Jeff20B

iTrader: (13)

I've been working on a nice early 4 port 13B for my REPU. I'm sure you 1st geners would appreciate any info about 4 port 13Bs so I decided to post it here. Heck, the only thing keeping it from dropping right into a 1st gen is the oil pan.

Darn camera. Pictures are coming soon. No, really.

mazdaverx713b

iTrader: (91)

hopefully you'll have pics up today some time! are you just waiting on an SE oil pan to fit the engine in an FB or SA? what kind of "work" are you doing to this engine?? some porting perhaps???

Siraniko

iTrader: (13)

be sure to mod the stock ROPR to get higher oil pressure. Slighly wack the tip. Right ROPR will give you 80+ and appx 30 at idle.

Latin270

Did you just grind that down?

Siraniko

iTrader: (13)

Left is stock.
Right is modded and I wack the tip to make the spring stiff for higher oil pressure.

Its that simple. Wacky just save you $80. Thats priceless!!!

Stevan

iTrader: (17)

Webster's dictionary:
WAC= a member of the U.S. Womens Army Corps.
Wacko= Crazy.
Wacky= Sligtly demented, odd, an eccentric person.(LOL)

No definition for "wack", you mean "tap" with a hammer ?
I will save that pic for future reference.
Thanks Wacky, you always have the frugal fixes.

Jeff20B

iTrader: (13)

Jeff20B

iTrader: (13)

Jeff20B

iTrader: (13)

This one's for Wacky.


I was mainly concerned with getting coverage on the bellhousing. The rest won't really be seen.

Directfreak

iTrader: (2)

You could also Shim it inside with some washers.

rxtasy3

iTrader: (2)

same engine i was running in the 808 but now is in the 7. i forget what pan i used to put it in the 7 tho. and ur reshaping of the exhaust port looks like what mine is too, only i didn't to the porting on mine. it was done many years back by mandeville. looks nice, just not a fan of painting aluminum pieces tho. let us know how it runs.

Siraniko

iTrader: (13)

Yup but that on the ones that with removeable cap like in Jeff's pix (I have them too btw). Now, you can do the same on the newer ones but it requires more work. You have to drill a hole on the opposite side of the roll pin so the roll pin will slide out. Then the spring/cap come out. To stiffen the spirng, you can either put washers on the tip side OR install a cotter pin. shoved the spring back in and use cotter pin again to secure it (to replace the roll pin). Thats too much work.

For those who has no clue, this is what we're talking about.

Siraniko

iTrader: (13)

I prefer the 2nd description. lol

diabolical1

iTrader: (3)

you guys and you cool **** make me sick!!!



(it should go without saying that i'm just kidding. i'm just a playa-hatin' bitch!)


Jeff, how many projects are you doing at once?

trochoid

iTrader: (6)

Jeff, that exhaust porting looks so nice that I would be happy to have a template of your fine work sir. I haven't decided on which set of 13B housings to use for the engine build for the REPU. I have 3 choices. Old school 74-78, SEs, or a carbed version of a a TII. If I build a TII block, I may go ahead and FI it for a later turbo install. Is the chrome on the early 13Bs as good as the later ones? I never can remember.

As usual, great work.

jfachner72

Why do I live in an apartment.......

I need to live in a garage!

Dammit!

J

Latin270

Jeff I'm just curious to see what year center iron you used or did you just port out the primary runners. (no pic) I do believe the 74' intake runners are tiny. I decided to use 83 center iron because of this.

Directfreak

iTrader: (2)

You win sir, you are correct. That IS too much work. But some people are uncomfortable hammering on an a perfectly good engine part.

On my engine, As per my Tuner's instructions, I did hammer it. But I also put washers in where it screws into.

So far, so Good.

Jeff20B

iTrader: (13)

I used .140" of washers in the ROPR. Should be good for about 90 PSI. I plan to supercharge this engine at some point. The extra pressure should be good for the extra bearings.

Hey, you know the picture above showing the non adjustable ROPR? See the little pits down near the threaded end? I drilled out the side and tapped the pin out. Then added some washers and a piece of a drill bit since the pin was a little less than perfect. Then welded it back up so it wouldn't leak oil pressure (kept the heat low so it wouldn't mess with the spring). I never saw how much pressure it had because the car didn't have an oil pressure guage. It'll find its way into the next engine.

Notice the 3B plates all around? All came with nice tall '74 spec ports. They should do very well with the truck's low geared 4.625 diff. I merely smoothed out all the harsh 90° edges and casting flash with the dremel and left a rough surface using a stone with a chipped edge at the lowest speed. Then I pressed hard to slow it down even more. They should prevent fuel wetting out in the ports when I stomp on it.

Notice the dirty rotor? There's no point cleaning it because it's just gonna get dirty again in no time. A couple of the side seals were a little sloppy for my likes but none were looser than the edge of spec for '74 engines. Some were perfect while most were in the .0035 range, which is spec for the later engines. It was a nice running engine and had a scary amount of power in the MG. Now with new apex seals and tight slots (.0015 - .002), competition outer oil springs, replaced oil seals (because the early engines always wear them out quick) and new springs all around, I think this engine will make adequate power in the truck.

trochoid, you asked about chrome. The '71-'73 engines had relatively weak chrome and you must use carbon apex seals regardless of rotors (6mm or 3mm). '74-'75 were a little stronger but it's a good idea to use '74-'75 apex seals with the full length wear surface and the little triangle pieces that ride down below. They don't seal as well as '76-'85 seals with the triangle piece that does ride on the chrome, however there's no chance for a gouge to form, unless the '74-'75 seals wear down into the triangle pieces. The '76-'85 chrome is most probably the toughest of all the 6mm and 3mm engines. I don't know what changes Mazda made to the chrome of the '86 and later engines, but I do know it doesn't flake as easily. Perhaps the flaking is only caused by 3mm seals?

In this engine, I chose to use Atkins apex seals because A: I had a new set sitting here, B: they're softer than OEM seals so the chrome will probably survive longer, C: the triangle piece is actually quite wide and therefore spreads its force over a larger area thus reducing the overall likelyhood of a deep gouge forming over time. It will be a wider, shallower gouge. D: their seals have been shown to work fine with their superchargers.

As for the template idea, I don't use them. If you recall from my exhaust port thread(s), I have an S4 T2 rotor housing laying around with two lines at the closing edge the first line claerly shows the stock closing the second line is where I closed the '74-'75 housings. That's physically the largest port I can do without removing the sleeves. See how small they look? Mazda made larger sleeves in the later years as a way to quiet the exhaust by allowing the pulses to expand quickly right as they exit the port. Well this is different in '74 housings with the smaller sleeves. I'm affraid this engine might be extremely noisy because the ports are practically the same size as the sleeves. Plus I'm going to use a header, for even more noise. Actually the entire exhaust system needs to be built and I was planning on using a real RB REPU header that's only about 10 years old (my previous one was at least 20 ). Then it's some thick wall RB 2" ID pipe into a 20" Rotary Engineering glasspack wich still contains plenty of glass material, I'm happy to say. Then I might fire it up just to give it a listen and guage the noise levels. If it's too noisy I have one more RE glasspack and then I'll just bring it over the axle and out under the bumper probably with a 17 year old Monza dual tip which was actually on this truck about a decade ago, and my friend's truck back in the early 90s. Why not buy new? Too many projects, not enough money. And it still looks good. (I'll save the new stuff for the 20B lol)

I'm not sure how many projects I have going at once, but it's nice when you get stuck on one, you can move on to another. The MG will get some attention after the REPU is running since they both need exhaust work.

Jeff20B

iTrader: (13)

Latin270, I thought long and hard about which intermediate plate to use. Tall port? Short port? Talking with Carl and rotarygod about ports, velocity, reversion etc, I decided to go with the stock 3B short port plate. Why? Because its short ports actually extend the primary runner length noticeably further before it expands at the port inside. While a tall port can and does work, I was curious about the short port plate, and whether it actually has potential, especially for NA use.

This engine contains two compromises. One is the short primary ports. The other is the large exhaust ports. The short primary ports should do extremely well for NA use with a stock manifold and carb, which I luckily have and are in decent shape. However if and when I get an SC, they might hinder some flow. I might have to specially request a manifold with shorter primary ports... or maybe not even worry about it. When it's getting forced in there, NA rules don't really apply anymore.

The large exhaust ports are great for either an SC or better yet a turbo (yeah left). The easier it is to push it out, the easier it can get pushed in. Or something like that. Anyway for NA use, the exhaust ports might hurt the extreme bottom end power like say from idle to 1500, maybe, but they shouldn't hurt mid to high range power. There is also a chance they won't affect idle or ultra low power at all.

As I said it was a compromise. I had the parts laying around. Might as well put them to work. Hopefully the good points will outweigh the bad points (if there are any).

Latin270

so Jeff, you dont recommend reusing the stock 74 seals? These are like mint and I think they will last a LONG TIME. When is yours going to be ready to fire up?

brandon davis

iTrader: (3)

looks great Jeff!!!

Jeff20B

iTrader: (13)

'74 seals are fine. I just didn't want to use my set because they had some wear on the sides allowing them to slop back and forth in the apex slots. Also when these rotor housings and '74 seals were in my bro's RX-4 engine, it didn't have very much power. I suspected the reason was due to the crappy D ports. Well, it was part of the reason. The rest was from leaky seals. some leaks around the apex seals due to slop, and the rest was around the edges of the side seals. Still more was a vacuum leak at the secondary ports on the manifold because the intaker gasket was cracked. The engine was running lean for a while thanks to the raw air entering the engine all the time. The lean condition overheated the apex srpings, which flattened out some and firther reduced compression.

Another strange thing about the RX-4 engine was somebody had mixed an A rotor with a C rotor. That's a big no no. My REPU engine had a B and a C. We went with a GSL-SE rotating assembly with two C rotors in the RX-4 and all new seals and springs. This left me with the A, C, C and B. I put both Cs together into the MG engine and the A and B in the REPU engine. I wanted the closer weights of both Cs in the MG since it's a smaller lighter car with a light steel flywheel. I figured the A and B would be fine with the stock heavy 30 pound REPU flywheel. I'd rather have the vibrations, if any, in the truck, because it's a truck.

So go ahead and use your '74 seals. I'd use mine if they weren't so narrow. They were like in the low 2.9somethings. I'd prefer them to be at least 2.99 or 3.0mm, or whatver the normal spec is (can't remember what kind of tolerance they're supposed to have off the top of my head, but they fit nicely in the rotors). As for height, they were like 7.8mm or so. Just too sloppy side to side for my taste.

It'll be running after the tranny crossmember thing is done and the tranny is installed. Then gotta find time to drop it in the bay and hook up all the other stuff. I still need to come up with a waterpump gasket too. I'll probably have to order one.

kbeefy

dang jeff, I think I learned more in this 10 minute read about rotaries than the last ten years of tinkering with them! Thanks!

Jeff20B

iTrader: (13)

I think I found a solution to the waterpump thing. I have a new 2nd gen waterpump impeller section with a new gasket just sitting here. It was going on another project for weight saving. It would only be a total of 6 pounds though, so it's not really a big deal. And since I'd like to put an SC on the '74 engine some day anyway, why not?

'74-'85 cast iron waterpump - 15 pounds
'86-'88 NA waterpump - 9 pounds

The only housing I have sitting around is an S4 T2. These aren't fully compatible with NA and earlier engines (and weigh a tiny bit more too). They had a thicker casting with extra bells and whistles here and there. I think the only thing keeping it from fully seating is a little too much aluminum on the back. The casting is slightly different back there. Maybe it was Mazda's attempt to change just enough about something to keep it interesting for people like me, but deter the less adventerous. They did that on the clutch fan bolt spacing in '84, moving them out a couple mm, but it can still be used with the earlier fan spacer if you have a small round file. Things like that.

Test fitting it after grinding. Looks like it will lay flat against the front plate and not hit the front cover now.


Here is where I worked it.