Sumo's RX3 Retro Racer

[rxsumo]

Now I've had a chance to get the car out of the garage, and get some photos, it's time for its own page.

This is how the car looks now.

I've just spent last weekend reinstalling the close ratio gearbox, race diff, and the fast steering box.

The car was also missing the centre dash console, along with the factory guage set, so a new one of these arrived in from the States early last week.

So this weekend was to restall the dash centre, the factory gauges, and the additional guages, the heater controls and get the centre console in. I also had to get the decals on.

So the interior looks like this now, a vast improvement on the gaping hole

SO the car is a 1972 Mazda RX3 Coupe, that has spent the last 15 or 20 years as pretty much a dedicated road legal race car.

When I first encountered the car, it was owned by some members of MREC Tauranga, and was running a 13B J Port, and was a class winning car at Taupo at the time. It eventually found its way to Wellington, and was repowered with a 13B Turbo, and the usual Supra box. The previous owner had acquired it as a rolling shell, and had decided to go 10A PP.

So the specs....

Driveline:

10PP running around 180hp.

Mazda factory 4 speed close ratio gearbox.

Mazda factory 4.9 competition diff, with a Mazdaspeed race spec LSD.

Suspension:

Front is coilovers, with Koni adjustable shocks, and Knightsports Camber adjusters.

Wilwood 4 spot calipers, with Wilwood rotors

Mazda Factory race steering box - 2 turns lock to lock

Rear is cart springs with lowering blocks, and as per Group 2, two forward control arms

Brakes are series 2 RX7 - adapted to fit the RX3 handbrake setup - pretty much like the Group 2 setup

Mazda 626 RWD swaybar

Body

At the moment

Savanna lower nose cone

Aftermarket Fender flares

Savanna rear bumper

Savanna Geniune accessory Bobtail

Savanna GSII rear quarter badges.

Body parts at hand....

Savanna Race two piece front Splitter

Savanna Race single piece front Splitter

Savanna Race rear blade spoiler

Savanna Race Group 2 Fender Flares

The plan.....

I want the car to run either of the two Race fronts, and probably the two piece front spoiler. I'll also have another boot lid done so we can set either the blade or the bob tail. I need to get some molds taken of the fender flares, and then they will go on the car, as well has having the guards chopped out. Then we will look for some 9 or 10 inch wide rims for the car. At the moment I'd like a set of 15 x 10 Watanabes, although depending on price I might also look at the similar Panasport 2 piece rims.

The idea is to keep it as a period race car kept pretty close to the Group 2 specs. Ultimately the car will probably end up with a 12A PP, as that is pretty much how the Japanese cars run in the day. The only real difference is the period Japanese cars ran a gutted interior, no bumpers, no headlights and a megaphone exhaust.

So we have a few tidyup items to do before its first outing in a couple of weeks.

Finish off tidying up the dash wiring

Fix a leaking radiator overflow pipe

Replace the Fire Extinguisher

Gets some numbers made up for the car

Get some towing eye decals

Time the engine, as its a little retarded at the moment.

Discussion Link

[rxsumo]

It survived its first outing at Manfeild - just!

I managed to run a best time of 1:27:24, which is rather slow for the car, but we were having issues with a major misfire in 3rd and 4th gears, which meant I was off power for most of the straights.

See it did get to the track...

I managed to lose the air cleaner on the second to last run, probably due to the misfire vibration.

But had an awesome day, the car has a really good balance, really good tractability, and is really nicely setup. When we had power (in 1st and 2nd gears), the car was magic.

So the to do list.....

New Air Cleaner (and probably a cold air box)

Upgrade the fuel system (my PP guru reckons I'm running too smaller fuel line)

Get the tail lights painted, the correct candy apple red

Rebuild the oil cooler mounts, on Saturday morning when doing the timing I spotted the oil cooler floating, so patched it up for the weekend.

Get the car WOFed, and registered, once I get the Motorsport Authority Card back from MNZ

Work out why the fuel gauge doent work

Get a new battery

Build some brake ducts for the front

[rxsumo]

Some more bits arrived this week...

A brand new ignition assembly from my friendly Mazda dealer

The old ignition was a little shagged, and the key wouldn't stay put in the hole

And it has geniune Mazda keys

I had a Paddy Hopkirk steering wheel, which is actually a Motolita, which came off an old BMW, that I wrecked, as the wheel was fitted to the BMW in 1974, its got to be the right period piece for the car.

I managed to score a fitting kit for it off Ebay, which also showed up.

[rxsumo]

Been a little busy over the last couple of weeks, mainly wiring and cosmetic sort of work.

Found it had 12A headlight buckets, which is why the car looked a little crossed eyed, so now it has 10A ones back in so the headlights fit in the correct position in the headlight bezels.

The car now has a WOF, and is registered, so now we should be able to road test the car, to see if we have got rid of the fueling issues.

The fuel system is now sorted - hopefully.

The fuel lines already had 3/8 lines, but heaps of potential restrictions, fuel filter...the fuel lines were using the original position, so the lines came out of the pump and immediately went up, and it was a little messy around the banjo.

The fuel pressure was too high for the IDA...set for 7psi instead of 3 psi

So now there is 1/2 inch feeders from the tank to the filter and to the pump, it then drops to 3/8 to the carbie, we have removed the return lines, and now fitted a pressure guage.

So the boot plumbing looks a little nicer now

And the slightly tider engine bay...

I've fitted the carbon fibre air box, its a little modern, but it came with the car - so the price was right , and I can get a cold air feeder to the carbie via the headlight pods

The Paddy Hopkirk wheel fitted, with the correct screws and trim ring

[rxsumo]

Its been a few weeks since the last update, and the car has had its second outing at the track, and its now got a best time of 1:25.18, so we have taken 2 seconds off the lap times, and hopefully more to come.

Since the last update I've really been focusing on getting the engine running right, although we have done a couple of the small tidyup tasks.

I managed to score another "correct" white rim early grille off one of the fellow Mazda sprint competitors, so the car now has a grille with the grille emblem mounted.

The leaking RHS wheel bearing seal has been replaced.

Also repacked the rear muffler, which was virtually empty, which has quietened the car down heaps.

I've spent hours trying to sort out the misfire issue, which didnt go away after the reworking of the fuel delivery system.

So after chasing a over pressure - and subsequent carb flooding issue, and replacing the fuel pump and regulator, and the needle valve in the carbie, we have learnt something......

Holley fuel pressure regulators must have fuel being sourced from a straight pipe.....no elbows on the inlet, otherwise they dont work....

Anyway we got to the track, and after all the work on the fuel system, the misfire was still there.

Time to back the timing off, we eventually got the car running cleanish, but the timing marks are way off "normal", which leads me to suspect that the dissy might be one tooth out, or some other timing issue, potentially created with the conversion from twin to single dissy.

With the timing that far advanced, I suspect we have been lucky that we havent detonated the engine.

Anyways its on the dyno this week - hopefully to sort out all the isses for once and all.

Got some in car camera stuff for anybody that wants to go for a ride in the passengers seat at the track.

The sound quality is crap....like some of my lines....but here you go.....

Practice

Run 1

Run 2 - got the quick time on the 3rd lap

Run 3

Run 5 - wet

[rxsumo]

Some pictures from the Sportimages website...

[rxsumo]

It been a quiet few weeks on the car front, as the RX3 isnt living at home right now.....

A couple of longish dyno sessions, including one with a engine analyser, and finally a break through on the engine miss problem.

The good news is the we think we now know was is causing the high rpm misfire, the bad news is that the engine is now in pieces.

In the first dyno session, the guys sorted the fueling, and got close to the correct timing, but ran out of time to look at the misfire, and at that stage they didnt have access to the engine analyser to see what was actually happening with all of the electrics.

Its had assumed that the engine state was okay, as while the engine had been built for 7 years, it hadnt done a lot of kms, and had been built by a top NZ rotary engine builder, who specialised in old school PP engines.

Between the dyno sessions, the compressions were checked and there was quite a difference in front to rear compression pressures, however the variance between the pulses on a per rotor basis were within Mazda tolerances.

We hooked into the second dyno session on Tuesday, and after a couple of hours of diagnostics including swappng the distributor and igniters, and the coils, it was concluded that the electrics werent the cause of our issue, so it was something else.

We did a couple of runs just observing the engine, while the misfire occurred, and it became apparent with the exhaust header colours while running up, that the rear rotor was lazy. So the air cleaner was removed and the main jets checked, and swapped front to rear, and the engine run up again. At that stage we saw that there was a huge fuel standoff on the rear rotor when the misfire occurred, at that stage the issue was isolated to a mechanical problem.

There was only likely to be two possible reasons for the standoff, blocked/bad exhaust, or internal engine issue.

So we dropped the exhaust off the headers and run it up again....and that run was interesting....it was unbelievably loud, and the HP was halved, so from a high of 150hp at 7000, it was around 80, the fuel standoff reduced somewhat, but the misfire was still there.

So now there was only one possible outcome....engine out.

We pulled the motor down yesterday, and think we have nailed the rear rotor issue. One of the apex seals, was extremely tight, and wouldnt move freely throughout its full movement range. We also found that there were excessive side seal to corner seal clearances on both sides of the rotor, so that probably wasnt helping the overall compression pressures.

[rxsumo]

Its been a while between updates, the motor finally went back in the car a couple of weekends ago, and its first outing again was on Sunday last.

The issues list from the engine was quite extensive..

Sticky Apex seal - rear rotor

Side Seals cut too short - rear rotor

Rotor Bearing Clearances to tight - both rotors

Rotor Stationary Gear moved out of position creating zero rotor to end plate clearance - front rotor

Oil Pump drive chain not aligned

We managed to get the laptimes down to a 1:23, and then down to a PB of 1:22.43 when I reattached the rear rollbar.

Heres some video of the last run, all but the last lap clocking 1:22s - enjoy

http://s13.photobucket.com/albums/a273/rxsumo/RX3%20Racer/?action=view&current=SeptFinal_zpse3517099.mp4

Heres a inside cockpit view of the practice session (I had a bit of a lose with the GOPRO - too smaller SD card...so only got practice captured). The flying laps were 1:24s, and you can see I was struggling a bit with understeer, that improved in the later sessions once the rear bar was attached. The sound is a little better than with the rollcage camera, still work in progress. FYI, the changeup light is set at 9500 rpm.

[rxsumo]

Its been awhile between updates - had a work thing going on, so the car hasnt been touched.

The last outing was pretty cool as it showed what potential the car has, now that the motor has been sorted.

There are some images of the RX3 on the Sportimages website

http://racepics.biz/gallery/main.php?g2_itemId=340273&g2_page=10

So now its time to sort out some of the niggly little things....

Both the front lower ball joints need replacing

Fit the anti-drive blocks in the front- apparently this will sort out the remaining understeer

Find some cold air ducting for the air cleaner

Replace the RR wheel bearing - the retainer has some pitting which is causing an oil leak.

Solder the starter motor pig tail wire onto the starter motor

Replace a drippy oil coller line

Long term plans are....

Rework the oil cooler into the factory race postion, and replace the Savanna lower nose cone with the period splitter

Redo the seat mounts

Find some "teacup" tail lights, and fit rear indicator lens

Rework the throttle cable

Rework the bonnet release cable

Fit the factory flares, and then go to 15 x 8 rims - Watanabes?

[Guest rxsumo]

Update time again..

The car has run okay up to the last event just before XMAS, and I havent done too much since then.

Just before the December event, I swapped to the spare C/R box, as I was having issue down changing into first. This wouldnt be too much of a problem for normal road cars, but with the PP and the C/R box, I use first out of most corners - so having a crunching gearbox wasnt much fun.

The car has shown quite a good turn of speed, and we ended up second in class for the year

Heres a Utube shot of one of the runs in December - while the focus is on the Black Pulsar, you can see the 3 going through the field. The last lap is quite hard case with the front left wheel well and truly in the air coming through the esses

I've fitted the caster blocks a couple of weekends ago, and I've taken it out for a drive just to make sure everything is still attached.

Spent today replacing the rear wheel bearing, and hopefully getting rid of the oil leak from that side of the axle.

The other little mission was a pure cosmetic one.

One thing that has nagged me was the front number plate mount - it consisted of long screws with a double nut arrangement, that meant the number plate didnt sit in the "right" position, and the screws kept loosening. The correct mounting plates are like rocking horse poo, however I managed to find a set in the UK off ebay, so now the number plate sites correctly.

Ugly arrangement - number plate too low on the bumper

The new mounts - a quick paint to stop them rusting, however at some stage I get them cad plated

Without the number plate

All finished - and a little better airflow to the oil cooler

Next issue to be sorted is the rear shocks, I've been noticing a thump from the right rear, and had a look at the rear shocks, with the lowered springs and lowering blocks - the shocks dont have enough compression length and appear to be bottoming out - so a new set of shocks will be on the shopping list.

Next up is racing next weekend - 1st round of the new season

[rxsumo]

Well the first round didnt go so well

The good news...

I ran another 1:22

I managed to complete 1 run, although the last lap was slow so that I ended up in second place in class for the round

However the bad news.....

Engine broken again - albeit my fault - I now know that running the oil below half on the dip stick will result in oil surge issues.

So at the moment - its broken apex seals on the front rotor, probably due to running (and spinning) the rotor bearings, and some damage to the crank - although this might be recoverable. There is also wear on the end plates.

So hopefully will have the engine back together in the next couple of weeks ready for the next round at the end of next month.

[rxsumo]

The car is back together - now all I've got to do is run the motor in before next weekend.

 

Looks like it was running too lower oil level, caused the oil pressure to surge.

We are guessing that the bearing locked momentarily on the crank - caused the rotor to move around and it broke the apex seals....

 

The damage...

Not so fine apex seals

These aint fancy multi piece seals...

 

And the bearing...

These early rotor bearings are located by a grub screw....unlike the modern bearings which have a punched tab.

When the bearing spun - it causes the grub screw to distort the bearing  - which in turn locks the bearing to the crank

 

The bearing spun for nearly 360 degrees

 

And eventually ground down the grub screw

 

Lesson learnt - dont let the oil level fall below the full mark.....

[rxsumo]

The car went pretty good over the weekend - no dramas apart from the understeer issues - that got parked while the priority was getting the engine back together.

The weather was pretty iffy with a damp track in the early sessions and high wind in the latter sessions - so only 1:24s

 

Heres a clip taken from the front of a Lotus I was out with - I think this was our second run, I managed to get passed it coming into Coke on the last lap (not the cool down lap - as the comments say) interesting to see the RX3 from a rear perspective - certainly dance around lots in the corners

[rxsumo]

Update time - and more tails of woe.

The weekend after we got back from Japan - it was time for the Intermarque sprints again, dug the car out of the garage after its 6 week rest.

The Intermarque went okay - albeit slow lap times, as the track was wet to start, and then just slippery, before the rain settled about 1:00pm, and I called it quites.

Last weekend was the last round of the Road and Track series, so I thought I'd take the car out for a run.

Things got off to a bad start, when I had coolant flowing over the bonnet during the practise run (due to me, not putting the radiator cap on properly), but got a whole lot worst when the car dropped the front rotor again.

 

One of the apex seals, and its spring wasnt to be found in the engine, along with a broken corner seal, and a broken side seal (suspect this was caused by the seal getting stuck in the corner seal - that wasnt located because of the missing apex seal)

 

We are guessing this might be the culprit....

One of these plugs aint like the other one.....

 

So either the tip coming away has smashed the apex seal, or detonation caused by the plug misfiring (or not firing), has taken its toil.

 

So at this stage, I think the 10A will be rebuild to see the season out, but I'm seeing a 12A in this cars future.

My spares pool of NOS 10A parts is getting severely depleted, with the builds, and I dont want to be in a position of not havings new parts for the Cosmo Sport, so its time for a change in direction....

[rxsumo]

Well the engine is back in the car again.

The damage wasnt limited to the rotor external bits mentioned above, the engine also destroyed the Rotor Gear locating roll pins, and they were a bastard to get out. It got to having to have some of them removed by spark erosion, and then it took a day to get the new ones in.

The motor still didnt want to play ball, as once in the car, it decided to leak oil from the rear stationary gear o-rings, as well as mis-firing through the mid range - on brand new NGK plugs.

 

So we ripped the gearbox out and sorted the rear seals, stripped and blew out the carbie, still had a mis-fire through the mid-range.

We found some old used plugs lying around the workshop....and this improved the mis-fire.

 

Over last weekend I fitted another set of fresh plugs....and all the issues disappeared.

 

On the cosmetic front - I landed a set of the "proper" Savanna GS-II/GT bonnet vents for the car

[rxsumo]

Oh - and I've brought a 12A PP - so the old gal might be a little more reliable once fitted, with more HP to boot

[rxsumo]

Its been a pretty sombre affair of the last month or so.

After rebuilding the motor again - at the last outing, we didnt even get practice out of the way before something let go. Suspect its something on the side of the front rotor this time - as the engine went very smoky, was fouling plugs, and blowing oil out of the catch bottle - however the apex seals are intact this time.

 

Enough is enough, so the 10A is going to be gone from the engine bay shortly.

 

With having our overseas holiday earlier in the year, and breaking a few engines, its time to ease up a little and let the finances recover.

 

We have a few things to sort out prior to the 12A going into the hole.

I need to sort out an exhaust - mainly headers, get some new clutch discs for the Tilton twin plate - the 12A has a brand new flywheel, with a Titon twin plate setup, but the plates are setup for the larger splined FD gearbox, and some of the minor ancillaries - like water pump.

One otehr thing to sort out was the needle valve in the carbie. Apparently the 12A will empty the IDA fuel bowl on the dyno at high RPMs - and the standard "big" 3mm needle valve was the issue, and the needle valve had been drilled to at least 4mm to resolve the issue. The exercise in drilling the needle valve sounded a little iffy to me - and I knew that Gene Berg did modified valves - so this is also on the to buy list.

So we have ordered

- a new set of Headers in from Racing Beat in the states

- some 4 mm "racing" needle valves for the IDA from Gene Berg in the states

- next on the list is the new clutch discs

 

 

In the meantime - I decided it was time to sort out the engine bay wiring loom - that had been seriously monkeyed with over time, along with the main battery feeder.

The previous setup had no inline fusing - the old fusible link was still installed, but was included almost as almost a secondary power circuit - so effectively was useless

So we have a nice new maxi blade fuse setup on the battery feeder

The old battery kill solenoid has also been removed - as this would drain the battery if left on - as well as the battery terminals were exposed - not good!

 

Hopefully some more photos later.....

[rxsumo]

A parcel finally arrived from the States - but only after giving the NZ Customs Service a donation....

Anyway nice shiny bits

 

Racing Beat 12A race header - for a pre RX7 12A, as well as some extra flange plates just in case we decide to rebuild the centre section of the exhaust at some stage

[rxsumo]

Not to much to add at this stage.

The 10A is out, and we are prep'ing the 12A to go into the hole.

The clutch packs have arrived - but when we came to mate the motor up - we worked out that we had a late model flywheel - doh

So now we have another shiny thing to go on the car....

 

 

Shot over to Brissy on the weekend to pickup my radiator - more shiny bits - at 2/3 of the price that the NZ agent wanted for unit

 

 

While we were over there, decided it might be time to visit Phil's Rotarys and pickup a set of his replica "tea cup" tail lights - so I can get the true early Savanna GT look

 

[rxsumo]

Well its been a frustrating few weeks - after the drama with getting the right clutch - and the right sized flywheel - nothing much else could go wrong - right?

So we went to install the engine again - and the bell-housing was wrong - the single dizzy engines run a different stud pattern to the twin dizzy engines.

 

I tracked down a suitable bell housing - so we were all go - except as the bell housing was unknown - I thought it would be a good idea to replace the gearbox input shaft seal - so order a new one down.

The flywheel was still away getting balanced - so we took the opportunity to get the motor in the hole and rebuild the front part of the exhaust to match up with the 12A headers.

 

The seal arrived - went to fit it - groundhog day - the seal was too small for the bellhousing - WTF. It would seem that a previous owner had machined the seal to take a 44mm seal rather than the factory 38mm - and the shaft size was too big as well - so down to the seal shop to see what we could source - time to order a seal - as none in stock.

 

So last weekend was spent fabricating rather than getting the engine fully installed.....

So the 12A air cleaner has been modified for the RX3 - the carbie sits back further - so the air cleaner was hitting the brake fluid reservoir . We have to use the 12A assembly, as the Carbon Fibre one from the hits the bonnet - as the inlet manifold is taller.

The water pump housing was welded up - to remove the bypass around the thermostat - standard RX race modification - and a excess water line removed

The radiator had its heater feeder welded in - PWR had supplied an non heater unit - but shipped over the feeder pipe - top service from them.

The intake manifold needed a vacuum take off welded on for the brake booster.

 

Some Pictures...

Relocated Oil Cooler

 

Tea Cups fitted

 

 

So now we hurry up and wait for the flywheel to come back from the balancers, and the seal to arrive in.......