7th injector motor


New Member
Nov 12, 2008
i have a stock bottom end motor that has developed an engine knock,i am thinking about purchasing a built motor with the 7th injector set-up how reliable and usable is this motor i am new to turbobuicks but want the best bang for my bucks.Is this technology of the 7th injector setup old and outdated or can it be used also wat can be done to change it to the regular 6 injector setup if it is outdated.
I think it would be better to stick with a 6 injector setup. Not as much support anymore for the 7th injector. Lots of chips available with just upgrading the 6 injectors to something bigger.

Lots of tuning and combination options also available. I believe the 7th injector setup was popular when the ECU upgrades were not widespread and thus the 7th injector was a way to get more fuel into the engine without modifying the ECU.

Of course this was before my involvement with TB's so some Senior members might be able to chime in and confirm.

7th injector is old technology...was designed to provide additional fuel to the back 2 cyls which tend to run leaner...I had one...problem was it did provide more fuel to the back 2 cyls but also more fuel to the other 4 cyls...so it always ran rich...just get a power plate...
would i be able to use the same fuel intake set-up and just change injectors or would i have to get all the related stuff over like the intake
I wonder what would happen if say you had 60lb inj but then ran 65lbs inj on 5&6 cyl with no plate? Just a thought has anyone ever tried this? It would prob screw up the fuel curve or the fuel psi on the back side of the 65's would be to low. I don't know just a brain fart. lol :redface:
Pull the 7th system, and install 65lb Motron injectors and use a Turbo Tweak, Full Throttle of any of numerous chips out there to make it function. Buying everything from the same vendor usually helps ensure you are getting matched stuff.

I use to use a 7th AND 8th injectors and really liked them, Real simple to tune with them. Here is a pic of my 7th/8th injection set-up. MUCH better than the Red or ATR system, though a little more involved. Better spray patterns. I tested both ways with the injectors 90* and straight on, And the 90* set up would create droplets of fuel swirling off of the pipe. The ATR system......well....it just was dumb. I even installed a few of those back in the day. I think I installed every part that ATR sold. Some of thier stuff was real nice, some of it was non functional. (it may have looked cool, but didn't function as advertised) Man, those were the good old days.
Now we use a 7th "injector", but we run methanol through the 7th, not gasoline. (Alky systems aka AlkyControl on this board) There are lots of alcohol systems out there, but Alky Control has incredible personal service. Julio is a stand up guy!
This 7th/8th set up is for sale for anyone that wants that "retro-look".:)


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The powerplate is a proven way to equalize the airflow into all cylinders. Has been used by many on this board. They are made by RJC and alot went into testing with these by RJC to prove that they did what they said.

Then you will just need to:

1. get rid of the 7th injector setup.
2. put the RJC power plate in.
3. Upgrade your injectors to 60lb motrons (bigger than 60 injectors can't normally be used on unmodified ECU's because their low impedance is too low and can blow up the injector driver IC's in the ECU).
4. Order a chip from turbotweak/gbody/fullspeed throttle giving them your setup info.

If you want to upgrade your setup from stock for more HP then you can add various things to your combo.. First hits on the list of things to increase your HP is as follows:

1. Replace and put in a bigger downpipe.
2. Replace your injectors as described above.
3. Replace your turbo with something a litle bigger.
3. Get and install an Alky kit.

Either way here is link to the turbotweak site to see what info you need to gather from your setup: TurboTweak Home


Thanks for the advice DLAFONT and evryone else who took the time to answer as you can see i am very new at this but look forward to having a great car
The RJC plate does work well with a chip. If you have a FAST XFI with a distributor then you can do individual cyl tuning ;)