Hey guys, I decided to try a zero to 60 mph run the other day and and when I launched I ran hard through 1st and shifted. I was not watching my tach and at wide open throttle my car shut off. I was turning pretty hard. It scared the S$&*# out of me. I coasted to a stop and put the car in park and it started right up and ran fine. Do I have a rev limiter or fuel cut-off on my 85 L98? It's never done that before ar since. Can anyone help?

 

you were in a hard turn? How much gas did you have? Less then a 1/4 tank may have starved your fuel system.... Just a guess though, as I am not sure. If it were from an Idle and it cut out, I would suggest timing or something similar... but to cut out while shifting to second?

 

If you were at WOT and it starved for fuel it likely would shut down.

The only rev limiter on your L98 is the intake runners.

 

Your point about timing is possibly valid. I had bumped the timing up to 8 degrees to see if I would gain anything. To answer your question I was going in a straight line with a half a tank of gas. Now back to the timing. The factory setting is 6 degrees btdc. I bought this engine with the cam and heads already on the motor. I don't know if it was degreed-in or dot to dot. I have been reading threads where some of you guys are running 8 and 10 degrees. I am running 4. If I go above 4 I seem to start loosing power and knockng under hard acceleration. I also got a code 42 when the engine shut off. Is it possible that my cam was degreed in maybe 4 degrees btdc already and I am just pushing my timing way too high. I have tried to contact the guy I bought the engine from but haven't been able to reach him. By the way at 4 degrees this car has pulled a 0 to 60 mph time of 5.0 seconds three times. So it's not a sloutch for an L98.

 

Don't get your cam timing and your ignition timing mixed together. Either can be changed independently from the other. Most cams are ground, such they are installed 4* advanced, dot to dot. If it was installed 4* advanced from dot to dot, that is a lot.

There is nothing wrong with 8* ignition base timing, if that is really what it is. Of more than 4* is too much you may want to verify true TDC against your timing marks. The downside to too much advance is pinging or knock counts, retarding the timing.

It doesn't sound like either cam timing or ignition timing are the cause of your problem. Neither would shut off the engine.

RACE ON!!!

 

So what would you say could be some reasons my engine starts pinging at 6* when that is the factory setting? When I set my distributor in the engine I determined TDC and my timing mark seemed to be right on the money. I never removed the timing cover to check the cam. I am also running 93 octane gas and my car doesn't detonate. But if I go back to 6* it just barely knocks under hard accelleration. I'm at a loss. Are all early model L98's "knock limited"?

 

I'm confused, first post says "I was turning hard" second post says
you were going in a straight line. Please clarify...

 

Turning high RPM's. Sorry

 

Are you actually HEARING pinging, or are you getting counts on a scanner? If the ESC and the knock sensor are working properly, you should have very little audible pinging. The knock sensor should pick it up and retard the timing to prevent or stop the pinging. Is it audible knock, there may be several problems. First, as mentioned, the ESC. A TRUE 6* to 8* degrees of base timing should NEVER ping in a 9:1 engine on 93 octane gasoline. My long block is the same as yours, and I have 14* base timing on 85 octane.

"I determined TDC and my timing mark seemed to be right on the money. I detect a slight bit of "lack of confidence" in the way you worded that sentence. It may pay to truly verify the timing marks.

RACE ON!!!

 

What I hear sounds like detonation. While it's not a loud pinging it is audible with no stereo playing and the windows down. And it's only under heavy load on the engine such as pulling a steep hill in or hard accelleration. Are you saying my knock sensor should keep me from hearing detonation at all? If that's the case a new knock sensor? It seems to me if the knock sensor is retarding timing I am still loosing performance because it's pulling my timing back. Is this right? I am having my car put on a scanner on Friday morning to see everything that's going on. The guy who's doing the diagnostics is a Vett owner, tuner, and went through tech school for Chevy. Hopefully Friday I will know what gives and I'll let you know. I appreciate everyone's input and respect your knowledge.

 

What you describe sounds like knock. It could also be an exhaust leak. The ESC should start pulling timing as soon as it is detected. Prolonged pinging would put the ESC circuitry in question. Yes, if it IS working properly, the timing it pulls DOES reduce performance, but so does the knock.

The scanner will show the timing, the knock counts, and the amount of timing the the ESC is pulling out. However, the timing the scanner will show is the advance added in by the EST and not the total. These cars don't have a crank position sensor, so it can't know the total. You have to add your base to the scanner number to get your total. Of course, if your base is off because the timing marks don't line up properly, your totals will be off, too. GIGO.

RACE ON!!!

 

I have never seen the need to set the timing at anything other than stock because my EPROM will advance it. It is programmed with a different rate of advance than stock.

Check compression. Could you be having some hot spots in the combustion chamber? A little knock at WOT is acceptable and is picked up by the ECM. If your KS is not working, you should be getting a code. Something to note, could your fuel pressure be low or could your injectors be faulty? If you don't get enough fuel, it will ping because of a lean condition.

 

Let us know what you find after the scanner...

 

It went pretty well. All in all there was nothing serious that showed up. The timing problem doesn't necessarily seem to be the timing but possibly a slipped harmonic balancer. The rubber is squeezed out and the outer ring my have slipped. I'll change it out this weekend. Also my fuel system is not holding pressure after the engine is turned off. Fuel pressure is normal while engine is running. Possibly leaky injectors since they are original but I don't get any black smoke when I first start it after sitting a while. I suspect the fuel pump is leaking down. Hadn't had a chance to test it yet. Probaby do that this weekend too. I'm going to go ahead and buy new injectors just because mine are almost 20 years old. Would the Bosch 24's be OK whith the mods I've made? (Alum heads, roller cam & lifters, Edelbrock TPI base intake, headers, dual exhaust)
I also found out that I do not have a stock chip in my computer. I have no idea what kind it is or how it's programed. The scanner is set up to recognize the GM chip code and it didn't recognize mine. That could deffinately cause me some problems at wide open throttle,... maybe. I suspect it may be generic like a Hyper Chip or something.
Also adjusted IAC and TPS. Got base idle back to where it should be. Had no codes set at all and the tech said she sounded and ran really good. I just need to upgrade a few things and I think my small problems will go away. When I add new injectors and runners, do a little flow work to the plenum, and a new breather system, then I'll spring for a new chip too. What do you think guys? Again thanks for all the help and advice guys.
Troy

 

I need a new hamonic balancer for my 84 also. Any recommendations, and if I buy one will it work on my 400 I am planning to build? Right now I have a mostly stock 84 350.

 

No! Not unless you have your 400, internally balanced. That would cost a lot more than the correct 400 damper.

RACE ON!!!