After installing the V8 in my 91 convertible RX-7 I have wondered how much weight that I have actually added to my car. A stock rotary powered RX-7 convertible weighs about 300 pounds heavier then a hard top version due to added structural bracing and weighs 3,140 pounds. I had my car weighed today at a local performance shop and here was my results:

No driver, quater tank of gas, convertible top was down
Left Front = 943 lbs. Right Front = 739 lbs. Front total = 1,682 lbs.
Left Rear = 708 lbs. Right Rear = 873 lbs. Rear total = 1,581 lbs.
Total weight 3,263 lbs. Front 51.6% Rear 48.4%

Driver inside car, quater tank of gas, convertible top was down
Left Front = 1,008 lbs. Right Front = 760 lbs. Front total = 1,768 lbs.
Left Rear = 807 lbs. Right Rear = 908 lbs. Rear total = 1,715 lbs.
Total weight 3,483 lbs. Front 50.8% Rear 49.2%

To sum things up, I've only added 123 lbs. of weight with the V8 conversion and with me driving the car with a full tank of gas, the car would almost be exactly 50/50. Now that the car been weighed, these are facts, not my opinion. Keep in mind that my car is a convertible (heavier) and during the conversion I did a lot of things to help balance the car (moved the battery to the trunk, used aluminum heads, etc.) Needless to say I was both happy and surprised with the computer scale results and this should take away the argument that the V8 conversion destroys the 50/50 weight distribution of a stock RX-7, at least with the convertible RX-7 anyway.

I'm going to post this message in a few other RX-7 forums. I'm curious what the RX-7 purist out there who usually flame the V8 RX-7 concept are going to say to these numbers.

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V8RX7.com

Congrats on getting the car essentially finished. That is one sweet looking conversion. I must say I think it is the cleanest and best looking one out of the members cars here.

Can you record a short video of the car in action? So we can hear the exhaust.... maybe see you paint some black strips on the street? yep yep yep.

I'm stoked that you finally got the car done. Bad thing is that when you go to test at the dragstrip and run faster than 14's you will need a rollbar. Only a 6pt if you are slower than 12.0's..... I would suggest getting one anyway for safety purposes.

So tell us about he car. Does it just rip or what? Are you turning heads everywhere? Any stories of beating up on other street cars yet? What about lack of rear traction? Do you plan to run Nitto DR's or just good hiperf. street tires?

And this car is CARB certified to be legal in CA right? I specifically remember you saying it had to pass smog.

Congrats again.... also your car weighs more as you have a pretty wild stereo system too.

Later,

Mark GNX7

:yeah:

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'93 FD/LS1/T56 18x10.5 CCW's-439rwhp/385rwtq thru cats! 2800lbs with full fuel 1.13g's in SCC Mag "USCC", 11.42@127.4mph n/a SOLD http://209.177.55.37/scc.htm
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Cool. That is pretty impressive. However, expect a flame war and accusations that you are lying, the scales are wrong, Elvis interfered with the weighing, etc.

As stated by Mark, you will need a roll cage if you are 13.99 or faster in a convertable (helmets are reqired at 13.99 as well). MY local track is pretty lenient - I saw a 94 firebird convertable run low 11's (Vortech supercharger) more than a few times last season with no roll bar of any kind.

I would like to see some more pictures. Maybe some of the engine compartment. Hopefully my brother in-laws will weigh under 2700#'s. I found a road race hood that is square, On my 86 i am going to take out the pop headlights and the headlight motors, (more weight off the front.) I am going to put some small rectangle headlights in the holes below the pop up headlights.

Awesome car need more pictures.:wave:

Mark thanks for the props, but I'm not sure that I will ever be "done" with it though. I still need to replace the clutch setup, then it should ready to take to the strip, and a few more hoses it will be ready for the peoples republic of California (CARB). I will keep you guys posted. as for more pics

Your car looks great!

Absolutely beautiful! And look how much room is in the engine compartment (especially compared to a 4th gen Cambird...)

I still wonder about the 200lbs difference left to right in front without you in it... AND the 173 lbs going the opposite way in the rear. Sounds like some springs are off, because the engine should be centered, as should the trans. The battery shouldn't affect it THAT much side to side, nor should fuel. In fact, normally the battery on the right rear would counterbalance the steering gear on the left, and the body should be even.

That side to side difference is larger than the total amount you added with the conversion...

Is the chassis bent?

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We have all heard that a million monkeys banging on a million typewriters will eventually reproduce the entire works of Shakespeare...Thanks to RX7Club.com, we know this is not possible.

He does have an insane stereo in the car... maybe it is all the amps and box?

ChrisV- there is a ton of room in these suckers..... that big open space in front of the shock tower is just begging for a single turbo setup on either an LT1 or L98. A homebrew TT 5.0 stang driveline could be attained I think as well I feel pretty easily. Those 4:10's out back are the only thing not perfect for either setup.

I love the 2nd gen's..... I truly do. Just wish the interiors were as nice as the 3rd gen's.... but then again the 3rd gens did cost over 3x as much as a base 2nd gen..... nearly 4x the price?

GNX7

I was wondering about the side-to-side difference myself, so I asked the guy weighing the car about it since the shop weighs a lot of cars. He didn?t seemed too surprised or concerned at the difference in weight side to side and went on to say ?in some older cars we would crank the torsion arms a little and that usually helps.? He also went on to show me how little things affects the scales a lot. (like the top being up or down, door being open, etc.) he even told me to shut the hood during the weighing because it would affect the results. I do have Eibach springs on the car, so I?m leaning on that at the moment as a possible explanation, but without doing the same weighing on a stock vert it?s hard to say why, because I have no ?reference? from which to gauge what ?normal? or ?Stock? is on a vert, and yes, I do have a pretty crazy stereo system in it. But I figure it?s only adding about 40 lbs., because of how I did it. (the box was built very lightweight) The car has never been wrecked, so I doubt the chassis is bent I just wish that I had the foresight to weigh it before the conversion.. but then again? I wasn?t planning to have to defend myself ?.I never imagined my car would be in the center of controversy in the RX-7 community.


Mark:

As for the interior of the second gen. Think about this,.... this car was designed in the early 80?s to be released in late 1985,..... I think it?s held up (cosmetically inside and out) incredibly well for a car that was designed almost 20 years ago. :yeah:

"? I wasn?t planning to have to defend myself ?.I never imagined my car would be in the center of controversy in the RX-7 community."

Hail the defender of the faith..... For he has a most wicked V8 powered FC3S that shall lay waste to all 13B powered RX-7's and most Stangs/Camaros/Firechickens/Vettes.

Looking on the rx7club.com board your car has really got those guys thinking. Many if given the chance will now be more inclined to check into this conversion. Your car does look pretty sick.... and I must be more aesthically oriented with my car after checking out yours. The engine bay is absolutely CLEAN and the paint/rims on the car look great!

When there are GN/L98/LT1/LS1/5.0 versions of the car complete with track results (road race/drag)/dyno'd etc.... we should contact TurboMag/KitCar/CarCraft/HotRod/GMHi-Tech and get our cars in print. That would be a cool issue. There are around 4-5 GN powered cars, a few L98's, a few LT1's and no LS1's that I know of yet. The carb'd V8 ones were probably the first ones ever done.

GNX7