carb conversion
12-22-04, 01:29 AM
#1
carb conversion
I have an 85 SE with 140,000 km's (about 80,000 miles) and want to rebuild (I'm not a kid, car is sweet and I can afford to do it right). I was thinking about using the 12a centerplate from another engine I have due to the bigger ports. I wanna see a noticeable improvement in performance. It already has the full racing beat exhaust. The local RX7 shop says it won't work well with the stock efi, idle will be a problem and big loss of torque, I'm better off going carb. I've heard nice things about a weber conversion, seems costly though. Is it worth it? What experience do any of you have and what advice do you have to offer? Thanks for the input.
12-22-04, 02:15 AM
#3
the SE deoes have the 13b. But you can use 12a parts in a 84-85 13b. Some may ask why this is not posted in the 1st gen section, it's becasue I want 13b answers, all 12a have the little nikki carb and it would get too cluttered with replies that are not specific. Just want to know what "actual" results people have had.
12-22-04, 03:03 AM
#4
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Originally Posted by 84stock
The local RX7 shop says it won't work well with the stock efi, idle will be a problem and big loss of torque, I'm better off going carb.
Last edited by NZConvertible; 12-22-04 at 03:10 AM.
12-22-04, 03:10 PM
#7
Hey,
The main problem that I can see is finding a manifold to mount your carb on. Carbs are easier to work with than EFI in that they're mechanical pieces instead of electric. Here in the first gen section we don't just use the stock Nikkis, though many of us do run heavily modified ones made by Rx7Carl and Sterling. We also use Webers, Dellortos and Holleys.
The modified Nikkis flow much more than stock, almost as much as the Holley the sell at RacingBeat (www.racingbeat.com). For an engine that hasn't been ported, either should do quite well.
Racingbeat also sells Weber carbs. They offer great tunability, and are simpler to work with but are a little more expensive. The disadvantage being that 2 barrel carbs are harder to work with in cold weather and notoriously harder on gas because they don't have the smaller "primary" barrels that 4 barrel carbs have.
As for using a 12a centreplate in a 13b engine, you'll have to get someone else around here to give you input on how to do that. For bigger ports on a 13b, usually what I've seen is using the ports from a TII because they had a 4-port design like the 12a had, instead of the standard 6-port gas-saving-but-power-robbing design. The upside is that with TII housings you can use a TII manifold.
I hope this helps get you started. I dont' know much about the setup you're trying because I own an '84 GS which has a 12a. So main things to consider are : which carb should you use (Modded Nikki, Holley, Weber, Dellorto), Which Housings Should You Use (12a, TII), and how are you going to mount the carb to the engine (RB has manifolds for Weber and Holley, you can go custom, or try to get a TII mani and an adapter).
Jon
The main problem that I can see is finding a manifold to mount your carb on. Carbs are easier to work with than EFI in that they're mechanical pieces instead of electric. Here in the first gen section we don't just use the stock Nikkis, though many of us do run heavily modified ones made by Rx7Carl and Sterling. We also use Webers, Dellortos and Holleys.
The modified Nikkis flow much more than stock, almost as much as the Holley the sell at RacingBeat (www.racingbeat.com). For an engine that hasn't been ported, either should do quite well.
Racingbeat also sells Weber carbs. They offer great tunability, and are simpler to work with but are a little more expensive. The disadvantage being that 2 barrel carbs are harder to work with in cold weather and notoriously harder on gas because they don't have the smaller "primary" barrels that 4 barrel carbs have.
As for using a 12a centreplate in a 13b engine, you'll have to get someone else around here to give you input on how to do that. For bigger ports on a 13b, usually what I've seen is using the ports from a TII because they had a 4-port design like the 12a had, instead of the standard 6-port gas-saving-but-power-robbing design. The upside is that with TII housings you can use a TII manifold.
I hope this helps get you started. I dont' know much about the setup you're trying because I own an '84 GS which has a 12a. So main things to consider are : which carb should you use (Modded Nikki, Holley, Weber, Dellorto), Which Housings Should You Use (12a, TII), and how are you going to mount the carb to the engine (RB has manifolds for Weber and Holley, you can go custom, or try to get a TII mani and an adapter).
Jon
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12-22-04, 03:30 PM
#8
One thing for sure, if you are going to run a 12a center plate you would not have the injector holes to run injectors. If you take your stock EFI manifold off you will see your GSLSE injectors. I run a 13B GSLSE engine in my 79 with 12a plates, it converts to 4 port which is easier to port than a 6 port. If you keep it fuel injection you would have to either weld injector bungs into your manifold or run a custom manifold with them on. Your computer will probably be obsolete anyway and I am pretty sure you woul;d want to run at least 4 injectors instead of 2. I run a Holley on mine but had to take my car to a Rotary tuner, my engine has some radical ports which if you don't take it to a pro, you will pay for it later. A weber or holley is a good choice. The modified nikki carbs can work also but you still need to get at least a REPU 13B 4 port manifold or RX-4 manifold and if it's a 12a NIKKI carb you would still need to massage it some to the old school manifold unless you get an original 13B NIKKI carb out of the same REPU or RX4.
12-23-04, 10:57 PM
#10
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Originally Posted by vipernicus42
Hey,
As for using a 12a centreplate in a 13b engine, you'll have to get someone else around here to give you input on how to do that. For bigger ports on a 13b, usually what I've seen is using the ports from a TII because they had a 4-port design like the 12a had, instead of the standard 6-port gas-saving-but-power-robbing design. The upside is that with TII housings you can use a TII manifold.
Jon
As for using a 12a centreplate in a 13b engine, you'll have to get someone else around here to give you input on how to do that. For bigger ports on a 13b, usually what I've seen is using the ports from a TII because they had a 4-port design like the 12a had, instead of the standard 6-port gas-saving-but-power-robbing design. The upside is that with TII housings you can use a TII manifold.
Jon
): You cannot combine TII sidehousings with your GSL-SE engine. If you'd want TII ones you'd need TII rotorhousings aswell, due to the seals being moved after '86. Using 12A housings doesn't seem very hard though, but you'd have to see what manifold would fit. Since we didn't get GSL-SE's here I don't know the exact differences between the earlier and later 13B's.
If you want to keep the EFI, you'd need 13B housings though. Maybe using TII housings (both side and rotorhousings) is an option, but this might get expensive.
If you go carb, 12A ones should work fine, maybe port them when you're at it.
Another option is going for old-style (pre RX-7) 13B side housings and using manifold/carbs for RX-5 etc.
12-24-04, 01:32 AM
#11
I think what he wants to do is use his GSL-SE motor, but swap the centerplate for a 12A one because the ports are bigger (from what I gather). Thats sounds great.
Am I right?
But, Why dont you just get a 4-Port 13B and build a Huge ported engine. Then drop a Weber 51IDA on there. The 6-Port engine is great, but from what I gather the 4 Port can give you bigger ports, thus more power.
I can't wait to see your GSL-SE Boggie past me on Deerfoot.
Am I right?
But, Why dont you just get a 4-Port 13B and build a Huge ported engine. Then drop a Weber 51IDA on there. The 6-Port engine is great, but from what I gather the 4 Port can give you bigger ports, thus more power.
I can't wait to see your GSL-SE Boggie past me on Deerfoot.
12-24-04, 05:21 AM
#12
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Originally Posted by Alak
I think what he wants to do is use his GSL-SE motor, but swap the centerplate for a 12A one because the ports are bigger (from what I gather). Thats sounds great.
Am I right?
But, Why dont you just get a 4-Port 13B and build a Huge ported engine. Then drop a Weber 51IDA on there. The 6-Port engine is great, but from what I gather the 4 Port can give you bigger ports, thus more power.
I can't wait to see your GSL-SE Boggie past me on Deerfoot.
Am I right?
But, Why dont you just get a 4-Port 13B and build a Huge ported engine. Then drop a Weber 51IDA on there. The 6-Port engine is great, but from what I gather the 4 Port can give you bigger ports, thus more power.
I can't wait to see your GSL-SE Boggie past me on Deerfoot.
Why not change all sideplates to 12A's, thus dropping the 6-port design, and use streetported plates. With a decent carb, that'd rock.
12-24-04, 07:02 AM
#13
So, basically what you are saying rotary emotions, is to use a 12A with 13B housings, right? I suppose then all you would need is a 13B E-shaft, rotors, and an SE oilpan and it should work, right? I am thinking that may be fairly cheap as you can find a blown rebuildable 13B and find a non rebuildable 12A and just use parts off it. Oohh ideas are coming into my head. I may have to try this....
12-24-04, 08:14 AM
#14
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Originally Posted by IanS
So, basically what you are saying rotary emotions, is to use a 12A with 13B housings, right? I suppose then all you would need is a 13B E-shaft, rotors, and an SE oilpan and it should work, right? I am thinking that may be fairly cheap as you can find a blown rebuildable 13B and find a non rebuildable 12A and just use parts off it. Oohh ideas are coming into my head. I may have to try this....
Yes, Sort of. What hes saying is to use the 12A irons on the 13B. Then you get 4port performance and the advantage of having oodles of room to port. He already has an SE. It ends up like an old skool 13B.
In your case all you need is a 13B and an SE oilpan IIRC.
12-24-04, 01:19 PM
#19
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Originally Posted by 84stock
I have an 85 SE with 140,000 km's (about 80,000 miles) and want to rebuild (I'm not a kid, car is sweet and I can afford to do it right). I was thinking about using the 12a centerplate from another engine I have due to the bigger ports. I wanna see a noticeable improvement in performance. It already has the full racing beat exhaust. The local RX7 shop says it won't work well with the stock efi, idle will be a problem and big loss of torque, I'm better off going carb. I've heard nice things about a weber conversion, seems costly though. Is it worth it? What experience do any of you have and what advice do you have to offer? Thanks for the input.
If you want more power and still have good reliable FI here is what I would do.
Get and S4 or S5 NA motor. Streetport it during the rebuild. Put your GSL-SE front cover and oil pan on it. Get a lightweight flywheel and match the counter weight to what ever rotors you run (s4 rotors s4 counter weight). Have your injectors rebuilt. At this time you could either run the stock s4/s5 ECU on you GSL-SE or run your stock gslse ecu. If you use the stock s4/s5 ECU get the wiring harness so you can run the 4 injectors. Use the pair of 720's and a pair of 550's.
If you use the GSL-Se ECU run the stock GSL-SE injestor and add two extra 550's with a megasquirt fuel computer.
At this time I have the S4 rotors/housings in my GSL-SE.
I am using the stock GSL-SE ECU but want to add two more injectors and get rid of the barn door style Air meter. HKS had a injector computer that is able to run 2-6 more injectors. I saw one on e-bay for 200 and did not pick it up. Now I wish I would have.
Well, good luck with what you do.
here is my motor,
12-24-04, 01:43 PM
#21
Absolute Power is Awesome
Originally Posted by Jeff20B
I think the Weber DCOE or DCO has a choke. One or the other. hormbm would know for sure since he has one.
12-25-04, 02:59 AM
#24
FD > FB > FC
DCOE has the choke, dco is the competition version with no choke
The weber works great on a 13b 6 port, granted mine is a s4 motor, but with the mods in my sig, im running 14s on stock port
The weber works great on a 13b 6 port, granted mine is a s4 motor, but with the mods in my sig, im running 14s on stock port
Last edited by hornbm; 12-25-04 at 03:01 AM.