I have a 2002 Z28 that came with 28.8lbs injectors. Last year I bought a brand new set of 243 heads and wanted to buy a cam and intall them. I researched the TR230 cam from thunder racing and bought it. I was told the the 28.8lbs injectors would be sufficent. After the install I had several people tell me to have the injectors resized to something bigger. I mean I dont know, the car was running fine. Over the winter I figured it couldnt hurt to send them out, the company that did the resizing reccomended to have them resized to 36lbs at a stock 58psi so I did. I was also told it would be a good thing to have the PCM reprogramed (mail order) so I sent it out to have it reprogramed as well.

I got the injectors and PCM back a few weeks ago. Thursday I installed the injectors and PCM, I also decided to flush the radiator and install new upper and lower hoses along with a fresh set of NGK plugs as the old AC delcos sat around all winter.

I fired the car up for the first time since the injector resizing and PCM I ran it for about 20min in the garage, ideling to get the thermostat to open and top off the radiator, god it smelled rich. I capped off the radiator and reved it up a few times, a ton of black smoke came out the tail pipes, once the black smoke stopped from me reving it I shut it off,

Today I got excited to drive the car, I tried to start it, it was very difficult, It would just fire up and die and fire up and die, I found if I held the idle up a little it would run, I tried taking it around the block, its got a bad misfire, I pulled the #3 plug and this is what it looks like.

On the left is a AC delco plug with about 6,000 miles on ot, on teh right is a brand new NGK plug with about 20min of ideling, something doesnt seem right here...

 

Looks like it is running pretty rich...is try and put the delcos back in then run it again

 

looks like oil fouled

 

A mail order tune with more than bolt ons will only really be good for getting you in the ball-park. Two identical cars will not react the same to identical mods. So a real data-log tune will be the only TRUE way to get you dialed in correctly since you are still running pretty rich.

Injector swap = rich. Add a mail-order tune to it and there will still be the possibility of it not being dead-nuts on.

 

That looks like a slightly colder heat range which when matched with the
larger injectors and 20 min. of idle can do that. I thought the 28lb inj's
were good to about 430 rwhp. Also you probably need a full tilt chassis
dyno tune....because the combo deviates so much from stock there are
plenty of idle, part throttle, and WOT tunning changes that are required
to get it right. Real time data (recording) is part of that lengthy process.
Way more than a mail order is capable of....spend the money and that
thing will tear it up !!!!

 

I agree, I will have to get it to a dyno tune, I just thought it wouyld be better to get a mail order tune now to get the car to the dyno. With the increase from 28lbs to 36lbs I didnt want the car running too rich... but apparently it still does. I have never fouled out a plug in a 4 stroke engine before, these plugs are all caked with soot in only 30min, granted most of the time was ideling though.

 

Who did the mail order tune. Frost did mine and it was dead on. When I do heads and cam on my 99 Z, He'll be the one doing the tune again. I can't tell what NGK plug that is but you could put a TR5 back in it and see how that works b/c that's the same heat range as stock.