IMSA GTU vintage racer build

[Dat73z]

@AydinZ71 in my experience welding the cast s30 strut material you'll want to preheat and ideally have a big bucket of sand or something to cool it slowly. It welds really easy but it will crack out if you're not careful. 

[tube80z]

On 1/9/2023 at 2:13 PM, AydinZ71 said:

 

Ah! hey, that's helpful Cary! Silly question, why the 13" wheels? 

 

The main reason was weight.  Moving to 15 inch wheels in the combo I was using added almost a hundred pounds to the car.  This was an autox/hillclimb car and not a road racer.  I wouldn't have used 13s on those.

[jhm]

2 hours ago, tube80z said:

The main reason was weight.  Moving to 15 inch wheels in the combo I was using added almost a hundred pounds to the car.  This was an autox/hillclimb car and not a road racer.  I wouldn't have used 13s on those.

 

I can second that!  I’ve had a couple sets of 13” wheels and really liked them for auto-x.  In addition to the weight advantage, the smaller wheels can lower the CG without compromising suspension geometry.

[JMortensen]

If you've got How to Make Your Car Handle, p3 (first page of actual writing) has a Z on 13s next to a stock one. Always wanted to do it, eventually ended up with brakes too big to make 13s work.

Edited January 12, 2023 by JMortensen

[AydinZ71]

Sorry for hijacking your post Clark! Looking forward to your next update. 

 

@tube80z ah yes! This brings back memories of a previous discussion. I recall you mentioning you got a Z down to ~1800lbs, and one way you did so was through clever selection of wheels and tires. 

 

 

@Dat73z thanks for the tip! The strut tube itself was really easy to weld-to. Il have to practice on some spare material from the cast lower section of the strut. Sounds like it’s much harder material.

 

 

[tube80z]

On 1/13/2023 at 4:22 AM, AydinZ71 said:

Sorry for hijacking your post Clark! Looking forward to your next update. 

 

@tube80z ah yes! This brings back memories of a previous discussion. I recall you mentioning you got a Z down to ~1800lbs, and one way you did so was through clever selection of wheels and tires. 

 

 

My car was 1850 with 5 gallons of fuel in the cell and had an easy 100 pounds that I could have removed.  I had to run that much fuel as the cell wasn't installed properly and it would have fuel starvation.  I dropped a bunch of weight from the front hubs/brakes when I redid them to lose much lighter Wilwood calipers.  Someone had spent hours grinding the 4-piston Toyotas down to the size of a Wilwood Dynalites.  Hubs were steel and couldn't have been changed to Aluminum.  Car had a steel driveshaft, R200 diff, and all the stock crossmembers.  I had a super-heavy Optima deep cell battery (65 pounds) because I had alternator problems until I switched to a modern Kubota tractor version.  All in all I thought there was an easy 100 pounds of weight I could have removed getting the car into the 1750 range.  I've seen other Z's that low so mine isn't an outlier, just not a normal compared to most.

 

Wheels, tires, brakes, clutch/flywheels, transmissions, subframe braces, all are hidden weight that really adds up.  Even too much MIG welding.  I started to look more and more at modern panel bond techniques as a way to save weight.  Riveting brackets that didn't need to be unbolted, etc.

[clarkspeed]

Hear, hear, now. This is my thread.  Just kidding, if anyone has any race car related posts, bring them on!

 

I spent a week or 2 trying to find a way to run 13's on my car. Tires are available for some wide wheels. And SCCA GTLite runs them. But in the end I didn't think I could get enough braking performance. So I focused on 15's and ignored 16's which is what everyone in my class runs. I have been super focused on reducing unsprung weight, especially rotating weight. A little less focused on sprung weight, so I hope that doesn't come back and bite me. But I do have some changes that could be implemented at a later date.

 

Interesting enough, the John Thomas 240 which has won like 8 or 9 solo championships, has like a Arizona big brake kit. Way overkill. But he also runs like 100lb of balast instead of a passenger seat. He won another in 2022 as a guest driver. Fast dude and super nice guy.

 

Not alot to show since last post. Sometimes you go backward to go forward. But definitely putting in some hours.  Been  planning and buying stuff for electrical and brake plumbing and clutch.  Also realized I have about 20 parts I need to 3d print, so I got the machine running 24/7 in Nylon.

 

I don't think I could build this car without the 3d printer. Example #64-i have 3" 3ft long orange brake hose. My run will need to be 4 to 4.5ft.  I will just design and print out a 3" dia. brake hose union. No problemo.

 

Here is a pic of the coolant tank mounted and my revised front control arm. I found the steering knuckles hit the original sway bar clevis I had welded in. So I relocated the clevis opposite the shock clevis. In the end this should actually be a stronger connection and give me a little more room for the brake cooling hose. 

[clarkspeed]

Finally got the hood located today. My original design using aluminum pins into the firewall did not look good. Pins were too long and created quite a lever arm. So I went back to my design from years ago but upgraded with some 3d printed brackets. Hood now slides into 3 cowl panel channels and will latch in the front. I drilled those holes in the hood like a confident person after measuring 3 times.

[clarkspeed]

Another new shop toy. Bought a cheap fuel injector cleaner/tester. So far so good. I wired a few dropping resistors to test the old Bosch low impedance stuff. Pulled a pile of old injectors out of storage and to my surprise most all fired. I will polish them up and sell the best flow checked results.

 

Main goal is to Flow test and clean my injectors between race weekends. Seems like good insurance against any power loss due to clogging. Pick up the idea from Jessie Prather. If you are into race car building, the Jessie Prather Motorsports YouTube channel covers some good topics. His videos give a good overview of the level of detail required to build SCCA championship cars.

[AydinZ71]

Greg turned me on to Prather. He is dominating E-production in that damn BMW. They had to put a restrictor plate on his intake just to slow him down a bit. I will be looking for injectors for the 3.1L, but have not figured out how big they need to be yet. I have the Jenvey ITB manifold. 

[tube80z]

On 2/2/2023 at 6:18 AM, clarkspeed said:

Another new shop toy. Bought a cheap fuel injector cleaner/tester. So far so good. I wired a few dropping resistors to test the old Bosch low impedance stuff. Pulled a pile of old injectors out of storage and to my surprise most all fired. I will polish them up and sell the best flow checked results.

 

 Did you get the machine with an ultrasonic cleaner?  I've been thinking about these for a while but it isn't high on my list at the moment.

[clarkspeed]

Yes it has a built in heated ultrasonic cleaner. Works surprisingly good. It pulses the injector while it is cleaning. I put some old weber parts in there and they came out squeaky clean. It is not a shiny finish. A little brass brush brings out a shine. I want to buy a bigger cleaner now for larger parts. I have a set of weber's I need to recondition. I could not find much info on what to clean with. I ended up with an 1 Oz. Of Simple Green and 1 Oz of pine sol with maybe qt. Of distilled water. Stuff needs to be pretty clean before if goes in there of you will be changing the tank often. I am using 95% alcohol as a test fluid. 

 

I made 3 mods to the unit. Added to resistors for low impedance injectors and changed out the pressure gauge for a 4" Measureman unit from Amazon. Also added some tiny o-rings to seal against the hose barbs. I now do all the tests at 43.5psi. Usually the 1st 1 or 2 runs give odd results, but then they become repeatable. It only takes a minute to test. Maybe 3 minutes to set up.

 

I justified the purchase because I have some older Mercedes injectors I think I can get some money for. When I combined the recovery money with some future checks for the race car, it tipped me over into the purchase.  Seems like good insurance for the race car.

 

The Prather videos are interesting when taken as a whole. He is a guy who grew up in the middle of SCCA competition with his father. He knows alot. Although he builds a boatload of Mazdas, he is not mark specific. He just applies attention to detail to everything he touches. No secrets. Same with engines. He is not the smartest guy, or the most innovative, or the most experienced with most cars. Just basics and attention to detail. Of course a lot of his details are lessons learned from past experience, but still mostly basic stuff. Like he always runs the same rear wheel/tire when doing dyna runs. Probably saw too much variation there. Jeez I think he goes to the Runoffs solo, but not sure. He supports multiple cars other than his. He built ground up 2 cars for Greg's brother Cliff who has 3 championships now in 2 classes I think. And they were Honda products.

[clarkspeed]

Aydin you are probably around 30lb injectors. Plenty of calculators out there for sizing based on HP. I ended up buying the white Siemens/Bosch for my 3.0. They all tested dead accurate out of the box. 

 

The problem I am having is getting a fuel pump. I like the Bosch pumps and I have come to the conclusion Bosch makes a small body and large body unit. They have about 1000 part numbers based on OEM inlets and outlets. The famous 044 pump is WAY overkill for a NA car. I had one and a fuel line rupture sent multiple gallons on the ground in a few seconds. Scary. And just circulating gas around only heats it up. So really you only need something maybe 20% over you needed flow, max. 

 

So my holy grail, is an OEM based Bosch pump, small body format, maybe 0.25 NPT on outlet and inlet, that supports 300hp and is CHEAP. I have a BMW part number somewhere that is close to that. I have been looking for a more generic universal pump with no success so far. Most of the generic stuff is made for big V8's.

 

Or other recomendtions?

[AydinZ71]

All I ever used in the past was the Walbro 255, but that was hot 20 years ago 😂. Literally the last time a purchased a fuel pump. I have a little time on the injectors and pump, since I plan to run the Z on the EP L24 w/SU’s to start. Sorry I haven’t check-in here very often. I have been bogged-down in body-work hell and have not had much exciting news to post. 

[clarkspeed]

On 2/7/2023 at 2:21 PM, AydinZ71 said:

 😂. I have been bogged-down in body-work hell and have not had much exciting news to post. 

Without a doubt, body work is the worst task of all. I will put molding large fiberglass parts a distant 2nd.  And everything in the garage will be covered in thick dust. On the lessons learned side, I wiped bearings in a relatively fresh engine after a few months of sanding. Without knowing, my engine builder ask if we had been sanding body filler in vicinity of an open engine.  I said "maybe", and he said "I have seen this before".

 

On the positive side, I ran the brake lines. First time I have ever tried running an entire system in AN3 fittings and flared cu-ni tubing. Pretty damn easy. And I was able to correct the few bending mistakes I made. 25ft roll of tubing, maybe 1ft of waste, and 4ft left over. And I rand the entire thing in probably 2.5 hours. No pressure checks yet.

[AydinZ71]

Sweet man! Yeah I have had cu-ni tubing and a flare tool sitting in my Amazon outbox for months now 😂 I’m trying to stay disciplined on planning ahead, as I still have several months of bodywork before I’m ready to move on. As you said… dust everywhere. Can’t imagine how I could bother putting anything back on the car given the extensive cleaning I would need yo do later. 

 

I have one door nearly complete. Hardest part is matching the contour with the rear quarter panel and fender. Using filler as a last resort, only when no other option is possible (like along a body line). I have the drivers door next, then both front fenders. Rear half of the car has been sealed and primered, ready for block sanding with 220-400-600 

 

il tell you what, doing things “right” is a PITA. Everyone told me to get down to bare metal, but this was a race car before I started resto. You can imagine what shape the underlying steel was. 

[clarkspeed]

I have decided to postpone majority of my body work. I really want to get it on track and start sorting before final finish. Most of the body panels are removable so not too difficult. I will probably shoot an epoxy primer on at some point and slap a number on the doors. Final paint scheme is still undecided and I have no stress about it.

 

When I started the build I formed a bill of material I knew needed to be purchased or fabricated. Also estimated the budget. I have tried not to purchase anything until it is needed. That has been a tricky thing with all the supplier delays. I ordered brake pads during the holidays because they were on sale at Porterfield. Lucky I don't need them yet. Raybestos has no ETA and no projected ship dates. Strange how some parts arrive in 2 days and some 2 months. I ordered 3 x 18" Allstar braided brake lines from Jegs. 2 arrived late and 1 on back order with no ETA. WTF?

[AydinZ71]

I hear ya on putting bodywork on the back-burner. That was my original plan. I wanted to throw everything back on the chassis once the interior and non-body chassis was painted. Once I started doing some filler work, I realized just how much sanding and dust I had ahead of me. I could not figure out how I would manage keeping all that dust from getting everywhere, so I decided to just finish the body before proceeding with mechanical and electrical. 

 

Yeah that has been some of the stress of ordering ahead. Two bird in a bush, one in the hand (so to speak). I try to buy what I need 1-2 weeks in advance, but once I pivot directions I end up with a bunch of stuff taking up storage space. Its incredible how much room a disassembled car takes up haha. 

[clarkspeed]

A shot of the front and rear pressure transducers and brake pressure switch.

 

Replaced foam in fuel cell tonight. Then immediately began ordering more parts I discovered I need.

[tube80z]

Nice mounting Clarke. Are you going to cover them to protect from rocks and track debris?