This car is really starting to get to me. I'm getting really close to just selling the thing. It's an 89 GTA with 140k. I've put quite a bit of money into it and would like to keep it, but I just can't fix it. A couple years ago, I rebuilt the motor, putting in small dome pistons, a 230/236 comp cam, holley aluminum heads, a converted lt1 intake, and had the bottom end balanced. About 10.5:1 compression. It's also sporting a 727 underhood ecm. I am using a knock sensor and chip for a sd 350 btw.

I installed a set of used 36# injectors that I got a really good deal on from ebay. Come to find out that half of them are leaking, externally. So I bought a new set of 42# injectors and installed those in the car. With the leaking 36's the car wouldn't hardly move unless I just repeatedly jabbed the throttle. Any sort of constant throttle and it would just die. I had no spark knock during this time according to my laptop. When I installed the new 42# injectors, I also readjusted the rocker arms. Now it seems that I have spark knock like crazy, while just idling, sitting there. I can feel the engine fighting back as well. Those are the only two things that changed. I've since readjusted the rocker arms twice with no results.

I've been turning the motor over by hand to get each cylinder on the compression stroke. I would back both rockers off and retighten to zero lash, then an additional quarter turn, and lock em. I'm pretty sure I'm setting the rocker arms properly. Or maybe not. Should I be going with an additional half turn or even three quarters?

I've checked my fuel pressure, and it seems to be fine, although my gauge sucks and just leaks fuel all over the place. Hooray, fun! It'll pressurize to 40psi and then leak to zero(b/c of the gauge). Also, now my timing light won't pick up the spark signal from my wires. It's an inductive pickup timing light. It works great on my g/f's little geo, but not on my car. I know the car is getting spark, as I've verified with a screwdriver.

I also pulled all of my spark plugs, and they are all covered in black, which I assume is running too rich. Before the new injectors, the plugs looked great. Slight brown tint to em. But the car wouldn't drive and they were leaking fuel externally. With the new injectors the engine will rev and hold rpms, and I can drive the car, but I don't want to with the spark knock. Could fouled plugs be causing my spark knock? A friend also suggested that I needed higher octane fuel. I put 91 octane in with no change. I also, wasn't getting any spark knock before with 87 octane.

I'm also wondering if there is water in the fuel. Would that cause the spark knock that I'm seeing. I'm sure it's something stupid and simple like that. It always is.

I also swapped out the distributor, just to rule it out. Well, now I can't get the damn thing started again. I'm sure it's just a timing issue, but I have no idea where I'm at because my awesome timing light won't work with my car. One step forward, two steps backwards. I don't seem to be making any progress here. I just want to finish this project up. I'm about ready to sell the thing, just to get it out of my hair.

Please help me out here guys, and keep me from making a rash decision and sell this thing. I really do love this car and would like to keep it. Thank you very much.

 

First off, I am not a fan of injectors that are too large. Do you have any stock ones lying around to use for now? You are obviously running too rich.

Start there and then set your initial timing by hand close enough to get it to start. That means timing mark at just before zero, verify up on number 1 (not number 6) and then pull the number one spark plug wire off of the spark plug. Hook a new spark plug to it and hold the spark plug somewhere on the intake to ground the electrode. Now, rotate the distributor back and forth until you see the spark. Lock your distributor down just snug so that it doesn't move while you're running. You should now be able to start the car.

Next replace the spark plugs. Start the car and hook up your timing light. Set it to around 8 at first and then run it a little. With smaller injectors and less timing you should stop the pinging and now be able to go up in small steps to maximize power from your setup. I like to start with smaller injectors and raise the fuel pressure until they are maxed before going up in injector size.

These are just my own opinions and suggestions. I hope they help.

 

I would have liked to have some smaller injectors, but these were readily available from a friend. He ran them on his turbo mustang for about an hour, and decided against the turbo. So he sold the turbo and had the injectors left. I didn't get a great deal on these, I could have bought brand new injectors for the same price, but heard good things about the lucas injectors. So I decided to give it a shot. I would like to keep these injectors for now, as I don't have the money for new ones.

Is there any way I can get these to work. Can I set the injector constant to maybe 44# or 45# in the chip? Could these larger injectors really be causing the spark knock? I'm using a stock axcn timing curve, so it's not very aggressive. I also still get spark knock if I disconnect the timing advance lead. The spark knock stays pretty consistent.

I also have full roller rockers, gear drive, and hedman shorty headers with dual 2.5" exhaust. None of which set off the knock sensor before, but could it be setting it off now?

Thanks for your help guys.

 

You must always go back to where there was no problem and then roll forward in time slowly until you see the problem...

All other mods mentioned, everything is fine. Swapped injectors and now there's a problem...

It doesn't matter what you set your fuel pressure at if you have leaking injectors. These leaks can cause the flooding, rich condition causing black spark plugs, and a pinging sound due to fuel puddles dripping down the valves...

Test the injectors. In the meantime, you may be money ahead with some used injectors that you can VERIFY work well. Such as running them in your buddy's mustang...

 

Thank you very much. I thoroughly appreciate your help. I will go back to the old injectors and move on from there. I agree the injectors are a little big for my application. How can I test the injectors to see if they are leaking? Can I just pull the fuel rail off and prime the system? How do I keep the injectors in the rail since the lt1 rail don't have the clip to retain the injectors?

 

I hooked the system up after I pulled the injectors; similar to what you said. My two last tests were V6 engines where the injectors pushed into the fuel rail hard with no worries about them falling out. I was testing to watch them spray fuel and it worked okay with a jumpered fuel pump relay.

You should be able to just jumper your relay and see if fuel comes out of any of them with the key off.

 

Cool. Thanks a ton man. I'll give that a shot and see how it goes.