If you were starting from scratch...what would you change about your build?

ckouba said:

I don't remember any P/N's and I can't poke at it for any at the moment but these pieces should look familiar:

~7,200 miles behind a ~350hp/350tq 302 into a -2 ZF box through a McLeod single plate clutch.

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Thanks----yes, they look familiar. Do you get any binding of the clutch as the car/system heats up? I replaced the master cylinder, and am getting the problem again.

/s/ Chris

1. 400-450 HP is way more than the 350HP it takes to build a nice street-worthy car. BUT more than 500 isn't necessary even for a full-on track car.....Really!

2. Others have spoken about gearboxes. They are completely correct. I would add the following. A properly built 5 speed G50 Porsche with all the reliability enhancements will handle 450HP all day long on slicks and last forever in a streetcar with a street tire. They are a completely mature platform and there are many many sources for parts as well as performance upgrades. Gear ratios are widely available for modification. If you are familiar with an SBF in a mustang then you already have a good idea of the first 4 gear ratios needed. Add a .8 5th to that and you are very close to a perfect set of gears for a combo track/streetcar. There are other gearboxes but you asked what I would recommend. Just be certain about numbers in circulation and ongoing support.

3. I will add this as a stand-alone point. An LSD is the most important single performance part in the car. Hands down. I would recommend a Quaife torque biasing diff or an equivalent type LSD system. Frankly, there is no point in building a GT40 without one as far as I am concerned. I don't believe you are interested in a trailer queen from what I see you have built before.

4. If I had to do it again I would start with race-proven brake system unless I KNEW I was only going to drive the car on the street. The difference is, real race calipers have much larger pistons in them and a much larger piston area as well as pad area. The larger piston area allows you to use larger master cylinders and the combination is easier to design from scratch. They also are not designed to use power braking systems. Rotors are limited by wheel size. See #5

5. Wheel and tires...............Oh my............ This will get them going! 18-inch wheels are the way to go. Very good tires are available in nearly every size as well as a good assortment of DOT track day tires and full-on race slicks. Even used ones can be had fairly cheaply!
Brakes will fit no matter how big they are. I would recommend 8 inch wide fronts and 12 inch wide rears. 10 rears if you really are only going to use it on the street in a relatively low-performance envelope. 12-inch rears also get you a wide body! way cool!

In any case, research 15 inch and 17 inch tire availability. 17 can work but even they are getting limited. I believe the industry had settled on 18 inch as a standard in a lot of cases.

6. A short note on F.I. be sure you have someone to tune it. Especially if it's an 8 stack.

7. Make sure the windshield fits before you finalize the center section position and door fit. And to a lesser extent the front and rear clip fit.

8. Make AC a priority.................cold as ice priority! Enough said on that score.

9. Lastly......how big are you? You should ride in one..........really unless you are 5'8" or shorter and less than 180 pounds. Thats not a make brake point but if you are a big guy .................well you should go for a ride.

Chris Kennedy said:

Thanks----yes, they look familiar. Do you get any binding of the clutch as the car/system heats up? I replaced the master cylinder, and am getting the problem again.

/s/ Chris

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Not to tempt fate but it functions flawlessly. Smooth engagement, appropriate pedal effort, no slippage, no dragging, feels exactly like it should.

PM inbound for you, sorry for the thread drift.

Good thing I'm 5'7" and 155lbs....and I like to sit NASCAR close to the steering wheel! If I get a project...I'll probably opt for the nearly complete package, but I have learned that it is cheaper to buy the correct parts the first time. Upgrading the brakes had crossed my mine, as the car will be tracked and street driven. I usually overbuild my projects so they stand up to the abuse and I don't have to spend time fixing/replacing parts. Thanks for the great advice Howard!

Gonna revisit this thread. My 66 GT350Rish build will hopefully be moving under its own power in a week or 2. After shaking it down and working out the bugs...body work this winter and paint next summer. I was shot down by Ford when my local dealer and I tried to get an allocation for a carbon fiber track pack GT500 (we had an allocation, but couldn't order the carbon pack). I'm on another list to order a C8 at MSRP this fall, but having second thoughts. I will be ready for another project by this time next summer (hopefully). I'm still looking at a Mrk1 GT build. Any more thoughts out there? RCR or AP would be the source for the build...unless I find an unfinished project out there.

So again: Start with the transaxle. Assume your engine will make 500 ft/lbs of torque and go from there. I am sold on Porsche G50's 01,02,03, G50/50s and the G50/52. The 52 is the one to go for but the G50 01-03, IF they are properly built and with added internal modifications as well as the necessary strengthened side plate are fine. Gear ratios are an issue but G50s have numerous alternatives available. I think 5 speeds are enough if the final drive ratio and 5th gear keep the engine rev under about 2800@ 80MPH. This will give you north of 180MPH top speed depending on max revs and still be comfortable on the highway at cruise speeds.

Why Porsche? Because they will fit in a GT40 length-wise, are good for the amount of power you will want, Porsche made 10's of thousands of them and you can get parts easily from many sources. They are well known and widely used in mid-engine prototypes like GT40s. There are also several rebuilders that are reputable and have been in business for a long time to get help from. My advice is to buy a built box from one of them instead of buying an unknown quality used box and then asking to get it updated after the fact. Here's my source and I recommend them fully. (I have no financial interest).


Now! LSD's.............. I LOVE the two Quaife TBD's in my cars. I have a G50 in my SLC and a R-21 Renault with the one-piece input shaft mod. Both have Quaife's in them. Any GT40 must have some sort of Limited slip IMHO. I like Quaifes the best.

Don't save money on the power train. This is the most difficult group of systems to try and change later. Buy uprated half shafts, stub shafts, wheel bearings etc, the first time.

Engine: 400 CI's is just about right. 400-500HP is plenty and an SBF 351 stroked to about 400CI will run on pump gas, use a hyd roller cam and be well mannered on the street while making more than enough to run on the track with ANY street tire. Add slicks and be a hero!

CARB verse FI............ Carb easy..........FI.............you better have a tuner who knows what he is doing.............search FI systems on this forum and ask around before you commit to FI. It works great when it's right and will make you crazy until it is.

Tires and wheels. Too much fo say for this response but I would go with 18 inch wheels TODAY if I had to make a choice TODAY. There just isn't much of a tire choice otherwise, and it's getting worse all the time.

Get the AC system right. You'll need it unless you live in Jolly ol England..............where you will NEED good rain tires. I'm kinda joking...........kinda.

Bodywork first or last? I go both way on this from time to time, You will more than likely do the mechanical systems and the body
simultaneously in reality. It all needs to get done and doing body work for weeks on end gets old............so do it the way that is most fun for you. Note: bodywork and paint prep is the place to save a LOT of money! Paint is another. My advice is to make the paint job suit the usage. Don't put a $20K paint job on a track car. Or for that matter on a streetcar that you are really gonna drive. I would study wraps and see if that would work for you unless you are building a show car. Track car? Wrap or cheapest single stage paintjob you can find. It's only gonna look good for a few outings anyway.

The main thing is to have fun!!!!!!!!!!

Joe I am like you I do everything but paint it just matters to your personal choice I just completed a GTR with the first Ecoboost motor very challenging build because no one has done the Ecoboost Gen 2 yet so noone to lean on by the looks of it you should be just fine with the RCR GT 40 the GTR has a lot more interior room

What about ordering? Are there things that would be better left to ordering down the road...such as wheels/tires, brakes, wiring kit, seats, etc? I will track the car, but will be mainly street driven.

I'd suggest ordering all the important components you need when you order the kit.

In the 1960s I worked at the National Radio Astronomy Observatory in the Electronics Division. We offered qualified college students an opportunity to working there as a "co-op", for a time and then return to their studies. One co-op worked diligently all summer in his spare time building a Williamson amplifier for his audio system. This was a highly regarded amplifier circuit that used taps on a special output transformer to drive the output tube screen grids to lower distortion. He machined a chassis and wired the whole thing over a period of two months. It was a work of art. After everything was ready, he ordered the required special output transformer from its manufacturer. He finally received a reply... from a law firm stating simply "This firm is in receivership". He was crestfallen- without that transformer, all his effort cane to naught. His experience taught me a lesson, too.