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Discussion Starter #1
Looking for some real info on swapping in a rotary to my newly acquired 1972 GT. Will the rear axle hold for up to 200 hp? And what are the stock gear ratios, 3.55 ?

Does anyone know the weight ratios? Fitment problems installing it? Exhaust issues, length of tranny issues along with mounting issues for motor mounts.
I have a motor/tranny lined up from a 1988 RX7. So nice fuel injection to boot, and easily modified.

Any info would help. I tried searching here, and in other places, with little luck, and even less actual information on this swap.

Thanks
Ed
 

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Not any help...

I know, I'm not any help... as I have no information.
I jsut wanted to express my interest in this matter. I saw someone in my area (San Jose, CA) driving what appeared to be a Chevy Vega with a Mazda rotary. That gave me the idea to put one in a GT.
From all I hear, rotary engines are somewhat more difficult to work on, or break down pretty easily, or something to that effect. Regardless, it seemed like a great idea to me, so any information you guys could come up with would be a great help.
 

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Well, I can say right now it will be a bit of a project. This is what I had planned when I first got my GT, but I was having problems getting a line on a motor and tranny. I do know of one guy that was working on the swap, had the rotary and the GT, but I haven't heard from him since he started dismantling things to swap over.

But here's the info I collected when I was looking at doing the swap...

Weight wise, the 13b weighs less than the 1.9L in the opel, it's also a shorter engine. As long as you keep the engine to the rear of the front axel centerline, you won't mess your weight ratio up. I never had a engine and tranny to figure out the length issues, but I think I had it figured out that you could get the 13b shifter to line up with the stock shifter hole if you redid it and moved it forward a couple inches. The way the shifter is designed, the input shaft can be shortened and a bracket made to move it forward.

The stock Opel rear end won't handle the power of the 13b though. I planned on getting around this with installing a ford 7.5" rear end out of a ranger pickup. This would give you the strength needed, plus lots of choices for gears, differentials, and brakes.

Exhaust isn't too big of a deal, take it to a good shop and they'll be able to put just about anything you want on it, then only thing you're going to run into is clearance issues if you try and place the muffler under the floorboards.

Mounting issues, you're going to have to design your own engine crossmember, no way around that. I didn't have the engine to line everything up and get it figured out, but it should just take a little sliding around to get it right, just make sure you keep the engine rear of the front wheels.

Are you going with a T-II engine? or just a normally aspirated? Are you planning on using the stock ECU, or some aftermarket like a Haltech? And are you planning on leaving any of the emissions stuff on the 13b? I think on the 88 they used the air pump to open the seccondary ports on the intake. Just a few things to keep in mind.


I wish you the best of luck on this, I've only seen pictures of one GT that completed the swap, it's a great idea, just wish I had the time and mony to go through with it. Keep us updated on how it goes.
 

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Dave Stoner used to be a regular at the Carlisle show. Last time I spoke with him he was about to pull his motor and put in a rotary. He hasn't been to Carlisle since....Hrmmmm

Anyone heard from Dave?

-Travis
 

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Discussion Starter #5
Well, I have experience with the rotaries. I fixed a 2nd gen that had an engine fire. And I own a 84 GSL-SE.
I will use the stock ECU, but will need to get a better chip.
Exhaust is not that easy with a rotary though, it is very dependant on lengths. They are tuned like a 2 stroke motor cycle engine. And the fact that if they are allowed to run very open to breath, they are LOUD and annoying. Not to mention the extremely hot exhaust gases that will burn out all cheap pre-silincers and mufflers. They also have to have 'straight through' mufflers, which increase the noise. And the GT is WAY to short of a car to have a 'properly' tuned exhaust.
As for the length and weight, I know these change with the year of the motor. Most specifially the length of the tranny.
I will run NA for this motor as I want the much high rpm limit. Got to love a stock motor where the internals are good to 10.5K rpm !!!
As for the secondary ports, lol. Pull those sleeves out and run open 6 ports. Or just take the actuators off, and wire the suckers open (what I did on my current car). The performance loss will almost be unnotticable on such a light car as the GT.

Other questions, cooling. How are people running their rads? I was thinking about tilting it forward like the newer RX7 uses. And have a good electric fan take care of it. I would rather not cut the current brace supporting the radiator now, but I can easily build a better one afterwards.

Not worried about building a cross member, that is easy, more of a question of WHERE people have put theirs.

Thanks for the replies. Hoping to hear from someone that has done this!
 

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Discussion Starter #6
Any help here? I would LOVE to talk to someone that has done this already.
It would seem to be a relatively easy swap. And one that could easily progress with power and handling without too many issues as well.
Thanks
Ed
 

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Ed

there are two rotary GT's in San Antonio TX

one belongs to John Curry

the other belongs to Marty Reimer

I stopped giving out there phone numbers

a lot of people would call but they where not serious about the swap

there are PICS of the cars on the Texas Opel club web site

if you can find it

Texas Opels. com
i think that's what it is

HTH
Davegt74
 

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My dad just got a 20b engine from japan, He'll let me use my GT as a test bed for the rebuilt engine before he puts it into an airplane. a 20b is the 13b plus one rotor and about another 75 to 100 horsepower. anyway the question is. Is there enough room in the engine bay for another 6 inches of rotory motor. the 20b is longer than the 13b. That is without cutting anything, I'll be going baci to either a 13b or original engine after the three years.
 

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A three triangular rotor wow!

that would be tough the real problem is the trans not the motor

the RX7 trans is real long

if you could come up with a shorter trans

the three triangular could fit but it would take some work

you would have to move the front of the engine up higher to clear the rack

and probably have to cut the radiator support out or modify it
kinda like the 6cyl GTs (i think there are PICS i the gallery)

it could be done
marty has been talking about one for a few years now

good luck

davegt74
 

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A couple a guys from Texas are running an E Mod BugEye Sprite in Solo II with the 3 Rotor engine. I saw it at the Notional Tour event in Ft Worth, April 2000, It was sooooo fast. The engine made just under 400 HP on a Chassis Dyno. If you are able to stick it in a GT, you'll have your work cut out for ya just to make to car safe to drive, much less be able to use all that POWER.

Good Luck
Paul
 

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Rotary Engine Swap

The Mazda RX-7 (Gen 2) transmission assembly is about 12" longer than the Opel GT unit, as measured from front of the bell housing to the shift lever location. The extra length is split roughly evenly between the bell housing and shifter linkage.

General engine dimensions are very similar, with the Mazda unit being 1-4 inches smaller in general dimensions.

I've heard that the Gen 1 RX-7's have a 5spd that is roughly the same length as the Opel, but haven't measured it myself.

I'm working on the conversion myself, and would gladly collaborate with anyone else out there who has done it.

The stock rear end may very well be OK. I know a guy up in Connecticut who uses a stock rear with a Mazda 13B engine putting out 170HP. No question it is stressing the unit more than the design loads. His car has very interesting acceleration.

Good luck on your project. I'm looking foward to getting mine on the road as well.
 

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Discussion Starter #12
What generation engines were used?
I have a 1st gen 13b in my rx7. But was trying to get a hold of a 2nd gen from an 89 convertible.
As far as the shifter location, I though that was more a thing of how it was mounted on the tranny. Meaning you can use a 1st gen tailshaft/shifter setup on a 2nd gen tranny (the TII tranny is a LOT stronger).
Other thing, wondering what would be easier for making the motor mounts, the 1st gen with the mounts off the front cover, or 2nd gen with them located further back?
 

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Mazda Engine Swap

The guy I know in CT used a Gen 1 13B engine (1974 engine (ported) with 1980 transmission).

My measurements are from a Gen 2 13B NA engine. I picked up the '87 RX-7 for $300 and got it running beautifully after diagnosing a bad ground to one of the fuel injectors. Tough to beat that price. I've pulled engines and transmission assemblies from both the Mazda and the Opel, and the measurements were made off the assemblies lying on the garage floor.

I've seen web sites that list the '89-'91 as increasing stock HP from 146 to 160 (relative to the '86-88), and the redline from 7K to 8K. Have you heard what Mazda did to get the power boost?

I'm still not convinced that the shifter location is going to be easy to fix. The fellow in CT ended up with the shifter 3-4" aft of the stock location and a custom interior shift console. I'd rather not do the same. The Mazda tailshaft/shifter unit is ~14" on the '87 NA model, and that accounts for most of the difference between the Opel and Mazda units. Anything more than 2" long would force either moving the engine fwd or alteration of the interior console. Do you have dimensional information on Mazda's tranny units, especially the tailshaft/shifter arrangements? That's probably the best way to talk about this.

I'd prefer to use the Gen 2 tranny and clutch assembly if at all possible as well. Matching the 1st gen tailshaft/ shifter to the Gen 2 tranny & clutch would be neat if it worked out dimensionally. Mazda worked hard to make the tranny components interchangeable (within reason), and it may very well work out. I'd been thinking mixing components as well. In a pinch custom parts could be built as well.

Not sure about your motor mount location question. The '87 motor mounts are something like 2" farther aft of the fan pulley compared to the Opel engine, so it should be feasible to use the stock GT cross-member with some modification. Where do the Gen 1 mounts come out, and would they be interchangeable with a Gen 2 engine? It would be nice to keep the engine as far aft as possible for obvious reasons.

Have you thought about the rear end very much? I autocrossed the GT for 5 years or so, and had big problems when 1 of the rears would pick up and spin. I'm thinking of putting in a posi-traction rear, and hopefully one that can take a bit more HP.

I'm real excited about the performance of the package. The GT's lighter weight should push 0-60 times into the low 5 second range, depending on tire slippage and performance modifications. I've got to keep up with my brother's Porsche 911 somehow!:D
 

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The two guys that I know that have done rotary's.

Went about it differently.

John has a 13B his is set back to where you would think the motor would go

both ways work fine

Also Don Kline had a Rotary with an auto trans that was a very fast autocross car he sold it to a guy and you will probably see it at the Solo II Nats.

And Marty has a 12A don't know a lot about John's swap only that he knows a lot about rotary's.

Marty's swap I just helped with the humping of parts.

A few things I do remember about Marty's swap.

Everything is set up so that the shifter comes out at the stock shifter location.

I think he swapped tail shafts to shorten the trans so he has a 5 speed but with a 4 speed tail shaft (does that sound right its be awhile)

anyway there might be a few Options, if you read Grassroots Motorsports article on the ROSPITS they used a TRANS out of a rotary truck--- not sure its different but it might be shorter

OK on the motor mounts Marty used a 1.1 cross member
which has the mount at the front of the engine bay
on top of that sit GM engine mounts the and adapter was made to use those 4 studs on the front of the 12A

Pretty neat he mocked up the cross member with some of that erector set stuff (metal) then had someone make it up
came out great.

HE said that he made a provision to go to a 13B motor in his setup (there is a spacer at the front of the motor)
He said all he has to do is remove the spacer and a 13B will fit.

lets see what else can i remember

The drivers side foot well had to be massaged a little
to clear that left side oil adapter thing
he does have a remote oil filter and a block off plate is where the 79 rotary oil filter adapter is. (hope that makes sense).

Custom gas pedal had to be made or I should say he bought a hot rod gas pedal and modified it.

custom oil pickup with modified oil pan
hyd clutch was straight forward (my contribution was to go to the junk yard to pick the part up)

Marty wanted to use a side draft but they stopped making the manifold he wanted to use

the goal or one of the goals was to fit every thing under the hood

so a racing beat 390 holly carb is used and a stock lower manifold

also he said a must have is this racing beat pre muffler (not sure of the right term) this part is used to get the sound down to where a regular muffler can be used

the radiator is on its second revision and its mounted in front of the radiator cross member

AOL just kicked me off again

so i better end this


oh the water pump thing (exit pipe) was heated up and bent

a few more things but i forget

oh the rear is not a problem since the rotary does not have much TQ


Davegt74
 

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well torque is a problem
a 12a engine makes about 110 hp and 100 ft/lbs of torque
a 13b na makes close to 125hp and 120 ft/lbs
i dk about the turbo models but just guess it gets big fast
and a 20b makes 300hp 300ft/lbs at 2000 rpm and goes down 10 % from 2000 to 8000
but torque is usually made at a higher rpm
but dont count on the rear to last very long
 

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Marty was just here in Austin on Saturday for the Texas Classic Car show where I had my GT. He doesn't have email. Are you the Hammer that was trying to sell a GT here in Austin a couple months ago? If so, I'm glad to decided to keep it.
There is a '69 GT in Fredericksburg that has a Rotary swap done in '74, with a Datsun rearend put in in '75. The guy is pretty much trying to get rid of the car (aka maybe free) I went and looked at it. It was more than I wanted to take on. But you might be able to get some ideas.
Here is a picture of the motor.
 

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Discussion Starter #17
Yeah, that is my car in the for sale.
It is still for sale actually. but as you can tell, I haven't been pushing it too much.
Hey GGT, anyway we can get together? I would like to go for a ride in your car. Been too long since I have been in a good running GT.
 

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Sure, give me a call 249-8836. I know after the car show this weekend, I got a couple people re-enthused about working on their cars.
My evenings are pretty open. Out of town this weekend.
I live off Oak Knoll, S. of 183.
 

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wiring and gauges

Hey I was just doing some searching on the forums and I ran across this thread so...
I have a couple of question about the rotary swap...
First, how difficult would it be to swap the gauges in the gt? i assume they will not run off the signal from a T-II's ecu, so I think Id have to get new ones.
Also, how difficult would it be to put the T-II's fuel pump in the Gt's tank, or woud it be better to mount it externally?...Lets see...oh yeah...cooling and intercooler...would it be advisable to use the stock T-II radiator and mount it at an angle in the engine bay or to cut out the mounting bracket and move it as far forward as possible (moving the battery) And where would the best place to put the intercooler be? leave it on top or get some better piping and move it to a front mount. The only problem with this idea that i can see is that it will cut radiator flow and heat up the incoming air...
I assume the intake could be mounted anywhere.
Anyhow, sorry to put all these question in one post,
Thanks,
Rob
 
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