tom94RX-7

iTrader: (5)

I was wondering if this was possible, to use the stock 550 injectors in the stock primary rail after it has been milled down 1/8" to use the 850 injectors. I have been using the 850s in there, but the idle was also too rich with the Power FC, and with my newly rebuilt streetported engine coming soon which will likely idle even richer, I decided to go back to the 550 primarys (I also have 1680s), and so I needed a stock un-modified primary rail but decided to see if I could still use my modified primary rail. See pictures attached. I got it all setup, I think there is no reason why this won't work. I just used 3 little washers, and longer bolts, to space up the cap about 1/8". And since the injectors don't fit down flush all the way against the rail (because the rail was milled down 1/8"), there is a little gap there where dirt can get down into the rail, but there is the big upper o-ring seal on the injector that won't let anything past it, and I put some electrical tape wrapped around the injector just above the o-ring seal to better seal off the top of the injector so no dirt can get down into the top of the rail. This would be the only possible problem but I think it will be okay. The injectors are tight in there, they don't go down in any farther.

Has anyone else ever done this? I searched and didn't find any talk about it, just some people selling the modified rail and getting a normal stock rail. I know I could have done this and got one for only $30, but why not save the money and use it how I have it now which seems good.

FD3S2005

iTrader: (11)

when it comes down to fuel, i wouldnt mess around, i would just get a stock rail.. think ENGINE FIRE?

tom94RX-7

iTrader: (5)

I know what you mean, but there is no reason that would happen just cause its not exactly stock.

93_fd

ill trade you for my stock rail?

tom94RX-7

iTrader: (5)

well I was gonna buy a stock rail but figured I would try this and it seems fine and I would rather keep this rail so I have it if I ever need more fuel and need to put the 850s back in.

FD3S2005

iTrader: (11)

could of just gotten 550s bord out to 850s.. or anything inbetween

tom94RX-7

iTrader: (5)

Before I bought my fuel system from kgparts I bought all 4 brand new stock injectors, to replace my old ones. so i have all 4 like new.

Dudemaaanownsanrx7

iTrader: (23)

I can't think of any reason why that wouldn't work. The injectors are sealed by orings, they are still in place and in the injector bore. Should work just fine. I don't think much dirt should be accumulating there so the electrical tape probably isn't necessary but it won't hurt anything either.
Getting injectors enlarged is expensive for what you end up with. Getting 550's enlarged to 850's to save a fuel rail from needing milled isn't worth it. Rails are cheaper then injectors, and if an injector ever failed you would then need to source another one, and then send it off to be enlarged. 850's are available everywhere and easily attainable. Hell, I have 2 850s and an extra 550 in a drawer just in case. If money isn't a big deal then going with a top feed primary rail with 720's or something would be money better spent.

tom94RX-7

iTrader: (5)

Actually maybe a better idea would be to put a little permatex orange gasket maker around that little gap where i put the electrical tape, that stuff would seal it up good and can easily come off if removing the injector. There was a little dirt around there when I removed the 850s thats why I wanted to seal it up better which may help the oring seal last longer if it is not exposed to anything. I put a little strip of tape around that top part of the injector before putting the injector in the rail, it has to be put on first and then it will stay there and last longer, it wouldnt stay if put on after the injector is in the rail. But putting some gasket maker around there after the injector is in the rail sounds like a better idea. Either way it should be fine.

Dudemaaanownsanrx7

iTrader: (23)

Yeah i wouldn't lose too much sleep over it. Even if some dirt made it to the o-ring I doubt it would harm it. It's not getting past it either. If it did then fuel would be spraying everywhere and u have other issues.

tom94RX-7

iTrader: (5)

true. Just some advice for anyone else reading this that wants to put the 550s back in. There is also filter screens there on the injectors so nothing can get into the engine, but those orings are squeezed in there so tight nothing can get past them unless they are super old and need replaced anyway, mine are new.