Carb gurus: Trouble with Idle circuit on Barry Grant
 

Please Help. Ran into trouble with the idle circuit on the Barry Grant install. Will crank but won't go to idle. The 2-3 bars of vacuum the 13B has is not enough to pull enough of the idle fuel through the fixed (non-adjustable) orifices. F*ck me to tears. God, this thing is beautiful and should be adjustable as hell through the rest of the tuning, but it will not stay cranked more than a few seconds and will not idle... even with timing advanced to the max.

Carb experts, what do I do? Is this one of those inside info things that rotorhead carb guys know and modify when they rig a Holley 600 for a rotary application ? Are there any others? Is this project salvagable?

Is the Sp 13B Holley from Racing Beat what I need ?

oh come now you are treading in unmarked territory, BUT there has to be a solution to your problem.

What is the recommended fuel pressure and what are you running your's at? I have never seen a BG so that's probably the best help I can give. How much vacuum does your sp pull?

What BG carb is this? A road demon? Like a 650? I know they are similar in circuit function to a holley AFAIK. They dont have idle mix adjusters on the metering blocks? WTF? Are you sure they dont?

7.0 psi fuel pressure. Nearly 3 on vacuum cranking (or turning over I should say).

Demon 575.

Speed Demon with mech. secondaries and manual choke.


Uhhh... I get the dumb ass award. We forgot about the Idle-Eze adjustment that will prevent us from having to "guess drill" holes through each butterfly or throttle plate. It'll be this afternoon before we can play some more.

Eh, just throw it away.

We've had a lot of problems with BG carbs. They might work fine for racing applications, but the drivability sucks even more than Holleys. Lots of times, the metering blocks are drilled wrong or something, and they just never run right.

Best of luck!

Take out most of the adjustment on the idle ease. Remember this is a 4 corner idle carb. Back off the throttle adjusters on the primary and secondayr side, then turn them in about a full turn each. Turn all a/f screws in all the way and then back each out about 1 1/2 truns. This will give a base to start from. The only issue I had with my 650 BG was sticking throttle plates which took a while to resolve. Driveability with this carb was excellent for me on my s/c 13b

Update: Idles great now, throttle response (unloaded) fantastic, no "bog" or 3200 launch required anymore. This is off the shelf with no jet changes yet.

Biggest initial problem was a HUGE vacuum leak. When I earlier said 2-3 on vac, that was myfirst time of ever measuring vac on a rotary even though I have owned one for 20+ years. After the leak (between the carb and the plenum seat) was fixed, the vac is now reading 16-18 now. Uh, no shortage of suck here !

So... it's awesome so far. Sounds like a cammed boinger. The air suck sound of the sidedraft (which I liked alot) is gone, but the engine and exhaust sound is cool. This is not going to be a problem tuning at all. I'll update as we go.

BTW, I spanked a Mitsubishi Spyder last night from a red light start in my 5 cylinder Colorado. At the next light he tried again. I was just wishing that I had been in the tuned 7 instead of a pickup trick.

I thought your vacuum sounded a bit low, lol. My 1/2bp only pulls 8-9. You're where you should be now.

What are you running for an air cleaner?

Air breather ? Nothing yet. I believe the turbokinetics hat will fit and send a 3" side outlet in the direction of the big space in the engine compartment forward on the passenger side. A K&N will be at the end of the cold air tube.

no. no , no, NOOOOOOOO! That will not work! Neither will the triangle shaped foam air cleaner. I tried the K&N carb hat with the large opening and huge filter (see pic) on my s/c SE and it fell on it's face at 6500 because it couldn't get enough air. A carb hat is meant to pressurize a pleanum above the carb, it does no provide an adequate plenum for a high volume n/a engine. The triangle filter with the foam insert the same(see pic). Go with a 14" drop base or use the "GM HEI ofsset" 14" base (also see pic) with a 2" K&N element. The offset base helps to clear the rad hose and turns the filter further baclk helping with hood clearance, witht his I flow past 8000 rpm.

ok. OK, OK, OKAAAAAAAAY. LOL.

I see what you're saying. Damn! Hell, I'll get velocity stacks and filter hats before I'd put a round OE style air filter on there. Now yours DOES look much better than the Racing Beat space ship thing. But if I talk myself into the same filter setup I had on a 1974 Plymouth Duster, then the next thing I'd be thinking that those chrome gas pedals that are shaped like feet would be cool. Hmmm. What about Cragar Classics? Know what I mean?

What about the hammerhead shark looking 4-barrel filters (if I've got clearance and $200+ bucks)? see pic...

I've seen that on a big block, hopefully it would work well. I do like that one in particular, just with the camden on mine I don't have enough hood clearance.

"After the leak (between the carb and the plenum seat) was fixed, the vac is now reading 16-18 now."

I'm curious as to how you fixed the leak? Was it the gasket / seal? I suspect I have to trace a vacuum leak, here lately, myself. When the colder temps hit, here, my idle seems rough. It did the same thing last winter.

Any tips as to where you took a vacuum reading at?

Thanks!

The used, but in excellent shape plenum I purchased and had powdercoated may have been not perfectly flat. We'd had one carb stud strip on tightening, too but the other three were held "pretty tight". Now all are bolt, lockwasher, flatwasher, carb, gasket, plenum, flatwasher, lockwasher, and nutted.

Measured from the top vac line from the carb that normally is hosed to the brake booster.

The Turbokinetics piece on your set up will deliver more than enough volume for your application. You are only pulling 575cfm maximum, and even with a 13b rotarys air velocity at higher rpm, you are nowhere near hitting the ceiling. Remember, the airbox is designed to move way more volume of air due to the fact its intention is lots of forced boost via a turbo, supercharger, or even nitrous. Here is the important part. Only use the best highest flowing filter you can, an insufficient(too restrictive) air filter is the only way you could mess up your excellent idea of using the turbokinetics piece. Solid engineering.

When I have the money, I'll be using a turbo plenum on my Edelbrock. I figured the 3" inlet and tubing would be plenty. If you think about it, its no different than any other intake system. Most of the plenums out there can flow in excess of 800cfm I would believe. Its the filter that limits the flow, as mentioned above. Use a large K&N filter with a 3" outlet. Should flow more than enough.