man i need to look on how to get the choke back on my car, it's getting colder and the cold starts are getting harder

 

This is a good thread.. Does anyone have any time slips or actual dyno figures showing before and after adding aftermarket carbs?? I am about to start a project helping my friend install a Holley 465 CFM and RB intake. Luckily he has already removed the stock intake and carb/ratsnest.

 

percentseven....... what is your current jet/FP/air corrector/needle specs, i was following your thread for a while but i dont think its was re updated.

 

I have a 45dcoe and a mazdatrix manifold.. i love the combo.

 

All I've done since I updated it was increase the fuel pressure to 4.5 PSI per Hyper4mance2K's suggestion. It helped, but I still need to go jet shopping sometime.

Current settings are:
40F9 idle (too lean; I'm thinking of trying 50 or 55F9)
180 main
180 a/c
F11 e-tubes
60 accel. pump (too small)
Don't know the needle specs

 

48 ida on a 13B LARGE extend port (14.4 @ 112mph ***** launch and 2-3rd) with holley red pump. Most NA tangs down here run ida setups.

 

Im running a RB 465 holley on my 12a streetport. I have upped the accelerator pump to 50cc and put on new metering plates, to allow my to put jets in the secondary side, and also changed out the vaccum secondary spring. I love it, its sounds nice, starts with no problem, pulls good with no hesitation and parts are readily available.

 

g/l with that upgrade. ur friend will like the increase power the holley will give. i used to run that same carb on a stock 12a and it definitely wakes up the stock port. i currently run the RB holley 600 on my old skool streetport 13b(74 rx4). the clutch wont stand taking it down the strip. the engine was last in a 75 808. i took the 808 to the strip after putting 8500 miles on the build. getting there late, the place was packed so only got a couple runs in. best time was 9.38 in the 8th mile.

 

dbl post, sorry

 

Over the weekend i rebuilt a 48dco that i had...i actually have 2 48's. After installation and a good idle i checked for revs it would just bog n bog, so rechecked floats and ensured there was no sediment in carb and also checked to make sure the needle would move freely(it wasnt) i found a tiny piece of sediment on the needle in the housing(sand maybe) that was binding it up. Put it all back together, it was better but not great. So i cranked the fuel psi up(on the 45 it was 1.5-2ish. well the 48 likes a healthy 4-5 psi.

Next was test drive....... This carb had 3 progression holes already for each barrel- the 45 did too??? take off is good, not EFI good but predictable. The 48 makes way more power than the 45, i havent taken the engine past 6500 as i just hit the 1k mile mrk on the rebuild but it feels like it will keep going. Where the 45 would fall dead.

The carbs specs are
needle/seat-3.0
idle jet 65f8
fuel pressure 4.5
emulsion tube is f-11
a/c is 160
main is 190
choke is 36 i think.
not sure what the accel pump is though pbly factory

 

nice brandon...i think your 13b likes the extra breathing room with the 48...almost like how my 12a likes my dellorto..

 

Just took a look at my buddies Holley 465 and RB intake he just got. Looks like everything will hook up and work good. Does anyone know how to hook up the chock tube. This carb has the old school copper tube that goes to the choke.. What do you hook this up to?

I still am leaning towards the 45 DCOE on mine. I know Holleys from my V-8 days, but a weber on a rotary just looks right! Kinda like dual webers looks "right" on a VW!!

 

I have 2 cars, with totally different setups.
On my 83 12A car, I have the stock carb. That may change soon.
On my GSL-SE, I have the RB Holley intake and an Edelbrock 600. That rocks. I'm actually thinking of getting an RB intake and another Edelbrock for the 12A, but I'll prolly go with a 500 eddy on it, unless I drop the holley 650 DP on the 6P 13B.....
Kinda funny, I'm no fan of Holley carbs, but I have 2 of them just waiting to be installed. May swap a buddy the DP for his eddy. He doesn't care for edelbrock's, in spite of getting 9+ MPG in his 460CID F350 crew cab, while towing a huge trailer.
Both cars have RB "Street" headers on them, but not the entire RB system.


You failed to list Edelbrock carbs in your options, so I failed to bother voting.

 

I guess Edelbrock would qualify under "other" in the voting!!
I have not messed with Edelbrock much either. Kinda reminds me of the old Carter carbs. I know people that like them. Guess it is what you are used to!!

 

Do the stock Nikki's have power valves? I just wonder why my car gets such horrible gas mileage and always seems to be running a tad rich. I have adjusted my idle mixture to where the car seems happy, but my exhaust pipe is always sooty and the 14 MPG is nothing to brag about.
If the stock carb has power valves, I wonder if mine could be sticking open which would cause shitty gas mileage...

 

Edelbrock carbs are basicly new castings, by weber, using the same molds once used to make the Carter AFB. Far easier to tune, compared to a holley, and the secondaries are never opened further than the engine can handle.

Stock Nikki carb's do not have power valves, as far as I am aware.
14 MPG is pretty lousy. I can get nearly that bad of MPG by spending a day at the track. On the hiway, I have gotten 26+MPG wih the 12A car. I have no clue what the 13B/edelbrock combo will deliver, as I've just gotten the car legal this week.

 

another update...... with last setup i was getting some bog into the progression phase. After changin the main jet to 170 and the a/c to 160 its the best its been yet. I have a inimal amount of partial throttle hesitation on 4th at 30-40 around 2-2500rpms. Any suggestions?

 

Unfortunately, the stock SA Nikki's just run rich due to the thermal reactor system. The best mileage I've gotten is 14.7 with some decent cruising(not on the freeway though). I'm thinking of stripping down my FB Nikki and see how that does for me. And I'll add into the mechanical secondaries responses, my vacuum secondaries open up about 3/4 throttle and pull great from 3k onward. I just don't think mechanical secondaries make sense. "You can open them up whenever you want..........just so long as it's after 3k rpms so it doesn't bog" Wait what?!?!? Just doesn't make sense to mess with something that works just like it's supposed to and does it great?

 

I have to agree, actually. I like mechanical secondaries for their simplicity, but at that point, you might as well just get a big 2-barrel. I'm sure Sterling will inform me why I'm wrong.

 

the bog is only very noticeable in 4th/5th gear, if you have it in 3rd you can pretty much still gun it, you may get a slight bog but it won't last long at all, 3rd is very responsive, you'll only feel it if you are in 3rd and about 1.5k lol....if you wanna take off with the secondaries open it'll be jerky as hell, it'll stutter for less then a sec then it'll throw you back on your seat i guess what i really like about mech secs. is that if you're going hard on it you don't have to "wait" on the secondaries after every shift you can pretty much stomp it and it'll be there. i'd say it buys a sec or maybe even 2 from vacuum secondaries shifting specially on high gears....idk i can't remember what it felt like to have vacuum secondaries lol.

 

There will always be a slight bog/hesitation when the secondaries open, after the mechanical mod. You can help to eliminate it by modding the accel pump, but it will never fully go away.
The reason is simple. In the lower RPM range, the engine cannot pull enough air thru all 4 barrels to *properly* atomize the fuel, therefore it bogs.
At higher RPM, the transition to the secondaries happens faster than the carb was designed to handle, and it takes a moment for the fuel mixture to adjust. This is why you have to relearn how to drive the car, after installing a Sterling carb.

The only 4BBL carb that is actually designed to allow for all 4 barrels to open at once, is the double pumper variation of holley, and others using a similar design. As the throttle plates open, extra fuel is needed. This is true no matter what brand/style of carb. The accel pump adds the extra fuel needed. On the DP variation carbs, there is a second AP that operates with the secondaries.

 

I dunno RW. With my Sterling, as long as I don't do something stupid like floor it at 1000 rpms, she never seems to suffer from any hesitation.

Really, the thing I like best about the mech 2nds (on both a stock carb, and a Sterling), is the fact that it puts you in charge of the throttle rather than a vacuum actuator. As long as you can be a little bit responsible, and not try to floor it at low rpms, you can use this to your advantage.

The easiest place to see this advantage is during hard rain. If your secondaries engage when you are not expecting it, you can easily end up facing the other way. With mech 2nds, they aren't going to open unless you do it yourself, so no surprises. I love racing autocross in the rain.

 

That's true, but ideally it wouldn't be a problem even with vacuum secondaries. Like I said, in my GLC I couldn't even feel it when they opened (it just got louder ). They opened precisely when needed, not too soon and not too late. The Edelbrock Thunder Series carbs have a valve for adjusting the vacuum secondaries, so you can get them just right. That's the theory, anyway. I've never actually messed with one.

 

Lets look at each statement. All of this is based on a PROPERLY operating stock carb.
"as long as I don't do something stupid like floor it at 1000 rpms". That's exactly what I mean. The vacuum secondaries don't open under that condition, therefore, no bog.

"If your secondaries engage when you are not expecting it, you can easily end up facing the other way. With mech 2nds, they aren't going to open unless you do it yourself, so no surprises " A properly operating stock carb will open the secondaries as needed, but only as far as the throttle will allow. They also will never open more than what the engine can *actually* use, nor faster than it can handle.

"the thing I like best about the mech 2nds (on both a stock carb, and a Sterling), is the fact that it puts you in charge of the throttle rather than a vacuum actuator. As long as you can be a little bit responsible, and not try to floor it at low rpms, you can use this to your advantage. " See above.

"I love racing autocross in the rain" Not me, I prefer to have the sunroof out, for more headroom. I also like to "hear" the feedback from the tires, not just go by feel.


I've tried the mech secondary mod, and I didn't care for the bog as it transitioned to opening the secondaries. This almost always happened as I was exiting a turn, and upset the car's balance. I unhooked the wire, and shaved 2 seconds per lap from the previous run, simply because I wasn't fighting with the carb. The secondaries still opened at about the same spot, but they did so in a much more controlled manner, allowing me to concentrate on hitting my mark, rather than dividing my attention between hitting the mark and throttle position.

 

i like this thread

lead currently goes to mazda engineers and the stock