I have a street ported 12a with a racingbeat intake and 650 holley (with no choke plate) i recently bought the car and i have never owned a carb without a choke plate so im not sure if this will be an issue or make the car less smooth. the car sputters when i hit the accelerator abruptly so i know i need to do some tuning. The CFM is ok but im not sure if the previous owner should have gotten a carb with a choke plate? also i have some issues in hard braking where i believe the bowls flood out and sputter. I found a thread on here for fixing some of the issues like "getting center mounted" floats. but i'm not sure if i should start tuning this carb or start with another. any help is appreciated.

 

So today i pulled a plug for show and tell. wanted to see if it could help me identify if i was running to rich or lean. They were supposedly recently changed. they are NGK 8's not the 9's. (might switch later). well anyway they were black, i mean black! so that's rich right? should this be a direct hint to lean out my air / fuel mix?

 

First place is to check the float and make sure it's not to high you won't be able to set the air screws if it is to high or low. Start there I am guessing the float is a little high that could cause the fuel to spill inside . maybe check your ignition timing while you are at it and let us know what you find .. If you don't know how to set the float say so and I will walk you through it ..

 

I have a Holley tech man and i see that it is just a set screw with a lock. i will adjust slightly then check view port again. i don't have a timing gun yet but i may invest in one.

 

i posted in the other thread. and yes it rich, mine is the same way. mine is from RB and it's only a 600. RB mods these carbs to work on a rotary. but others have tried to use regular off the shelf carbs. one mod i do know RB does is they do away with the power valve and install a plug. i couldn't tell u what jets i have without taking the bowls off. i have my idle mixture quite rich to help the problem i'm having with transition. there's alot i can live with that others absolutely refuse to do. if ur holley tech guy can tune it get u some jets and see what he can do for u.

 

When they plug the power valve it usually requires about 4 to 6 sizes larger on the jets from what ever size the carb is using depending on what it is on to make up the difference.

 

a 650 is to big in cfm....look for a 390 hp series.vairy tunable..get quik change jet bowl's and road racing floats......and you will have alot more fun

 

Well it's a 600cfm and its what's on the car so im just gonna tune it as best as possible. the whole setup was done by racingbeat a few years back and just needs minor tweaking. Today i adjusted the fuel pressure to 5.5 psi rather than 6 and tightened down on the primary float a hair. i can't drive her til friday due to work so i will have to let you know how it goes then. I am going to change the NGKs as well since they were black. i am not going to venture to change the air / fuel screw just yet. may not need it. Can anyone tell me what color accel pump cam they have had the most success with?

 

So last night i checked the timing. both the lead and trailing were on point. I took her out today to get gas and she drove like ****. almost stalled like 3 times. brought here home and tried to reset idle mixture. So i set her 1.5 turns out on both screws and then started her. idling around 1100rpm i began to turn the first screw clockwise at .5 turns she started to bog out and sputter. I reset her and tried counter clockwise (leaning) and got about 2.5 turns before she started to chug. I reset her and chose a mid point; about 1 full turn from 1.5 out so now she is 2.5 turns out on both screws. when for ride and she was still choppy and somewhat rough. I started to get frustrated and called "San Diego Carburetor" they offer tuning and rebuilding used a gas analyzer in the tailpipe. With how much i am spending on tools and gages to try and do this myself i thought i should compare that to professional tuning. They range from $200 with gas analyzer tuning (ballpark figure) to 350 for a total carb rebuild. this i thought was interesting because a new carb is like what; 200 bucks? anyway, I had to order the NGK's (9's) because no one seemed to have them on the shelf. they will be here tuesday, maybe they will help considering how black the prior ones were. blah blah

 

If you're going to spend that kind of throw away cash for tuning, start with the right carb first, otherwise just flush the cash down the toilet. The carb is too big and not a Racing Beat prepped one. Personally, Holley's don't belong on a rotary, period, but that's my opinion. I prefer the 2 barrel Webers, Dells or Mikunis. My favorite choice however is the Weber dual DCDs that I have on the widebody.

Your best option might be to find a Weber IDA setup and sell yours. If not, at least buy the right Holley from RB. Either way you will recoup the cost in fuel and tuning savings.

 

I have made some progress. I found a local (well sort of local) guy who is interested in my RB intake for his race application. for my intake he will build me a modified Nikki and will match it to an intake that is included.