IroczFan

86 IROC 355 9.7 to 1 compression double hump 202heads tourqer 2 cam 750 edelbrock headers 5 speed car ran 13.93 @ 103 with the 308 gears 1 wheeler rear end I am swaping a in a auberon posi and 373s this week what should I expect to pick up? will be running the car next Friday


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KWIK84

iTrader: (5)

Not knowing what tires, launch, and what kind of rpm's your running out the back door.....I would guess, as long as you can get it to launch, 13.50's.

IroczFan

just street tires and at the end of the track now I'm at 3600-3800 rpm


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quik88

get them rpms up. are you leaving from an idle or are you bringin the rpm up some before the green?

brandoz28

iTrader: (1)

if it still hooks, you should drop .4-.5 or so

IroczFan

I drop it at 1600-2000 and hooks most of the time


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IroczFan

well the car ran 13.8s consistantly but cracked out a 13.62 @103 always spun on the launch and in 2nd 2.2 60ft


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pancherj

Even with steet tires, you can get better than a 2.2 60' time. Work on that launch. 1.8-1.9 should be possible. You need to find the sweet spot to hold the throttle where you can release the brakes and start mocing without spinning. Once you start moving, slowly apply throttle. If you can get it to go with a small chirp of the tires but no real spin, your 60' time will come down a lot.

Orr89RocZ

iTrader: (20)

I would hope 2-3 tenths but may not help at all.
My tpi combo picked up each time from 2.77 to 3.27 to 3.42 for a total gain of 3 tenths. My ls1 car picked up only .05 from 2.73 to 3.73!!!

IroczFan

just kinda hard to launch with a stick car was thinking of maybe trying slicks or drag radials


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dmccain

iTrader: (2)

Drag radials would surely help ur times. It will make it grip and test that rear end also.

red rock

iTrader: (2)

What air pressure are you running? Street tires and drag radials, you need to drop the pressure to 12-15 psi.

KWIK84

iTrader: (5)

Drag radials and a stick shift will narrow up your tuning window a bit, If you have an extra set of wheels I would go with some 26x8.5 slicks

Z28FAST1

You need a sticky tire to take advantage of the "torque multiplication" which 3.73's will give you.

I went from 3.08's to 3.73's and dropped .3 tenths in the 1/8th mile because I would launch better and stay in my powerband.

IroczFan

around 30lbs and I would want a 26in tire so id know it would fit 10 Bolt is fresh so i hope it wouldt break


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red rock

iTrader: (2)

30 lbs. pressure is why it's breaking loose, you need to drop the pressure for some kind of a hook up on street or drag radials. And yes you will find your weakest link on the starting line.

IroczFan

how low should I drop them to? I Drive 40 miles to the track so keep that in mind id run my street tires


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red rock

iTrader: (2)

Well you run them at the correct pressure till you get to the track, drop the pressure to 12-15 lbs. and air them up before you leave. Some track should have an air hose there, if yours doesn't, bring a portable air tank or compressor with. And don't forget an air gauge. You also may want to pump up the fronts to 40 lbs. at the track and drop them back down before you leave, that helps the front roll with less resistance.

IroczFan

I lucked out and am able to use some drag radials for augest 1st ill keep updated with what it runs also swapped in a MSD distributer


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ASE doc

I hope Im not too far off topic. I ran my 87 IROC Z28 at Woodburn this past Friday. My best run was my first run 13.48 @ 104. I ran my 255-50-16 BF Goodrich G-Force TAs. 60 ft time was 2.185 IIRC, I dont have my time slips handy right now to be sure. I had a hell of a time trying to control tire spin off the line and on the 1-2 shift. I obviously have alot to learn about launching and shifting. I was sure after the first run that I could improve my launch for better time but it just got worse. Each run netted a higher time. I had my rear tires at 30 and fronts at 36. I'll remember next time out to to run lower pressure in the back.

red rock

iTrader: (2)

I would drop the pressure in half on the rears and heat them up in the box. Usually drag racers are very helpful with advice because most of the time your trying to beat yourself anyway. A good set of stickies would test how good of a mechanic you are.

ASE doc

Thanks red rock. I'm a just good enough mechanic to know that my wimpy stocker rear end would last maybe one pass with sticky tires. I've seen guys with less motor burn through these 10 bolt 7.5s like paper. I'm actually surprised that it's held up as well as it has over the years with this motor and my love of tire smoke. Good gear lube has something to do with it I think.

My boss and I were talking yesterday about how to beef up the stock rear, but I would rather just go with something stronger to start with and plan to put together a 9" Ford rear axle this winter. The car isn't set up for a great launch anyway. The suspension is built around corner carving and country back roads in the wee morning hours (my greatest weakness) with super stiff springs and dampers. Not great for weight transfer. Still, once I have a good rear axle, I'll see what I can do with some drag radials at least. I also think I might cut one more half turn off of these Eiback rear springs to drop the *** end just a little more. That should also help.

red rock

iTrader: (2)

I would start with a "built rear" also. What kind of RPM's are you turning at the speed trap? That will help in determining your gear ratio and peak rpm at the trap. What kinda HP you getting out of a 355 TPI to have a 3500 stall TC?

ASE doc

I estimate 420+hp @ 6,000rpm. Peak torque should be about 450ft/lb @ 4,000. You can see the basics of the build in my signature.
I don't remember what I was turning at the trap, maybe 5,500. I know that I engage 3rd at about 4,000, right about 1/8 mile, from the 6,200 2-3 shift. The motor gets to run up pretty well in 3rd before the trap.

My plan for the rear end is to use a Quick Performance housing and axle set and provide my own center section. I'll probably just have a local diff shop, Paden Drivetrain, do the center section with 3.27 gears and tack loc. They are very fair on price and do great work. I have them do any axle we don't do here in house, never had an issue with any unit from them. This would all run about $1,500-1,600, vs. $2,200 from Strange for a basic unit with open diff.

I could almost get by with the stock unit for the way I generally run the car. It's really held up pretty well since I went through it 15 years ago. However, while it may survive on the road behind this motor, I don't expect it do as well behind the 600HP 406 that I have planned for the near future. Plus, when I do get to the strip, maybe once a year, I want to know that the whole car is up to the task.

red rock

iTrader: (2)

We just never have enough power, do we? Lol Good luck on your build and have fun at the track.

ASE doc

Never enough. I'm starting to think though that the key is to stop comparing my car to other cars. Especially the high tech and supercharged offerings coming out of Detroit these days. This car is so vastly improved in every way from what it was new. "Optimized" was my original mission with this car. I loved the IROCs from the first time I saw one. I just felt like the OE could have done better with the performance had they not had their hands so tied. The potential of these cars was obvious almost immediately from the improvements possible with just a few upgrades. When I first built the car 15 years ago, it was faster than anything coming from the car makers. The new horsepower wars have pushed new car performance way beyond what it was in 99. Even with that, my IROC still holds its own. TPI and all.

My original mission was to double engine power and set up the already impressive suspension and chassis to be closer to its potential. Now that I've got it here, I just keep thinking of how much more I can do and step by step, I continue building on it. I see all the great things others are doing and get excited about doing these things myself. The fact is, this car is excellent as it sits. Driving it is a thrill. It will never be the fastest car on the road because someone will always build one faster. That's okay. This 87 IROC Z28 ran dead even with a 70 Chevelle 454 and walked past a string of fast cars in the 1/4 mile. That's saying something. I was impressed and so were alot of spectators. I love my little IROC Z. When I'm finally done with it, it will pass on to my son who also loves it and the legacy will carry on.

red rock

iTrader: (2)

Great to hear your having fun with your car, that's what it's all about. HP and torque are a never ending goal. That 70 Chevelle with the 454 was the king of the heap back in the day. One thing to remember about our Third gen's is, we are over a thousand pounds lighter than the new cars, so the weight to horsepower we have we have is, "less is more". There are many little things you can do to reduce even more weight if you get "serious" about the strip. A few pounds less here and there, decreases your times and adds MPH at the trap. I also have an '87, which i believe, in my own humble opinion, is the best year of the Third gen. with the introduction of the 350 back in the car's. So, strap in and hang on, and work at traction, weight, and reaction times at the tree.

IroczFan

car has been sold


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red rock

iTrader: (2)

Oh dang. No more fun, or are you looking at getting another?

IroczFan

ive already got anouther 86 iroc 383 auto been finshin up the motor swap, the car I sold was just a impulse buy was a steal doubled my money


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84firebird383

I have to disagree with you on this. Street radials have hard sidewalls and no tubes. They will tend to cup with to little air pressure. When I used to run a true street radial I would do a good burn out so I could inspect the tire contact patch. You want the widest and most consistent dark color. You want to be able to hook with the most air pressure you can, as it will reduce rolling resistance. I used to run 11.7@119 mph in my 383 1980 z28 with 235/60/15 true street radials @ 30 psi with a 1.8 60'. I had to do a lot of pedaling for sure, but it was slower for sure with less tire pressure. All I had for suspension mods was south side machine bars, frame connectors, and solid body and motor mounts.

red rock

iTrader: (2)

Just so you know I'm not blowing smoke here, this was taken off the Mickey Thompson web site. QUOTE- "ET STREET RADIAL

On the racetrack DO NOT use starting pressures below 11 psi.

Recommend pressures for:

P295 and larger sizes: 12-16 psi

P275 and smaller sizes: 14-18 psi"
In my experience on a actual track, I find 12-15lbs works great. I have seen guy's run 30 lbs and have they have dropped their times a full half sec. by lowering the pressure. If 30 lbs works for you and you like to pedal the throttle that's fine. As far as a "black patch", my NITTO's lay a even patch with 12 or 30 lbs. Maybe your tires are too hard of a compound?

84firebird383

I was talking about everyday street radials, not sticky drag radials. every company has different recommendations for their drag specific tires. Example would be, back when BFG came out with the first drag radials they did not recommend going below 25 psi.

red rock

iTrader: (2)

Even with street tires, dropping the pressure can help. It all depends on the brand of tire and type of tread and rubber compound. If you have a hard rubber compound tire vs. a soft one, dropping some pressure will help. I had a set of Proxes that were so hard, you could smoke them, but they would not leave a black mark on the road.

84firebird383

I just thought I read that you were suggesting an every day street radial should be treated the same as a drag radial for air pressures. Not saying a person shouldn't experiment with pressures on a true street radial, hell that's exactly what I did. I would be surprised for any true everyday street radial to run faster or 60' better with pressures below 25 psi. I've always had better luck I the 30psi range myself.

red rock

iTrader: (2)

Again, it all depends on your tires. Street tires will never hook up as good as street strip drag radials, and street strip drag radials won't hook up as good as drag slicks. It all depends on the tire compound. But if your going to a drag strip, that's why they have test day and practice runs before the race. So you can experiment with tire pressure and tuning.

84firebird383

I actually hooked just as good on my normal street tires as I did with the original bfg drag radials. That is why I raced on regular radials at the time. Yes I know that is not what you will find with Todays drag radials, and even then the 235/60/15 BFGs probably would have been a nice improvement on a 13 second car. Just to clarify though. I was only disagreeing with your statement that a regular street radial should be run the same as a drag radial. You don't have to explain anything to me about tire compounds and testing, I've been doing this stuff for a while now, and have a pretty good grasp.

red rock

iTrader: (2)

You can disagree all you want. Not all street tires are like yours. Many people, me included, have hooked better on street tires with less air. I think your original BFG's were hard tires. So for anyone out there, if you run BFG drag radials, run 30 lbs. in them. Thats why we test.

84firebird383

My grey 77 Firebird with 275/50/15 Mickey Thomson drag radials. 15 psi.

84firebird383

And I wasn't trying to get into an argument. But you wont find any racer running an everyday radial running 12-15 psi.

red rock

iTrader: (2)

Most racers don't run everyday radials, only the ones starting out. Nice video by the way.

84firebird383

So don't tell them to run 12-15 psi in their normal radials. Its bad info

red rock

iTrader: (2)

Boy oh boy. It's not bad info, a lot of guy's i know, me including have done it, and it works. If it didn't work for you, fine. Then let it go.

84firebird383

Honestly I'm fine with agreeing to disagree. I would like to meet some of the people running that low of pressure with good luck on a regular radial, for real. It just doesn't seem the norm, so I consider it bad info. I plan to run a 76 Trans Am with a 12:1 454 solid roller next year at WIR, and most likely it will be on a 255/60/15 or smaller normal radial. I see you are from Wisconsin, so If WIR is your track I'd love to meet you, and maybe throw some ideas back and fourth on how to get it into the 11's with all that torque. and no slicks and drag radials aren't an option.lol

84firebird383

By the way my tire pressure was 35psi not 15psi in the video. Pretty sure 22 psi is what I ran normally with those Mickey's. 10.9 was the best et with the drag radials. I ran 10.7's on a 28" slick.

ASE doc

Next time I get to the strip, I'll be sure to have some way to adjust air pressure and experiment a little with it. Have to do better than last time. I'm sure temperature played a role. My first run was the best, from there it just got worse until it was like trying to hook on grease. All the rubber on the track couldn't have helped either. By the next time out, I'll have the fuel system taken care of and new exhaust, but most likely no improvement to the rear axle at that point. Rear axle will be probably be next year's project. We'll see how it goes.

IroczFan

Small world I run at WIR to lol