, I usually mod a holley reg for carbs.

 

rising the fuel pressure is one thing im a little confused, told 2 diffrent storys about this subject some say the 7psi from the holley will easyily fill the bowl when the needle opens and that pressurizing the floats like i have done will stop fuel going backwards



how do you go about modifing the standard fuel pressure reg

 

First of all you need a fuel pump that pumps 3psi more than intended boost pressure. A holley blue will be fine, they regulate at 14psi. A holley red will not as they're a 7psi pump. Whoever told you that pressurizing the float bowls will stop fuel going backwards doesn't understand basic physics. The only way to do this is to use a rising rate reg. Fuel pressure is set at 3-4psi at idle and as boost increases so does fuel pressure, pound for pound. That way fuel pressure is always 3-4psi above boost pressure. If you try to set it up any other way the carb will either flood all the time or lean out under boost and your engine will go POP. Modifying the reg needs to be done properly or it will not work correctly. It needs a nipple fitted to the top cover(above diaphram) and the breather up the side of the adjustment screw sealed off. I assume your in NZ? Send it to me and I'll do it for $20.

021646170.

 

awsome man ive just txt you , thank you so much for that info ill definatly get you to do that and i hope this write up will help other people with the same questions as me

 

nice, i'm trying to figure out if I want to turbo mine. Have a 14b froma 1g talon I was thinking of rigging up. Let me know how it works.

 

I did a pressure check on a Nikki to see if the floats would hold up. I pressurized the carb to 30psi and they were fine.