Modding primary rail
 

Im in the process of putting together my gt35, i have a fuel rail, fuel pump, and 1600 cc injectors. Im planning on using my 850 as my primaries.

The problem at this point is I dont know what i need to do to modd the primary rail. I read about it but cant find a thread about it showing what needs to be done..

Any help, or link would be much appreaciated..

You need to take it to a machine shop and have them cut .125" off the top of the rail. This allows the 850's to sit lower in the rail and prevent leaks.

David Garfinkle also does this modification for only $5. PM him "Garco Motorworks."

Oh and just so you know, tuning with 850's in the primaries can be a bitch. Hopefully you have someone good to take care of your tuning.

wow thats stupid cheap...I see most shops charging 50 minimum

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/how-modify-850cc-fit-primary-82244/

I found this just to make sure I wasn't imagining something.

Thank you all for the info.. I will be contacting someone from the list to get it done..

Thank you once more.....

you can also just use two o-rings

You should do more than just machine the top of the fuel rail. Take a close look at where both the upper and lower o-rings seal and you will see what I'm taking about....

Milling 1/8" off is all you need. Besides taking the slight burr off the edge I'm not sure what else you would need to do. I've sold over 20 modded fuel rails with no problems ever...

We used a belt sander...took like 2 minutes.

Unless you are planning to make a lot of power, 850 primaries are hard to properly tune idle and low cruise.
Use 550 primaries with the FJO driver for the Bosch 1600 secondaries, and you will have a lot of fuel with a system easier to properly tune.

My duty cycle at 15psi boost is only 69% with this setup. Before with resistors on the 1600, it was in the high 70%.

Agreed. I will never again do 850cc primaries with the PFC. Too many negative side affects..

i will trade you i have a modded primary rail and i want the factory one to go back to 550'ss

I have top feed 850's in my car and the car idles great! I've also installed a modded primary rail with 850's into a couple peoples cars and they run just as good as the factory ones. On one car it actually idled better after the 850's went in!!! :dunno:

Same here! I just installed 850's in primary and 4 1000's injectors in secondary. At first I thought the idle was slightly lumpy because of the 850 injectors, but after messing with the idle adjustment and air bleed screw on the TB, I have it rock solid! Plus I still use the Idle Speed Control... Injector duty at idle is 3.5%, not sure what that means, but with my stock twins it was 4.5%...

Another thing to note, I'm using an Xcessive LIM, which elimates the air injection at idle to the primary rail...

I have no problem tuning 850 primaries either, idle & drivability are perfect.

sorry bud, I had it done the first day after I found out what to do.. Otherwise I would have done it for you.........