Stredrotor's RX4 Coupe * Project 20B *

Stredrotor · 12-19-2009, 09:19 PM

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!

Stredrotor · 12-19-2009, 09:24 PM

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

Stredrotor · 12-19-2009, 09:29 PM

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.

Stredrotor · 12-19-2009, 09:36 PM

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 :!:

Stredrotor · 12-19-2009, 10:12 PM

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.

Madaz · 12-19-2009, 11:56 PM

WOW! What a project you have there.

Looking forward to updates.

Modified Dave · 12-22-2009, 01:24 AM

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?

Rogue_Wulff · 12-22-2009, 01:56 AM

Trans mount really needs some rubber thrown in somewhere, or it's liable to have massive vibration issues.
Otherwise, awesome project.

Stredrotor · 12-22-2009, 02:26 AM

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.

Stredrotor · 01-03-2010, 05:28 AM

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.

85rx-7gsl-se · 01-03-2010, 09:55 AM

This is a great build you have going here.

estevan62274 · 01-03-2010, 08:08 PM

Nice!!! keep up the good work!!
Cant wait for more updates!

13bpower · 01-11-2010, 11:55 PM

Great build i like whene people put new tec on old school car,hay ma keep up the great work nice looking rx4....

Stredrotor · 01-17-2010, 03:15 AM

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! .

Stredrotor · 01-17-2010, 04:28 AM

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.

12-19-2009, 09:19 PM	#1
Stredrotor Rotary Fan in Training Join Date: Nov 2009 Location: Tasmania, Australia iTrader: (0) Posts: 53 Rep Power: 15	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!

12-22-2009, 01:24 AM	#7
Modified Dave The Newbie Join Date: Apr 2008 iTrader: (0) Posts: 17 Rep Power: 0	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 01:28 AM..

01-03-2010, 08:08 PM	#12
estevan62274 counting down till DGRR Join Date: Mar 2008 Location: Melbourne, Fl iTrader: (0) Posts: 358 Rep Power: 17	Nice!!! keep up the good work!! Cant wait for more updates! __________________ -74 RX-4 -84 REW GSL-SE Past rides -05 REW Swapped RX-8 -93 FD base

12-19-2009, 09:24 PM	#2
Stredrotor Rotary Fan in Training Join Date: Nov 2009 Location: Tasmania, Australia iTrader: (0) Posts: 53 Rep Power: 15	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

12-19-2009, 09:29 PM	#3
Stredrotor Rotary Fan in Training Join Date: Nov 2009 Location: Tasmania, Australia iTrader: (0) Posts: 53 Rep Power: 15	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.

12-19-2009, 09:36 PM	#4
Stredrotor Rotary Fan in Training Join Date: Nov 2009 Location: Tasmania, Australia iTrader: (0) Posts: 53 Rep Power: 15	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 :!:

12-19-2009, 10:12 PM	#5
Stredrotor Rotary Fan in Training Join Date: Nov 2009 Location: Tasmania, Australia iTrader: (0) Posts: 53 Rep Power: 15	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.

12-19-2009, 11:56 PM	#6
Madaz Rotary Fan in Training Join Date: Jan 2009 Location: Burleigh Heads QLD Australia iTrader: (0) Posts: 56 Rep Power: 16	WOW! What a project you have there. Looking forward to updates.

12-22-2009, 01:56 AM	#8
Rogue_Wulff Non Member Join Date: Jun 2008 iTrader: (0) Posts: 310 Rep Power: 17	Trans mount really needs some rubber thrown in somewhere, or it's liable to have massive vibration issues. Otherwise, awesome project.

12-22-2009, 02:26 AM	#9
Stredrotor Rotary Fan in Training Join Date: Nov 2009 Location: Tasmania, Australia iTrader: (0) Posts: 53 Rep Power: 15	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.

01-03-2010, 05:28 AM	#10
Stredrotor Rotary Fan in Training Join Date: Nov 2009 Location: Tasmania, Australia iTrader: (0) Posts: 53 Rep Power: 15	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.

01-11-2010, 11:55 PM	#13
13bpower Rotary Fan in Training Join Date: May 2008 Location: New hope mn iTrader: (0) Posts: 57 Rep Power: 17	Great build i like whene people put new tec on old school car,hay ma keep up the great work nice looking rx4....

01-17-2010, 03:15 AM	#14
Stredrotor Rotary Fan in Training Join Date: Nov 2009 Location: Tasmania, Australia iTrader: (0) Posts: 53 Rep Power: 15	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! .

01-17-2010, 04:28 AM	#15
Stredrotor Rotary Fan in Training Join Date: Nov 2009 Location: Tasmania, Australia iTrader: (0) Posts: 53 Rep Power: 15	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.