Jeff20B

iTrader: (13)

Check out how thin this thing is!

'84-12A-GSL

....Decent....

Jeff20B

iTrader: (13)

The flywheel only weighs 8 pounds! That would be 11 pounds with the rear counterweight. That's less than this aluminum one, which is friggin aluminum! https://www.rx7club.com/showthread.php?t=700854 Aluminum actually weighs more! lol

Man, I thought the MG had quick acceleration before with the 13 pound RB light steel flywheel. Maybe I should rephrase that. Man, I thought the MG was scary before with the 13 pound RB light steel flywheel. I think I will be pleasantly disturbed.

I only have an idea of how the car will behave with this flywheel as there is an identical super light steel in the white '83 GSL, and it performed exceptionally well. PercentSevenC and I were impressed and really enjoyed the driveability. It made the '74 ported 12A really come alive in the 1st gen chassis. The MG is a smaller car with a bigger engine (same porting).

Jeff20B

iTrader: (13)

Oh and I forgot to mention I weighed a few other parts too. The previous pressure plate was 10 pounds but the one I put on the super light flywheel weighs 9.5 approximately. It looks and feels lighter as well. I wonder if bucking will be an issue with so little rotating weight?

RB light steel flywheel: 13
super light steel: 8
"heavy" pressure plate: 10
normal pressure plate: 9.5
stock 215mm disc: 2.5
RB HD 215mm disc: 2.5

PercentSevenC

Geez, it's only 8 lbs.? Lol, no wonder the '83 GSL revs so quick. It does require a bit of a light touch on the clutch, but no worse than the GLC with its short pedal travel and tall-geared rear end. But it doesn't really buck at all with that nice Nikki carb. Just get the Hitachi tuned right and the MG should be very pleasant to drive, too.

'84-12A-GSL

Will these light components affect the red line at all?

Jeff20B

iTrader: (13)

I doubt it.

rxtasy3

iTrader: (2)

it affects red line in a big way. it comes up really quick.

John SPL 311

It would be interesting to see the two cars together. Oh yes it does move on.

sla90lx

Hi Jeff, I'm new to the site. My name is Chris and this is my very first post. I have a 74 midget and would love to become rotarded myself. I would like to ask all kinds of questions about your car but I don't mean to steal this thread. Should I start another one or maybe pm you? Thanks, Chris

Jeff20B

iTrader: (13)

Welcome. Start another thread.

Just so you know, my car had a twin dizzy engine in it when I got it so I didn't do the actual rotary conversion. All I did was modify mine to accept a '74 13B and tranny. I don't have first hand knowledge of what must be cut and removed in order to fit a rotary into a Midget.

If you have the will, there is a way. That's all I know.

'84-12A-GSL

Bahah!

I was thinking it might lower it slightly.

68midget

I have the same project.

Just wondering how it went for you and what the update might be.

I'm doing the rear end swap now, painting the car and perhaps adding a turbo.

Let me know your thoughts, I would love some advice on this!

Jeff20B

iTrader: (13)

Yay for the rotarded MG owners amoung us. Don't know of any advice other than you will not need a turbo. And whatever you do, it's best if it all fits under the hood.

Here's an update. I decided to switch engines. Now it's got an Atkins built 4 port 13B with GSL-SE housings, Y plates, ported really far apparently (they look big from the outside), '86 NA rotating assembly, regular Racing Beat light steel flywheel (to help offset the weak low end torque of this ported monster), stock clutch disc and pressure plate (it's a light car) but with short pedal travel so it feels ok, upgrading the current tiny 2" or 1 7/8" exhaust to 2.5" with Maganflow components, and finally topping it off with a Holley 600.

If the carb is tuned right, on this port size and exhaust size, it might make 170 peak HP at like 8k. Maybe. It's been a while since I worked out all the numbers. Frankly I don't really care what it makes as lomg as the 2.5" exhaust flows enough so it doesn't run the carb out of breath, which has been the problem in other vehicles. All these parts were available and the engine is well broken in compared to the other one you see pictured earlier in this thread, which was a fresh rebuild and more liley to run hot and cause other problems, so I pulled it and threw this in. Just gotta make a carb adapter to keep the carb low enough so the air cleaner sits under the hood on a stock high flowing '76 reverse runner manifold. 1/2" should do it.

Do I really need this type of engine in this car? Of course not. But it will be fun to give it a try. If I doesn't work out I've got a decent '74 ported Y plate engine in mind to try next. Gotta get a bunch of other engines built and running first. Helping a fellow forum member with a turbo install as I type this so I gotta get back to it.

Jeff20B

iTrader: (13)

Another update: New engine! 4 port 13B. Is there really any other choice? When I'm involved?

The lightest Y plates I could find, ported to about 55 degrees so half way between 74 spec and RB streetport size.

Exhaust ports open at T2 spec and close just a few degrees shy. Remember these are old school housings with the MAZDA font so any porting at all is practically a miracle.

RB's aluminum flywheel with a stock 225mm disc and pressure plate which is way more clutch than needed, but it will last longer than a 215mm by a little bit, which is good because you have to pull the engine to change the clutch... And I had these parts collecting dust. Hopefully they'll have enough mass to be a good driver. I could have gone with a light steel flywheel instead...

Speaking of lightness, the rotating assembly is S4 NA. Probably not a bad choice. Again hoping it drives well. As for adding lightness, I did the aluminum on aluminum waterpump mod. Also a lightened dizzy drive gear from an FD (seen below - upper right corner) and a drilled oil pump sprocket (not seen).

Intake is a 76 reverse runner manifold with carb adaptor plate. RB prepped Holley 600. I don't need a carb this big in this car, but I tested it on a 74 ported engine already, and it worked ok. It technically was prepped for the RB 60 degree streetport templates, but worked ok on 74 spec so I'm sure it'll work great on my 55 degree port job. Also low end and idle will be better too.

A Holley is a shorter carb than a Hitachi and lots shorter than a Nikki. I do have a weber DCOE, but the Holley, even with an adaptor plate, is still shorter than a Hitachi, so I can use an air filter. A good idea. Plus the weber needs to go on an S4 NA engine where the 6 port stuff will actually be of some benefit to a carb like that.

Still to do: long primary exhaust and a fuel pump swap. The fuel pump is an ancient facet which I regard as junk. Why did RB? Oh I guess options were pretty limited back in the 80s. It'll get a modern Mr Gasket Co which is basically the same footprint so it should fit. I'd like to do a Carter, but no room.

The exhaust will have some RB presilencers and should be about 80 to 90 inches long before collecting to 2.5". Can I fit that much under a tiny car like this? I don't know.

Don't mind the strange things in the picture. This is the only pic I have of the engine at the moment. Ford blue and aluminum engine paint combo. Looks nice. I'll get pics up later after some more work has been done. For now I'm busy on other stuff. Someone asked so that's why I updated this thread with what I could. And don't ask about the dual chain thing. I didn't use it.

Jeff20B

iTrader: (13)

Just an update. The RB presilencers have been freed from what the PO did to them - he welded on a set of flanges and didn't use gaskets. I had to cut through the welds while trying not to disturb the gasket surface. Then I decided that was taking too long and opted to weld them in their new home with just straight pipes instead of flange as flanges would take longer to do and weigh more with zero benefit during install/removal due to using an RB dual pipe flange up front. Plus they'd be more likely to leak with four gaskets (one on each side of each presilencer).


Also I found these pics of the lightened dizzy drive gear and oil pump sprocket. Cool, huh?

banzaitoyota

Looking good

Bugeye RX

Looks great Jeff and glad to see the Midget getting some luv.

cfamilyfix

iTrader: (15)

good stuff

Rotary-MG

iTrader: (1)

Hi Jeff,
I decided last month to lose the stock injection system for my '84 6-port 13B. Although it was working fine when I pulled it from the donor car, I found out while dismantling it that some of the plastic connections had deteriorated. Even if I got it running again with the EGI, it would have had numerous issues eventually.

Now that I'm shopping for a carb set up, I thought that you'd be the man to ask about hood clearances.

Just a little reminder:
65' MG Midget (wire wheel / square rear arch)
84' 6-port 13B (stockport)

I going to buy the carb setup new. But I'm wondering if any of the available types may have hood clearance issues. I have already relieved the passenger side box to make clearance for the lower intake manifold.

I'm currently looking into getting one of these intake setups.

48 IDA - RacingBeat
600 Holley - RacingBeat
45 DCOE - Mazdatrix

Either supplier is within an hour drive from my home.
Do you have any preferences/comments regarding any of these or other systems?

So has Old Man Winter kept you from making any progress on your car?
I've only been doing minor stuff, but that's more progress in the last two months than I have done in the last 6-7 years.

Fabbed a new pedal box for the Tilton/Wilwood assembly. Can more the pedals forward.
Installed a quick release steering wheel.
Fabbed sliding seat brackets for an aluminum Kirkley Vintage seat.
Removed EGI intake and pruned the RX7 wire harness.

After careful consideration I purchased the rear knock-off wire wheel adapters for a TR250 from Victoria British. Cheaper in price from Moss Motors. The 4x4.5 bolt pattern and stud diameter are a perfect for the GSLSE rear end that I'm going to shorten. My 13" wire wheels also clear the brake calipers by 2-3 mm. I should be able to use the wires for the street, and then switch to 15x7 Panasports, 40mm offset, for the track. The outter sidewall distance will be nearly identical with either wheel. Maybe use 245/50's Hossier R6 for the rear only. Tubbing the rear to keep the tires within the body lines. Triangulated 4-link. For the front I will see if the MGB +1 knockoff Minilites will work, 15x5.5 from Moss. I'm going to have to move my Frontline shocks for front tire clearance. Could devise a pushrod front suspension.

I'm wondering how the TR250 15x5.5 centerlaced HD wire wheels would fit. But I doubt that I'm going to find this out. We are talking about over $300 per wheel here.

Cheers!

Jeff20B

iTrader: (13)

Ok since you already clearanced the passenger box, you should do like RX-Midget and get a DCOE. The reason I say that is because the IDA is a tall carb, even in a 1st gen engine bay. Forget trying to make one fit in the MG. The RB Holley won't fit either because it has a really tall manifold. I had trouble fitting one in the GLC with their spun aluminum air cleaners. I'd have to use a chopped foam filter.

My MG can fit a RB Holley only on a stock manifold with an adapter and a chopped foam filter. The reason is because the Holley is a short carb and I've got a 4 port 13B. You can't do this with a 6 port.

By the way I do have a 45DCOE that I was seriously considering for the MG. It's complete with the 4 port intake manifold (both pieces from RB). But I also have an S4 NA engine that's going together soon (just added seals to the rotors this evening!). It will get the DCOE to take advantage of the aux ports for some secondaries. Should be good on a 2bbl carb for driveability.

I can tell you if all I had to use in the MG was a 6 port, it would get the DCOE, no question. But the 4 port gives me two options.

Jeff20B

iTrader: (13)

As for winter, yes I've plunked the MG's engine in the REPU for some test running since the MG has no exhaust, no brakes and a totally inadequate fuel supply. I decided to pull the engine primarily to swap in a light steel flywheel because I didn't want to deal with the shortcomings of aluminum on the street. It's not a track car.

Figured as long as I'm pulling it anyway, might as well try it out in the heaviest chassis I've got. If it pulls real well, I know it'll provide pucker factor in the tiny Midget chassis. You know the old gutless engine in my truck really came alive when I tested it in the MG some years ago. Now I can return the favor. Then the 6 port S4 NA mentioned above will go in the truck when the MG's engine is ready to come out. That'll tide me over until I can get the truck's actual engine rebuilt with some strong R5 irons and either a Camden or a turbo. Looking to double the HP in both the truck and the MG from whatever they came stock with.

REPU 74 13B had 110HP @ 6k and 117 torque @ 3500
MG Midget 1500cc had 65 @ 5500 and 77-82 torque @ 3000 (depending on which internet source you use)

I'm just looking to double the HP of both vehicles so all I need is 130HP in the MG. I think a stock Hitachi can barely do that with 74 spec ports and a free flowing exhaust, but I did a mild streetport job on this engine so I needed a bigger carb ie the RB Holley 600. It will pretty easily do 130HP by 6k, I'd think.

What flywheel have you decided on? Please don't tell me you're using the stock GSL-SE flywheel. Those are 26 pounds! Heck I threw a light steel flywheel in my '81 FB with R5 rotors that are the same weight as GSL-SE rotors, and it felt perfect. Same goes for back when I tested my REPU's old 13B in the MG - first time it ever drove with a 13B was with the old stock 30 pound REPU flywheel. Retardedly heavy. It could do burnouts at 2k RPM. Also couldn't accelerate worth a hill of beans. Then tried a light steel flywheel and varoom! It worked great. Probably could have gotten away with an RB aluminum, but never got around to it. I had one on the new engine which has S4 NA rotors, but didn't want to push my luck with aluminum.

Have you seen the lightened oil pump sprocket!?! That mod alone must have shaved off like ten pounds! Well, obviouslty not really. But I decided to go back to the tried and true light steel. No sense going to great lengths to source an S4 NA assembvly and the finky lightned bits to also use an aluminum flywheel and an underdrive pulley set. Duh. So I swapped back to a stock pulley and iron hub, and a light steel flywheel.

Actually right now it's got a stock S4 NA flywheel at 24 pounds while it's in the truck. Made more sense since the truck does weigh enough that light steel hinders launches, and I didn't want to put unnecessary wear on the disc because as you know, you have to pull the engine to change a clutch in a rotary powered MG Midget!

Hey what gearing were you going to use with your GSL-SE diff? stock '84 4.10 or the '85 3.90? Or some aftermarket ratio? Mine has a stock '79 MG diff at 3.7 or 3.6 so it's really tall.

Rotary-MG

iTrader: (1)

Alrightly, the 45DCOE then. I always liked how the sidedrafts looked more tidy on top of the engine. And it seems like it would be cooler up there away from the headers.

I haven’t given much thought to the flywheel, but the weight difference vs stock isn’t something to be ignored. I’ll be pulling the engine and tranny out at least two more times before it’s final, so this next time I’m going to get a closer look at the clutch and pressure plate. Though I think I’ve already decided to freshen them up. You talked about your experience with the effect of calming the wheel spin problem by going with the lighter flywheel. There’s only a $59 price and one pound weight difference between the lightened steel vs the aluminum flywheels. Shouldn’t I just go with aluminum since they are so close? Unless there is a durability issue. You sounded very happy with the lightened steel flywheel.

What is your opinion regarding clutches?
My guess is that something overly grippy would be bad news.

About the port actuators. Eliminating them would reduce some low end torque, correct? Wouldn't this be beneficial at reducing off the line wheel spin? I can't imagine that I'm going to want more bottom end torque in this little car. I still have my port actuators, but I'm on the fence regarding keeping them for simplicity.

Other than modifying the oil pan, I have yet to crack open a rotary engine. I see this as an inevitability since this path is certainly taking down that route. I don’t know how much to trust this engine since I have no real history with it other than it ran good and strong with no smoke once I put a new TPS in her. I tested the engine for a few miles in the donor car and then promptly removed her. I plan on replacing this engine someday with a 4-port built to handle a Camden. So much to sort out before that day. I’ll never waste money on a new car, so forgive me if I drop $10K or so on a rotary engine. I still have loads of parts to sell from the donor car, but currently I’ve spent $100 for the engine/trans/rearend/injection/etc.

Or I might build another one of these rotarded Midgets. But this time drop the shell onto a space frame. Or build a Locost from scratch.

I was thinking of just leaving the stock ratio for now. I may reconsider once the diff is pulled apart. The LSP isn’t acting like it should. When I hold one rotor and turn the pinion, the loose wheel turns freely. Shouldn’t the power transfer to the side which I’m holding?

As things stand, I have to pull the engine just to change the starter.

Jeff20B

iTrader: (13)

It's a $79 difference. This gap used to be bigger when steel was cheaper.

You got the terminology wrong. The light steel flywheels are not "lightened". They are 13 pounds plus the weight of the rear CW is 17 pounds total. The aluminum flywheels are 7.5 pounds, plus 4 is 11.5.

Since you have the old school heaviest 13B rotors ever made, at 11.5 pounds each, the rotating assemby math says light steel is 11.5+11.5+17=40lbs

Aluminum is 11.5+11.5+11.5=34.5lbs

40 pounds is perfect in an 81 FB. It also felt good in my MG back when I tested the old crappy REPU engine. I'd say go with light steel.

However since then I've gotten experience with aluminum and even the super thin GReddy 8 pound steel flywheel (pictured above) in 1st gens and I can say it's not that bad but still not as nice as light steel for daily driving. But this has all been with 85 and older heavy rotors.

I decided to do a light steel in mine again due to the 10 pound S4 NA rotors and the other lightened parts. I think with my experience driving the lightest flywheels I could get my hands on, I'm qualified to make a recommendation, and I chose light steel flywheel because:

10+10+17=37lbs
10+10+11.5=31.5lbs

31.5 is just too light.

You need to ask yourself what your driving style will be and whether you want to put up with a really light flywheel.

As for whether you'll make too much torque down low and break the diff, um no you shouldn't think of it like that. It only breaks if you rev it up and dump the clutch. That shocks the system and something's gotta give. If not sticky tires, then an axle or ring and pinion. My original thought was to lighten everything as much as possible until I realized it doesn't really work that way. So it gave me an opportunity to go back to the light steel flywheel. And yes since it will be 37lbs instead of 40lbs, there is that small advantage too which appeals to that little part of me that still wants to lighten everything. Does that make sense? Feels like I'm starting to ramble.

So anyway your options are 40 pounds or 34.5 pounds. Ever driven a light steel or aluminum before? If not, go with light steel. You will quickly fall in love.

As for the clutch setup, chose stock duty. Do not get a street strip pressure plate or HD disc. The car is so small and light that stock duty acts like an SS p-plate or an HD disc. RX-Midget informed me of this several years ago and I took his advice, so now I'm passing it on to you.

The oil pan: look for an R5 pan. Mine fits perfectly with a small cutout that the PO added for his RX-3 pan in the frame rail. Turns out the R5 drain bolt is in the same spot when you move the engien rearward by 20mm. I had to move it back because you can't go forward in these cars like you can in a 1st gen. I was changing the tranny anyway from a top mount starter 73 to a bottom starter 74. This tranny is longer and the 13B is longer. Can't recall the total amount I needed th driveshaft shortened. I also found out an NA FC starter fits perfectly. It has 2 or 3mm on each side - plenty for removal/install. The ribcase tranny is big and wide but the gearbox section is tilted (the top mount tranny has the gearbox section straight).

Does your starter hit the frame rail in reverse gear? Mine did, and the oil pan lip on the other side would hit in 1st gear. A set of competition motor mounts stopped the rocking and the competition tranny mount lifted things so no more metal to metal contact. But now I have less room for an air filter so I gotta forgo the phenolic carb spacer and just hope that my cool manifold mod is enough to keep the carb cool. Also my alt will be closer to the hood. I hope I don't need to relocate it.

Jeff20B

iTrader: (13)

By the way, a GSL-SE oil pan should fit but you gotta get rid of the level sensor and make a clearance cutout in the frame rail for the oil drain plug. You piece of thickwall pipe from an RB exhaust or whatever.

Or go the difficult route of fabbing or modding a pan. I'm so glad I dont' have to do any of that, other than fill in a temp sensor hole for the subzero fluid. You just fill it with weld and a short piece of bolt.

Camden? It won't fit the engine bay.