Vets-Vet

With the exception of a vacuum line coming off, my 87 runs pretty good. I do have to go into the plenum soon (and maybe get brave enough to do the china walls). I believe for a weekend driver, no autocross etc, what appears to be stock injectors are doing OK. To have them rebuilt was once an option, at 35 years old, is that choice still a smart one? I certainly would not go for just a cleaning. What is not replaced on a rebuilt injector ? Thanks for any insight.

Whaleman

Fuel Injector Connection - High Performance Fuel Injectors

Ask Jon here. I threw mine away and got Bosch. Dan

THE 383 admiral

Many advantages installing modern injectors. price to performance ratio.
Almost no point rebuilding old technology.

vader86

I'm using FIC injectors, why bother rebuilding when something just as good or better is sitting on the shelf, its not going to save you money to rebuild them really.

topfuel67

There isn't much to rebuild in them. It is basically snapping off the pintel cap and replacing a filter. The inner workings are very fine and and if they're bad they're done. Like others mentioned, it is worth upgrading. I found on my 92 vette the same flow rate bosch IIIs were common on Frod 3.0L V6s in the 96 Taurus and other cars. You can find Bosch IIIs that flow the same rate, but have 4 holes instead of 1 so the fuel spray atomizes more efficiently. I picked up a set of 8 for under $40 that had new o-rings and filters. Fits perfectly and plugs right in. You wouldn't even be able to tell I updated mine if you didn't know what stock injectors looked like.

Zip Corvettes

NO pitch them. Holley has new injectors if you can get them and you can use the Bosch III injector which is a great injector but it requires you to use one that has been setup for a TPI or LT1. We have a couple of part numbers depending on what size if you look on our website. The only thing a rebuild does is clean the inside of the injector, replace the filter in the top, pintle cap if your injector has one and new o rings. It does nothing for the coil if it bad and generally that is what goes bad.

Vets-Vet

Thanks everyone. I think there is a consensus here. Jon it would be L98 stock 22 or 24lb nothing that needs tuned. I am pretty sure Z52's had no performance mods other than cooling.


P.S. Goodbye Ian

MikeT 90 C4sixer

I would also vote for replacing them old injectors. So many options out there, for newer and better. I had my L98 IROC original injectors sent out, several times, for cleaning and "flow matching". I have had my IROC a long time, and over the years the original injectors became leaky, causing "warm" restart issues. I just wish I had changed them out sooner, as I have the Bosch III's in there now, and/also put them in my C4 back in July of 2013. Now, I'm never looking back on old injectors!

Zip Corvettes

22's are stock

MikeT 90 C4sixer

Correct, but I put in the Bosch III 24 lbers. I do my own chips, so I am able to compensate for them in the PROM.

Vets-Vet

Does 24 lb require compensation ? Is there a noticable performance difference between 22 and 24? Is there a fuel mileage difference ?

vader86

The ECM is able to adjust somewhat in closed loop between the two sizes, an adjustable regulator is usually what we rec when you do it, if you're not tuning the chip, just to help. I have both larger injectors and the AFPR, if I need to tweak slightly.

On a stock engine there is no difference in power and the 24s would only be very slightly worse on your mpg if you did nothing. Open loop operation at startup would show more difference in poorer mileage.

MikeT 90 C4sixer

Well, yes, in theory. Small or no major noticeable affect, if you dont adjust, also likely. Most experts that burn chips and change injectors will say you must adjust. I am quite sure, that the folks at FIC, will say go with the 22 lbers if you dont work with the PROM settings. I was able to get the injector offsets, vs bat voltage from them. Lots of support out there for the offsets, for various injectors. There is also an injector constant, that needs to be changed, for the new injectors which flow xx at yy pressure. FIC told me to run the FP at 44psi, IIRC. Then change the constant accordingly.

85 Z51

My 85 has 30,000 miles. I rebuilt my injectors myself this summer. Car runs great. With higher mileage cars replacement may be a better option.

MikeT 90 C4sixer

Wow, that's low low miles for the year! I bought an '88 IROC in 1992, and it had about 34k on it. Still have it, and now has about 93k on it. Put the Bosch III's in April 2020. Shoulda put them in sooner. I dont really think it is a mileage thing, but more of an "age" thing. Had mine rebuilt several times, but they still leaked down.....just saying.

85 Z51

I bought in April of this year. One owner car since Nov 1984. I think that it must have sat for a number of years before the PO passed away. Took a lot of maintenance on parts that had just aged out. Pretty well sorted now and a fun little weekend driver!

Zip Corvettes

Yes if you want it to idle right and if you want it to have the correct Lambda or AFR as WOT. He is adjusting it in the Prom which is just telling the ECM the car has 24's in it which everything will run fine for him after that.

JoBy

Stock fuel pressure is 3.0 bar or 43.5 psi.
Flow increases with the square root of relative pressure increase.
22 / 24 = 0.92 = 92% of flow.
0.92 x 0.92 = 0.84 = 84% of pressure
43.5 x 0.84 = 37 psi
3.0 x 0.84 = 2.5 bar

You can lower the fuel pressure by 16% to 37 psi to compensate for the larger injectors.

cv67

I wouldnt...if its all torn apart get some new Bosch call it a day. Those will last indefinitley and are fine with ethanol laced gas

I had my multecs done when I joined here, it was the trend back then. Wasted my money...then got some bad Accels...finally got it right
Car never ran better!

Edit...while you have it apart, good time to replace the Orings holding the fuel rail crossovers, fuel line orings at the front of the intake and possibly the FPR diaphragm. Guys here can steer you towards the quality ones.

PLenty of C4s burned down due to those Orings failing back in the day. Yes you got low miles but age can break them down. Once they are disturbed the chances of them leaking increase greatly. Parts are cheap its a no brainer. plastic vacuum lines...are they good or should you just run new rubber ones under the intake? Thats all reliability stuff.

Your 1st time taking the TPI apart will eat up some time...after that its cake. Keep track of the runner bolts where they go some are different sizes
There are some you have to get from the backside just so you know.