Tuned Port Cavalier Buildup
I will add the latest updates to the bottom of this page, check here
About the conversion: this is without doubt the hardest to do of any car I've built, and I built the full street/race tube-chassis in my '57 which I drive on the street, and helped my brother put a full tube street/race chassis in his '86 Z-24 Hatchback Cavalier, among quite a few other cars for friends. I guess one thing I'm trying to stress here is that we have a very well equipped garage (mig, torch, tubing bender, lathe, drill press, I think every air tool imaginable, plus both of us are machinists and have full access to all the tools at work) On everything I tell you about my Z-24 conversion I'll try to give you an idea of how you might be able to do it if you ever want to tackle a project like this but don't have access to the tools I have (it might cost a little more, though, than the way I did mine, but it can still be done) The thing that makes this (Z-24 conversion) harder is because I'm keeping all the creature comforts, switching the air conditioning over to 134-A, and not putting any holes in the hood or roll bars in the interior or anything else to give up the fact that this is not your basic FWD car. Okay here goes:
Making it fit: After disassembling the car, selling the original V-6 (which was a bad little motor to begin with) I had to remove the AC box and cut the trans hole, then move the outlets on the AC evaporator to clear the trans and weld new (134-A) fittings on; the heater core had to be turned 90 degrees and the outlets now come out of the side of the Heat/Air box above the drivers feet and go through the firewall by the steering column. (the new heater outlets I machined out of aluminum and had to glue onto the original plastic tanks of the heater core with a special glue I got from Graingers) An easy way to get around the Heat/Air deal would be to take the old box out and go with a street rod Air/Heat unit (Vintage Air is the leader in that market, but I have books from all the A/C companies for ideas and options); they have some nice units from $500 or so for the basic system to around $1000 for the killer digitally controlled temp unit that will easily fit in the space under the dash.
Steering; Front Frame: The steering rack is on the firewall and has to be moved to in front of the strut and below the oil pan on the motor, and you have to change to a rack out of a front steer car (mine is a power rack out of a Mustang, again common among street rods) . This front frame deal is the hardest to explain, I have a bunch of parts that I engineered and machined the parts myself to do this. The rack is right up against the oil pan on the motor, and I had to notch and modify the oil pan to get it high enough so my struts didn't have bump steer. I used the factory frame rails that the A-arms attach to and ran 1 5/8 -.135 wall (roll cage) tubing between them and then up to the uni-body frame, then triangulated back down to the middle of the cross bar that I first put in; with just enough clearance for the oil pan, tying it all together. With the 350 sitting in the car the cross tubes are inline with the side motor mounts, and this is what the motor is mounted on. This is a little hard to explain, I hope most of you are still following. Next, the sway bar has to be moved, I took it out and found out that I could just turn it around backwards and it now is mounted on the bars that I put in to mount the motor (that I just explained about). I had to make new mounts on the front of the A-arm for the sway bar to attach to, and also boxed the A-arms on both sides while I was at it.
Fitting the front wheels: This is the part that was the most challenging so far, the front spindle. If I had kept the stock rims or went with rims made for a Z-24 it wouldn't have been as big a deal, but I wanted to go to 16" rims and saw these OZ - 5 spoke "Monte Carlo" rims and just had to put them on it so I ended up getting some with a close enough back spacing to still look like a FWD car. I could only get a 4.5" bolt circle in the sizes/offsets I wanted, the front ones are 16 x 7.5 and made for a Shelby Charger, and the back ones are 16 x 8 and made for a Mustang. The front spacing on both look identical and I should be able to get a spare for the Stang or the Charger to work as my spare tire. I was originally just going to redrill the bolt circle on my front spindles, but I knocked the studs out and kind of bolted the rim to the stock spindle to see what it was going to look like with the car sitting on the ground and it stuck out of the fender well about 3/8 of an inch, which was unacceptable to me. So I took off the struts and designed and machined a new spindle for it that moved the wheel in 5/8 of an inch. It now sits in the fender well just like the factory wheels did, and while I was making the new spindles I also fit on a set of Wilwood 11 3/4" discs, and mounted the stock calipers on them. The new steering arm is also mounted on the new spindle that I made, and it has to be in just the right place to clear the wheel's backspacing when it steers. An easier way to do this for others might be to look at a newer Camaro front strut or some other cars in the salvage yards or even maybe some street rod front suspensions and see if they might work. I would prefer struts on a car like this because it's pretty limited on space, but A-arms when set up with the right angles will handle better in the corners. (I feel struts handle better in higher speed situations, though, 100 plus mph)

Motivation, the motor and trans: As you probably know it's a 350 with a tuned port EFI intake hooked to a '93 Vette 4L60-E. A carb will not fit under the hood. I was worried that I couldn't get a tuned port under the hood and was going to have to go with a TPIS "big mouth" (aftermarket) EFI intake to get everything to fit (it's about 3" shorter in height), which would have been better from a performance standpoint since it's a direct replacement for a tuned port and it will make 80 more HP just bolting it on. But I didn't want to spend the $800 bucks for it right now (plus another $300 for the fuel rail) And I kind of like the looks of a tuned port, anyway, I'm building this car more of as a cruiser (street rod style) than a flat out "as fast as it can possibly be" car. For the wiring harness I took the stock Cavalier V-6 harness, and modified it for the Tuned Port (GM's got the same computer running the '86 and up V-6 as '90 thru '92 Tuned Port V-8's have), but it wasn't as easy as it seemed to rewire, I had to buy almost all the sensor wire connectors because they changed the plug-ins on almost everything on the V-6 harness, I think next time I will just get the street rod (Painless Wiring) harness and just add the vehicle speed sensor to it (it comes without the VSS connection).

Trans Tunnel: The transmission tunnel was made out of .050 steel and (first of all there's a part of the frame that I built out of the 1 5/8" tubing running down each side of the trans with a tubing cross member that's also the rear trans mount) The tunnel was made by taking poster board 6 to 8" wide and making a pattern for each piece of steel and forming the steel after it was cut, then welding it in and going on to the next piece. The drive shaft tunnel was made in a similar fashion although I did it with 1 piece of steel, and bent the edges of the "box" over some roll cage tubing so it looked more factory.

Frame and rear end: the frame has two tubes going down the outside of the floor pan that I bent up so it would follow the contours along the edge of the floor pan, then they bend up and in where the stock gas tank used to be under the rear seat and connect with one of the stock attachment points for the stock rear suspension, and on up for to the place where the upper 4 link bars are going to be connected. The cross bar that I talked about a bit ago for the trans mount goes out to the edge and connects with these outer bars and the bars going down each side of the trans. from the trans cross bar back there's a pair of tubes that follow the trans tunnel lower corner that go back to the area under the rear seat, and then there's a sort of maze of tubes in the old gas tank area to brace the 4-link attachment points. After the tubes go over the rear axle they just go straight back to the rear bumper, and I now have a 16 gallon fuel cell behind the 9" Ford axle. I machined a filler neck for the cell so I could run the filler hose over to the stock side fuel door, and took the top filler ring out and simply welded the stock Cavalier electric fuel pump sending unit and float into the filler ring, I got a fuel pump from the local auto parts store that will handle the tuned port, and it just fit right on the Z-24 sending unit. For the 4-link I have the two bottom bars going straight forward and the lower bars attach directly in the old rear suspension mounting point, but the width was different so I fabricated a new plate for 1 side of the mount and tied both mounts to the rear portion of the tube frame that I ran back. the upper bars are angled from the center of the jug of the 9" Ford axle and it looks much like a Chevelle suspension. I used 1 3/8" - .134 wall tubing for the 4-link bars with street rod urethane bushings in the ends. I have 200 pound coil springs in the back and all the mounts for the rear were fabricated by me. The exhaust was done by a friend of mine who owns a muffler shop (I guess I can't do everything) and I left enough room in the old gas tank location under the rear seat to put the longest set of Walker Dynomax mufflers that I could get under there. I tried to leave enough room when I build the rear suspension to run the exhaust over the axle and back over to the side where the stock tips were, and when he put the exhaust on it was tight, but I was happy that he could do it exactly the way I wanted it to be done and it turned out great. Now the exhaust comes out the back through the same 2 1/4" tips in the lower spoiler notch that the V-6 did, making it look even more FWD-erish.

(11/21/97) Right now I'm in the process of putting the rear inner fenders back in (had to slit them down the middle to fit the wider tires in, the plastic interior panel looks like it will still fit over the widened fenders without much modification.

(11/24/97) Got the fuel lines ran, measuring the power steering ports so I can get the special (metric) tube-o-ring fittings ordered, looks like I might be able to fire it up shortly, but I still have to take the motor back out to finish some things and clean and paint the engine compartment before it's done.

(11/30/97) The power steering lines are ran, fuel lines are hooked up to the manifold, I was wanting to turn on the fuel pump today to set the fuel pressure and see if it worked, but ran out of time. I decided to go ahead and port the center top part of the TPI like they showed in High Tech Performance magazine before I fire it up so I've got it off doing that now. I started to run the brake lines yesterday, but the lines I have running from the wheel calipers hit the wheel because it has so much backspacing (found that out after I mounted the brake line tab on the frame) so I'll have to look for a different line with a sharp 90 degree bend at the caliper end, shouldn't be to hard to find.

(12/1/97) The top center part of the Tuned Port manifold is ported and I've got it all together ready to fire, anyone who has a TPI might look into this, the GM High Tech Performance mag says it increases flow with the stock throttle blades from 576 CFM to 688 CFM, and was worth .45 seconds in the quarter on their test car, and it only took me about 30 minutes to port mine. The issue the article was in was the November 1997 issue, and you can get to the magazine by clicking on the below link to get the back issue. 

After I got the intake all together I got some gas and checked the fuel pump to see if it worked. It wouldn't even run! I kinda bumped the top of the fuel cell to see if it was stuck or something and it ran for a short while, then stuck again. I was trying to decide if my new pump was defective or something, then it hit me, I wonder if the small ground wire running to the pump with the factory harness is large enough to run the pump now, because it's now mounted in a plastic fuel cell instead of a steel fuel tank. I jumpered a larger wire to the center part that the pump is mounted on and it works fine now, so I'll put a permanent large ground wire on it tomorrow. I had to do a lot of parts running today, so that's all I got accomplished. Here's the link for the above mentioned mag. High-Tech Performance Magazine

(12/2/97) Got it running - Worked all day filling the motor and trans with oil, priming the oil pump and putting Tuned Port 350 front shotthe distributor in, rough setting the fuel pressure so it was enough to fire, then I set it again after I got it running, taking the headers off and clearancing them for one of the plugs and putting them back on, pulling the exhaust down and welding it where they couldn't reach when they bent it up. It idles fine once I got it set, but the motor got a little warm, I hope it's just because the air all hasn't gotten purged out of the water passages yet, but I'm thinking that maybe the small aftermarket fans that I've got just aren't flowing enough air. I wanted to use the factory radiator fan because I haven't seen an aftermarket fan that would keep up with the factory unit, but space was pretty tight. If it doesn't start cooling I guess I'll have to make space. Other than that it has a little problem starting in that it won't start without a little throttle, and a EFI car should start with no throttle, I'll have to do some looking into that, but the guy I got it from had it on a Firebird Firehawk factory road race car and he said they had a chip made that put more fuel into it going into the corners, I'm sure I'll have to get a chip made for this motor. I'll probably take a few days rest from this, gotta go back to work tomorrow. (been off on vacation since the 27th)

(12/11/97) Due to a few E-mail requests, I've gotten a few pictures of the motor compartment scanned in, they're some older shots I took right after I dropped it in, and the motor compartment is still a bit bare. I don't have a scanner yet, so a friend did them for me, you'll have to bear with me and I'll try to get some more current ones put in, along with some frame and suspension shots.

(12/13/97) I worked on the brake lines today a bit, got the front ones almost all ran. I also did a little bit of work on the motor, adjusting the valves, fixing a small leak in the bottom radiator hose, ect. . The problem that I wrote about with the car not wanting to start without part throttle seemed to iron itself out, it starts fine now with no throttle at all. The block learn memory is staying a little closer to 128 now on the scanner, I guess it just had to learn the motor's requirements was all. I still need to get a chip made, though, the electric fans don't kick on till the motor is over 205 degrees, I think that's some of the problems with it getting hot, although it's doing a lot better on that, too.

(12/28/97)   Been busy with other things and haven't gotten this updated for awhile,  I hope some of you noticed my page changing buttons on the main pages - I know, big deal, but it took me 2 days to make them. I've now got a Microtek Scanmaker E-6 scanner  (Made my buttons with the scanner and it's software).  I should be getting a few more pictures put on; I guess I'll start with a rear suspension shot.
This shot was taken through the rear hatch with it open and shows the upper 4-link bars, lower bars, shocks installed, fuel cell, and springs. It was taken before I put back in the inner fenderwells, and I still haven't got the floor panel replaced yet. I should be pulling out the rear housing this week; blasting and painting it and the frame and assembling it all for the final time.
 I started to run the brake lines back to the rear today, I mounted my adjustable proportioning valve for the rear line and finished up with the front lines. Had to do a lot of parts running because it seemed like everyone around Topeka was out of 3/16 inverted flare nuts, finally found them at Napa, but then he sold me the wrong gasket for a 9" so I had to go back and get the right one. One of those days -

(1/2/98) Finished all the lines to the rear, just have to run the short pieces on the rear itself to the brake calipers, I figured it would be easier to wait until I get the rear out to run those. I built the brackets for the bump stops on the rear so it won't bottom out and then dropped the rear out of the car to do the cleanup.

(1/12/98) Still working on the rear end. I have to blast outside and it's only around 25 degrees right now, and I'm having lots of problems with the blaster icing up. Looks like it might start to warm up Thursday or Friday so I might have to wait until then to blast. I've got a few more pictures of the motor the way it is now and the underside of the car so I'll put them on now. I've numbered the underside picture so I can point out a few areas. Above #1 is the lower 4 link front mount which utilizes 1 side of the factory rear mount, and the other side is hooked to the roll cage tubing that I made the frame out of. Although you can't see #2 very well, right above it is the spindle that I machined. Item #3 shows the transmission cross member that curves down under the mount and extends from one side of the frame to the other. The last number #4 is on the driveshaft, but to the left of it is the bar that goes out to the lower 4 link mounts on both sides to strengthen them. Both the bars that curve down beside the driveshaft go forward to join the trans cross member above #3 on both sides of the tunnel.

(1/18/98) Got the rear end blasted, painted, re-assembled, and installed back in the car. I also got the brakes bled, and I'm trying to think of everything I need to do before I can take it for a test spin. I started it up tonight after I got done bleeding the brakes and spun the rear end up to 75 mph on the stands to see if anything vibrated or did anything it shouldn't be doing and it seemed okay. Shouldn't be to much longer before the maiden voyage now!

(1/25/98) Took it out for a little test run today - I wasn't quite satisfied with the way the brakes are working yet, I'll need to spend a little more time there. The rear springs seem a little heavy, also, so I'll get some lighter ones and try them. I also remembered that I still haven't got the right speedometer gear yet, and I can't remember if I got the TCC cable hooked up to the transmission inside the pan, for some reason I remember something was missing in there (seems to be shifting a little higher than it's supposed to) Just a little bit of debugging now -

(2/9/98) Messed with the brakes a little bit more, but no luck yet. I've got some lighter rear springs, but haven't put them in yet, and I'm going to put a flex fan on at least for now to see if it will stay cooler. I haven't had much time to spend on the Z-24 lately because I've been doing a lot of overtime for work.

(5/16/98) ....................Trying to sell it........

(2/7/99) Everything is sold - Working towards getting a shop of my own to work on my projects, I guess I just got tired of doing all my work away from my house

(11/22/01) It's been a while, I guess that shows how you can lose interest in a project, especially when you don't have the room or tools to work on it in (your own room or tools, at least in my case),  now I've got a new house with a 25' by 20' garage on the house, and a 30' by 40' garage beside the house, also have a mig, tig, and a plasma cutter.  Got the space and equipment to work on my Z-24, but no Z-24 to work on, well, that's the way it goes. 

I guess that pretty much covers it for now, back to the Z-24 page



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Last Modified: Friday, December 13, 2019 06:52:51 PM