Insane detonation after LA3 swap

[fengler]

teh general rule of thumb is that all the cylinders be within 5% of each other (i think)

[turbo2.3stang]

I thought it was 10%.
I know this car from before a little and I think I might know what is wrong here. The previous owner deleted the external pump and left the stock SVO intank pump in place. This could describe why he is leaning out and detonating. I did the same thing when I replaced all of my fuel lines. I left the stock SVO pump in and leaned out quite a bit. I put my 255 lph pump in there and it runs great now.

[litdog]

I thought it was 10%.
I know this car from before a little and I think I might know what is wrong here. The previous owner deleted the external pump and left the stock SVO intank pump in place. This could describe why he is leaning out and detonating. I did the same thing when I replaced all of my fuel lines. I left the stock SVO pump in and leaned out quite a bit. I put my 255 lph pump in there and it runs great now.

He put in a single 86 svo fuel pump and deleted the resistor wire and grounded it to the body good.

[litdog]

I thought it was 10%.
I know this car from before a little and I think I might know what is wrong here. The previous owner deleted the external pump and left the stock SVO intank pump in place. This could describe why he is leaning out and detonating. I did the same thing when I replaced all of my fuel lines. I left the stock SVO pump in and leaned out quite a bit. I put my 255 lph pump in there and it runs great now.

He put in a single 86 svo fuel pump and deleted the resistor wire and grounded it to the body good. I just need to get my fuel pressure gauge out and check...

[litdog]

All three things were done. The pump's part number comes up on autozone.com as the one for an 86 svo or a EFI 5.0/2.3...

[GAboySVO]

What do I need to unplug to keep the injectors from firing and such while i'm cranking?

Hold the go pedal to WOT while cranking and that will prevent the injectors from firing.

[fengler]

figure it out?

[litdog]

I'm not so sure it's really a detonation problem... possibly transmission/clutch noise or something? It almost makes the same kind of noise when the engine is chugging if i start in second gear at too low of a speed. I had it happen today a little...

[litdog]

Alright, I still have this problem...

I'm still running 8psi of boost, and it detonates bad at very low boost (2+ psi) in 3rd gear and up.

I still have the same codes, normal with the LA3 swap, plus code 54 (haven't figured that one out yet).

I put in 5 gallons of 91 octane and then went and put in 3 gallons of 101 octane race gas and it seemed to have made the detonation go away for a minute, but it came back with the same mix of gas in it.

It seems to not have as bad of a problem on cold start on these cold winter mornings, but once the engine bay/car warms up, it comes back again.

I re-checked my timing, still at 10* BTDC spout disconnected, and finally I just retarded the timing to 5* BTDC and there is no more detonation, but dang it's slow at 5* with 8psi of boost I may be able to at least turn the boost up now though, Haven't tried it yet.

The fuel pressure goes up with boost fine, but it's somewhere around 47psi with the vacuum line off. I removed the vacuum line and went for a drive, figuring the 47psi fuel pressure minus the 8psi of boost would be close to where it should be set stock... It made no difference at all in the detonation.

Next up is replacing the FPR so I can at least set the fuel pressure right, then i'm not sure where to go next.

I heard that the head on my car had been replaced, so I guess it's possible it has a N/A head on it raising the compression, and causing it to detonate with the LA3's timing, etc. The engine still has the stock dished pistons at least. What/where should I look to figure out what head is on there without removing it? All I gained from searching is that the casting numbers are hard to read sometimes and that the later N/A heads have smaller heart shaped combustion chambers, but not where to look for a casting number.

[litdog]

The plugs look a very light brown (no oil or blackness), no oil going into the cylinders from the turbo as far as I can tell. I assumed the LA3 has more timing than the stock 84 svo computer, so that's what I'm going by.

As far as I know, it still has a stock cam of some sort, either what came on it, or whatever came on the head they got. I'll be pulling the valve cover as soon as I drive home to Missouri tomorrow and fixing an oil leak, and looking into a cold tapping noise from the valvetrain that's starting to develop, so I can see what cam and hopefully find some numbers on the head somewhere.

[GAboySVO]

So what happens when you plug in the knock sensor? Did the bottom end ever get a rebuild. I know you said the piston are the dished type, but how do you know if you haven't had the head off? I know when I had my rebuild done, the Federal Mogul book had the NA piston listed for the turbo application. If the machine shop followed this, then that would explain your detonation. A similar scenario happened recently to a guy in Texas.

[litdog]

I took out the #1 spark plug and looked in there while rotating the engine watching the piston. I could see the whole top half of the dished contour where it curves on the driver's side rear of the piston and then angles straight towards the passenger front. It looked exactly like pictures I had seen of stock pistons.

I don't think the engine has ever been rebuilt. I'll go turn the timing back and plug in the knock sensor and see what happens, but all that I read says that the 84 intake/knock sensor doesn't work well at all with the LA3 computer.

What I find weird is that the fuel pressure is so high but the plugs look good, if not a little lean. I suppose this fuel pressure gauge could be off, but it's really a pain to take my other one off the Buick

[GAboySVO]

Did you have the 35 # injectors cleaned and flowed before you put them in?

The reason I wanted you to plug the knock sensor back in is to verify the noise as detonation. The car should really fall on its face if it is detonation and the EEC pulls timing.

Did you ever figure out what was causing the code 54. Is it still throwing this code? My book shows that code 54 is vane air flow sensor out of range. Have you tried testing the voltage reading as the flap swings open. It should read from ~0.50 to ~4.5v.

I tried one cylinder for 8-10 compression cycles and got 160 psi

I think the max reading should be 150 psi per cylinder. Mr. Fleming please confirm this.

[SVOeric]

Just because the pressure is high at idle, don't mean it's high at 3000 rpm.

[litdog]

Just because the pressure is high at idle, don't mean it's high at 3000 rpm.

That's high with the vacuum line off, not on.

I checked all the voltages on the vam, they checked out for everything I've read on it...

And i'd think that the noise wouldnt go away when I retarded the base timing if it wasnt detonation. I'll try the knock sensor thing anyway though.

The 35# injectors were on the car when I got it, only with the stock 84 computer. I suppose it can't hurt to pull them and get them flowed to make sure it's not just one cylinder, but I'd think that would show up in the plugs.