FI nozzle size / unit series relationship

[Robert Jorjorian]

Re: Impact of FI nozzle size

JOHN tell us what size nozzles whitey uses?

[John D.]

Z's *NM*

[John D.]

Re: Impact of FI nozzle size

RJ. Whitey uses brass nozzles. Think they are Z's though. Got them from a gmpartsman on ebay. Hear that guy was originally from the windy city area at one time. Jr.

[Robert Jorjorian]

FIGURES *NM*

[Mike McKown]

Re: A few questions:

In my experience of spending most of my adult life in an automotive assembly plant, your explanation sounds very plausible and logical concerning engine identification and line feed usage. If a Z06 engine took a different fuel meter and nozzles, there certainly would be some kind of id on the engine and at least a special notation made on the build scheduling sheet that followed the engine through the entire car assembly process. Further, there would have been someway for in-process inspection that this was in fact, the "correct" engine assembly for a Z06.

As far as the injector itself goes, it would also seem logical/mandatory that the FI model # be designated as for example, 7380, 7380-1, 7380-2 and 7380-3 depending on nozzle usage.

Sometimes the assembly process itself was chaotic and vague, the logistics and planning of how to do it almost never were. Hence, any deviation from the norm was documented and not left to chance and good luck.

I don't have the answer, just agreeing with your thought process. John's point is just as valid until something concrete turns up.

I'm still having a hard time with different flow rates on the nozzles. The spec sheet gives a pressure value. You set to that pressure. If you have high flow nozzles with a given pressure, you MIGHT dribble as Jerry stated. If you have low flow nozzles with the same pressure, you will definitely get a spray. So what do we do here?

[Michael H.]

Re: A few questions:

I think that if the small hole in the disk in the nozzle were created with laser the way it could be today, there probably wouldn't be different flow rates for a hole that is supposed to be the same size as the next disk. The .0115" dim is the target and likely near the actual size of the hole on the old nozzles but the shape of each would be ever so slightly different creating a different flow, even if so small a difference it would be almost impossible to detect. (that's the way it was explained to me anyway)

Same principal with Holley carburetor jets. The number stamped on the side is the flow rate, not the drill size. Holley engineers have proven that if you drill a jet just SLIGHTLY larger, it's possible, and likely, that it will flow less fuel than it did before drilling. According to Holley, this has to do with the ultimate shape and smoothness of the bore.

Years ago, when setting FI units up on the bench for racing, we used eight baby bottles to measure the actual fluid flow per nozzle. (baby bottles were fairly accurate in their volume) Amazingly, a matched set of 8 nozzles would always produce slightly different volumes of fluid. With the bottles moved to different nozzles, the results were just about exactly the same which eliminates any possible substantial volume variation from bottle to bottle.

[G B.]

What works

These are the best settings that I've determined by trail and error:

For a 283 with the 097 cam and Q (or R) nozzles, use .9 / 1.9 psi stop settings.

For a 327 with the 097 cam and W (or X) nozzles, use .8 / 1.9 psi stop settings.

For a 327 with the 30-30 cam and X or Y nozzles, use .9 / 1.9 psi stop settings.

The nozzle orifice sizes generally go up .01 mm in diameter with each letter in the alphabet. You can alter the stop settings somewhat to accomodate different size nozzles, but don't try anything drastic.

I've never encountered an engine combo that needed more than a 1.9 psi power stop setting regardless of what the GM calibration sheet says. That crap about a 2.7 psi power stop setting for a 283 with S nozzles is absolute BS. And yes, I've tried it. It makes more a very soft (over-rich) full acceleration run.

[Clem Z.]

we tested the same way but use 8 graduated

in CCs test tubes to collect the fuel back in 1957 with the NASCAR race car. we built a wooden stand,got the sketch from GM, to hold the unit and the test tubes and ran the pump with a electric drill. no we never had a explosion,guess we were lucky and later used non flamable solvent but it most likely caused cancer. these test showed that the volume was pretty equal. i guess we were looking more for plugged lines or nozzles because no one ever told us how to correct any difference.

[Michael H.]

Re: we tested the same way but use 8 graduated

That's funny, we used an electric drill also. I wasn't going to admit that though. Surprised you and I are still here to talk about it.

We couldn't afford the CC burrettes so the baby bottles had to do. (sure hope the baby isn't reading these posts. She'd be about 35 today)

Actually, If I would have known then that some cyl's run slightly lean/hot just by their very nature, the mix of different nozzles could have been useful.

Didn't have a hand operated vacuum pump then so, with the main control diaphragm cover removed, I would yank the axle link up. Could hear the 3/8" drill groan and the spray became vicious. Fuel vapor everywhere.