Well I finally got to track last sunday and did some bracket racing. I ran 2 classes so I could get some extra runs in. Only get 2 TT's in for each class. But what I did early this summer was some major drivetrain work. I had to have the tranny rebuilt since I lost first and rev last year. It got beefed up of course, and I allready have Transgo shift kit, corvette servo, etc....but what else i did was put in Vigilante TC stalling at 2800-3000, and a Spohn adj torque arm. All in 1 shot. I was really hoping for high 13s and sub 2.00sec 60'. I did get most of my 60's in the 1.9xxx range, except for 2 runs in the left (sucked) where I spun a bit offline. But my best ET was only 14.1991, and as the day wore on, heat +humidity, had most runs in the 14.2x or 14.3x range. I running Nitto 555DR, set to 18psi, and get in a decent burnout. They arent new but are still hooking decent.
Block and heads still stock, but done much intake/exhaust work, rear suspension, and my own chip tuning. I have a Jacobs spark box and wires. I wonder if I was running out of fuel on top end. I only hit 94.x mph at trap, and I used to hit 95-96 at the finish. My WB LM1 showed like 13.3-13-8 AFR during the WOT runs. I think I should be more rich? Maybe running out of spark on top end? I stick it in 3rd and let it run the course, shifts real sweet and right about 5000-5200. Not much spining.

So am I asking too much to get into 13s with my setup? I can give more details of my ride if needed.

Just that this kid next to me had a 92 Z28, mostly stock with original T5 stick, and he was running mid 13s. He did have Hoosier slicks on, but said his motor was not original, but a 350 from the guy he bought from. I looked it over, and it did look stock, minus AC, and he had headers and Accel ignition. Everything else stock. I dont think he really knew what was in his motor. I dont think it was stock!
TIA!

 

you should be launching alot harder with that converter and drag radials. 1.90 isnt bad, but you should be well into the low 1.8s

whats your pinion angle set at? do you have LCA's and relocation brackets? those will help traction issues

and what shocks/springs you running?

if your still TPI i think you have way too much gear. should be shifting at 4500rpms or so, and no more. TPI is killing off after 4500.

This is a starting point i'd say.

your trap speed seems abit low for a L98 with full exhaust mods. whats your base timing set at? And is your converter locking up at all during the 1/4 mile run? it should lockup at a certain mph and if i were you, i'd change that mph to something like 105, where you wont hit that in the 1/4 mile run. I ran faster with the converter open

 

max HP at WOT is 12.5-13.3 somewhere in there typically.

 

Thats weird I thought completely stock TPI's ran low 14's already???

Thats what a bunch of guys are saying to me in this other thread

 

they do, something is wrong with his car

my car with similar mods to his but less gear went 13.63. intake swap got me 13.49 so far in hot air.

 

elevation and DA play a big factor as well. Along with track conditions and prep. Car could also be a little out of shape (high mileage, cyl leakdown, ect.)

 

Good stuff folks, lots of ideas.
I do have Spohn rear LCAs, panhard bar, and the lower brackets. My mechanic set the pinion angle on the adj torque to what the directions recomend, and i know it is not stock. All shocks/springs are stock. My tpi is not stock, i have pulled it all off, and gutted it out, siamesed things, gasket matched, had the injectors sent out and flow tested &matched, FP at 48psi. I know the TPI runs out at higer rpm, but i think it shifts right around 5k. I tried shifting earlier last year, but it wouldnt go up when I manually did it.
I have mostly all good ignition, Hooker headers Jet-hot coated, gutted cat, and 3" with Flowmaster single outlet. I dont think I have too much gear. I kind of did things up so as I go with mods I will be set. Someday cam and heads will go on.

What about TP on my Nittos? I read that 18 was about average. My AFR could be too lean like someone said. Does the high stall slip more now, so I loose some mph on top end? Maybe went too loose with that. I can only hold about 2100with the brakes before it cuts loose. I am not locking converter during WOT runs. I have idiot light that tells me so. I have the TCC unlock prevention set to 100mph.

I thought completely stock 350 tpi cars ran high 14s. I know guys do run good with them. Engine has about 72k, on it, well maintained, run Mobil 1 15-50 full syn. Base timing is at 8deg, and I have the high load spark tables backed down to about 25 deg, to hold off spark knock. I read these old iron L98 heads dont need much advance. Always run 93 octane.
Keep the ideas coming.

 

sounds good man. you dont need much spark. I'm running the 89 AUJL bin i believe. it had about 23 degrees timing max, plus the 8 degrees base, and power enrichment.

A converter will definately lose abit mph on the topend but i still think you should be trapping near 98.
with ported and siamesed TPI, 5K shifting sounds good to me.

idk what else to say, sounds like the combo should be running alot better than it is.

18 psi i'd say is just fine. drag radials like higher pressures i hear. if your spinning try lower pressure or longer burnout.

 

Yeah it definately seems like you should be putting down better 1/4 mile times with everything you have done! I would probably try lowering your tire pressure, my buddy Brandon had an '81 Malibu with a rebuilt 327 with TH350 trans and Moser 4.11 10 bolt rearend, he cut almost a half a second off of his 1/4 ET by lowering his tire pressure to 12psi in his MT drag radials and pulled his drivers side tire off the ground about 6-8 inches

 

I just ran 14.22s at 97mph. I was happy with that. My best 60' was .122. But my 2.77 gears prob didnt help. I was shifting at 5500 though. May be that hurt my times?

 

even with aftermarket big tube runners/base on stock TPI motor cam/heads, i wouldnt shift much higher than 4500-4700. stock TPI i'd go for 4500 or so.

My HSR peaks at 5050. my fastest time so far was shifting at about 5100. i used to shift at 5300-5500.

2.77 gears arent the greatest for off the line but 700r4 first gear helps. I was able to go 13.89 at 97 with those gears on street tires on a 1.895 60 foot. 3.27s gave me some more mph on the top end but i couldnt launch any harder on street tires, only went 13.88 at 98 but on a 1.93 60 foot.


i just looked over this and was wondering if that 25 degrees was the value in the Spark Advance table at high load values? if so then thats fine. But if your total timing is 25, then i dont think that is very good. I think total timing is your base plus the spark advance table values (correct me if i'm wrong i'm just beginning this tuning stuff). which 25+8 base = 33 which is about where you want it. but if its 25 total i think thats hurting you.

 

How did you determine to run 18psi in the Nitto DRs? The radial design will cause them to cup up in the center with too little pressure, making you run on just the outer edges of the tire. Did you try higher pressures first and then work down? You may find better bite at a higher pressure, I did on on the MT ET Street Radials. Sweetest at 26 psi for me. And don't discount front tire pressure, take it up to 35 or so for less rolling resistance.

 

Good stuff, good to other racers' thoughts. When I talked about spark, i was also wondering if my ignition system was putting out enough juice at high rpm. I got a killer coil, but my Jacobs spark box is mild. I need to talk to them. I do have all my TPI stuff ported out heavy. I have been cutting back on SA to get rid of knock. I didnt get any of that data at the track, just the WB AFR. I am running a modified ARAP bin. I think I just need to do some more tweeking. I did notice this weak I am a little lean on my BLMs, plus the not so rich AFR on WOT runs, so got some work to do. But not the topic for this forum.

The 25 deg in the SA table is the total advance, from what I know. These old iron L98 heads dont need much advance.

As far as 18 psi on the Nittos, i did a little experimenting when I first got them, but settled on 18. I did notice they needed a breakin period. But mostly that is what other guys running at the same track are using with the Nittos. So what works for them......plus I dont spin that much any more. Just that the left lane was real slick, and i spun there.
I could easily go back and try some different pressures.

Maybe I just dont have the motor to get into the 13s. I think I had 230hp stock in 1988.

 

arap bin contains some big spark numbers, i dont like it. it seems like it adds way to much spark....as most bins i've looked at so far contain significantly less spark.

i have run the stock arap bin to some other bins on my car and i've gotten the best 60 foot on the arap bin, but still ran slower. i think the low end timing increase helped torque, but the large top end timing killed the top end lol

did you do a compression test to see if the motor is in great shape?

 

My old 87 IROC 3.27 gears hit 14.2 @ 95 with 1.97 60 ft on regular tires. It was basically stock except B&M shift kit, SLP converter, and old 2 on the left Flowmaster. Other than that I did some "free mods" Like AC delete and TB bypass. Was still still on the stock chip and old worn out suspension.
That was at Lebanon Valley in NY. Always had good luck there. I used the same engine in a V6-V8 Firebird swap with a T5.. only changes were dual cats, and worn out V6 suspension.. got that to a best of 14.3. Got that at Atco in NJ.

So I would think you should be able to hit 13s.. what track are you racing at?

 

how are you launching the car? are you leaving at idle or brake stalling it as much as you can? i have found my best times are with full brake stall, and NOT leaving off idle, but some cars will vary so you'll have to try both

 

it is a stock 350!! (i think) lol

good luck with the 13's!!!!

 

Hi there, there is the kid with mid-13sec blue Z28! I figured you would find me!
We are racing in Cicero at ESTA safety park. Might not make it back up there till sept.

arap bin contains some big spark numbers, i dont like it. it seems like it adds way to much spark....as most bins i've looked at so far contain significantly less spark.
Yea I hear you on that one, I took some numbers from that bin, but mostly running my stock 88 bin main spark advance table. But I have tweaked them a bit over the years. I havent done any compression tests on motor.

how are you launching the car? are you leaving at idle or brake stalling it as much as you can?

What I do is what I have always done, hold brake hard with left, and rev up with right to as much as I can. Now with new high stall converter, i can hold maybe 2100 max, before cuts loose. Stock could hardly rev much more than 1000. But today I talked to a friend who runs a Mustang, and said I should use the line lock to hold car, not the brake pedal, and just release it and go. Said it takes more time to let all 4 brakes release than just 2, and plus you can release the button quicker than using your 2 left feet. But you still have to mash the gas same time you release the button. Any thoughts on that?
I guess I need to practice that!

 

i never really heard of that being done but sounds like it could work.

line lock tho just holds the front breaks so you can do burnouts with out the back brkaes on, so its easier and less wear on the pads/rotors etc.

but stock front brakes are weak and dont really hold the car at the line well, atleast in my case it doesnt. i could stall it up more if i had better brakes, and thus would run better times. just holding the fronts would probly not yeild as good results in my case, but you can try that

 

Well Orr89, I talked to some another guy at work, and he said it would be better to just use the line lock to hold the car, then just release and go. But like you said, just the fronts dont hold as much. 4 brakes are better than 2!! Tonight i tried it in the road by my house, and could barely hold 1800rpm. But I think I can see how it might be quicker off line. I wonder if my brakes arent up to speed, or maybe my stall converter isnt doing its job. I would like to hold more r's before I launch, that for sure. Need to test it out more.

 

yep, play with the combo as best you can. you'll get those 13's

 

Sounds like a plan for me too!