Jonathans RCR 40 Build

The brakes are as provided by RCR. They are 11.75 inch rotors front and rear with 6 pot willwoods front and 4 pot rear. Both master cylinders are the same size. The bias is pretty much on the center of the bias adjuster. It does not take much of an adjustment before you have too much rear bias though.

Comparing the two cars is difficult. They are so different. The GTM is much more of a road car. It has power windows, power mirrors, and a more refined interior. The GT40 is a replica race car. It has a fairly crude interior with just a little toll window for air. Both do have AC though.

I prefer the driveline I have installed in the GTM. I have a carbureted 302 Ford and an Audi transaxle in the GT40. The GTM has a fuel injected LS1 and a G50/05. I have always been a Ford man, but I really like the LS1 engine and the G50/05 has better gear ratios than the Audi. I do prefer the sound of the GT40 with the cross over pipes though. I hate to even put this in print but an LS1 with crossover pipes in a GT40 would be an awesome combination.

On interior comfort they are both difficult to get in and out of. Both would be pretty tight for anyone much over 6 foot 2 inches. I think the GT40 is a little more comfortable unless there is someone in the passenger seat and then the GT40 feels really tight. Both have a real mail-slot view to the front and rear. I would say comfort is pretty close between the two cars. The seats in the GTM are a little wider so if you are heavy the GTM may fit you better.

As far as handling, I really can't tell a lot of difference yet. I have not pushed either car hard enough to know their limits. On paper the GT40 clearly has better brakes. I have old school 15 inch rims on the GT40 and 18 front and 19 rears on the GTM. The GTM may hold a corner better due to tire and rim selection but I have not pushed it hard yet (I don't have a 1000 miles on it yet.)

If what you are after is attention then the GTM wins. It seems to draw more of a crowd then my GT40. I believe the more modern shape attracts more attention, but the bright copper paint on it may have a little to do with that as well.
 
I do prefer the sound of the GT40 with the cross over pipes though. I hate to even put this in print but an LS1 with crossover pipes in a GT40 would be an awesome combination.

Johathan,

This line made my day :)

Thanks so much for resurrecting your thread, as I missed it! Enjoy the cars, what a great combination!

Best regards,

-J.
 
J- I am not surprised that my statement about the LS motors made your day. I have always been a die hard Ford fan, and I especially like to put a Ford motor in a Ford replica, but I have to admit certain advantages of the LS motor over my 302. Fuel injection and added cubic inches are two of the big ones. I still cringe at the blasphemy of a Chevy engine in a GT40:)

I have always wanted to add stack injection to my GT40 but the price and complexity has kept me from doing it.

I do like the LS motors. I think Ford went down the wrong road with their new engines. I like the simplicity and the smaller package of the LS motor compared to the new Ford engines.

Someday I may build an SLC. If I build a SLC it will most likely be LS powered. Probably an LS3. Hard to be the power to cash ratio on that engine. No blasphemy in putting a Chevy engine in an SLC.
 
I had a brand new crate 383 iron SBC just sitting around. Sold it in favor of an LS engine for my SL-C. Love it! Easy to turn the intake manifold and fuel rails around
to place things for mid-engine too.
 
One thing that I neglected to compare between the GTM and GT40 was the build process. The GT40 is much easier and quicker to build than the GTM. The quality of the body for the GT40 is better. I have done body work on 3 kit cars and Fran's cars are the best I have seen. His are the only cars I have ever seen that you could confuse a polished gel coat body for a painted car. One thing that is harder on a GT40 than a GTM is the door installation. The doors on a GT40 are notoriously difficult to install.

There are several items on the GTM that are more time consuming in the build than the GT40. Paneling the chassis is very time consuming on the GTM. I estimate that my GTM has around 2,000 pop rivets in it. Each one required drilling a hole in the aluminum and most required a hole in the chassis as well. Fran's cars do not require any paneling. Installing the AC system on the GTM is significantly harder than the GT40 (but the AC system on the GTM is nicer). Engine installation and access is worse on the GTM as well. The GTM also has a lot more accessories, which are nice to have but are time consuming to install.

The suspension on the GT40 is quite a bit more time consuming to get aligned than the GTM but the suspension has a much greater range of adjustment. It is difficult to get enough caster in a GTM. The GT40 will allow you to get some pretty extreme alignment figures if you want.

One other item that is worth mentioning is the driveline choices you get with Fran’s products. Fran can provide you with a pretty wide range of choices of engines and transmissions that you can put in his cars. With the GTM you pretty much need to stick to an LS motor and a Porsche or Mendy transaxle unless you want to do a lot of your own fabrication work.
 

Randy V

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Jonathan since you have built both and they share a windscreen how would you compare the cars? Are there any characvteristics which make one a better driver than the other?

This is curious to me... Do the GTM and GT40 have the same Windshield?

Pretty cool to own one of each eh! :thumbsup:
 

Fran Hall RCR

GT40s Sponsor
I can tell you that they are the same...I have a partially built GTM..(for sale cheap btw) that I took as a trade in against a new SL-C kit and for fun we dropped an RCR40 screen in place....boom...boom..
 
I thought I would put a few updates on my build. First of all I have about 8,000 miles on the car. The ride has softened up a bit in that time. Originally even small things like bridge expansion joints would really jostle you. Now that has mellowed. I suspect that the change is from the shock absorbers softening up. Also the car seeks center much better now. Originally I thought I needed more caster but just getting a little wear on the ball joints has caused the steering to loosen up a little.

I have also made a few upgrades to the car recently. I added a belt tensioner to my serpentine set up. It is off a 2004 Corvette. I had one handy off my GTM so I could measure it to see that I could make it fit. See the attached picture to see how it mounted up. I could not get the belt tension set to not slip when the engine was cold and the AC was on and not chew up belts like crazy. This has fixed both issues.
 

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I have also worked on some details I had been ignoring. I finally made a wiper arm for the car. My kit came with the Lucas style motor so it took combining two different arms into one to get something that would work. I also added some check straps to the rear clam shell out of aircraft cable. It looks more finished than the twine I was using. I used some of the cable to make door check straps as well. My driver door was starting to split at the front from opening it too far. This was easily glued back up.

I also spent some time aligning the doors more. I found the driver’s door would not shut well any more. The RCR hinge has a ½ fine pitch bolt as the hinge pine and it was starting to gall into the holes which created a lot of play in the hinge. I replaced the pivot bolt with bushings and shoulder bolts. It really tightened up the hinge. I finally got the door adjusted where I want it.
 

Randy V

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Hi Jonathan,

Good to read you're back on your GT40 project. In the process of mounting and un-mounting my doors 50x or so, I realized that the way my hinges were configured that the two bolts actually traveled on different plains - so I eliminated the problem in much the same manner as you. I bushed the chassis side of the hinge, but used an 11" long 1/2" GR8 bolt as a single hinge pin. This also serves as an achor point for my Anti-Intrusion beam so _ killed two birds with one stone. Of course it also elongated my build time substantially...
Do you have the Spider reinforced by your roll-cage? That's something else I did to make sure I would maintain the same repeatable gaps/shut performance..
 
Something else you may be interested in is how my GTM and GT40 compare on the road. Now that I have a few miles on both I can give some decent comparisons. I have not driven either car close enough to the limits to really give anything but general impressions. I feel like my GTM can corner harder than the GT40 but that is most likely due to tire choice. I have 15 inch rims on the GT40 and the tire selection for those is somewhat limited. The tires I have on the GT40 are not very sticky. Acceleration is close but the GTM feels a little quicker, but that really comes down to engine choice. The GTM has a little softer ride than the GT40. Turning radius is a lot tighter on the GTM. The GT40 takes a lot of room for a U Turn, even more than my F150. The GTM has a turning radius more like most production cars.

Interior comfort is an interesting comparison. Both cars are hard to get in and out of. The GTM has a diagonal bar in the door opening that you have to get over and no cut out in the roof like the GT40. I find it a little more difficult to get in and out of the GTM than the GT40 (assuming some @$$ has not parked so close to me that I cannot get the doors all the way open on the GT40). Getting out of the GTM requires really bending forward until your chest is nearly on your knees to get your head out the door.

I also find that the GT40 has more leg room. The GTM has a very tapered and shallow footwell. Both cars leave you with little room for a dead pedal or good place for your left foot. The right foot leg room seems a little better with the GT40 (I am 5’ 8” and 170lbs for reference). Short master cylinders would give you even more room on the GT40 if you need it.

The GT40 is much better for elbow room when I drive solo but if I have a passenger it is shoulder to shoulder. The GTM you sit outboard and the left arm is always hitting the arm rest when trying to steer, but you have plenty of room between you and the passenger. The seats are wider in the GTM for big boys or for those endowed with shapely hips.

One thing that I still love about the GT40 way more than the GTM is the lovely wail the cross over pipes make. The GTM does not sound near as nice as the GT40 does when it hits 5K and the pipe start to scream. That sound will never grow old.

Now I just need to build a Superlight Coup to do a 3 way comparison.
 
Randy, I bushed both the plates in the door and the plate attached to the chassis. I have two 3/8” diameter shoulder bolts as the pins. I like your idea of adding an intrusion bar but I never added one so the two bolts work fine. I had to create a 2 foot long allen key to tighten the bottom hinge bolt because I never liked the access hole solution that others were doing. I remove the upper hinge bolt and insert my long allen key thought the upper hinge hole to tighten the lower bolt.

I only have the 4 point cage and it is an early one’s so it is in the engine compartment and not the cab so I do not have any reinforcement on the spider. The spider really doesn’t seem to move much. Most of the reason my door was not fitting correctly was my rear bulkhead was positioned differently on final assembly than when I did my fitting. I never secured the bulkhead at the bottom when I fitted the doors originally and when I secured it on final assembly it was holding the spider in a different spot. The final solution involved a hammer. A slight bend in the rear panel and everything finally went back to where I wanted it.
 

Fran Hall RCR

GT40s Sponsor
Great write up Jonathan...thanks for the feedback.

Youa re correct though ...you do need an SL-C to compare...including build times..
 
It is an interesting comparison between the cars. They are similar in many ways and different in many ways.

I am waiting for the barchetta version of the SLC. When are you going to have it ready?

Then I will have to make the hard decision of what car to sell to make room for it. I have a Cobra, GT40, GTM and a two car garage.
 
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