Off-the-Shelf Carburetor
03-26-07, 09:02 PM
#1
Off-the-Shelf Carburetor
I hear lots about how off-the-shelf carbs need a lot of work to run on a rotary.
What does this work consist of? I have an off the shelf here, and I plan on running premix. already fabricated the bracket for the throttle cable (no choke).
Any answers/ideas/points to be made are greatly appreciated!
Jeez
What does this work consist of? I have an off the shelf here, and I plan on running premix. already fabricated the bracket for the throttle cable (no choke).
Any answers/ideas/points to be made are greatly appreciated!
Jeez
03-26-07, 10:52 PM
#3
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if it helps, i took a holley 600 straight outta the box, bolted it all up, and started the car. it needed a little tuning and tweaking to make it run right. i ended up putting in jets that were a few sizes smaller, and i daily drove it for over a year. btw this is on a mild streetport 13b.
03-27-07, 12:13 AM
#4
love the braaaap
It all depends on the type of carb you choose as to how much tuning it will need. We need some specifics here. Mostly if your running premix, all you need to do is tune it right. Sounds like you got the throttle down, so thats out of the way. Tuning is the biggest thing.
03-27-07, 09:20 AM
#6
It doesnt matter what brand you get, it has to tinkered to get the full potential. If you're not up willing to take that task, you may as well forget about it and buy a car with "fuel injection."
There is a difference between "it runs" and "runs very well."
There is a difference between "it runs" and "runs very well."
Last edited by Siraniko; 03-27-07 at 09:25 AM.
03-27-07, 09:32 AM
#7
Waffles - hmmm good
iTrader: (1)
+1 on what wacky said. There's a huge difference between running ok and running well.
Heres a list of some of the things various after market carbs have done to them and what problems are being addressed.
1. Add nipples to accept the MOP lines at the proper place in the carb throat so it mixes well with the air gas
mixture. (not an issue if your premixing).
2. Adjust floats or add float options so that the float bowl doesn't slosh or go empty during high G turns. Dellortos and Holleys come to mind here.
3. Modify jets and air feeds to get the right mixture for a rotary. Very different depending on the carby being used.
4. Intake manifold thats is designed for the type of carburator and flows well especially with respect to port flow characteristics specifc to a rotary.
5. Accelerator pump mods to make the transition smooth when the throttle is opened. Mostly an issue on progressive two barrels like Webers and Dellorto's.
This is just off the top o my head, I'm sure others will come up with more.
Heres a list of some of the things various after market carbs have done to them and what problems are being addressed.
1. Add nipples to accept the MOP lines at the proper place in the carb throat so it mixes well with the air gas
mixture. (not an issue if your premixing).
2. Adjust floats or add float options so that the float bowl doesn't slosh or go empty during high G turns. Dellortos and Holleys come to mind here.
3. Modify jets and air feeds to get the right mixture for a rotary. Very different depending on the carby being used.
4. Intake manifold thats is designed for the type of carburator and flows well especially with respect to port flow characteristics specifc to a rotary.
5. Accelerator pump mods to make the transition smooth when the throttle is opened. Mostly an issue on progressive two barrels like Webers and Dellorto's.
This is just off the top o my head, I'm sure others will come up with more.
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03-27-07, 11:18 AM
#8
Waffles - hmmm good
iTrader: (1)
Look at this thread, theres some good info about what goes into tuning a holley as well.
https://www.rx7club.com/1st-generation-specific-1979-1985-18/about-holley-635311/
https://www.rx7club.com/1st-generation-specific-1979-1985-18/about-holley-635311/
03-27-07, 08:27 PM
#10
Originally Posted by t_g_farrell
+1 on what wacky said. There's a huge difference between running ok and running well.
Heres a list of some of the things various after market carbs have done to them and what problems are being addressed.
1. Add nipples to accept the MOP lines at the proper place in the carb throat so it mixes well with the air gas
mixture. (not an issue if your premixing).
2. Adjust floats or add float options so that the float bowl doesn't slosh or go empty during high G turns. Dellortos and Holleys come to mind here.
3. Modify jets and air feeds to get the right mixture for a rotary. Very different depending on the carby being used.
4. Intake manifold thats is designed for the type of carburator and flows well especially with respect to port flow characteristics specifc to a rotary.
5. Accelerator pump mods to make the transition smooth when the throttle is opened. Mostly an issue on progressive two barrels like Webers and Dellorto's.
This is just off the top o my head, I'm sure others will come up with more.
Heres a list of some of the things various after market carbs have done to them and what problems are being addressed.
1. Add nipples to accept the MOP lines at the proper place in the carb throat so it mixes well with the air gas
mixture. (not an issue if your premixing).
2. Adjust floats or add float options so that the float bowl doesn't slosh or go empty during high G turns. Dellortos and Holleys come to mind here.
3. Modify jets and air feeds to get the right mixture for a rotary. Very different depending on the carby being used.
4. Intake manifold thats is designed for the type of carburator and flows well especially with respect to port flow characteristics specifc to a rotary.
5. Accelerator pump mods to make the transition smooth when the throttle is opened. Mostly an issue on progressive two barrels like Webers and Dellorto's.
This is just off the top o my head, I'm sure others will come up with more.
1: You answered that yourself already
2: OER carburetors have floats hinged so that high G turns/ up and down hills hardly affect it.
3: Modify as in Drill/tap or just change jets?
4: Already have a side draft mani
5: Describe this to me! haha, OER is basically a modified webber
03-28-07, 09:57 AM
#11
Waffles - hmmm good
iTrader: (1)
3. For the Dellorto RB changes jets and drills extra holes in the emulsion tubes. See http://www.gruntled.com for details.
4. But does it flow and match what your putting on it well? Only someone that has a flow bench can know for sure. Thats what you pay for when you buy a setup from a tuner like RB. They've done the up front engineering to make sure you've got a good setup.
5. I know in the Dellorto and the Holleys some work is done to modify or adjust the AP. In the Dell case a thicker gasket is added to get a bit more fuel in the squirt so it doesn't bog on transition and the AP mechanism is adjusted just so to make it work optimally. I've read that the Holley's get a special treatment to their AP but I'm fuzzy on that one. Dell is basically a Weber knockoff as well and its considered an improvement yet RB still had to tweak some things to make it completely streetable.
I think thats the difference sometimes. If your using an aftermarket carb on the street as a DD or for stop and go traffic then the tuning from idl through to the main air/fuel circuit has to be tuned prefectly or you get rough idles or poor transitions from low revs to higher revs. Which on the street translates into rough running in traffic and stalls and so on. If your using these on the track then there's a much more focused rpm range to worry about and transition from idl to full throttle aren't an issue and you just learn to keep the revs up so you don't foul out. So whether you can use an off the shelf really depends on your expectations. When I read that I translated it into streetable.
4. But does it flow and match what your putting on it well? Only someone that has a flow bench can know for sure. Thats what you pay for when you buy a setup from a tuner like RB. They've done the up front engineering to make sure you've got a good setup.
5. I know in the Dellorto and the Holleys some work is done to modify or adjust the AP. In the Dell case a thicker gasket is added to get a bit more fuel in the squirt so it doesn't bog on transition and the AP mechanism is adjusted just so to make it work optimally. I've read that the Holley's get a special treatment to their AP but I'm fuzzy on that one. Dell is basically a Weber knockoff as well and its considered an improvement yet RB still had to tweak some things to make it completely streetable.
I think thats the difference sometimes. If your using an aftermarket carb on the street as a DD or for stop and go traffic then the tuning from idl through to the main air/fuel circuit has to be tuned prefectly or you get rough idles or poor transitions from low revs to higher revs. Which on the street translates into rough running in traffic and stalls and so on. If your using these on the track then there's a much more focused rpm range to worry about and transition from idl to full throttle aren't an issue and you just learn to keep the revs up so you don't foul out. So whether you can use an off the shelf really depends on your expectations. When I read that I translated it into streetable.
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