Thanks. Yeah I decided to leave them at 11.something and did all three that way.

When you say leave the runners rough, do you mean leave them stock? Or clean the casting flash off but don't smooth them?

Everyone out there always cuts through the casting flash but I'd guess it's up to the person doing the port work as to how rough they leave the runners. I recall Judge Ito said to smooth them but not to where it's glass-like. Just leave them a little rough? I'll have to go back and look in the porting FAQ for the exact quote.

When I do 74 spec ports, I leave the runners stock since that would be technically stock for 74 plates. Now since this 20B is technically mild ported, I suppose I could do a mild job on the runners where I don't enlarge them, but only remove any casting flash and leave a surface that's not glass-like. I've got a nice dremel stone that works brilliantly for just this.

Others have said on a carbed setup, you're supposed to leave a finish that is slightly rougher than on an EFI setup. They explained something about laminar flow and that carbed setups required a slightly rougher surface. When I think about the differences I come up with more similarities. My conclusion is that a slight roughness in the runners is a good thing and it will run better in the low end, and if it hurts high RPM performance, it will probably be like 1hp. So I'll use my special dremel stone in the runners after I've removed the casting flash.

 

my friend just ports his engines by opening up the hole in the side plate, and leaves the runners stock, and he's had great results. i don't think anyone ever told him to clean up the runners, and he has no clue who judge ito is...

if there is some big casting flash, knocking that off would probably be good though.

 

Sounds good. I took a break from the 20B so I could work on something else. Glad I did. I'll go ahead and get rid of the casting flash but I'll consider leaving the runners otherwise basically stock, but my way. Why follow the crowd? My build so far has been a little bit different. I'm the only one I know who has ever blocked off the EGR/ACV holes in the rotor housings during a sleeve swap; I did it based on info I gathered myself, not from what I read on any forums. The way I separated the front rotor journal from the e-shaft was a little bit different from the usually accepted way. The MegaSquirt was set up a little bit differently. I prefer inline fuel pumps to in-tank fuel pumps, so I can hear them to know that they're working (you can't hear them when the engine is running so why so much negative for inline pumps? I don't get it).

Hmm, I think I understand the logic most people use when they smooth their runners. They figure if they're changing the shape of the intake port by making it larger, they must also smooth and enlarge the runners while not fully understanding what that does to velocity at low RPM. Then they wonder why their car becomes such a jungle cat. Or maybe not. All I know is when I do a typical 74 port on a set of Y or R5 plates, I don't touch the runners and my results have been incredible. I had a fresh rebuild fire up and idle perfectly at 800rpm in less than a second of cranking after two previous crankings to start seeing oil pressure on the gauge. Right after the guage moved up to like 25psi or whatever it was, I hooked up the fuel pump just to fill the carb, pumped it a couple times to get fuel squirting from the accel pump nozzles, then that super short crank and it fired and idled. I couldn't speak for a few seconds while it hummed along. I had to pick my jaw up and realize I needed to shut it off because it was just a test firing before I put any coolant in it. I fired it up a time or two more to let the carb run out of gas and that was it until I could grab the fan out of the FB and hook up the coolant hoses and stuff. The rotor housings only heated up a little above room temperature. Heat moves fast through aluminum.

This engine ran so well I'm dropping the Camden in as soon as it is pulled from the FB, which was today. I ran out of time but I'll get to it probably tomorrow. Gotta clean up the gasket or throw on a new one. I'm also adding an oil temp guage to make sure everything is comfy as it breaks in.

So anyway this was a long winded way of explaining that leaving the runners stock on technically stock timing ports (for 74) allowed for instant starts but I believe had I followed the group think mentality of "if you port it, you gotta enlarge the runners every time because otherwise it's not worth porting it because it just won't flow..." it would have some trouble starting and would never run all that well. In fact I have an older built engine that is this way. It never idled smooth because the runners were smoothed. It ran fine with the Camden, but an NA carb setup has always had a lumpy idle. It doesn't detract from driving it, but it does prove that smoothed ports hurt idle quality while not really increasing high end power more than maybe an HP or two. Totally not worth it in my book if this engine is ever really going to be used as a daily driver. Sooner or later the time comes where you're kinda wishing for something that runs a little better or is easier to drive all the time. I've been there. I don't like heavy clutch pedals on daily drivers for the same reasons. "You get used to it" is the usual response bit I'll argue that if you drive several different cars all the time, you don't get used to any ONE and you tend to prefer the ones with the nicer feeling clutches, amoung other things.

 

ive driven/been around two cars he ported like that, maybe 3, and i didn't know until after how he ported em.

both or all three cars started with either new or really low mile engine parts. they both idle nicely, and have really good low rpm power too. you wouldn't know its ported really

 

That's really great news. I'm just wondering whether I opened my primaries too early to idle nicely. But then I remind myself they're only opening like 2mm sooner than a typical 74 port. I've never ported an EFI engine before though so it's my lack of experience talking.

If I might borrow your experience for a bit, how would you say my engine will idle and drive based on the porting I've done so far? I won't enlarge the runners at all. I'll just remove casting flash lumpiness then go over it with my broken dremel bit run at low speed to give it a slightly roughened finish, just like I do inside the ported areas when I do a 74 port.

 

I just found another pro leave the runners untouched: https://www.rx7club.com/single-turbo-rx-7s-23/freshly-ported-irons-919022/page2/

The guy, rx72c is making 700rwhp with stock runners and only timing changes to the ports themselves. Nice!

 

i dunno, if i can get the P port to idle without the brap, i think it'll be fine? especially with efi.

the P port can go from the "normal" brap brap idle to a normal, but weak combustion idle, and oddly, the brap brap, is offers much better drivability, letting the clutch out on the "normal" idle, its really weak...

the FC motor my friend did, ended up doing 392RWHP @12psi, with a 60-1 turbo, 3" exhaust, and stock intake manifolds.

 

Yep, with EFI you can get away with more.

It looks like I'm going to port the Cosmo exhaust ports up a little. The sleeves do support this, but you can't really go down. I could go up high enough to remove the bevel, then add it back. That would be a nice mild port job. I'll also polish the insides fo the sleeves, because I do recall that's perfectly ok to do. Well, maybe not polish, but clean up and smooth.

 

yeah i was looking at the sleeves on an FD rotor housing, and the match between the bottom of the port and the sleeve is really good, but on the top side they left about 1/2 to port UP before you match the sleeve, i took it as a hint..

 

You are correct, sir! Too bad on the Cosmo housings they ramp down below the FD sleeve. At least you can but up the same amount as an FD.

 

I meant to say at least you can PORT up the same as FD housings.

 

I've got a question about "corner seal rubber inserts" and my streetports. They'll fall into the intake ports due to how early they open. Looks like I have to pull them all out.

How horrible will my idle be now?

 

I've never used them. They were either missing already, or they were so hardened that engine assembly was impossible.

 

Same experience here. I just had a set of low mile corner seals with the rubber things already in them to replace the high mileage ones from the 20B. Figured I'd ask to be safe. Glad they're coming out.

 

I'm swapping from the corner springs I got from Atkins to some known FD/20B springs. Why? I noticed they corner seals don't seem to be as springy as I thought they would be.

I have reason to believe the corner springs from Atkins listed as 93 to 95 costing only $23.76 are the same as RX-8 springs listed on Mazdatrix also costing $23.76.

Links for info:

Where I first was made aware of the difference, thanks to Jobro. https://www.rx7club.com/showpost.php...15&postcount=6

Atkins link http://atkinsrotary.com/store/catalo...t-p-16714.html

Mazdatrix RX-8 (N3H1) springs http://www.mazdatrix.com/getprice.as...m=11-C24B-N3H1

Mazdatrix FD (NF01) springs http://www.mazdatrix.com/getprice.as...m=11-C240-NF01

If you add up the price of 12 springs, you'll see the N3H1 springs match Atkins' price. The NF01 springs cost more. Also printed on the bag I got from Atkins containing the springs, it listed the Mazda part number as NF01-11-C24B. The C24B is the same as the RX-8 springs while the NF01 is the same as the FD springs.

What's going on? I don't know as much about part numbers are j9fd3s does, but it seems to me these are RX-8 springs sold as 93-95 springs. The part number and price are the give away. So is the slightly less lift I get out of these. I will swap to some known NF01 springs and report back whether there was any noticeable difference. I'll save the Atkins springs for a non boosted application.

 

Wow, there is a big, noticeable difference in corner seal lift for NF01 vs N3H1 springs. Around 1.8mm vs 1.5mm. Which would you choose?

I ordered a set of NF01 springs from Mazdatrix.

The Atkins are brand new. I'll use them in either a 6 port 12A or a non boosted 13B for my rotary MG Midget.

 

It's entirely possible that the FD part number is being superseded by the RX-8 number, and either the FD number is being used until supply is exhausted, or ordering the FD number gets you the RX-8 part.

I'm not entirely certain that FD corner springs are a good idea with Atkins seals. It seems to me that the spring and the joint in the apex seal are close enough that the corner seal spring can hang up. It looked like that was happening on the engine that flattened a whole bunch of FD seals - the one end of most of the springs was ginked a little bit.

My next engine is going together with wire springs, mainly because I'm throwing the engine together with 100% stock internals. Everything was in good measure, actually. Plus, I don't plan on revving it very high since it's a 3mm seal engine. Going to cap things at 7500.

I am not terribly pleased with the longevity of the Atkins seals. Granted, I did abuse the snot out of them, but they wore the housings horribly. If the housings are reuseable, I'll just get carbon-aluminums.

 

NF01 should be NF01, and N3H1 should be N3H1. i DO agree the price is a big tipoff, they aren't accidents...

interesting the Rx8 spring is flatter too, i wonder why

 

i like the carbons so far. i see no real downsides so far.

 

just spotted this thread,, and while it has some handy stuff in it,, i wonder if the title is a little misleading
i would liked to have given some input as to jeff20b's observations as to the various factory porting configurations over the years
and also the various discrepancies with some of the information previously on the net

- on the whole,, i have made similar observations to jeff20b
and can see some errors in the paul yaw stuff repeated ad nauseum
( its rather unfortunate that the combined IC/ IO numbers hide the real primary and secondary separate timings )

ie, 1st and 2nd generation 6P's have vastly different aux timing to each other -just for a starter-

though jeff makes the same blue by stating that all the 2nd gens have N0 inlet timing

6 ports have much later IO and earlier I/C primary porting to the s4/5 turbo engines

s4/5 turbo engines actually have bigger and earlier open primary than ports RE or REW

and yes they can be taken up and out to the same specs as the RB secondary /r5 extend template
( but not down )

and yes FC secondary inlet porting open and close is much the same timing as RE and REW and R5 though doesnt have the lower bottom portion of the port
( as jeff has pointed out above,, no bearing on port timing )

i have also made very similar observations as to the 12a and NA 13b and GSL-SE and FC/FD exhaust port timings


i would like very much to enter into discussion on the various porting and plate combinations from the factory, US and JDM and euro and AUS
3B, R5 ( 1,B and C ) , Y , N ,G, H ,X and E and i could go on

i wonder if jeff would consider moving perhaps the first series of his posts into another thread so that the discussion on the various OEM configs is not muddied with the stuff Jeff20b is doing specifically for this engine

 

Keep in mind that gtorx7 rotor's were beveled/scalloped, so his port timing isn't the only thing to go by. Also he was running a custom intake.

 

I've noticed that, for anything using any stock-type manifold, going crazy on the port closing isn't such a great idea. It shifts the powerband up real high, but you can't flow any air into it because the manifold sucks.

My latest port experiment has early closing. Shockingly early. We'll see how it do. I'm finishing the port work tomorrow, might have it assembled later in the week, but it can't go into the car until mid-November at the earliest. Just in time to put the car away for the winter.

 

interesting! we didn't get the X casting here, and i have a set that's got factory filled intakes, be neat to know WTF it was for originally

 

There is a lot of relatively minor incorrect information in this thread.

A better start than quoting other sources would be good standardized pictures seeing as its neigh on impossible for a single user to have a plate for every engine from 75 to 2003 in their shed.

Breif footnotes

 

X ( front plate ID ) , R5 ( middle plate ID ) , X ( rear plate ID )
originally sourced from a late rx4 13b engine,, engine number starts as ( D )

X front plate ,,
when compared to an R5 one is 48mm tall in the port,,,
and the R5 port is 42mm tall
the X front plate,, compared to an R5 one
is delete one through bolt, delete chain tensioner,
and has a blind grub near the bottom of the plate into the water passage

- some of the casting around the aircon bracket is also deleted
does not appear to be a factory nitirded plate

the middle plate is conventional R5

the rear plate is X,,
delete through bolt
and is missing that diagonal wedge / dowel landing that the R5 ( and s5 ) have at the oil filter pedestal

obviously a later progression to the R5
( so,, in rx4 we have 3B, then R5,, then X )

and since the s4 turbo stock inlet is in fact 50mm tall
and noting the progression in through bolts and in chain tensioner
that it is perhaps this "X" plate that engineers developed into the aussie/ jap s4 turbo "G" one

---------------------------

i have s5 turbo plates here ( with the rear wedge AND the front O ring support )
and they have the same 50 mm port ( but the wedge )
and -- very importantly----they are also marked "G"

since i have yet to see any example of factory having different ports on plates coded the same
and especially since i have lost count the amount of s4/5 turbo engines i have stripped ,, and ported
( youd think i would notice when i put the template on it ! )
-and never once noted any internal differences beyond that O ring support and dowel landing -
it can be taken as fair evidence that both s4 and s5 T plates are in fact the same port
both are "G" plates ,, if you order s4T new plates,, you will be given s5T replacements
- cause they are the same port,, but an evolution in strength
and mazda see the sense in not carrying essentially the same part twice

PS,, i also have R5 "D" end plates but am yet ,, beside nitriding ,, to see what the differences are between the 4 different coded R5 end plates



X, R5,X


X

delete through bolt, delete oil chain tensioner


water gallery is tapped


template on R5


template on X


X and R5


R5 'B" plate for comparison