Help me plan my new project

[jkrueger]

So with the Roadster sold, it is time to start planning the Coupe project. The primary use for the car will be to compete in the One Lap of America race with my dad who will also be helping me build it. My Dad and I have run a V8 powered Mazda RX-7 the last 3 years in this race and have done pretty good for a couple of amateurs. So the car needs to be reasonably comfortable on the street but a fast track car as well.

This is what I got so far, but I am open to new ideas and peoples opinions. So let me know what you think.

JC



Goal:
To build a performance oriented streetable track car. It must have as many safety features as feasibly for both the track and street. It must have a reliable 400-450 hp, it must be as reliable as possible and use as many off the shelf parts as possible.

Performance goals:
Excellent handling (1.0g cornering on street tires, 1.0+ on track tires), excellent brakes, capable of 160-180mph

Uses:
One Lap of America Race (www.onelapofamerica.com)
HPDE track events
autocross
NASA time trials
possible future use as a race car



Chassis:
Factory Five unpainted chassis
NASA/SCCA legal door bars, firewall to front suspension bars, fuel cell protection
painted white

Drive train:
stock LS3 or LS6 engine (400-450 hp goal)
T-56 6 speed w/mid shift (w/ .5 6th gear for fuel economy)
SFI bell housing and performance clutch and pressure plate
Ford 8.8 IRS 3.55 or 3.27 gears, traction-loc limited slip

Exhaust:
custom headers or something off the shelf if it will work
3" side pipes with single muffler/glasspack
jet hot coating

Oil system:
road race oil pan
oil cooler
3qt accusump w/ eletric valve
remote oil filter
SS AN lines

Cooling system:
-stock Factory five radiator and fan
-stock water pump, maybe electric water pump

Fuel system:
22 gallon fuel cell
low pressure pump feeding 1/2 or 1 gal swirl pot
high pressure pump feeding engine

Brake system
13” cobra ft brakes or 13” 4 piston Brembo or AP racing brake kit
11.65 cobra rear brakes
Wilwood pedal box (dual brake MC, single clutch MC)

Wheels and Tires:
18x10.5 TSW Nurburgring (Black) (27mm offset, approx 6.3” backspace)
18x9 TSW Nurburgring (Black) (32mm offset, approx 5.75” backspace)
315/30/18 Michelin PS2
275/35/18 Michelin PS2

Suspension: (this is where I need the most help)
IRS rear
Koni DA shocks (from factory five)
???? # springs
Front speedway engineering sway bar (size = ??????)
rear sway bar?

Electrical:
Ron Francis complete harness
battery cut off switch

Saftey
high back seats
5 or 6 pt harness
fire suppression system

Interior
Factory Five supplied autometer gauges
A/C and heat (north race cars)
some sound deadening and carpets

Body:
Blue with white stripes paint
meatballs
BRE mirrors
3rd brake light
HID headlights or Forte’s headlights

[Jacob McCrea]

Sounds good to me. Your game plan is pretty similar to my own, although I am using a 302 and T-5 transmission. The LS engine seems like a nice way to get lots of reliable power without breaking the bank. Feel free to contact me re: the frame mods that I did so far, which are set forth in an earlier thread titled "Frame Mods to Type 65 Coupe." I added fuel cell protection tubes and will be adding the balance of the SCCA-required tubes in the coming months. Also, Hank L. has posted a great design for Nascar-style door bars. Good luck!

[jkrueger]

Jacob

I have looked over your and Hank's threads with great detail, and planning on doing a lot of the same mods you guys have. How much cockpit space do the door bars take up? Thinking about comfort again during those 6-10 hour transits during the One lap race.

Everyone:

Really need a lot of help with the suspension set up. I recently read through Karen's three 25hr race threads and got a lot of good ideas, but her suspension set will be different from what I need since this won't be full blown race car.

JC

[John Card]

Personally, I would not recommend the IRS for race use. It's not durable enough for heavy use, and you are mostly limited to stock parts - which are barely adequate. The geometry is also not optimum. IMO, you would be much better off with a well set up solid axle (3-link or 5-link) and the only downside is a slight reduction in street ride quality. I can go into more detail if you want.

[jkrueger]

Personally, I would not recommend the IRS for race use. It's not durable enough for heavy use, and you are mostly limited to stock parts - which are barely adequate. The geometry is also not optimum. IMO, you would be much better off with a well set up solid axle (3-link or 5-link) and the only downside is a slight reduction in street ride quality. I can go into more detail if you want.

John
Please go into more detail, I'm sure it would benefit us all. The only reason I was leaning towards an IRS is that is what we have on our Mazda (using a Ford 8.8 center section), and it seems like it is more tuneable (sway bars, toe and camber adjustments). If I can get a good handling car that is more durable with a solid axle I'd go that way. It would be cheaper and have less parts.

JC

edit: I was just thinking that I might not be able to do a live axle if I go with a t-56 transmission since it is so much longer than the T-5. I need to get some dimensions.

[John Card]

You're right, T-56 with a solid axle is a no go - the driveshaft ends up being tiny - even tinier than normal. I'd go with a 5-speed instead, as there really is no need for a 6-speed unless youre one of those "5 is more than 6" guys. T-56's are heavy too. My preference would be a lighter 5-speed with a solid axle, but that's just me. For most cars, 6th gear is just there for fuel economy.

The IRS has several issues when used in a race application:
There arent very many choices for rear brakes. And you need a LOT of rear brakes on this car. I don't know of a single coupe yet that has enough rear brakes.
The axles and CV joints are barely adequate for heavy duty use. Karen's car has had issues with them coming apart on track. Street use is no problem.
The Stock motion ratio on the shock/spring makes it tough to damp the very heavy springs that become necessary in the rear. Hank Lopez came up with a modified shock, geometry, and lower control arm to get this sorted out.
The heavy springs place a huge stress on the lower control arm. It should be reinforced in a situation like this.
The stock lower arm tends to twist under heavy braking with slicks. A stronger design is needed for big brakes and sticky tires.
The stock geometry appears to place the roll center fairly low, needing stiff springs to combat that - which aggravates the motion ratio issue.
It could use more camber gain in the upper arm.
All of these things don't show up in a street and light track use situation, so most IRS owners have had no problems.

A lot of people just figure that the IRS just has to be better because it "theoretically" is. In the real world, sometimes simple is better. The FFR IRS was designed to use stock Ford parts and fit well in a street car, but it has never really been developed with race use in mind. Karen's is the only one that has seen that type of work, and it still has a way to go before we'd really be totally happy with it. The only real advantage I see is the ability to easily add rear camber. The car doesn't seem to want much in the way of rear toe-in. 1/8" in maximum in my experience. If anything, the rear is a little too planted on a big track anyway.

Advantages of a solid axle:
A well-built solid axle should be bulletproof as far as durability is concerned.
Brake options are unlimited.
You can have an easily adjustable roll center with an adjustable panhard bar or a watts link setup.
Motion ratio, spring rates, damping - all a non-issue.
Disadvantage: No rear camber (or very little) but since a solid axle rolls with the pavement somewhat, it needs less than IRS, which tends to roll the tire over with body lean.

Sway bars can be tunable in either type.

It is a LOT easier to get a solid axle thoroughly sorted out, and can be plenty fast. A perfect example of this is Paul Brown winning the World Challenge championship this year (and several races) with a solid-axle Mustang against cars with with factory IRS - including Camaros, BMW's, etc. Similar weights and power levels and same tires, and the Mustang won, even though they kept penalizing the Mustang with added weight to slow the car and "equalize" the field. Gordon Levy recommends his 5-link solid axle setup over the IRS for track use, and will tell anyone that asks that it is faster. Karen's coupe had IRS when they got it, the NEW race coupe she is building will have a solid axle.

[Jacob McCrea]

JC,
To answer your question above, I am not sure how much cockpit space the door bars will take up, but I am pretty confident that it's a tight fit. My understanding from talking with Hank L. about his Nascar-style design is that you need to be pretty careful about where you run the door bars since space is very tight. Also, in one of my later posts I widen what amounts to the "rocker panels" to give myself another inch of room to locate the bars and the cockpit aluminum. I have another design in my head - essentially x-style bars across the doors - but it is inferior to Hank's design insofar as it offers no real protection from something entering the cockpit from behind the driver's left hip. Either way, from what I can tell interior space is not plentiful.

[Hankl]

JC,

As Jake has said, space is at a premium, but it also depends on how big you are......For an average size person, who uses a seat less than 17" wide, room will amount to about 1-2" on either side of the seat, that's worse case scenario. With the Kirkey's, you end up with some more room, and if your smaller that 5'9", you'll get lost in the cockpit. It just depends.

To chime in on John's comments, the 3 link is the best bet, if you don't want to play with the IRS like I do. The 3 link has plenty of data behind it, the Spec roadsters use it, and there are currently three, 3 Link Coupes being built for competition. BUT!! USing the T56 will push you towards the IRS, because of the length of the tail shaft of the transmission. If you go, TKO600, you won't have that problem, and you'll be able to go with the 3 link.

Hank

[crossle45f33cf]

JC
Since you're planning to put a Bowtie lump in, you're probably going to need to do some frame/motor mount modifications to make everything play nice together. You could start at the back and work forward to provide sufficient room/mounting for the Chevy and a T56 and whatever rear axle you decide to go with. Basically, you're going to be writing your own assembly manual since you've chosen to deviate so far from the path most Coupe builders take. Clean sheet of paper, dude. Make it whatever strikes your fancy. People have put Allison aircraft engines in Fiat Topolino's. What you want to do is "easy". LOL

[jkrueger]

Good info on the solid rear end, John. If I wasn't so stuck on wanting a 6 speed, it would be a no brainer. The One lap race has 3500 road miles in it and getting good mileage and have a lower engine rpm for noise is a big plus. I'll have to do some more thinking and calculating. I think I'll drop an email to Mike Forte and find out what gear ratios are available for the the TKO and T-56 transmissions.

Another good point John makes is the lack of brake and brake pad options for the IRS. I did some research on Hawk's website and they only make three different compounds, but that seems like the only options out there. Does anybody know if any other companies make pads for the Thunderbird's brakes?

Hank, I'm only 5'11 and 155lbs so I'm sure I'll fit. I'm more worried about my Dad, He is 6'0" and about 190 and pushing the upper end of his 60's so he isn't as flexible as he used to be and not as tolerant of uncomfortable cars as he use to be.

Trout, Good idea about moving everything forward. That would be more involved than just buying Forte's Chevy conversion engine mounts, but I am not afraid. After putting the V8 into the RX-7 (which wasn't that hard), I'm sure we could do it.

JC

[John Card]

You may want to look at options for 03/04 Mustang Cobra rear brakes as well - as it is basically the same setup and I believe is interchangable on the T-bird or Mustang Uprights/hubs.

In either case, the brakes will be too small on the rear. The coupe has about 55% weight on the rear versus 45-47% on the bird or the Mustang. We have more rear tire than they do, and we have less forward weight transfer. All this adds up to a situation where a balanced brake setup for a Mustang is not enough rear brake on the coupe.

I'd use a taller gear to compensate for the loss of a .5:1 OD in the T-56. You'll get the final drive ratio you want and still have enough power to boil the tires in the lower gears, so you don't really need as much gear as you think. Guys with 400+ hp and a low first gear and a low rear gear end up with a useless first gear and a semi-useless second gear where you have to go real easy on the go pedal if you aren't pointed straight.

[Tpa65cpe]

John has hit (the nail on the Head) except for the interchange of the T-Bird / Cobra IRS. The T-Bird has 28 spline and the Cobra has 31 but the Knuckel's are the same so is the center section except for the (posi) also the bearings may be different. I am researching this option for my build (427W,T-56,IRS) but this may change as I gather more info about the rear ends. Since you are going with a LS and are going to move the eng foward this will change the weight bias so watch this, it may help you to keep the T-56 and go with the solid rear (more pad options and brake packages) also ckeck out Gordon Levy for his 5-link set up it is very nice with lot's of adjustment! HTH tpa65cpe

[jkrueger]

So can I use a thunderbird center section, axles, and knuckles with 03/04 Cobra hubs calipers and rotors? If so there are a large selection of pads available for those calipers.

I just looked at North Race Cars website and it looks like he sells a bracket that put a 11.65" rotor and caliper on the thunderbird IRS knuckle.

I also found this kit from Wilwood that would probably work with the same bracket from Richard.

http://www.wilwood.com/BrakeKits/Bra...ra/%20Mach%201

JC

[Tpa65cpe]

Hey J! I think that the Wilwood kit comes with it's own bracket, and the pad options are much better. Just be sure if you go IRS you find a Cobra one 2001-2003 the spline count is higher and axels are stronger, but IMHO if you are going to go LS with T-56 and you are moving the motor foward to do this to get a better weight ratio 50/50? then you may want to think about the solid axel option with the 5-link it is much stronger and easier to set-up plus cost is also a factor! See if you are near anyone with a Coupe and stop by and take some measurements this will help too with your unusual set-up and could make your choice a lot easier on what rear to use!! HTH tpa65cpe

[John Card]

I always wondered what it would take to swap the entire 03/04 Cobra rear subframe right in. In theory, it would bolt into the 4-link and quad shock mounts like it does in a Mustang, but I'm sure there's something else in the way or FFR's mounts are just different enough to make it not slip together. It is still probably do-able though.

[jkrueger]

Found a pic of a cobra rear end. Not sure if that would bolt right in. If I go the IRS route I'll have to look for an 03/04 Cobra set up and get some shorter 1/2 shafts made.

IRS2.jpg

[Tpa65cpe]

Hey J ; are you thinking that you have to make the mounts for the IRS! Because when you order from FFR that is part of the upgrade cost! They weld in the mounts and you get A arms (upper & lower) and I think you also get new half-shafts! But to be sure ask BRIAN Z AT FFR. Also you can order the extra parts from them (center section,knuckels,and hubs!!) Look in the parts catalouge on the home page! Hope this clarify's this some more! HTH tpa65cpe

[Bob Cowan]

I occasionally dream of builidng something just like this. So here's some of my thoughts:

- The main goal for this kind of car is reliability. Use as many factory and non-custom parts as possible. If you break a drive shaft you want to be able to pick up the phone and have one over nighted to wherever you are. If something fails, it would be nice to get a new one from NAPA.

- Any custom made parts should come in 2-3 sets. You'll need to carry the spares with you, or have a home base person who can package up what you need and UPS it the first thing in the morning.

- consider installing a trailer hitch so you can carry spare parts, tires, beer, etc.

- It sounds like you need to choose between a 6 speed trans and IRS. They just won't easily go together AND meet the above mentioned requirements.
--- Maybe move the engine foreward 4".
--- Or move the rear differential back 4"

- Personally, I would stick with a Tremec TKO 5 speed; smaller, lighter, cheaper, indestructable, and bolt in easy. The additional OD gear isn't as valuable as you might think. Again, that's my personal preferance.

- Since performance is more imortant than comfort, I'd use a solid axle with Gordon's 5 link. As a side note, Gordon's front suspension pieces make my heart go pitter-pat.

- The engine would have to be rediculously strong/durable. If you race once a month and you break something, you have time to fix it before the next race. You won't have that kind of time. I'd spend the money on a Dart block, and forged or heavy duty everything. I'd even consider Unobtanium valve covers. Not for the highest performance, but for durability.

- I would not use a chevy engine. I have nothing against the LS engine - they're some of the finest engines on the market. If you were building a Corvette Grand Sport, that would be an excellent choice. But you're not - you're building a car designed around a Ford drive train. Read through the forums and see what it takes to install a GM engine. Then think about fixing those issues on the road somewhere. I don't think it's worth it, but you might.

- But don't build the engine too radical. Dynamic compression aroun 7-7.5:1, "mild" solid roller cam, moderate stroke/bore so you can use off the shelf pistons, Ford oil pump, etc. Make power through displacement.

- I dream of installing a Dart based 427W, and using a dry sump oiling system. The dry sump will protect the engine in all situations. But it will also allow you to lower the engine a few inches. That's important in a Coupe, and it lowers the CG.

- if you use an Accusump, skip the electric valve. They're not that reliable; mine didn't last very long.

- You will be traveling and racing in a huge variety of conditions: weather, altitude, moisture, etc. The engine should be able to self adjust to meet all those conditions. IMO, EFI is the only way to go. In keeping with the non-custom theme, I would look at Mass-Flow EFI. Works well, uses stock Ford components, reasonably priced. The Ford components often last 100K miles, and are readily available in almost any town in America.

- I prefer manual steering and manual brakes. Less weight, less cost, less complexity, and one less fluid to leak. It's a trade off between absolute performance and comfort vs. simplicity and durability. I have manual brakes and can out-brake almost any car on the track. I have manual steering which works well on the street and road course, but would be a real handicap in autocross. Again, personal preferance, and a pretty tough decision. If you choose power, I'd use Ford hydroboost components. Maybe not the very best on the market, but durable and easy to come by.

- Rear gear choice can be pretty tough, but the 3.27 will probably be a little better. You'll have to do the math for the tracks you'll be using and the transmission you choose. Neither will be perfect, so pick the best comprimise.

- Don't use the ford clutch pack LSD for the differential. You get greater durability and performance from a worm gear like the Detroit TruTrak or Torsion.

- Keep in mind a 22 gal fuel cell won't hold 22 gallons of fuel. The bladder, collecter, foam, etc takes up some space. Mine only holds 18 gal.

- Keep the fuel system simple. With a return style system, you don't need a swirl pot or two fuel pumps. Get one quality pump like an Aeromotive A1000 and be done with it. Unfortunatly, just about any non-stock pump is a special order item; you'll need to carry a spare and set it up for a quick change.

- Brakes need to be big - really big. And strong. But still pretty much off the shelf. Use Wilwoods, and carry 1-2 spare sets of pads. Gordon Levy can hook you up with a complete, truly bolt on kit. Don't forget the cooling ducts for the front brake rotors.

[LDave]

JC - I've got an LM7 5.3L installed into my coupe with a T56 transmission. It really was not hard at all to get it in there and all mounted up. PM me if you would like more details on the matter.

[jkrueger]

LDave: PM sent

I am just about sold on the solid axle. Trying to weigh all the factors (cost, durability, performance) with the trade offs (tuneability, driveshaft length, ride comfort), it seems like I am leaning more towards the solid axle. Looking at the Moser axle that FFR sells, it seems like a very stout axle and a good price.

Playing with tire size and rear axle ratio it looks like the TKO transmission with the .64 5th gear will give me 2000 rpm at 70 mph. That is very doable for road driving. With a 6500 rpm redline that will also give me 150 mph in 4th gear. Plenty fast for most of the tracks I go to. Not using the T-56 also lets me use the solid axle now and is cheaper.

I still wan to go with the LS engine. For the performance you get from a stock engine, you can't beat the price. I looked at building a Boss block 331 with Forged internals and Mass-Flow EFI and I was over $10K. I can get a LS3 crate engine with harness and computer for under $8000. I know the exhaust is going to cost more for the LS engine, but I was not going to use the stock exhaust with the ford engine anyways.

I may have to jump in on FFR sale before the end of the month.

JC