Hello all, this winter I started playing around with the idea of building my own carbs for the 12A engine, since Ive already built several over the years that went to happy owners.

I bought an RB holley 465, and was totally let down by its performance, the workmanship that went into it, its price and the way it actually ran on one of these cars.

Made me think in the last 10 years the 4bbl carb selection for our cars was pretty much crap, and that we only had one, crappy option for one at the moment.

So I decided to build my own!

I started building them through some relations I have through Jegs, and Holley and ive come up with a very nice carb for street/race use in the form of a holley 4bbl with an FPR and fuel pump included, all at less cost than the RB 465. It also is correctly calibrated for use (IE jettings, at least in the eastern US).

My carb has all of the same modifications made to it that RB does, and some others they dont do, too

It would be packaged as a 4150, (2 metering blocks) an improved fuel bowl design, manual choke, and vac OR mech secondaries depending on the customer.

I start with the same 0-1848 465 cfm carb that RB does, and I throw 70% of it away.

I have a few running very well on test cars here in western PA, and I can give real honest results (maybe a test drive if youre close enough).

I can get some pictures and share a little more about the carb if anyones interested

 

This sounds very interesting. I'd be interested in this for our fb performance project.

 

Are they perched on RB manifolds? And I'd love to know more.

 

Yes, its an RB mani. The carbs ive built have all gone on 84-85 12'as, although I dont think theyd be very different for the earlier generations.

Ill get some pics of the set up tonight.

 

pics please and maybe a price range

 

 

Last shot I did was of the interior I got to do the last 5k miles worth of testing in :P

Sorry if the carb and engine bay looks dirty, but ive been doing some pretty grueling testing with it since I finished this model.

The one pictured is slightly different than what id sell, in that it has a "jet plate" in place of the metering block, which as I found out is actually more expensive to do then actually doing the work to convert it to a 4150 with 2 metering blocks.

The regulator is a JEGS Performance Products 15909 JEGS Billet 2-Port Adjustable Fuel Pressure Regulators (included)

Fuel pump is a http://www.jegs.com/i/JEGS-Performan...rentProductId= (included)

You'd need to supply the throttle cable bracket, and intake mani.

Total cost for everything would be approx 750$.

Cost without FPR or FP would be about 650$

 

: /

 

Vac sec. carb going to dyno wednesday

 

Did you think about using the Edelbrock?

I've heard good things about them being easy to setup on rotaries.

 

Doesn't sound like much of a deal, when RB non port and streetport carbs are at 638.00.

 

And that price from RB includes craptastic side hung fuel bowls, metering plates that you cant swap jets on on the secondary side, a crappy heat stove auto-choke, junk standard holley throttle plates, and are generally delivered in a shitty state of tune. Ive ordered 3 from them over the years, and never had one ready to run the day I installed it. They always needed jetted up, and had pig rich idles because of the IFR they choose to run, which is garbage. And the worst part about it the RB, is after you actually get it running properly, you have no idea what hp it makes, bc they tell you any changes to the "default" jetting reduces MPG's and HP.

But if you want a poorly tuned 4bbl, that surges and cuts out in any sort of corner, that youll eventually have to dyno tune for power, and want 17 mpg; the RB is a STEAL at 638$

Lets not forget you cant order one from them with no choke, and certainly not with mech secondaries.

If RB was selling these carbs outfitted the way they are, it would be a 1000$ carb.


My carb is 650$ bc theres 200$ extra in just quality of life parts like the bowls, choke and metering blocks. Not to mention full quality AED brass parts in the metering body...

 

Yes, the edelbrock is a nice carb, for the 13b. Not so for the 12A. I tried them first, and I couldnt tune the emulsions finely enough on the 12a to control its ratio from mid range to top end. You couldnt have your cake and eat it. If you fattened up the mid range for torque, or to fix a dip in lean condition, you were too rich on the top end. If you leaned it out for power on the top end, it was lean everywhere. The stage circuits in the edelbrock dont offer the tuning you need for a small engine pulling air the way it does. I can get one to run "right", where it has no bogs and feels strong, but its down on power that way, at 16-17 mpg. If the 12a was ported and provided a stronger signal, the edelbrock would be ideal... maybe. Id need a SP 12a to play around with.

The vac secondary holley pictured above is getting me 19 mpg with combination city and highway driving, cruising at about 75 mph. Only thing I would change on the holley, would be that tune surges and bucks on decel, but doesnt pop. It feels like driving a manual mustang with a cam :P But then again, all 3 of my RB 465's did that out of the box too... I just cant figure out how to tune that bit out.

 

Ok youve got a point there. What brand metering block and bowls are you using aed also? Aed makes really good parts for Holley carbs, especially there metering blocks wankel=awesome.

 

really?

 

Genuine holley "HP" blocks, AED bleeds+jets.

 

Yes.

 

Carb has been to the dyno! Turns out the surging thing the holley carbs are subject to on decel was cured with a slightly different timing than stock.. not sure if this is normal.

The vac. sec carb is ready for sale now, if anyone would want one. I still need to put both the mech secondary and the 450 cfm chokeless versions on the dyno.

Still offering test drives to anyone close enough to local who might be interested in buying modded carbs, or paying for just the mods

 

You going to post the dyno results?

 

As for the hp results the car generated 127ish hp, but im waiting to dyno the other 2 versions on other engines for a real number. The particular car that this one was on has a rebuilt engine with what the owner calls a "cleaned up" port, so I cant really say this one is a stock port. Im going to have to wait and see how one does on either my mazda rebuild, or the 80' LS we just put the mech secondary carb on. It has the lowest miles, and is an original engine that hasnt been rebuilt.

The dyno time we did the other day was to pick final jet size and emulsion combinations lol, not for hp bragging rights. :P