jlfx car audio

My dad gave me his 86 C4 convertible it's been to the body shop in the past due to hitting a dog by previous owner so it's nothing really nice any more.
Things I've done so far;
17x9.5 zo6 wheels rs3 255 40 17 tires
Banski rear suspension
Bilstein shocks
Autopower roll bar
Champion 2row radiator
6x12 trans cooler
Neg 2deg rear camber/2.5 front
Lowered 1" in rear
Drilled and slotted rotors
Hawk pads
Stop tech brake fluid
Things I have for fall build;
Tpis race headders
Victory 200cc heads milled. 028(60cc)2.02/1.6
Ex274h cam/1.6rr
Lt1intake conversation
28psi injectors
7qrt road race pan.
Felpro 1094 head gaskets
Batcap 800 rear mount battery.
Motorvation custom tune.
You guys have any recommendations for brake lines or anything else that would aid this setup?
I run at Mir in memphis tn and the 4+3 works pretty well so far after finding out how to shift it the smoothest coming off strait (od4 - od3) Then entering the "Ms" I go out of od for the remainder of the lap,tho the tpi don't like it above 4500(main reason I'm moving away from it)
Motor runs below 200 the entire run (with 175 thermostat)
Brakes didn't faid all weekend during the 6 20min sessions.
Would like to do some venting in the hood but not sure the best cheapest approach

c4cruiser

I use my '87 4+3 coupe for track days and I never engage the OD unit. From what I have read over the years here about the OD is that it does not like being abused such as WOT engaging or disengaging.

Unfortunately, my '87 won't hit much over 125-128 with the stock 3.07 diff, but local tracks don't have really long straights.

In any event, it's important to keep fresh ATF in the unit and change the filter once a year. I had also read that you should not use a synthetic ATF, just use Dexron III fluid. The filter is the same one used in Ford FMX auto transmissions found in some Mercury Cougars, Ford Fairlanes and some F-150's. Here's some part numbers:
Carquest 85926
AC Delco TF 184
FRAM FT1024
NAPA ATP14717

If you do use the OD on track, it may help to add a separate trans cooler.

It will be a big help to add a power steering cooler and use Red Line full synthetic PS fluid. I still have the original PS pump in my car and it's quiet. I mounted mine just in front of the front crossmember.

For brake lines, either Goodridge or Earl's are great for the flex lines. I would suggest upgrading the front brakes to C5 components. Vette Brakes has a kit but you can also get the custom adapter bracket on eBay and then just start to buy the C5 front brake components. Also with the C5 brakes, get the Doug Rippie custom brake bias spring for the master cylinder. It makes a big difference in bias once the C5 brakes are installed.

Use a mid-70's Chevy pickup oil filter (AC Delco PF-1218 or Mobil-1 M1-302) to gain more oil capacity. It should fit with a bigger pan and also clear the headers.

Bad Karma

I'm curious why such a narrow tire on the 9.5" wheels?

For brake lines I would go with Doug Rippie braided SS.
You are adding power to the car this fall, you may want to consider adding more brake. And a lot of guys stay away from drilled rotors as they are more likely to crack under extreme heat.

If you want to vent the hood on the cheap, look at cutting up the stock hood and making vents yourself or installing some universal ones.

jlfx car audio

I have a trans cooler (I forgot to mention) 12x8 and I'm not using the radiator trans cooler at all.
The drilled fronts I figured were better but if I have issues I will be sure to just get slotted next time. The rears are only slotted (guessing that's good now) . As for the tires I had nothing to go off of other than the stock 9.5 wheels used 245 tires so I went to 255s cause those don't add any points (nasa point scale) tho I can't complain they hooked up amazingly even my instructor was shocked at how much corner bite the car had I was pulling 1.3g in 2 different 180s one @65entering-80exiting the other 40-60mph. And never heard the tires and never felt them giving up.
I tried leaving it in 4th down the strait but revving the tpi into the 6300s I didn't like (115ish) with over drive I was able to get to 122 entering the braking zone into the caricel

jlfx car audio

I need to change the od filter. I did replace the fluid when I added the cooler tho.

rithsleeper

Brakes are always the fail point for me when I first started to mod mine. They still are weak point. Sounds like some of your mods are hurting than helping. Definitely steer clear of drilled or slotted. Unless you are spending $300 on a set the slotted will just crack faster. I've had terrible luck with hawk pads unless they are over the blues (still toast blues on a race tire). Zip sells steel braided lines and they are the cheapest I've found and work fine. Raybestos pads are super cheap and have just as much bite and heat resistance as hawk.

You lowered the rear but not the front? That is OK I guess but why not lower the front by slicing down your rubber pads on your spring. Easy one day project.

I thought same thing with tires but if you are fitting a class that makes sense. If the 4+3 is doing well drive it till it fails but me I always like a true manual. The 4+3 just felt like i was missing gears on past corvettes. The 6 speed was just what I needed. Both zf and t56 have about same ratios. And you could convert the trans cooler to a oil cooler. As soon as you port heads and change cam you will need it big time.

You didn't mention a seat iirc. Put a true racing seat in and you will cut 2 seconds off your lap time easy. I put off doing that for so long because I thought it didn't really matter. Just a luxury. F that. Huge difference. I'll do that first from now on.

jlfx car audio

Good points. As for the seat tho I'm still new to the track thing so I must have a instructor with me and as I move up thru the classes they have to ride until I'm in the Tt classes and have my comp license. So if I got a seat I would ha e to have a matching seat on the other side...
So what brand rotors are going to be the way to go then? And yes a oil cooler setup will be coming when I pull the motor out

c4cruiser

For seats, look at the Corbeau Forza FX1 Pro or the Forza Sport seats. They are decent entry level seat and actually pretty comfortable even for street use. Get a pair and install them so the instructor will have the same seat as you. A good 5 or 6-point harness is a must.

Once you get to where you don't need an instructor, then you can remove the passenger seat and harness and keep it as a spare.

jaa1992

FYI - all those mods you are gonna wind up in TT3 so build for that!

Get the weight down - I'll bet dry you can get to around 2000lbs
Big brake kit for the fronts - you'll need to change a bunch of stuff in the front suspension to go to j55 brakes - might as well go whole hog.

Try out Carbotech pads instead of the Hawks - I love xp12/10 combo on my 92
Mine has the j55 brakes and stock replacement rotors - with these I can brake from 125 to 50/60 around the 100 marker going into T10A at Road Atl.

Cage it - don't just put a roll bar in - shoot its a track rat now!

Bad Karma

Can't believe i didn't mention seat either. Putting a real racing seat in was probably my best mod, followed by the Wilwood kit up front. Make sure you sit in whatever you plan to buy. Based off of pure size and what should fit I would have ordered the FX1, but once I sat in one, it just didn't fit my body comfortably.

I thought most places that have a requirement just required the same restraints on both sides, so you could get a true racing bucket on the drivers side and grab a Corbeau A4 for the passenger/instructor, which is more comfortable for differing size instructors to take a ride; and we have a forum vendor who sells them with options to add a hole in the seat for the sub strap, and an option to shave the seat base foam for more head room.

Any future track build I do will always have a heavy focus on brakes after I chased overheating brakes on my C5Z and ended up with the Wilwood and full race pads with cooling ducts. I'm actually at the point where I have more brake than I have tire. An '86 with only single piston calipers would worry me for taking a severe beating.

lefrog

Some things to think about (in no particular order):
- brake bias spring
- brake cooling ducts (especially when you upgrade to bigger brakes)
- fuel starvation fix in the gas tank if it has not already been done
- racing seat + harness
- steering wheel (like a Sparco 383) with eventual quick release
- larger tire sizes?

rithsleeper

All these guys are on the right track. I don't think some really know your c4 that well. J55 is basically same as c5 caliper (z also same). They are two piston front and one piston rear. The carbotech are good but expensive. I think jaa1992 meant down to 3000 (not 2000). But lightening is easy and cheap to get down to 3000. A full cage is a huge investment.

I am an instructor with NASA so I know what you are going through. You can pick up a set of used racing seats usually for $400 for a set. Belts are cheap since people sell out dated stuff that is perfectly fine for de groups. If you ever get around to installing a set of seats and have trouble I'll send you pics of my install.

Chances are good you won't fit any class before all said and done. Unless you go straight up building around a class. Which might cost you less in long run but sounds like you are doing what most do and spend a little by little just tinkering.

You said you have a suspension upgrade on rear but what about the front? Is your car a z07 car? If it is you are super lucky and have be best front spring offered in any year c4 (1992 z07).

jlfx car audio

Thanks guys I don't quite see it as tinkering but it's all I can do with 1job and limited funds, so some might call that tinkering. Lol
The car is a 86 convertible. It had the preferred fear spring but is soft up front spring wise (can't remember the spring atm) but it is working right now. Can can handle what I'm throwing at it. The instructor told me I could drive it harder into the corners and go faster thru them cause he felt the car wasn't on edge (never heard the tires talking, and responded very well) but I don't want the limit to sneak up on me.. So I have chose to sneak up on it instead. Seats sound like my next expense, cause I do think that was limiting my corner speed by sliding around inside the car thinking it was the car sliding instead of Me. Not to mention being in a 1.5 G right hand 75mph turn... I'm leaning all over the door.... Didn't like that.
I'm going to stick with the brakes as long as it feels safe but upgrade the hoses, but if & when they Crack I'll look to the c5 conversion
Tks for the replies! Spend my money! Lol

Bad Karma

There are slight differences in C4 J55 to C5 setups. From memory... (feel free to correct me if I'm wrong)
C5 rotor is thicker (I believe 1.1" to 1.25"). The C5 caliper may have more material to it to help prevent flexing (?), and the pads pay have more surface area on the C5 setup.

Also if my C4 history is correct the J55 option came into play in '88; so, his '86 from the factory is still on a single piston caliper and 12" rotors.

jlfx car audio

So what's the fuel starvation fix?

rfn026

The OD thinking is interesting. I never use mine at the track. I could probably use it on the back straight at Sebring but I usually just back off. Hey, it's a track day - not a race.

There's no reason to ever use the OD at Homestead.

I've never really had any brake issues except for the time I cracked a drilled brake rotor. Not those silly little cracks. I'm talking a huge sucker that actually made a noise.

I've been running this car for 20 years now and my advice would be to minimize the modifications. We're talking track days here. You will never be the fastest car on the track so what's the point?







Richard Newton
On Track and STP Insurance

jlfx car audio

Cause one day I will be racing and I would rather build up to that point instead of driving my car on a track. I want to race! That's my goal and purpose eventually within a budget anyways.

So I'm needing info on 2 things
1, fuel starvation issue fix
2, 5th belt /harness mount between your legs, how you mount this one to floor properly?

rithsleeper

Here is the fuel issue fix. What I was planning on doing. I get slosh at 1/4 tank.
Now as for the mount, if you make a good cross bar from you seat mounts you can use that. That fiberglass won't hold crap. If you can picture my mount: I have two pieces of 1" aluminum square tubing that bolt to the original seat mounts. Then I bolt the new racing seat to those. Then I run another tube creating an "H" and some cross support. This actually bolted over the seat mounts. I wrapped my 5th belt around this bar. If the aluminum breaks on a wreck I have way bigger problems....

jlfx car audio

Has anyone used the hydro Matt?

jlfx car audio

Thanks for the visualization of what I need 2 do I'm going to do a bar under the factory seat to connect the crotch strap. Yes this means I will but running the belt up thru the factory seat (yes I will have to cut a slit into them... Lol but not before trading my mom for her ripped seat bottom on her 87) until I can afford a race seats