Buggy

iTrader: (8)

I know a lot of people over the years have run the rotary engineering dual weber 36 DCD setups on a lot of different engine combinations so I'm looking for the collective wisdom of those people to guide me on mine. I just picked up a set and I'm planning on running them on my 4 port 13B half bridged frankenrotor engine in my Rx-4. I had the poor 48 IDF weber maxed out to flow as much air as it possibly could so I'm hoping the dual 36's should work a bit better. I'm just looking for suggestions on what size jets and venturis (chokes) I should be looking at running to start with. I have a dyno at my disposal so this thing will get tuned I just need a good starting point. As far as I can tell the carbs are set up the way they came from rotary engineering at the moment. I haven't torn them right down yet. Any help is greatly appreciated. Thanks.

23Racer

That's a dang cool and rare setup!

I will be very interested to see how this works out.

Eric

j9fd3s

iTrader: (3)

i would just start with what is in there, and see where you're at. besides you need to tune them for your engine anyways...

Buggy

iTrader: (8)

Ya it should be a pretty fun setup once it's all up and running. I'll have to bring it by the track sometime Eric. I was pretty much just going to run them as is other than the primary venturis. They are quite small. I'm thinking I'll have to go bigger on those for sure, maybe even put the same size in as the secondaries. I think it's running 25mm primary and 32mm secondary venturis at the moment. I'll have to double check those numbers.

zak rabbit

Wish I could be of more help, I had a set on a monster street ported 13b about 20 years ago now and that setup made the most wonderful noises at WFO!!! Problem is, it was set up by a friend, and I have no clue what those were.

Buggy

iTrader: (8)

No one else has any more input on this topic? I'm hoping to get the engine built and the car put back together this month.

kirkosaki

I have a question about timing of the 36dcd webers.
from what I gathered Leading and Trailing should be advanced by 5 degrees for synchronization. After balanced and synchronize rev engine to 4k rpm, advance the leading to 18 degrees for street use? 0-3 degrees tdc @ idle.

15 degrees ATDC = trailing?
0-3 degrees BTDC = leading?

@ 4k rpm = 18 degrees BTDC leading

I've been trying to read the manual that someone posted in the forums, but its hard to pick out the words and I don't think I fully understand timing.

Buggy

iTrader: (8)

I got both manuals frim foxed.ca I haven't gotten mine running yet so I haven't even looked into setting the timing yet.

kirkosaki

Foxed.ca is a great site! Thanks for the info

Buggy

iTrader: (8)

I got mine running last night. Been driving it around a little bit. Seems to work quite well with the rotary engineering jetting. I haven't gotten the timing checked as my Gilmer drive pulley doesn't have any timing marks. I need to get my stock pulley out and make marks on my Gilmer drive. I also need to get a synchro meter and install my widebands in both header runners to really fine tune it.

kirkosaki

I just marked my stock pulley the other day and added 5 degree increments from 20adc to 20btdc. Installed the twin alt. Pulley with the double belt setup. I am still running the stock nikki and will test it with the new exhaust system before installing the dual webers. I'm just waiting on the fab shop to make the exhaust up.. it's been a long wait.

Buggy

iTrader: (8)

I got mine marked and set the timing at 5 degrees advanced base timing just to start. The setup works really good on the primary side. Very smooth low rpm and transitions considering it's a half bridge. Also has noticably more torque than before. I have to do some tuning on the secondary side. The engine doesn't have the same high rpm pull it had before. I need to get my wide band installed and then get the car on our dyno.

Buggy

iTrader: (8)

kirkosaki

Looking quite clean and tidy.
May I ask where you hook up your PCV coming off the engine. Can you run them just to the ground (road draft tube?) Pics would be great! Thanks.

Here's my engine bay

Buggy

iTrader: (8)

I just have a small filter on the pcv tube that comes off of the filler neck. There are spots on the bottom side of the air cleaners though that you can punch out and put a nipple in to run your pcv back into the air cleaner. My one air cleaner has it, but I just blocked it off as mine vents through that filter to atmosphere. You can see the filter in that pic I posted just below the oil filter.

kirkosaki

Yes. My rear carb has a tube running to it. This is T to the gas tank ventilation and the oil fill neck.

So my understanding is you are running the pcv to atmosphere via air filter ? No vacuum source involved?

Buggy

iTrader: (8)

Yep that's about it. I don't have vacuum hooked to anything other than the brake booster. Fuel tank and pcv are just vented to atmosphere.

kirkosaki

Thanks man. There's been so much talk about what to do with the crankcase vent on forums.
I'll just vent to atmosphere and hook up a filter/breather to it.

The fill neck tube vent close to the oil cap and the gas tank vent will go to the rear carb intake like in the picure attached.

Btw, You shouldn't vent your gas tank vent to atmosphere... it can be a fire hazzard.

Buggy

iTrader: (8)

My car has a fuel cell in it and it is all vented there well away from the engine bay heat.

Buggy

iTrader: (8)

I've been playing around with the carbs for a couple of weeks now. It's tuned about as good as I can get it with the 25mm primary venturis. I had to increase the secondary fuel jets a few times and went one size bigger on the primary side. It feels like it has as much if not more power than before. I want to dyno it as it is now and then install larger primary venturis.

kirkosaki

Buggy! Did you get your timing set up? I'm still confused with the leading and trailing timing setup. Mine is 1 degree tdc leading and 15btdc trailing. Do you think this is right?

Right now the front carb is flooding a little. I guess the needle and seat is dirty / weak. The idle mixture is also not working right when I screw it in. It does nothing. Most likely due to the intermediate flooding. But other then that it runs dairly good !
I'll clean the seat and needle today and install my fuel tank, it was rusting inside :/

Buggy

iTrader: (8)

My timing is still just set at 5 degrees advanced (btdc) on the leading and whatever the trailing is set with the distributor. I can't check trailing timing as I have the Gilmer drive and I don't have the trailing mark. Sounds like you also need to completely tear your carbs down, clean, and rebuild them. Get yourself a synchronizer too if you don't have one. They are nice for setting the carbs up properly. I also had a wide band of sensor in each runner of my header so I could watch the a/f ratio for each rotor and carb. What are you using for ignition?

kirkosaki

I found a problem with my float. The float was too low. I adjusted it and swapped it onto the other carb. I'm still having the same problem as before. Raw fuel into the barrel.
I also must have a vacuum leak because the idle mixture works when I screw it out, it makes it rich and stumbles, but does nothing when I screw it in.
I cleaned the passage way and the progression curcuit works fine and fuel is getting to the mixture screw.
It gotta be a leak in the throttle shaft or somewhere else.
Note: thoese carbs I bought had some play in the throttle shafts. I try fixing this with jb weld to make a tight fit.. I guess it's not the best seal.

My ignition is stock. 3 degrees leading and 15 degree trailing.

Can I ask whar your float level is exactly at as well?

I have no tools for tuning.. Just a piece or hose to listen inside the carb.

kirkosaki

I got my carbs running! I test drove it today and its running smoothy. No flooding and great idle. Those webers really wake the engine up. The intakes sound amzing.

I fixed the throttle shaft leak with jb weld and it's a tight seal now.

I still need to fine tune the timing. I might go another degee advanced on the leading.

I just need a split choke cable now

Buggy

iTrader: (8)

Sorry I totally forgot to reply to your other post. My floats are set to the factory weber spec. They are an awesome carb setup for the rotary. I would advance your timing a bit more especially if your engine is ported at all. I can't remember if yours is stock or ported.