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Old 12-19-2009, 08:19 PM   #1
Stredrotor
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Default Stredrotor's RX4 Coupe * Project 20B *

Thought I'd start a thread on my 1974 RX4 hardtop.

I bought around 2 years ago after previously having a 13b turbo 1973 RX4 hardtop and an '86 Series 4 RX7 turbo over the last 15 years.
The car had a carby 13b and first gen RX7 5 speed, it ran well but I needed more power. I think of the RX4 as mazdas "muscle car" so it needed a engine with the muscle, hence a 20b

The RX4 as I bought it....





Striped and painted the crossmember and replaced tie rods, sway bar and bushes.


All installed!






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Old 12-19-2009, 08:24 PM   #2
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The next acquisition for the 20b project, a series 5 gearbox .


I got a awesome bargain the other day, a bloke at work tipped me off to some 16 inch F90 Simmons at a second hand shop. A bit of bargaining and these were mine for $140.


All 8 inches wide.

Picked up a Microtech LTX12, coils, loom and Eboost


Just got the engine in place to work out the engine and gearbox mounts

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Old 12-19-2009, 08:29 PM   #3
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For Fathers Day I asked for some kid free time to work on the Mazda, so I got around to doing the old shorten shifter housing mod......


Modified the gearbox cross member to suit the old RX4 one.....


Made some plates to mount the engine off and exhaust manifold flange ......




Now I just have to install the engine and box and fab the mounts off the suspension crossmember.
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Old 12-19-2009, 08:36 PM   #4
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Here's the prototype mounts
The engine and gearbox is mounted 50mm further back than the 13b to help with clearance at the front of the engine bay.




RH engine mount now finished



And test fitted.


Left hand mount completed, sits quite nice .




Should be strong enough :!:
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Old 12-19-2009, 09:12 PM   #5
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R/H side mount installed.....



...and L/H



Getting there



My latest purchase 60mm Tial waste gate and a GT42, ball bearing, water cooled A/R 1.06 exhaust. Now have to get in and make the exhaust manifold.

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Old 12-19-2009, 10:56 PM   #6
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WOW! What a project you have there. Looking forward to updates.
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Old 12-22-2009, 12:24 AM   #7
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Very nice fab work on the engine mounts, but how come you didn't throw a gusset or two on the inside of the L shape on them? Looks like there's plenty of space for a few gussets, though maybe that'd be overkill given the thickness of material used?

And a GT42?! Wowzers, how much power are you planning to make?

Last edited by Modified Dave; 12-22-2009 at 12:28 AM..
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Old 12-22-2009, 12:56 AM   #8
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Trans mount really needs some rubber thrown in somewhere, or it's liable to have massive vibration issues.
Otherwise, awesome project.
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Old 12-22-2009, 01:26 AM   #9
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Yea, it's now got a 10mm thick piece of rubber between the mount and gearbox bracket plus the crossmember is rubber mounted as well.
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Old 01-03-2010, 04:28 AM   #10
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A bit more forward progress.....

Got the pipe layout sorted, think it will flow ok





Just got to sort out the transition piece on top

Couldn't help myself and did a test fit in the engine bay





Now have to have a think on how I'll plumb the wastegate.
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Old 01-03-2010, 08:55 AM   #11
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This is a great build you have going here.
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Old 01-03-2010, 07:08 PM   #12
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Nice!!! keep up the good work!!
Cant wait for more updates!
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Old 01-11-2010, 10:55 PM   #13
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Great build i like whene people put new tec on old school car,hay ma keep up the great work nice looking rx4....
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Old 01-17-2010, 02:15 AM   #14
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Finally got a few days to make this manifold

Tacked manifold to 25mm plate to help stop distortion......


Welded and turbo bolted on.....


Fitted to engine to see how it fits.


Now to fit the wastegate pipe! .
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Old 01-17-2010, 03:28 AM   #15
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After a lot of thought decided to plumb the waste gate straight off the collector under the turbo.
I know it's probably not the best location for flow but there was really not enough room to run three separate runners.

Here's the pipe tacked up.......



...and test fitted in engine bay.



Pipe welded on and wastegate fitted




And bolted onto engine




Next is step is to send it off to get the mounting faces machined flat.
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