Other Engine Conversions - non V-8 Discussion of non-rotary engines, exc V-8's, in a car originally powered by a Rotary Engine.

rotary engine or torque?

Old 12-07-10, 04:01 PM
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Cool rotary engine or torque?

Hello, I've been using this board for quite some time as a means of research and learning, and after owning my 83 gsl for a couple of years, I would like to ask the community for opinoins on something..... I have in my posession a spare running 4.3L v6 chevy motor, and I have been heavily considering slapping this baby in my car. Currently, my 12a is still nestled in there and running fine, but the car seems to have quite a few problems in terms of performance. Does anybody know what kind of numbers could be expected from the basic upgrades of the 12a?
I've been leaning towards the chevy motor due to specs for quite some time now... but is it worth stripping emissions, installing electric fan, building exhaust, etc. to try and get some halfway decent numbers out of the stock motor?

Also, if any people reading this have done such a swap, is it necessary for me to reinforce the body of the car to make sure I don't tear it up from torque? I was planning to install basic shocktower brace and swaybar, but I'm curious to know if this will hold up well until i get the tube chasis and 240 IRS installed. Thanks for your time!
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Old 12-07-10, 04:05 PM
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Oh boy... bring on the flaming....
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Old 12-07-10, 04:12 PM
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Originally Posted by 81WideMariah View Post
Oh boy... bring on the flaming....
I completely understand and expected that to happen, but for a budget build, i can fiberglass the whole front end of the car in an attempt to counterbalance the weight of the motor, from there the only question is cost vs. performance....
To elaborate.... for the free cost of installing the motor and running some wire, I go from 80 HP to 195. Now I'm sure at this point people will tell me i can turbo my 12a (or buy a 13b) motor and get 200HP pretty easy, but for how much cash? I spend the same amount of cash on that v6 and get 300+ just as easily, and it would still be more economical then going with a v8 setup, and infinately cheaper than an LS motor...

I'm not trying to troll here, I'm just curious if the rotary is worth keeping around or trying to build up

Last edited by hemotape; 12-07-10 at 04:15 PM.
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Old 12-07-10, 04:29 PM
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The simple fact is you have a spare 4.3L sitting around. Aside from the pure'sts saying stay a rotary (hence the flames), by all means try to do the swap. You will probably see more HP out of that motor than adding boltons to the 12A. [Que the turbo 12A guys].....Tearing down, porting, turbo, etc. Will cost some $$$. If you have the motor; by all means - try it.

I would personally say go to a 13B or TII, so let me clear the air on that, but if you have a motor for a swap, go for it. There are plenty of 5.0 Ford swaps on this forum.........As far as the torque, you're not looking at huge gains, so a simple STB and stiffer suspension should be fine. I wouldn't worry about that. My concern is the engine mounts, etc.

Good luck and post your results. I have not heard of anyone doing that swap as of yet. If you have the motor and the time - do it. It will be cheaper and you can have bragging rights to a chevy in a RX-7. Not my cup-o-tea but ignore the flames from this point forward.

For all the haters - at least he's keeping the "7"..........Good luck.
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Old 12-07-10, 04:39 PM
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lol thanks much. I'll be tearing the whole car down over the christmas break to try and sort out what parts of the car i want to keep... as of right now I think I'll be gutting everything rear of the dashboard, ditching the hydraulic clutch setup, installing a trans am wing, 3rd brake light, front hubs and brakes from an infinity, taurus radiator and fan, intentionally and needlessly puttin a rice hoodscoop into a fiberglass hood, and building custom sub boxes over the rear wheel wells to help push the *** end around from time to time. I'll post pics in weekly increments
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Old 12-07-10, 05:46 PM
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Rotary torque is much different than piston torque. While peak torque tends to be lower than an equivalent piston engine, the torque band is very broad through the rpm range, not peaky like a piston engine. This means you can actually have more net total torque, the area under the dyno curve, than with a piston engine. While it may be cheaper to produce piston hp, once the hp goal achieved with a rotary, upkeep and rebuilds can be cheaper/easier for those who DIY.
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Old 12-07-10, 05:53 PM
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To each his own, to me there isn't a whole lot better than hearing a healthy rotary, and seeing everyone stare because they don't have a clue.
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Old 12-07-10, 06:17 PM
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I just don't get it ... how do all these big engines produce so little power stock? 185 HP? I bet my 165 HP 12a could chew it up nicely
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Old 12-07-10, 06:21 PM
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As I have both, it can't really be partial to one or the other.

I will say that the 4.3L will have torque, perhaps more than a 12A however, the weight that comes with the 4.3L and its SBC Transmission, will unbalance the car without some creative mounting. IIRC the 4.3L weighs only 50lbs lighter than its 8cylinder cousin and that's close to 500lbs w/o transmission etc. My fully dressed LS1/t56 comes in at approx. 80lbs heavier than a 13BT according to my racing scales thanks to the abundance of aluminum on the v8.

If you go 4.3L you will want to make sure it has vortec heads on it or you are wasting your time.

Last edited by nofords; 12-07-10 at 06:25 PM.
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Old 12-07-10, 06:23 PM
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the kit from granny's is only $600, so if you have a tranny then go for it.
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Old 12-07-10, 07:57 PM
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Originally Posted by dj55b View Post
I just don't get it ... how do all these big engines produce so little power stock? 185 HP? I bet my 165 HP 12a could chew it up nicely
bet titles?
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Old 12-07-10, 08:18 PM
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next time I'm down in that area ill give you a good shot .... but it'll probably be supercharged by then, on a road coarse I can normally keep up with cars around double my power pretty good
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Old 12-07-10, 08:19 PM
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get the 8.8 rear end from granny for the rear end its cheaper ,u be wasting more money with 240sx irs trying to get the geometery rite and a alot of labor if u are sending it out to a chassis shop, but if u are doing it yourself go ahead
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Old 12-07-10, 08:25 PM
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lol I was just thinking take video runs of a drag strip, but why would you want a supercharger on a car that revvs out as far as the rotary? I would think a little bit of nitrous and a twin turbo setup would be a bit better? :-\

Originally Posted by mario1386 View Post
get the 8.8 rear end from granny for the rear end its cheaper ,u be wasting more money with 240sx irs trying to get the geometery rite and a alot of labor if u are sending it out to a chassis shop, but if u are doing it yourself go ahead
I thought about that, even considered using the trans am rear end so i didnt have to make as much room for the tires, but honestly, I spent alot of time researching the things people are doing to try and balance out the first gen's for cornering and drift, and I havent seen a whole lot of people who can really take a built car with IRS..... for now I'll stick with stock, but as soon as i blow it up, or when summer rolls around, I'll be trying this setup

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Old 12-07-10, 09:36 PM
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I've done the 4.3 swap. Depending on the year of the engine, it's quite a PITA. And that is coming from someone who has swapped GM motors in to a half dozen different chassi over 20 times. I've also done the 3.8 swap, and it's much easier.

and to those hating because it's rated at 190hp stock, it's also rated at 260lbs of torque, stock. With some headers, cam, mild porting, you'll get it up to 300hp/350tq pretty easily.

Weight distribution is not thrown off more than any one will notice. That's what they've always said about the V8 swap, only to be proven wrong time after time.

Also, you won't need a different rear. If you do pop it, swap in a TII rear, and you're golden.
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Old 12-08-10, 09:38 AM
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Originally Posted by hemotape View Post
lol I was just thinking take video runs of a drag strip, but why would you want a supercharger on a car that revvs out as far as the rotary? I would think a little bit of nitrous and a twin turbo setup would be a bit better? :-\


I thought about that, even considered using the trans am rear end so i didnt have to make as much room for the tires, be honestly, I spent alot of time researching the things people are doing to try and balance out the first gen's for cornering and drift, and I havent seen a whole lot of people who can really take a built car with IRS..... for now I'll stick with stock, but as soon as i blow it up, or when summer rolls around, I'll beo trying this setup
My best run was 14.6 and that was before my 165 HP, and quite a bit of increase in torque. I was at around 125 ft-lb, now I'm 134 with it being even flater, so I think I could be down to 14.3, Ive only been to the strip maybe 5 times in my life so not by any means the best at it neither ... thats my numbers, time to show yours

Competition always brings out the best in you, so this is your challenge Just so you know I'm only saying all this because I'm more pure to the rotary and nothing else ... so please don't take this the wrong way.
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Old 12-08-10, 10:26 AM
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Originally Posted by Eat-Pez View Post
I've done the 4.3 swap. Depending on the year of the engine, it's quite a PITA. And that is coming from someone who has swapped GM motors in to a half dozen different chassi over 20 times. I've also done the 3.8 swap, and it's much easier.
Agreed! and being a former highly modded S/C Grand Prix owner, the engines for the most part are bullet-proof. They are lighter and have a larger aftermarket for big power. Mine was well into the 400whp/400tq mark on stock heads/internals and propelled my 3400lb grocery getter into the 11's. I miss my boosted 3.8L Sounded like *** tho.
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