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Andrew NZ
Joined: 22 Jun 2004 Posts: 744 Location: New Zealand
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Posted: Wed Nov 28, 2007 7:02 pm Post subject: Project RX924 begins! |
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Hi Guys,
My apologies to the purists, but it's time to do something I've wanted to do for a long time - install a 12a bridgeport
So far it's looking quite promising, with the 924 clutch disking fitting perfectly with the RX7 pressure plate and flywheel, and the 924 spindle being exactly the right diameter for the Mazda spigot bearing.
Other than making a bellhousing, the only other major is going to be modifying the crossmember, which is going to need a lot of altering to allow the engine to fit, unless I shorten the torque tube about 100mm to allow the engine to sit just behind the cross member.
I'll keep you all informed of the progress as it happens, but it's probably going to be a long term project!! _________________ Andrew
1977 RX924 race car
12a bridgeport supercharged
www.race4-dcup.co.nz
Last edited by Andrew NZ on Sun Oct 10, 2010 5:46 pm; edited 2 times in total |
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v8carreragts
Joined: 05 Sep 2003 Posts: 665 Location: Tucson, AZ
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Posted: Thu Nov 29, 2007 4:53 am Post subject: |
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Sounds like a cool project. I thought about this swap in the past but since I don't know much about rotarys, I didn't try it. They can be modified to make a lot of power and they rev high.
The only thing that I know about rotary swaps is they are hard to cool. This just means that you need a big radiator. |
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Rasta Monsta
Joined: 12 Jul 2006 Posts: 11724 Location: PacNW
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Posted: Thu Nov 29, 2007 5:43 am Post subject: |
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Why not a 13B? My buddy had one in a first gen RX7, and all he did was put a header and a Holly on it, and god was it fast. You could also watch the gas gauge drop every time he floored it. . .it got about 5 MPG when driven hard.
rasta _________________ Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Rich H
Joined: 10 Jun 2007 Posts: 2665 Location: Preston, Lancs, UK
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Posted: Thu Nov 29, 2007 6:54 am Post subject: |
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Rotary weight
Rotary power
Rotary economy _________________ 1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec |
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Andrew NZ
Joined: 22 Jun 2004 Posts: 744 Location: New Zealand
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Posted: Thu Nov 29, 2007 7:09 am Post subject: |
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v8carreragts wrote: | Sounds like a cool project. I thought about this swap in the past but since I don't know much about rotarys, I didn't try it. They can be modified to make a lot of power and they rev high.
The only thing that I know about rotary swaps is they are hard to cool. This just means that you need a big radiator. |
I've already got a bigger radiator, so shouldn't be too much of an issue as it's bigger than an RX7 radiator. _________________ Andrew
1977 RX924 race car
12a bridgeport supercharged
www.race4-dcup.co.nz |
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Andrew NZ
Joined: 22 Jun 2004 Posts: 744 Location: New Zealand
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Posted: Thu Nov 29, 2007 7:15 am Post subject: |
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Rasta Monsta wrote: | Why not a 13B? My buddy had one in a first gen RX7, and all he did was put a header and a Holly on it, and god was it fast. You could also watch the gas gauge drop every time he floored it. . .it got about 5 MPG when driven hard.
rasta |
Two reasons - There's a big weight penalty for a 13B in the race class I'm going in, and the 13b's are 20mm longer, which will make the crossmember even harder to mod!
Because the engine angle and centerline are limited in a 924 by the torque tube, I can't sit the engine on top of the normal crossmember. With a rotary the eccentric shaft runs through the middle of the engine, not near the bottom like a piston engine.
I've had 5 RX7's, 1 RX5 and 2 RX2s, so I know all about the fuel usage!! _________________ Andrew
1977 RX924 race car
12a bridgeport supercharged
www.race4-dcup.co.nz |
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Peter_in_AU
Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia
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Posted: Thu Nov 29, 2007 9:40 am Post subject: |
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Make sure you take lots of big, clear pics. _________________ 1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)
Learn to love your multimeter and may the search be with you |
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Andrew NZ
Joined: 22 Jun 2004 Posts: 744 Location: New Zealand
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Posted: Thu Nov 29, 2007 10:36 am Post subject: |
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Peter_in_AU wrote: | Make sure you take lots of big, clear pics. |
Will do! _________________ Andrew
1977 RX924 race car
12a bridgeport supercharged
www.race4-dcup.co.nz |
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Petrovich
Joined: 27 Sep 2005 Posts: 235 Location: Rockville, MD
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Posted: Sat Dec 01, 2007 4:55 am Post subject: |
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Is the crossmember clearance problem due to oil pan, or the actual engine block?
IMO rotary is a great swap motor for 924. Light, small, exhaust on the same side - just let us know how you do the bellhousing, that's the hardest part, pretty much. _________________ 1982 924 Turbo, now Lemon |
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Andrew NZ
Joined: 22 Jun 2004 Posts: 744 Location: New Zealand
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Posted: Sat Dec 01, 2007 5:39 am Post subject: |
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Petrovich wrote: | Is the crossmember clearance problem due to oil pan, or the actual engine block?
IMO rotary is a great swap motor for 924. Light, small, exhaust on the same side - just let us know how you do the bellhousing, that's the hardest part, pretty much. |
The crossmember clearance is mainly due the engine housings rather than the sump.
The bellhousing looks pretty straight forward, I have a S1 RX7 bellhousing ready to cut about, and the spacing back to where it needs to bolt to the torque tube is identical to thye 924 (150mm). The hardest bit I can see now is going to be changing to a hydraulic clutch.
I have an engineer freind coming around tommorrow to look at the bellhousing for me, so I'll let you know. _________________ Andrew
1977 RX924 race car
12a bridgeport supercharged
www.race4-dcup.co.nz |
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endwrench
Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana
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Posted: Sat Dec 01, 2007 7:33 am Post subject: |
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This is going to be great project to follow! Mostly because I know your not "all talk". You get shit done Plus, you don't have a bottomless bank account so we're bound to see some pretty good "ingenuity"
Todd _________________ '79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!.... |
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Petrovich
Joined: 27 Sep 2005 Posts: 235 Location: Rockville, MD
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Posted: Sat Dec 01, 2007 7:58 am Post subject: |
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Have you considered making the engine a stressed chassis member? Bascially, remove crossmember and install short bars on both sides that will make your entire engine your new crossmember. I'm probably talking out of my ass because I never looked at the crossmember all that much, but it got me thinking now.
I wonder how easy it is to convert to a 944/931 master cylinder, and whether it will work fine with 7's slave. Would be something I'd investigate first. _________________ 1982 924 Turbo, now Lemon |
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jamez
Joined: 03 Nov 2002 Posts: 401 Location: Chehalis, Wa
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Posted: Sat Dec 01, 2007 8:28 am Post subject: |
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The stressed chassis member is an awesome idea, I wish I would have thought about that when I did my conversion, the motor could sit alot lower.
edit : the only problem I see with this is the steering rack. But a new steering rack mount could be made and the engine would still be able to be a few inches lower than if the cross member where there. |
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v8carreragts
Joined: 05 Sep 2003 Posts: 665 Location: Tucson, AZ
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Posted: Sat Dec 01, 2007 1:46 pm Post subject: |
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It's not that difficult to convert an early car to a hydraulic clutch. I did it on an early 77. You need the hydraulic clutch pedal, the clutch master cylinder, push rod and associated hardware along with a flexible hose to connect to the slave cylinder and the brake resevoir from a 924t or 944 (it has the connection for the master cylinder feed). In my case, I used all 924 turbo parts.
You will need a chassis punch to punch the hole, I think it is 1" diameter. The left front wheel well needs a little dinning with a hammer to make clearance for the front end of the master cylinder. You will need to drill two holes for the master cylinder attaching bolts. And a VERY important thing is you will need to make a backing plate for the master cylinder to distribute the load from the pedal. Trust me, you need it. Mine worked for a few months until the master cylinder pushed through the firewall. Then I made a 16 ga. plate and welded two bolts onto it (for the master mounting) and put it behind the firewall. Starting sometime in 1979 this area had an added piece of sheet metal spot welded in for this purpose. Then you just swap the pedals and mount everything.
After I added the plate, I drove that car every day for about 8 years without any problems. I did this so I could put a 944 transaxle in the car. On my 79, I just used a late Mustang disk in the 924 n/a clutch to fit the 944 transaxle. On the 79, everything was in place for the hydraulic clutch except for the two mounting studs for the master cylinder. This included the mount for the spring and nylon bearing that helps reduce the force of the pedal. You really don't need the spring. I didn't use it on my 77 and never had any problems. |
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jamez
Joined: 03 Nov 2002 Posts: 401 Location: Chehalis, Wa
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Posted: Sat Dec 01, 2007 2:42 pm Post subject: |
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v8carreragts
I did the same with the backplate for the master cylinder on a '77 924. I used a cylinder from a corvette. |
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