I changed the 2 rotor housings as well as the rear housing when i ported my engine.On of the dowel bolts are to short now.

The intermediate,front and rear housings are `82 Rx7.The rotorhousings are from a Capella +- `76
(same bolts location).

The bolt in the location marked by the red dot is too short(its a standard bolt that i took out on dissasembly)
The yellow dots shows to the one that is longer(factory)

The bolt out of the yellow location is also too short.
Any ideas ?Why did this change,seeing that the rotor housings are the same of the Capella and Rx7.

Sorry for the long post.
Karis

 

The red dot was removed from the rear plate in later years. Same with one near the top. Yours looks like an earlier one though. Hmm, good question.

Are those your second set of cheeseports? Man, those are so cool! BP sound without too much loss in low end, but a little more power than a streetport.

 

yea man, sorry to chaneg the topic but have u ran those "cheese ports" yet? if so give us some insight on how they perform, I for one am very interested.

 

Yip.This is my second cheesport.The first one only had one row of holes,the current one has two rows.

Well,the dowel bolt problem is keeping the new cheeseport from running.If i can solve this,then it can go back into the Rx7.

I like cheese ports,allthough there are some "purists"saying its a waste of time.

Waste of time,it is definately not.I have seen and felt the differnece it makes.

I hope that it will now be equal to a 8mm Bridge port(some call it a standard bridge)

 

have you drilled the holes stright through or are they champhered on one side? any dyno sheets or guestimated HP orany info. im jsut curious cuz this si the first i have heard about the "cheese port"

 

Holes drilled straight through.Chamfered a little larger on the rotor side of the housing, to about half the thickness of the housing.

I`ll be shooting for 150hp..i think i`ll be hopefully able to get.It doesnt sound much,but remember i`am more than 5500 ft above sea level...

 

Tunde is that you?

 

who me ? Nope,i`am not Tunde

 

 

Is that engine a 12A? If so, just grab a 13B tension bolt and cut more threads on it (if necessary), then shorten it by whatever seems appropriate (like 20mm) to get it to thread into the hole and torque correctly. The yellow dot is supposed to be longer, but you already knew that. I'd love to hear a sound clip of the cheeseport running.

 

Thanks for the info Jeff.

Well,it turned out that there shouldnt be a bolt.Its going into the water jacket in the front cover.
So i blanked the hole off in 2 places,and i`ll be hoping for the best now.


Luckilly this engine wont ever be Turbo,so i dont think it will twist.

I`ll try to get you a clip as soon as possible..
The engine is finally ready for installation...i think i`ll try to start installing tonight.

Karis

 

Cool! I just installed an engine which is missing two tension bolts. I think most FB engines were like this. It's actually a 4 port 13B with streetporting and '77-'78 rotor housings and '80-'85 side plates. It's missing the oil pressure threaded hole under the oil filter, and the two tension bolts in the rear plate, the intermediate plate has tall intake ports and no EGR valve on top (pretty cool!), and the front plate has only one threaded hole in relation to the missing holes on the rear. The other tension bolt position in not even drilled or threaded, kinda like your front plate.

What's interesting about this engine is that I recently picked up a core 13B 4 port for parts and found them to be exactly the same except for the rotor housings which look more like '79-'80 because they have the spark plug hoods like 12A rotor housings do. The '77-'78 ones have three bits that stick out instead of a full hood. Either that, or these were japanese-only rotor housings. Anyway, the side plates are exactly the same. I drilled and tapped an oil pressure hole under the filter like most engines have. I need to figure out what else I need to drill and tap before I assemble this engine. I'm thinking of doing a partial bridgeport because this engine will be going into a REPU and I need the low end on the primaries, but want better than streetport power at higher RPM. The cheeseport idea is still kicking around here though. But then again, I've got a different engine that requires carbon apex seals ('73 12A), so high RPM above 8500 isn't much of an issue.

Question. Do you drill with a 6mm bit and them chamfer to 8mm on the rotor side? Also, do you do any smoothing and port flow directing on the intake side?

 

I sent you a PM Jeff

 

Jeff after I screwed up my first set of plates by "overporting" I found a set of plates exactly like the ones you mentioned. The plates that I screwed up where missing a couple of tension bolts, currently they are assembled, but the engine won't start, maybe I can save them with some JBweld.

The ones I'm porting now are missing the oil sending unit under the oil filter but I already drilled and tapped a sensor there. These are marked R5 plates.

Karism with the cheeseport I take it that you don't need to use carbon seals, I'm I right?

 

plate difference by year and nationality

This might help...I think I got the Australian version which I'm currently street porting...not bad

seems like I screwed up a set of good plates...

 

Nope,no carbon seals needed.I would have liked to have some,then i could really use the increased rev range of the engine.

I`ll be using 8500,eventhough it will happily rev past 9500(it has in the past,but not often)

 

That's a cool link. I've got grey R5 front and rear plates. The intermediate has an R under the oil filler tube. I think I've seen an N somewhere as well. The rear has 17 tension bolts and the front has 18 holes. All nitrided. I can't wait to build this sucker. Just gotta decide on porting first.

 

I washed some rotors for this engine today. I've got three rotors that would work in this engine. One is fine. The next has sloppy seal slots (I could try tapping them back together before junking the rotor). The last has a bad bearing, but good apex slots. I've got to see if this rotor with the bad bearing has a letter close to the good one. I think if it's like one letter up or down in the alphabet, it'll still balance correctly. If it's two away (like an A and a C), they aren't compatible.

Hmm, Blake Qualley says to not try half bridgeporting. He probably wouldn't like cheeseports either. He suggests either lots of overlap with a streetport, or just go full bridge. He knows what he's talking about, but I've read what others have posted here about their non-standard ports, and I am convinced that half bridgeports could work alright in certain vehicles.

If I try a half bridgeport and it doesn't work out, I could tear the engine back down and bridge the rest of the ports. It's just a bit more time and money (gasket set), that's all. Infact, cheeseports could be converted over to bridgeports as well.

I think I've decided to half bridge my R5 13B and use iron apex seals and limit the revs to about 8400. It's going into my REPU and I'll be using the stock heavy flywheel because it'll be used for towing. Plus I like the drivability of it. I could always go with a RB light steel flywheel at a later time (such as when my tranny needs an overhaul, which should be fairly soon).

 

Jeff I suggest since u have the experience to go ahead and do the halfbridge, if cost is a problem then do what u can...it's more work if u need to tear it down, but heck we are all not rich right? sometimes getting the carbons throws the budget off the charts...I got carbons and I refuse to do the bridge yet...I went for a small street port with new steels...I want to have like 3 engines for racing but wanted to try something mild

about the letter and balancing I'm really lost on that...1


Hey I got a question Jeff...

I just closed my engine, I finished at 1:30 a.m. looks very nice, painted the R5 plates blue. The question I got is regarding the counter weight. I searched and learned about the differences in weight by years...the problem is that this engine came with a light flywheel and counterweight. Since I had a nice clutch and a resurfaced heavy weight flywheel on my previous engine I switched everything to heavy FW, CW from the old engine to the current one. I think this engine has lighter rotors and I have just put the heavy FW and counter weight...will this cause a problem?

..I wanted to save a few bucks on the clutch and the resurfacing of the flywheel, I do have the correct light weight flywheel, clutch, counterweight but I have to spend on resurfacing and a new race clutch etc... should I spend the money and put this on intead????

Man I'm worried... I wonder if switching to heavy FW and counter weight affects the engine when the rotors were matched to a lightweight FW...

please tell me it's ok... please....

damn it's late

 

Jeff : So you have got the nice housings..mmmm!
Do a half bridge,i`am sure the performance will be adequate,and it will be driveable enough!

Some people are purists,others try new things.I`am not saying Mr Qualley is wrong with what he is saying,but theres sure as hell nothing wrong with the way your doing it.

My 0.02.. :-)

 

mperformance, if you know the years of your parts, this link will show you which years interchange. Scroll down a bit http://www.mazdatrix.com/b5.htm

Also be sure to check this link for flywheel pictures. Hopefully one of these will match yours: http://www.mazdatrix.com/faq/flywheel.htm

karism and mperformance, thanks for the positive feedback!

I know why he recommends full bridge over half. He says the Weber IDA carb is superior to the Holley and you know what that means; one barrel feeding one rotor. There are no secondaries in a carb like that. I should know; I just rebuilt an R5 13B with a dellorto. So in a worst case scenario, I could get a Weber IDA or DCOE and install it on my half bridge and it would flow somewhere between a streetport and a full bridge. I know the carb can be tweaked to run well with that style of porting because it works well on fully stock, mild streetport, extend port, full bridge, and probably J and monster ports (peripheral as well I think). And for less than the cost of the carb itself, I could fully bridgeport and rebuild the engine.

Wow, I've learned a lot in a couple days.

Oh, also, Rotaryshack sells Webers. Does this look like a good deal? (it looks like a DCOE sidedraft and I think the IDA is a downdraft) http://www.rotaryshack.com/pages/fuel.html

 

Glad i could give some feedback!
Dcoe & IDA is the model names that Weber gave them.Sidedraught and down draught is a common term we use here in old South Africa.

Hope all turns out well !

Wish me luck,the engine is going in tonight.After thats finished,i have to built a header (my own design),and build the AFR for tuning

I have to be ready be the 7th of July for a track day,break in period covered and everything.


Karis

 

good luck karism...I hopefully will fire up my engine today. Karism I was reading your signature and it says u have a 40DCOE, man if u run that cheeseport with it it will starve...u need at least a 48 now. I got a 45 and am a bit worried with my streetport.

well I decided on keeping the heavy FW, and heavy CW...let's see what happens...

Jeff IDA =downdraft DCOE=sidedraft...

I can tell u weber is a good carb no matter what some people say. It is far easier to squeeze the power out of them than the stock nikki and for racing purposes it's hard to beat. THe holley is also good but somehow I think a rotary loves two barrel carbs much more.

There was a guys selling a complete kit for a 51 IDA and intake in ebay a few days ago. Nevertheless it was expensive but not too expensive considering it was sold at the same price as a new DCOE w/intake.

IDA is far superior than DCOE in the sense that most people recommend it and seems to provide more power. I really don't know why, I have read some comments on the way it's designed and the acc, pump it has, I only have experience with DCOEs, I've had mikunis and now weber. I do want to switch to an IDA but $ is an issue and like u said these carbs are a bit on the expensive side...

 

Good luck guys.

 

The probelm is money..the prices here are just crazy..i`ll be paying more for a IDA than i paid for the car....

The carb is just temp.I have fuel injection lying around that needs to be fitted.

For interests sake :The 2 barrel IDA was never fitted to a production car,it was made only for racing purposes.

Thanks guys!