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-   -   Thinking about a Custom Cobra Build, have questions (http://www.clubcobra.com/forums/scratch-builders-forum/89409-thinking-about-custom-cobra-build-have-questions.html)

MChat 07-20-2008 08:33 PM

Thinking about building a Cobra...
 
I've been a fan of the old Cobra since my dad first told me about them (I'm 36, not that it matters). I even built a "pine derby" car based on the Cobra (mind you, I carved the body from memory):
http://www.azchatfield.net/pictures/...Cars%20004.JPG

Anyway, I happen to have an engine, albiet not a conventional one for this type of car, but an engine that's put down 600hp to the wheels (on race gas) and propelled a 3100lb (with driver) front-wheel-drive car down the 1/4 mile in 11.7 seconds @ 124mph on pump gas & street tires (I never got to run it on race-gas & slicks). Anyway I'd like to use this engine, build a tube chassis and use a Cobra body. But, I have some questions I need answered to see if this will even be feasible.

1. I need some dimensions. I've searched the internet and have only come up with wheelbase, overall width, height & length. What I need to know specifically deals with the engine compartment. The most helpfull measurements would be the body height at each corner and midpoint of the hood along with the length & width of the hood (at the front & the rear).

2. Body. I've searched and found loads of places that sell kit cars, but it's unclear from their websites if they sell just the body, and if they do how much it would cost. Also there is the question of quality, so my question is which manufacturers have the best "bang for the buck" and which manufacturers to just stay away from.

In case you were wondering, the engine is a 2.4L Dodge SRT-4 engine. It's a built, turbocharged, dual overhead cam 4 cylinder. It's 26" tall, 10" wide and 21" long. The intake manifold adds just 6" to the drivers side so there should be plenty of room for steering, clutch, brakes, etc. The turbo hangs off the passenger side, but I imagine there'd be plenty of room over there. I've found an adapter plate and bell-housing which should allow me to bolt up a Viper T56 6 Speed transmission. And to keep things simple I'd probably use a 4 linked solid axle in the rear with a Mustang II based front suspension. I have all of the wiring from the engine "donor" plus the clutch & brake pedal assy and steering column (which also has lights, wipers, ignition, etc).

I know what I'm trying is probably unconventional, but think about this: the engine weighs probably 1/2 (or less) of what any V-8 putting out the same power would weigh. Which means hopefully I can keep the overall weight just under 2000lbs. Here's some vids of it in the old car, which had a race built 3-speed auto w/ a 3500 rpm stall converter in it:

Just Cruising around.
Tuning at the track.

Hoofa 07-21-2008 06:31 AM

I've been making my own body style, I'm into non conventional too. I've been looking for a lighter engine for my next one. That SRT is on my short list. I hope you do it so I can learn from your mistakes!!!!

http://i121.photobucket.com/albums/o...s/P1010525.jpg

Ron61 07-21-2008 06:44 AM

Mchat,

The body measurements will vary with wheel base. Also you need to figure out which chassis you are going to use to make sure to get a body to fit it. A good person on the site to talk to about this would be Bill Emerson of Emerson's Motorsports as he builds bodies and custom cars. I like your ideas and that would be a bomb once you get it together.

Hoffa,

I like your body. It is nice to see something different for a change. Keep up the good work.

Ron :)

MChat 07-21-2008 07:07 AM

Quote:

Originally Posted by Hoofa (Post 862990)
I've been making my own body style, I'm into non conventional too. I've been looking for a lighter engine for my next one. That SRT is on my short list. I hope you do it so I can learn from your mistakes!!!!

Depending on your HP goals, the SRT engine is definitely worth looking at. I took a 100% stock engine, added bolt-ons (maily fuel mods) and a bigger turbo (AGP Turbo's GT3076R Kit) and put down 427whp/432tq on pump gas (23psi boost), 491whp/502tq (28psi boost). 28psi boost proved to be too much as the #1 rod decided it had enough and exited "stage right" through the block. But right around 23-25psi and 420-450whp seems to be a good limit as there are alot of cars with stock engines running right there without issue.

Adding aftermarket rods & pistons will take you to the 550-600whp range. And a fully built engine (as I have) will go to 800whp and beyond. It's all a matter of what turbo to run. Currently I have an AGP HP66, but for the next project (be it Cobra or something else) I'm going to drop back to a GT3582R -- still a big enough turbo to go beyond 600whp, but not so big that it's super laggy.

And that body is definitly original... at least I've never seen anything like it. I like it. That's alot more fiberglass work than I want to do. :D

Quote:

Originally Posted by Ron61 (Post 862996)
The body measurements will vary with wheel base. Also you need to figure out which chassis you are going to use to make sure to get a body to fit it. A good person on the site to talk to about this would be Bill Emerson of Emerson's Motorsports as he builds bodies and custom cars. I like your ideas and that would be a bomb once you get it together.

I be building the chassis myself and (obviously) fitting it to what ever body I end up with. Right now I'm wanting to try to picture how the engine is going to fit under the body. Mainly I'm concerned with the height of the body over the engine as I would like to begin working on the turbo manifold, aftercooler placement, and piping before I get a body. But if it's going to be too close, I'm going to have to wait until I do get a body.

Hoofa 07-21-2008 07:25 AM

I'll have molds, it bolts right on to a Factory Five chassis.

MChat 07-27-2008 01:17 PM

And so it begins...

http://www.azchatfield.net/pictures/...Body%20002.JPG

Project Photo Album

I drove down to Eloy, Az and picked up the body, hood, trunklid and doors late yesterday afternoon.


Planned Specs:
Custom Tube Chassis
Triangulated 4 Link rear suspension w/ live axle.
Spooled Dana 44 rear w/ 4.56 gears, 35 spline 1.5" axles.
Front Suspension ????? up for suggestions (thinking C5 Corvette or "old reliable" Mustang II)
Built SRT-4 Engine w/ Garrett GT3582R Turbo (high 400's on pumpgas, low 600's on racegas)
Clutchmasters FX650 Twin-disc clutch
Viper T56 6-Speed transmission.

Probably won't start any "real" work for at least 2 months as I am selling my old car to make room for this one.


I will either continue to update this thread w/ pics and progress or start a new thread with a better title...

Three Peaks 07-27-2008 03:03 PM

In the end, you may be better off to buy the chassis from Tim also and fit the engine to it. Should be an easy fit as they fit just about everything else- SB Ford, BB Ford, etc.... Then you would also have the footboxes available, suspension pick up points and geometry would already be figured out, and an easy rear install. The rest, trunk aluminum, cockpit aluminum, dashboard, steering column, and all the millions of little bits and pieces would be easy to figure out and you wouldn't have to reinvent the wheel.
The Sagebrush roadsters body is designed like the originals to fit over the birdcage frame, unlike the "stressed bodies" that are made to stand alone and/or be bonded to a rectangular tube chassis. Big difference in weight and mounting options by time you add it all up.
At least you would know the body would fit and go from there. You will still have the joy of creating the hood, trunk, door hoops and all the mounting hardware, fitting, etc....

Don't ask me how I know all this.......:)


Bob

MChat 07-27-2008 05:09 PM

Quote:

Originally Posted by Three Peaks (Post 864789)
In the end, you may be better off to buy the chassis from Tim also and fit the engine to it.

I will actually be buying many parts of the chassis from Tim. Mosly the bird-cage structure and his pre-bent tubing for the doors, hood & trunk.

The main structure of the chassis will, however, be different.

fasterpatrick 07-27-2008 05:48 PM

Quote:

Originally Posted by Three Peaks (Post 864789)
In the end, you may be better off to buy the chassis from Tim also and fit the engine to it. At least you would know the body would fit and go from there. You will still have the joy of creating the hood, trunk, door hoops and all the mounting hardware, fitting, etc....

Bob

Ah!, Just build it yourself it's easy;). Your going with a much smaller lighter powerplant you might be able to downsize some of the other parts and make the chassis lighter. I reinvented the wheel it was not that hard if you know what your doing. send me a email and I might be able to help.

Patrick

MChat 07-27-2008 08:50 PM

Quote:

Originally Posted by fasterpatrick (Post 864825)
Ah!, Just build it yourself it's easy;). Your going with a much smaller lighter powerplant you might be able to downsize some of the other parts and make the chassis lighter. I reinvented the wheel it was not that hard if you know what your doing. send me a email and I might be able to help.

Patrick

I read through your build thread it was very inspirational. I'm thinking of a chassis that will probably look very similar to a pro-stock car when finished since I'll need a full cage at the local drag-strip to run it. I plan on setting it up mainly as a street car with some weekend duty at the local track. I hope to keep the weight down, hopefully right at or just under 2000lbs total.

Tom Kirkham 07-27-2008 10:19 PM

The SRT-4 engine has a lot of potential. Jorgen (RaceDeck) told me his 32 Roadster was making over 1,000 HP. http://www.racedeckracing.com/cars.html

MChat 07-28-2008 07:45 AM

Quote:

Originally Posted by Tom Kirkham (Post 864884)
The SRT-4 engine has a lot of potential. Jorgen (RaceDeck) told me his 32 Roadster was making over 1,000 HP. http://www.racedeckracing.com/cars.html

Yep. Darrell Cox Racing (DCR) built the engines for both of the cars on that page. My engine is built using DCR's parts and is pretty much the same as the engines in those cars. I originally built the engine to handle 850+ wheel horse power (~1000 crank). The actual power output is more dependent upon which turbo I use and nitrous (if any) added into the mix.

In the last car I was using an AGP HP66 turbo, which was capable of pushing close to 750hp @ 40psi boost, and I had a 170shot direct port nitrous system w/ a progressive controller. Along with a standalone EMS, 4-coil ignition system, 1600cc fuel injectors, etc... Between all of that & the automatic, the car just became "un-fun" to drive around town. And the combination of the standalone and the auto made it a pain to tune, so I couldn't even run it like I wanted to at the track, making it "un-fun" to drive at the track too.

The car was alot more fun before I went crazy. It had a GT3076R turbo (maxes out around 520whp), stock engine (oilpan to valvecover), bolt on upgrades (mostly fuel & ignition stuff), a 3" turboback exhaust, a manual trans with a twindisc "race" clutch. I could drive it to the track, bolt on a set of slicks and run mid 11's all day long (best time was 11.3@126.9). And around town, after getting used to the "on/off" race clutch it was still fun to drive (only stop and go traffic was tiresome).

I tried to sell the car outright, but who wants a $30k Neon, even if it does have $45k in parts and the capability (with more tuning) of running mid 9's. So I'm putting the car back to a more sane level (with a stock engine, but upgraded turbo), where hopefully it will still run (high) 11's (on pumpgas), and be fun to drive again. Then I'll sell it, and use the cash for the Cobra build, having learned my lession from the Neon, I'm reducing the size of the turbo (the GT3582R should "max out" around 650whp) so it spools up at a decent RPM (full boost @ 3600-3800) and using stock electronics with "piggy back" tuners for fuel and ignition control. That should keep the "fun" factor while still having a very quick car.

Another trick up my sleeve, to keep the car streetable (and fun to drive on the street): I can keep the power under control in the lower gears by using an AVC-R Electronic Boost Controller. This controller allows me to dial in a different boost for each gear. In the Neon when I used this controller I dialled the boost down to 12psi (~300whp, as low as it would go) in 1st, 17psi (~350whp) in 2nd and 23psi in 3rd, 4th & 5th (~420whp). Other than 1st gear the car hooked up wonderfully on the street. And that's a 3000lb FWD car with 245 series tires; I imagine it'll be a bit better with a 2000lb RWD car with 315 series tires :D.


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