Hi all:

I've some questions for the experts here. I've been autocrossing my stock '94 Z for four years now. After getting through grad school and being newly employed again after a nearly year long layoff, I'm thinking I'm ready to massage some more performance into the car. It has 112K currently and is stock sans a K&N filter. So here are my questions:

1.) exhaust: I've done some research, and listened a few brands, and I'm down to either a Borla or SLP Cat back system. Anyone have experience with either? I'm concerned about loosing too much (if any) torque with a new system.

2.) rear diff: I think mine's slipping or shot. It'll lay down two patches in a straight burn out, but I notice the car seems to rev higher without going faster exiting some turns (auto-x only). I've also notice this when it's wet (sometimes it doesn't fish-tail). I take these as indication the diff is slipping. I replaced the fliud with Amsoil synthetic 3 years ago this spring. I've heard the clutches can be repacked and it'll be good (or better) than new. Any input?

3.) Can suspension bushings be replaced in a parking lot? I've no garage yet, and like to do as much work myself as possible. Plus, money is a slight issue since while I was laid off the 'need' list grew as big as the 'want' list, if ya know what I mean.

Thank for any advice.

-Tim
'94Z, 6-spd, black, 416 FS Chicago reg

 

Borla is a very nice cat back and I would recommend it. There are 2 paths out w/ the borla (1 through the muffler and one straight out) and you have different templates that you can insert to either block off or open (in various diameters) what bypasses the muffler. If you block it off, your torque curve will remain just about the same as stock (peaky around 2400-4900 rpms, its pretty flat between these rpms). If you open it up, the curves change, and I think you still gain some but only at the upper rpms (and loose some in the lower, not what you want for autocrossing). But if you continue w/ headers/y pipe etc, the opening will help create more power. You can get an electric cut out that is a butterfly basically that will open/close this opening (called a 'cut-out') from the drivers seat. Fully open its almost NASCAR loud though... and the gains are minimum (like 10hp or so for what I can see).
http://www.mccordcg.com/mpp/mpp.htm

If you get a cat back, change your intake as well to a CAI (Cold Air Induction). Your K&N helps a bit, but the CAIs will use a cone filter and place it lower in your wheel well, with a plate blocking the air from the engine compartment, so you grab only outside, cool air. People worry about hitting puddles and getting it wet, but from all the posts I've read, unless your driving in conditions that you really shouldn't be (as in a flooded street), you should not experience any problems with it. I bought the G2 CAI and this is the one to stay away from if your upgrading (for the money, the gains are small, and the other CAI designs are much better). All the others are really the same (SLP, Moroso, K&N FIPK, etc) as far as gains go.

As for your diff, are you at 112k on your original clutch? Since it does lay down in a straight line and your problems are in the turns, it could be the diff though. I think mine is going as well. I was going to replace mine with the Torsen Racemaster T-2R. Its Torsen rather than limited-slip design. Here's some info:
http://www.globalwest.net/torsen_tra...fferential.htm
These guys dont sell them anymore I dont think, but you can find them elsewhere.

Which bushings are you talking about? At the end of the shocks or the rubber ends on the springs?

--Kevin

 

Kevin:

Thanks for the info. As far as I know the rear diff is original at 112k. I bought the car with 62K on it, and the dealer told me the previous owner had replaced the tranny clutch.

Since I'm planning to stay in F-stock, I don't think I can put the CAI on and stay legal. Or am I wrong here?

I was referring to suspension bushings in the control arms, front and rear. I'm under the understanding that at 112K the stock rubber is probably pretty worn out. I'm tempted to go to poly bushings, as I doubt anyone would notice at either the local or pro-solo level.

Thanks for the additional thoughts.

 

My Chiltons says to replace the rear diff fluid every 7,500 miles, if you haven't been then this could help explain "early" wear, plus I'm sure it doesn't love burnouts.

 

The bushings in your upper/lower a-arms and the ball joints there are probably near shot/shot. I would also take a look at the bushings on the swaybars and their endlinks. (Im doing my endlinks now). To stay stock you would not want to use the CAI, except for G2s (which uses the stock location and filter size, but the tubing is seamless and I think a bit wider). Not sure if its 100% legal, but I dont think anyone would give you problems w/ it. But I would save your money there. I believe you can change your front swaybar to 32mm (1LE has that).

Question: Can you put 'some' 1LE parts in your car or do you have to make EVERY 1LE change or none at all for stock class? I doubt anyone would give you a hard time about it unless your at Nationals though...

I decided that I wanted my car to be the most it can be and ignored classes (Im in Street Mod). I wont win there (best I can get here is about 3rd). There are several people in this area that compete Nationally, and 2 are in my class.

 

Thank all for the info!

 

Hold on there fella's.... He wants to stay in F-Stock. He can't use a T2R, he can't use an aftermarket intake, or non-stock bushings (except on the front bar).

First, know what you can and can't do in Stock. You CAN change shocks (not springs), but they have to mount just like stock and have a spring perch the same place as stock. You can change the front sway bar and it's bushings. I run a 35mm FWIW. You can install a new limited slip (and yes, yours is shot), but it HAS to be an OEM auburn, not an upgraded or aftermarket one. You can change brake pads, fluids, install a K&N, and run a cat-back exhaust. You can run R-tires, but they have to be on 16x8's that are within .25" offset from the stock wheels. That's about it.

Anything else pretty much sticks you in at least ESP, maybe even SM. You don't want that unless you have a lot of money and desire to build the car.

My FS setup won me the ProSolo title this year, and I lent the car to a friend and he was 2nd @ Nationals in it. I was racing (and winning) ESP.

 

Sam:

Thanks for the additional info. I am planning on staying in F-stock, basically becuase I've too many otehr hobbies competing for my pocket book's attention. I'll be clearer on my intentions in a future as know mostly what I can and can't do in F-stock.

An autocrosser in MD (can't remember her name) told me she had her diff repacked and to a higher torque threshold ( or something like that). Basically I understand it that is runed the diff closer to the performance of a torsen? I need some more understanding here.

Thanks again.

 

Listen to Sams advice he knows his stuff.

As he said the Torsen is out as are non stock bushings.

So what you are looking for as far as gains (assuming I dont know what you already have) is an Extra set of stock type wheels. SLP sells take offs for $200.

Next will be shocks. Konis single adjustable in front around $450 (I think)
And you can throw some Bilsteins on in back.
Then the front bar. Go with the 35mm S/T bar. That is my front bar also. Although it is on an ESP car. Sam uses the 35 on an FS car (like he said) and it makes perfect sense. The springs are pretty soft so this is helping to make up for the lack of spring rate. Which means it controls camber better, which means more grip.

FWIW I use Hawk HPS pads front and rear. This should work very well for you too.

I would replace the bushings eventually. You can do it in two days. Strip everything off one day and take it to someone to have them change the bushings. Then put your arms back on the next day. Not a #1 priority but they probably are trashed.

As far as the diff..I dont know the exact procedure but what the lady was talking about is: You can add extra clutch disks to the stock diff. These can be used disks too. Just sand (lightly) each disk and then add a few thin disks to it. This will preload the diff some and it will hook up better than new. If you find the exact procedure or find someone who know how to do it it may be worth your time to find all the used auburns you can(for the extra disks). You want a used one because the thinner disks are easier to shoehorn in there.

 

Sorry it seemed I gave you bad advice, but you didnt say you wanted to stay stock until after my first post (Hence the Diff confusion)

For your lower front a-arms, you need to get the ball joints pressed in there. You can order the 1LE replacement arm and it comes w/ a balljoint in place already (I believe both upper and lower). I have heard some comfusion about part numbers, because GM like to crossrefernce eveything. So the 1LE part will sometimes get you the stock replacement. You need someone to look at the part numbers on the actual part to verify it for you. The 1LE part will have a higher durometer rubber for the bushings for a little less deflection, and keeps you stock as well. So if a garage is going to do this for you, getting the replacement arm will probably cost less because of less time (paying per hour) to replace the whole arm than to repress a new balljoint in there and burn out the old bushings.
W/ the upper arm, you need to drill out the rivets and replace them w/ bolts. You can get the upper ball joints just about anywhere too. Not sure about the bushings though (they came w/ my arms). I think the bushings on the upper arm are also sometimes tricky to get out (havent done it myself and have heard people refer to 'burning them out w/ a torch').

Good luck!

 

Thanks all for the very useful (and hopefully followed in the very near future) advice.