andyz77vette

I put a 350 in my 87 T/A that originally came with a 305. I am using the TPI setup that came on my 305. I have a chip for a 350 and I found out from the dealer that both engines use the same pressure regulator. I have 19lb injectors that came off my 305, but i know that the 350's came with 22lb injectors. I don't have the 22lb injectors, so can I use my 19lb injectors? Will the engine run okay? The motor has 110k on it and I was wondering if it would hurt the motor if I ran the 19lb injectors?

five7kid

iTrader: (14)

It will run okay. You might run out of fuel at higher power/RPM conditions. An adjustable fuel pressure regulator would probably let the 19 lb injectors handle a mild 350.

andyz77vette

I have found a set of 24lb LT1 injectors. They look like they will work in my TPI setup, but does anyone know for sure? Also, I see a lot about adjustable pressure regulators. What's the purpose of an adjustable pressure regulator? I'm not to familiar with what the poundage on injectors means, but I'm guessing that it means that it will flow 24lbs of fuel per hour. If this is true, how much of a difference in gas mileage (under normal driving conditions, not rawhiding) would you get going from 19lb injectors to 24lb injectors. Someone told me that a jump like that in size of injectors, I would loose 2-4 mpg. I don't think that's true. Does anyone have any ideas?
Thanks.

five7kid

iTrader: (14)

You guessed correctly on the rating of injectors.

Since EFI pulses the injectors to get the proper fuel for a given condition, larger injectors will pulse less at any given condition. They also tend to "mist" the fuel a little less. Therefore, use the smallest injectors you can for best fuel economy.

Higher pressure delivers more fuel per pulse, and tends to "mist" it better than lower pressure. But, there's a limit as to how much pressure injectors can take.

So, you set the pressure as high as practical (the reg lowers the pressure under high engine vacuum conditions) and use injectors as small as possible to deliver the best economy and power.

Ebby

I'm going through this right now. I have brand new 22lb injectors installed on a 350 that's supposed to produce 350-385 horses and there supposed to be too small. So now I have to replace them.

I've heard that if you run smaller injectors at higher RPMs, you run the risk of engine damage since the smaller injectors will cause a very lean condition, i.e., lots of heat. I'd get the original 22lb injectors, they don't cost too much. Just make sure that they are the saturated types with the higher resistance rating.

andyz77vette

The 22lb. injectors are almost as rare as chicken lips. I've called 20-30 j-yards, and been to 5 around where I live. I even tried to get some off of e-bay, but no luck. The only set that I can find was $190. Ford Motorsport SVO 24lb. injectors are around $100/set used. I bought the used 24lb injectors off the LT1 for $50. Now I need to know if I can use them with the original pressure regulator or do I need an adjustable regulator. The engine is stock, I haven't done any mods to it. What do you guys think?

Lo-tec

I think it's going to be fat. You can get a chip burned for the larger 24lb ones to work right. Personally, I would find a set of used 22's and get them cleaned & flowed instead of messing with a chip.

andyz77vette

Does any one know where I can get a set of used 22lb. injectors-CHEAP? My wife is about to strangle me for all the $ I'm spending on my car. I know Ebby said they put a set of 22lb. injectors installed and now has to have a larger size injector. How much do you want for your set of 22lb. injectors? Or does any one else have a set of 22lb. injectors for sale?

Ebby

I first have to have them removed. Either I'm going to do it or I'll have to have the car flat-bedded to a shop to get it done. I'm hoping to be able to remove them without taking the Plenum off. I figure I could loosen the fuel rail bolts so that I could lift the fuel rail high enough to be able to get the injectors out.

What do you guys think? Think I could get them out that way?

Anyway, I think I paid a little over $200 for them from www.fiveomotorsport.com.

But if you want to wait until I get mine out, I'll sell them to you cheaper. I'll probably put them on e-bay when I get them out. I'd need to see how they look when I get them out. The cars been turned on literally 10 times and that's only to make sure the battery doesn't die - which it now has since I haven't turned it on in about 8 months.

WHAT A MESS THIS THING HAS BEEN!

andyz77vette

When I had to change the injector seals, I just took off the upper plenum, the loosened the bottom bolts on the plenum tubes. Then I could unbolt the 4 bolts that bolt the rail on, take off the cold start valve line which hooks up on the back side of the driver side rail, and lift the whole rail and set of injectors out.

Ebby

I'll try it. I'm waiting for a response from the tech dept at summit as to which injectors I will have to get. As soon as I know, I'll order them and take these out.

Thanks.

andyz77vette

I finally bought the 24lb. LT1 injectors and a BBK adjustable pressure regulator (boy, someone is getting rich off of these. If I knew what I was going to get, I could have made it for less than $15). The instructions on the regulator tell you to check the pressure of the original one with the key on, engine off. If the charts are correct, if stock is 42psi and 46psi is ideal for daily driving, then what ever my initial reading is, just set my adjustable regulator 4psi higher right? Should it read 42 psi with the stock regulator with key on, engine off or is the 42psi the pressure with the engine on, but the vacuum line disconnected from the regulator, or should it read 42psi with both of these situations? Any help would be appreciated.

five7kid

iTrader: (14)

I'm getting a little over my head because I've only dealt with this to a small degree on my EFI FWD V6's. But, the typical method is to check the pressure with the engine running and vacuum disconnected, which should be the same as key-on and engine-not-running. This just gives you longer to watch/set the pressure, since key-on/engine-not-running will only give you a few seconds before the fuel pump relay times out.

You should probably set your adjustable somewhere in the 42-46 range. Adjust to tune after that - you're using it to adjust the injectors to the engine.

Ebby

According to the bible (TPI Fuel Injection Swappers Guide) all injectors are rated at flow at a specific fuel pressure, typically 43.5lbs 13 bar.

You must keep in mind that raising the fuel pressure makes the injectors work harder, thereby drastically shortening their useful life. According to the book however, you can safely raise the pressure to no more than 10%-15%.

You must also remember that the bigger injectors will most likely require a computer re-calibration and if you change the pressure that will again alter the injector’s flow rate. The equation to convert the static flow of an injector to that of a higher pressure is :

The New Fuel Pressure Flow Rate = the SQUARE ROOT of the New Fuel Pressure DIVIDED BY the original fuel pressure TIMES the original flow rate.

Good luck!