S3 6 port with a bridge and a carb plan
07-25-14, 10:41 PM
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S3 6 port with a bridge and a carb plan
Alright, so this may be a pretty lengthy post, but bear with me. Some background: Used to have an fb with a 12a in it as my first car, loved it, but sadly totalled it due to a patch of sand in the road combined with me being a not-so-thoughtful 18 year old. Always have just absolutely been a nut for rotaries though. So fast forward to now, I came across a very nice looking 13b crate engine on craigslist not too long ago, supposedly with 0 miles on it, for $900. It was very clean and has a DCO 48 SP (throttle plates enlarged to 50mm) that looks basically brand new sitting on top of it, with a racing beat upper intake (stock lower intake with the EGR blockoff plate). It was very clean too and looked relatively brand new besides some shop-dust and grime on it that cleaned right off. Blue irons with new paint and rotor housings that are bare aluminum that also look brand new. Story was, The guy's old uncle had owned it and had it built by somebody (Back in 1995!) and then he just let it sit in the back of a diesel shop where he worked and eventually passed away.
So I bought it, and after removing the intake manifold, I discover that it's a 6 port. Slightly less than optimal, but oh well, still happy with it. Haven't been able to compression test it but spinning it over by the flywheel it has very very strong exhaust pulses. The aux port sleeves have been removed but the rods were still there. Stock intake porting, as far as I can tell, there's a bunch of rough casting **** still in the irons. The reason I believe it is an SE engine is that it's definitely got 3mm apex seals, and it has the front cover mounting points of an fb chassis. (Lucky me, as I slightly prefer 3mm seals). So far on the things I've removed and observed to get it down to the short block I've noticed that whoever built this engine knew what they were doing, all the bolts felt like they were at the correct torque, complete OMP system and vac lines still all in place (vacuum lines still perfect too after 18 years which doesn't make sense), brand new dry OEM oil filter on it, anti-seize in the plug holes, and RTV everywhere there's supposed to be. The coolant passages to the intake manifold have been blocked off with freeze plugs, it has the RB dual belt 4" crank pulley and dual belt alt pulley, running just WP and alt. There was no thermostat in it which.... meh, don't know how I feel about that, probably just use a stock one with two small holes drilled in it.
The distributor on it is... interesting. I guess it's an SE dizzy (More familiar with the igniters-mounted-on-the-side 12a version), But it's been modified a bit, the springs have been removed from the mechanical advance, and the trailing pickup has the wires clipped and capped just outside the dizzy (with the green and red wires coming off the leading pickup to a plug)... so I guess they were planning to run the timing split at 0 using only one pickup... which seems strange to me but if you can clarify, please do.
The spark plugs in it are (all 4) NGK R6725-11 fine wire plugs that look like they just barely been used (The inside from what I can see through the exhaust ports which are also stock, there's almost no carbon on the rotors or anything, and the housings look perfect as well as the apex seals. There's a small puddle of clean oil at the bottom of the housings, and when I drained what little speck of oil was in the pan, it looked newish, still amber with tiiiiny metal sparkleage in it, so I believe it was run a little bit after being built. The water outlets and exh. ports were covered with tape while it was stored.
ANYWAYS----
So now you know the story of how it came to me, now here's what I've done and plan to do (going in an FB as I still have a spare FB trans, my old rewinds, and lots of spare parts). All input is appreciated and sorry this **** is so wordy. Many thoughts I have.
INTAKE__
So far I have only gasket matched the stock SE intake manifold, plugged all emissions holes inside with JB weld and blended them in, and got rid of any burrs/excessive material as well as I could with my dremel. I didn't get anything mirror smooth, and didn't really touch the mid parts of the runners but I figure with a carb, a slightly rough surface is preferable to keep a good mixture. There was a good little bit to be cleaned up at the ends, just enlarging them ever so slightly (to match upper IM and intake gasket). I did this same thing to my 12a manifold with the old car and liked the results, so I figured I'd do it again!
Also I took the rods out (the outside end had already been long cut off) and cut them very short to the point of where they no longer stick out into the intake runner. I then put them back in to act as basically just a plug now.
The carb, as said before, is a weber DCO 48 SP with the throttles bored out to 50mm and 44mm chokes (And it has AEM throttle plates on it, which I thought was kind of neat). Barely required any cleaning at all, looked new inside. As for jetting, it has 65f9 idle jets, f15 e-tubes with 225 main jets, and a #65 acc pump with the acc pump exhaust block off check valve.
IGNITION__
I'm not sure to do about this odd dizzy set up, and whether or not I should run the MSD box with two coils, or three, or what. I need to to more researching on that. Anyways, I went to the junkyard where my old FB lies and got the Dizzy with ignitors, the coils, and the pieces of wiring harness. I'm not too concerned about this at this point because the bigger part must come first.
PORTING__
Now, some may ask me why I want to even disassemble the thing since it is basically a new engine, but I don't know whether or not to trust the coolant o rings and gaskets that have been sitting for so long. That's the main reason. Since I believe the seals and springs inside it are new, I'm simply going to take it apart and port it while I re-seal it. I know that many may frown upon trying to bridge a 6 port, but hear me out. I feel like the 6 port could do well bridged if it's done just a certain way. What if you were to simply overlay a standard 12a bridgeport template (Not one that requires cutting the rotor housing) onto a 6 port engine? It seems strange, but the corner seals all follow the same path in every mazda rotary, so even though the secondary port is different the bridge would still have to be there in the correct place. All I want is to use a bp the same way a 4 port does: to advance the intake timing and increase port area during the part of the intake stroke where it matters. My plan would be to do this, just cutting the bridge from it's starting point up until the divider for the aux port, and then completely leaving the aux port alone (Maybe put some kind of sleeveless ramp in there or Form a ramp from Devcon, reducing the area of that port a bit. I would do a slight shaping/ street port of the secondaries, and either a) do a tiny bridge on the primaries, or b)just streetport the primaries the little bit that you can on SE irons. Not sure which one would be best to go with the aforementioned secondary bridge and the intake mani/carb I've got...
As for the exhaust, I've got SE housings I think (no diffuser, just large sleeve and smallish port) which is good because the later opening time of these housings I think can make more use of the power stroke. I will probably just do a little bit to increase the overlap here, moving the closing edge up about ~3mm and widen them slightly, without touching the opening time besides maybe a little bevel.
So, there's my novel, tell me what you think, or if I'm being stupid and should just run it as is. Either way, if anyone's interested I can post pics of things.
So I bought it, and after removing the intake manifold, I discover that it's a 6 port. Slightly less than optimal, but oh well, still happy with it. Haven't been able to compression test it but spinning it over by the flywheel it has very very strong exhaust pulses. The aux port sleeves have been removed but the rods were still there. Stock intake porting, as far as I can tell, there's a bunch of rough casting **** still in the irons. The reason I believe it is an SE engine is that it's definitely got 3mm apex seals, and it has the front cover mounting points of an fb chassis. (Lucky me, as I slightly prefer 3mm seals). So far on the things I've removed and observed to get it down to the short block I've noticed that whoever built this engine knew what they were doing, all the bolts felt like they were at the correct torque, complete OMP system and vac lines still all in place (vacuum lines still perfect too after 18 years which doesn't make sense), brand new dry OEM oil filter on it, anti-seize in the plug holes, and RTV everywhere there's supposed to be. The coolant passages to the intake manifold have been blocked off with freeze plugs, it has the RB dual belt 4" crank pulley and dual belt alt pulley, running just WP and alt. There was no thermostat in it which.... meh, don't know how I feel about that, probably just use a stock one with two small holes drilled in it.
The distributor on it is... interesting. I guess it's an SE dizzy (More familiar with the igniters-mounted-on-the-side 12a version), But it's been modified a bit, the springs have been removed from the mechanical advance, and the trailing pickup has the wires clipped and capped just outside the dizzy (with the green and red wires coming off the leading pickup to a plug)... so I guess they were planning to run the timing split at 0 using only one pickup... which seems strange to me but if you can clarify, please do.
The spark plugs in it are (all 4) NGK R6725-11 fine wire plugs that look like they just barely been used (The inside from what I can see through the exhaust ports which are also stock, there's almost no carbon on the rotors or anything, and the housings look perfect as well as the apex seals. There's a small puddle of clean oil at the bottom of the housings, and when I drained what little speck of oil was in the pan, it looked newish, still amber with tiiiiny metal sparkleage in it, so I believe it was run a little bit after being built. The water outlets and exh. ports were covered with tape while it was stored.
ANYWAYS----
So now you know the story of how it came to me, now here's what I've done and plan to do (going in an FB as I still have a spare FB trans, my old rewinds, and lots of spare parts). All input is appreciated and sorry this **** is so wordy. Many thoughts I have.
INTAKE__
So far I have only gasket matched the stock SE intake manifold, plugged all emissions holes inside with JB weld and blended them in, and got rid of any burrs/excessive material as well as I could with my dremel. I didn't get anything mirror smooth, and didn't really touch the mid parts of the runners but I figure with a carb, a slightly rough surface is preferable to keep a good mixture. There was a good little bit to be cleaned up at the ends, just enlarging them ever so slightly (to match upper IM and intake gasket). I did this same thing to my 12a manifold with the old car and liked the results, so I figured I'd do it again!
Also I took the rods out (the outside end had already been long cut off) and cut them very short to the point of where they no longer stick out into the intake runner. I then put them back in to act as basically just a plug now.
The carb, as said before, is a weber DCO 48 SP with the throttles bored out to 50mm and 44mm chokes (And it has AEM throttle plates on it, which I thought was kind of neat). Barely required any cleaning at all, looked new inside. As for jetting, it has 65f9 idle jets, f15 e-tubes with 225 main jets, and a #65 acc pump with the acc pump exhaust block off check valve.
IGNITION__
I'm not sure to do about this odd dizzy set up, and whether or not I should run the MSD box with two coils, or three, or what. I need to to more researching on that. Anyways, I went to the junkyard where my old FB lies and got the Dizzy with ignitors, the coils, and the pieces of wiring harness. I'm not too concerned about this at this point because the bigger part must come first.
PORTING__
Now, some may ask me why I want to even disassemble the thing since it is basically a new engine, but I don't know whether or not to trust the coolant o rings and gaskets that have been sitting for so long. That's the main reason. Since I believe the seals and springs inside it are new, I'm simply going to take it apart and port it while I re-seal it. I know that many may frown upon trying to bridge a 6 port, but hear me out. I feel like the 6 port could do well bridged if it's done just a certain way. What if you were to simply overlay a standard 12a bridgeport template (Not one that requires cutting the rotor housing) onto a 6 port engine? It seems strange, but the corner seals all follow the same path in every mazda rotary, so even though the secondary port is different the bridge would still have to be there in the correct place. All I want is to use a bp the same way a 4 port does: to advance the intake timing and increase port area during the part of the intake stroke where it matters. My plan would be to do this, just cutting the bridge from it's starting point up until the divider for the aux port, and then completely leaving the aux port alone (Maybe put some kind of sleeveless ramp in there or Form a ramp from Devcon, reducing the area of that port a bit. I would do a slight shaping/ street port of the secondaries, and either a) do a tiny bridge on the primaries, or b)just streetport the primaries the little bit that you can on SE irons. Not sure which one would be best to go with the aforementioned secondary bridge and the intake mani/carb I've got...
As for the exhaust, I've got SE housings I think (no diffuser, just large sleeve and smallish port) which is good because the later opening time of these housings I think can make more use of the power stroke. I will probably just do a little bit to increase the overlap here, moving the closing edge up about ~3mm and widen them slightly, without touching the opening time besides maybe a little bevel.
So, there's my novel, tell me what you think, or if I'm being stupid and should just run it as is. Either way, if anyone's interested I can post pics of things.
07-25-14, 11:21 PM
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Oh yeah, and I'm keeping the omp functional, but with the adapter plate so I can have a separate tank for 2 stroke oil. Then I'll just run some good synthetic 20w50, probably 15w40 diesel oil to break it in though. As for an oil cooler, I'm not sure if I need to use an fb air to oil cooler or if a slightly smaller aftermarket one with a good fan would suffice. Opinions?
07-26-14, 01:39 AM
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That's the other thing. I WANT to open it up, because I want to know what other goodies it might have in there, if there actually are any problems at all inside, etc. I'd love to open it up and find some 3 window bearings and a 17.5mm oil pump, you know what I mean?
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07-27-14, 05:14 PM
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except for cleaning/checking stuff i would run it as they had it. it seems like they knew what they were doing...
07-27-14, 07:23 PM
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OH. And I forgot to mention the most interesting/important part. The clutch and flywheel assy. that was on it was a kennedy engineering piece made to adapt the engine to a VW transmission, so I guess that was the plan for it. However, I'd rather optimize it and put it in an FB where it belongs.
07-28-14, 10:51 AM
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Yeah, I need to find a rotary volkswagen forum or something so I can sell it. Hell, I'd do a straight up trade of the flywheel and pressure plate for a RB light steel flywheel. I already have the rear counterweight.
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