I was doing some searches on setting base timeing and came across two posts where people said they had heard / read somewhere that in an '85 only - the base timing causes better performance at 2-4 degrees, instead of the factory 6. (Instead of going up)

If I set at 6 or try to increase, I get ping at moderate load, so I'm guessing this is probably correct. I'll be setting it lower tonight and trying it out, but I figured while I'm still stuck at work, I'd see if anyone knows if this is correct.

Can anyone confirm?

 

Mine is being painted or I would go out and check...but I think I remember the sticker under the hood saying 6 degree's btdc and thats were mine is, also no ping. :cheers:

 

SHansen, are you able to get 93 Octane up in Nova Scotia? If not, that may be your problem (assuming the motor's never been rebuild, with the heads decked). If your compression ratio is stock and you have access to 93 Octane, you should not ping at 6 deg BTDC. ALL of the L98s to my knowledge are to be set at 6 (again using the aforementioned assumptions). If you don't have access to 93, you may have to back out 2-4 degrees of timing or so like you're seeing. Also, if the motor has been rebuilt, the compression ratio would likely have gone up. Decking the heads, boring the block, or using pistons with a lower dish volume would all raise the CR, causing the problem you're seeing. On my '87, I knew it every time I got a bad batch of fuel on my previous motor (10.4:1 on the stock cam).

 

I am running stock bottom end at 8Degrees, with a splitsecond knock between gears, which is what it should do with the chip I have..
I heard too that at 2Degrees the car is supposedly faster, but when I tried it, the car wa WAY down on power. I put it back at 8, and everything back to normal..

 

I set my 86 at 8*

 

One thing to check is whether your harmonic balancer is seperating. The outer ring with the timing mark on it can seperate and rotate causing you to think it is set to 6deg but it really is much different. I had this problem.

 

shanson...............you are disconnecting the spark advance before timming right ? :chevy

 

This is about the only explaination for a stock '85 pinging at 6*. Unless you have one horrific build up of carbon. About the only difference between your '85 L98 and my '84 L83, is the intake system. We both have 9.0:1 compression ratio. I run 13* advance on 85 octane gasoline. Good luck, and...

RACE ON!!!
1984 Crossfire
Member NHRA

 

Thanks folks for all the posts.

Some responses;
I get 92 octane gas here and I do buy it.
I have tossed in octane boost and got rid of the ping, but I don't want to tack on an extra $10 per fill up.
I do disconnect the wire before testing timing.
I've checked the balancer and it's OK.

My mods are: Headers, dynomaxx mufflers, no cats, k&N, cutout cover, de-plugged MAF, moved IAT, hypertec thermomaster chip, 160 stat, ported / polished plenum and runners and AFPR - which I'm currently running at 48 pounds. The throttle body was cleaned a month ago and the plenum / runners at the same time. (Yes, I realize that a custom chip would be better - this was put in before custom programmers were so prevalent.) I should have included this at the start.

Actually, if memory serves me, the chip was the first mod I ever got. It's instructions was to install, and advance timing until I got ping, then back off a bit. I did, probably got it up around 8 degrees back then. Since then, I've given the engine more air coming in, and less hassle getting the exhaust out. Do these mods effect timing severly? (I am still playing with the AFPR, but I want to get one tune in solid before playing with the other.)

It's raining today, so I'm going to back it down to 4 tonight and give it another few runs tomorrow.

 

You need to hook up a scanner. The fuel presure is high, stock is 38lbs. I'll bet your BLM's are low because the ecm is trying to compensate for too fuel fuel.

 

It was a magazine article from the 80s that stated the ECM resets knock counts by dropping the timing to 2 degrees. This decreased 1/4 mile times. I have mine set at 2 degrees, and all I've noticed is a little increased throttle response, but because of misbehavior I haven't been to the track (leaking injectors). But the timing comparison is going to happen, along with the MAT relocation comparison in 1/4 mile times. Hopefully by this summer. :seeya

 

But isn't more fuel pressure a good thing?

 

Too much of ANYTHING will kill you. If the excess pressure causes fuel flow the ECM can't manage, it's NOT a good thing. Sounds like it's time to do some tuning. Good luck, and...

RACE ON!!!
1984 Crossfire
Member NHRA

 

Extra fuel pressure is not necessarily a good thing. With the mods you have, the extra pressure is unneeded. It has the same effect as putting in larger injectors, which you do not need. BTW, stock fuel pressure is 43, not 38. Fords run at 38. The ECM will trim fuel based on O2 sensor readings in closed loop, but the amount of trim is very limited, and at WOT it's not trimming fuel at all.

On initial detection of knock, the ECM does pull ~2 degrees, but if it detects knock again in this retarded timing state, it goes into panic mode and pulls a TON of timing out. On my '87, the first time I got a bad batch of gas, I hooked up a scanner and saw 32 degrees of knock retard.

As far as your mods go, the exhaust has been opened up far more than the intake. The ported and polished plenum essentially does nothing if the runners and base are stock. If you had seriously opened up the intake and not the exhaust, I would say that you're having enough residual spent gas in the cylinder that you're getting bad combustion cycles due partly to the burned gases and partly due to the residual heat in those gases. However, that doesn't seem to be happening. Next two questions...what is your milage and what type of oil are you running? If it's a high milage engine and you're running dino oil, you could be burning some oil which will make the 02 sensor read extremely rich, which would pull fuel out and could cause knock. This was one of the problems with my old motor at the time of the rebuild.

 

I just dyno'd my car a few weeks ago and I played with a few things and one was that I went from 8 degrees to 4 degrees and in the grand scheme of things I lost a whopping 2 hp. I now will just set the car to not knock as mine doesn't seem to care.

 

FYI, 85's use 24lb injectors and run a fuel pressure between 34-39psi. Later years use smaller injectors and therefore use a higher fuel pressure.

 

CFI-EFI: "Too much of ANYTHING will kill you" :D :D Ok, I'm getting my mind out of the gutter for a minute. - what a way to go!!! :D In this case, thanks - you and the others are certianly indicating that I've got to lower that pressure.

I backed the timing to 4 degrees and even though I didn't change the pressure; (Which I'm gonna) the ping went away.

CorvetteZ51Racer: I never thought about the oil burning. I do have a 90K mile engine and burn some dino oil. So if the O2 sensor is indicating to the ECM to pull fuel back, then that's extra reasoning for less press, I assume too?