Sorry for the long read but I wanted to put everything in there

Ok... I went to the local drag strip last weekend for the first time and ran my car. The humidty was low, air temp's were in the mid-high 60's, and my car was running pretty cool on every run.

My first rip down the track was hilarious... not being used to the tree and never launching right I ran an awesome 15.611 ET @ 82.59 MPH lol ..pulling a 2.40 60'. I screwed up lots of things (letting off before I went through the traps, not stomping it once I got rolling, etc etc) but it was a great laugh

The next few runs I got consistantly better...all of these were done by putting it in drive, transmission was shifting at about 4700 rpms in every gear

15.336 ET @ 89.44 MPH -- 2.300 60'
15.013 ET @ 89.82 MPH -- 2.101 60'
15.172 ET @ 89.83 MPH -- 2.202 60'
15.161 ET @ 90.01 MPH -- 2.259 60' <--- this run I was actually watching all the guages and feeling how the car was responding as I passed the traps, to me it felt like the engine was screaming " MORE MORE MORE!!" but it felt like I had a sock stuffed in the intake

At the end of the day I could not figure out why my MPH was not at least low to mid 90's which would have given me a timeslip in the high 14's somewhere.

My car doesn't have any real heavy duty mods but here is what I have...

Hedman Hedders (1 5/8" prims, 3" collectors)
No cat, 2.5" exhaust all the way back which dumps into a new Flowmaster 80
700R4 tranny which was just built with every "go fast, strength, durable part you can put in it)
Subframe connectors
DropZone lowering springs
new adjustable panhard bar
new rear trailing arms
ported intake with a airfoil
K&N airfilters over a cut out airbox
ported plenum
AFPR which I had the fuel pressure set to 50 psi at WOT (42 psi at idle and vacuum connected)
Stock injectors have all been cleaned, flowed and matched by Rich at Cruzin Performance
new timing chain/gears
No AC or SMOG pumps...just the altenator, power steering and water pump
Complete tune up with Taylor 8.0 mm wires, new AC Delco plugs, and all the sensors (IAT, etc etc) adjusted properly

Stock stuff: 3.27 posi rear end which pulls good on both tires, 5.7L engine with just over 100,000 miles, and a new Royal Purple oil change. Engine doesn't burn any oil, blow white/blue smoke, or drip any oil. Stock heads and cam.


After I got home I started asking questions to a few people of why my MPH wasn't where I thought it should be...

One person asked me "What's your timing set at?"

I said " 0* BTDC " ... this is where my buddy set it to (I never thought to look here for the proper timing setting as my sticker in not on the hood). That is when I had a lot of people say " It should be set to 6* BTDC as the stock setting"... DOOH!!!

I never set timing before so I didn't really know the difference, car felt OK on the street, no idle problems, etc etc, but I do notice that when I blip the throttle at the throttle body she has that split second hestitation...

So here are my questions

1. What kind of power/MPH or ET was I robbing myself by having my base timing set to 0* BTDC?

2. Now that I know the stock timing is 6* BTDC, how far advanced can I set it? I know this question doesn't have a cut and dry answer as all engines/mods, etc etc is different.

I am going to the track next weekend and I want to have a rough idea where I should be running in the ET/MPH and what I can do to drop my ET's.....I know that isn't a cut and dry question either but I am looking for a ballpark.... my setup should be doing better than 89 MPH and low 15's I think (or maybe not). Reason I say this is that my buddy with a 88 GTA has the same engine, exhaust, mods with the exception of a mildly ported/polished set of stock L98 heads and he ran a 14.10 @ 99 MPH cutting a 2.1 60'

 

You might be able to pick up a few MPH (and a corresponding couple of tenths) by upping the timing. Total timing is just as important as initial as you'll actually be in the advance almost the whole way down the track. Most small block chevs with iron heads can run up to about 36* total timing. Some a litle more and some a little less. Too much timing will lead to detonation which will cause a loss of power and may cause damage. I am sure other L98 owners will be able to tell you what initial setting will you give you 36* total (likely 6-10).

I'd expect about about 14.7 or 14.8 @ 92-93 with your setup. As for comparing to your buddies times, I don't know if he raced on the same day or not but different quality air on different days can lead to several tenths/MPH of variation at the same track. Also,
I don't know what altitude your track is at but elevation above sea level can also slow you down.

Hopefully you can cut some more 2.10 60' times the next time out.

 

wow all you coud pull was 15.1's out of a 5.7 tpi?

my 89 rs ran 14.94 @90 mph and all i have does to the car is a flowmaster muffler, lakewood 50/50 drag shocks , and lakewood lca's, i took out the spare tire and junk, back seat and took off air cleaner. thast with stock 305 tbi, 700r4, and 273 gears, i hade a 2.197 60' time and

 

I know...sad eh

 

Base timing doesn't mean much. As mentioned above, you need to know what the total timing is. Base timing can be 2 - 15* advanced. If the car still idles ok then don't worry about it but when you move your base timing, you're also moving your total timing unless the distributor is recurved at the same time to keep the total timing at the same place.

The computer controlled distributors are a little different. You need to unplug the timing wire to set the timing. When you plug the wire back in, the computer controls the spark advance. With the wire disconnected, bring the rpms up to about 3000 rpm. Chances are the factory timing curve peaks out higher than that. For performance, the timing should be at full advance by 3000 rpm. While at 3000 rpm, check the timing to see how far advanced it is. You'll need either an adjustable timing light or a degreed balancer. At a certain point, the timing will stop advancing. That's your total timing. If it's only 30*, bring it back down to an idle and bump the timing up 8*. Recheck the total and it should be at 38*

Not all cars are the same. Just because one car like 36* doesn't mean yours will. It's a trial and error method to find what timing works best for your engine. After you figure that out, all the other changes you do with fuel etc, won't affect the timing.

 

Cool.... well I guess I have to play with the timing first before anything else. Once I get the timing right (make an adjustment, go for a run, make an adjustment, go for a run... until I get the best ET/MPH ) then I can mess around with the fuel pressure...

Thanks!!

 

Sorry,
You are totally wrong about the TPI dis...


They do not have any advance mechanism at all!
If you disconnect the signal wire - you will see the car jump to 22* degrees when you hit the throttle. actually in your case more like 16* becasue you are - 6*..
The reason you see this is because ECM goes to limp mode and defaults timing to 22 degrees fixed .
You will see the timing will jump far with the slightest move ment of throttle but you are not concerned about that - set timing at ldle. Your total timing is set in factory prom, the only way for you to know what that is with a scan tool unless you ride under hood with a friend driving to watch timing as car is under full load - thats a whole other lesson all together though.
All of my timing is changed via laptop- never have to move distributer again.
You should jump over to the DIY forum and learn to burn your own proms when you become a little more advanced, you will learn alot.
All advance is controlled by ECM alone on the TPI cars!
Deffinetly put your timing back to 6 before TDC and even try more at the track 8-10* and see if that gains more MPH.

You should see a nice throttle response gain with the timing and some good Horsepower.
My best times were @ 10 degrees before TDC when car was stock
with only headers and exhaust -13.78 @ 98

Timing is to be adjusted with wire disconnected and car restarted after adjustment is made to clear ses light.