belairguy

Alrighty, so heres where I'm at. I have a 85 IROC-Z. It has a zz4 crate engine, holley 650 good for about 400HP or so. Stage 2 700R4 transmission with a shift kit and 2300 stall. True duels and sounds heavenly, but my predicament is this.

Im running the old 10 bolt rear... you think I can manage not to break it?

Also, what are some things i should do to the car to improve its performance on the track?

Maybe if i were to only have 20psi in the tires (not slicks...yet) then maybe i could get the car to hook without destroying my rear? right now just driving it around it'll spin the tires all the way into 3rd if i hammer it.

Anyways, I just need any thoughts and advice you can give me as I'm new to legitimately competing in drag racing

belairguy

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zz4

belairguy

WickedBowtie

I'm still running my stock 10 bolt. Its only a matter of time when it taps out. In currently saving for a 9 inch.

I say run it the way it is and see how you do. Then next time try it with some actual tires meant for racing and start comparing from first time out. Some suggest keeping a book to write down everything you change or do each time you go out. I simply just write it on the slips...lol.....

It is a constant uphill battle between man and machine. There's going to be many struggles emotionally, financially and mechanically....lol...atleast there has been for me. But it's all worth it to me. There are a lot of people on this forum with great information. I suggest you take as much in and roll with it.

WickedBowtie

Nice car by the way.

pancherj

With an auto, your 10 bolt should last for a long time. You could get a reinforced cover with preload bolts for the main caps. I guess that helps some. I have hundred of passes on my 10 bolt. Most of those passes were on drag radials or slicks and low 12 second/high 11 second passes with 1.60 60' times. Once you get all the bugs worked out, I would suspect mid 12's out of your combo.


To help the 10 bolt live, never do a "dry hop" with slicks or drag radials. In other words, heat the tires up and slowly lift out of the gas as you roll to the line. Stage immediately. I see guys heating the tires and then pulling up a little and hitting the gas. This shocks the rear and gets rid of some of the rubber you just tried to make sticky. I never understood why guys do that.

AlkyIROC

You can't do a waterbox burnout with street tires to make them sticky. A street tire is a hard rubber tire and is not made with the same rubber compound that slicks are made from. They're not designed to heat up like a slick.

With street tires, drive around the waterbox towards the inside. They sweep dirt and gravel to the outside and you don't want to drive through that. You can do a short dry hop just to spin the tires to get them cleaned off before moving up to the staging lights.

Tire pressure in radial tires should never go below 28 psi. They work best in the 30-35 range. Radial tires have a very stiff sidewall and if the pressure is too low, the center of the tire will curl up off the ground and give you less traction. For a slick, start with a tire pressure that's around the ET you'll run.

five7kid

iTrader: (14)

A stock 10-bolt has several weaknesses. An optimized 10-bolt only has a couple of weaknesses. I had my optimized 10-bolt into the high-11's (only a few times at lower elevations), mostly ran it in the low-13's/high-12's (at our high elevation). Over time, I went through a factory Auburn posi, two sets of factory gears, and an Eaton posi, each time putting the 10-bolt back together because of time and funding constraints when I was getting the car running or after the rear end broke. In the end I put enough money in it to buy a new 9", new 12-bolt, or new S60.

An '85 will have 26-spline axles. Weakness #1. Later 10-bolts had 28 spline axles. You can put them in your '85 housing, along with a 28-spline posi, but aftermarket axles highly recommended.

The 10-bolt housing flexes under power, and the higher the gear ratio you're running, the worse it gets. An aluminum support cover helps, but only to a point.

Factory gears are a bit weak. Aftermarket recommended.

I hate clutch-type posi's for drag racing. The Detroit True Trak is a great unit, it was the last unit in my 10-bolt.

But you really should save your nickles & dimes until you can get an aftermarket rear. There are several choices, as implied above. The main limitation in a 3rd gen is the need for a torque arm mount.

9" - Best aftermarket support, many choices of manufacturers, probably the most popular racing rear end. Drawback is it takes up a lot of real estate in the tunnel. If you intend on eventually hitting this thing hard, start with 35 spline axles and get the S&W torque arm kit (after all, it's only money...).

12-bolt - Only a couple of choices I know of, Strange and Moser. Drawback with Moser is they use threaded torque arm mount bolt holes instead of through-bolts like everybody else. Takes up less real estate and is more power efficient than 9". Arguably not as strong as a 9", but if you aren't going 10's or doing 6000 RPM clutch dumps with a manual transmission and sticky tires, probably not an issue.

S60 - From Strange, based on the Dana 60 rear end. Quite beefy, but also the heaviest of the bunch. But you'll probably never break it.

More and more 3rd gen owners are modifying Ford 8.8" rears for their 3rd gens these days. Whatever floats your boat, but seems to me like a lot of maze for not much cheese when there are good aftermarket choices out there.

I agree with the no-water-burnout-with-street-tires part. A few years ago Cruz Pedregon did an article in National Dragster where he said street tires really need to be heated up because their rubber isn't like slicks. He went on to say the reason the big boys do a burnout is to get heat into the drive train, not to get the tires hot so they'll grip (the other reason is the fans love it). Interestingly the tire manufacturers also say a big burnout is not necessary, as "the traction is in the compound" (I saw two different manufacturers use the exact same words) - the "burnout" is just to clean off the tire surface. If you need any further proof of that, one race a few years back John Force had issues during the burnout and staged without having produced even a whiff of smoke - not only did the car stick, he won the round. While I haven't raced on street tires for a long, long time (except the Vette, which has wide tires and is slow), since I heard all of the above my burnout is just long enough to dry off the tires (when the engine starts to pull down), then I let off the line lock and spin out of the water box until I am clear of all water. Then I stage. The amount of smoke produced is irrelevant as long as the tires are dry.

Oh, and I can't pull around the water box to the inside here - no room. Our track used to sweep the water box to the outside, they now sweep to the inside so people can drive around on the outside where there's room without dragging junk onto the track. Each track is different, so be aware of what you can do at your track.

Never heard that one. I'm running 20 psi in my DOT slicks, guess I'd better drop them down to 12 (and wander all over the top end... ).

belairguy

wow okay thanks fellas, big help from y'all. It is VERY appreciated.

Here's an idea, what if I welded the rear axle tubes on the rear end to add some insurance to that 10 bolt, did a rear cover with the bolt up stabilizer piece and ran my street tires to hell at say 22-24psi? Then with that combo, theoretically I should be able to make a good many passes with the car without blowing any parts to hell (or at least try)

I for sure want to beef up the rear later on down the road, but probably won't worry about it until I beef the engine up OR blow the rear ( which I have a feeling I will at some point )

Also, how about Nitrous? Any experience with that? (if, ands, do and don't) ?????

QwkTrip

iTrader: (22)

I think you'll have better traction running normal air pressure in a conventional radial street tire. As explained earlier, the tire doesn't have the kind of construction that responds well to low air pressure.

I don't know anything about the 10 bolt, but the goal is to stiffen the center housing to prevent misalignment of gears, is it not?

belairguy

certainly agreed, I'm thinking about having a friend of mine who does welding to fab something up to reinforce the rear for now at least. And I will certainly change tires eventually but for now I'm going to run what I have. Sure, I get that those tires might not respond great to low air pressure, but it must make some difference because they are hard rubber.

five7kid

iTrader: (14)

Welding the tubes won't hurt anything, but it isn't as important as it is in a non-torque arm vehicle.

The case will still spread some from the pinion gear acting on the ring gear. I don't know of anything you can do about that with a 10-bolt.

22-24 PSI in street tires will probably cup the tread and reduce the contact patch. Experimentation is the only way to know what pressure works best.

Just say "No" to drugs.