Holley Carb Vacuum Secondaries - Help

[84Toyota4x4]

Ok, so Im a complete newbie with Holley carbs, but Im far from incompetent I would hope, haha.

I have a Holley 4160 (I believe) which has a vacuum secondary system that isnt working. I verified this twice by using both the bread tie and the paperclip tests (putting each on the vacuum pot shaft and driving full throttle through 3 gears), there was no movement at all.

I pulled the secondary vacuum pot and discovered the diaphragm was leaking (compressed shaft, held port covered), so I took it to Jim Greens and they got me a new one. They also got me new metering block and bowl gaskets about a week earlier as the carb had the wrong ones on it. I also picked up a yellow secondary spring (very light) while I was there. I blew some light compressed air into the vacuum port, and air comes out the hole under the butterfly in the primary venturi, so its not clogged. I read about a hole possibly in the secondary venturi also, but I didnt see/hear one?

I got home, installed it all, and repeated the test. No movement still. I pulled the whole thing back off, put a new o-ring between the carb body and the secondary vacuum pot, reinstalled it all, still no movement. With the engine off and the throttle held wide open, the secondary linkage and butterflies move freely and easily, no binding at all.

Ideas? The carb is sitting on a Mazda rotary engine, so its not a typical application, but I figure there are enough people here with some experience that it might be a "common problem" and not necessarily "application specific". Here is a link to the carb kit (which was bought used):

http://www.racingbeat.com/Mazda-Performance-Parts.html?PartNumber=18034

It also has these float bowls:

http://www.racingbeat.com/Mazda-Performance-Parts.html?PartNumber=16641

Im running a Holley blue pump and regulator, fuel is set to 6 PSI, float levels are correct. As I said, the carb was bought used, so its possible someone mucked with something, but it seems like a fairly simple system, and I dont get why it wont open the secondaries...

Thanks in advance!

~T.J.

 

[messix]

if the engine isn't drawing a vacuum at wide open throttle it won't open the secondary. = it doesn't need that big of a carb.

run a vacum gauge into the passenger compartment and drive the car and see what the vacuum reading is at wot.

 

[84Toyota4x4]

if the engine isn't drawing a vacuum at wide open throttle it won't open the secondary. = it doesn't need that big of a carb.

run a vacum gauge into the passenger compartment and drive the car and see what the vacuum reading is at wot.

So simple. No wonder I didn't think of it.

17 in mg at idle, 1-2 in mg at WOT. Is that enough to open those? I suppose it depends on the spring? That sure doesn't seem like much...

Could horrible A/F ratios hinder that? I should think so. This carb isn't tuned for this motor yet and is running pretty rich I think.

Thanks!

~T.J.

EDIT: I'm wondering if what I'm seeing actually isn't just gauge error? The zero area is a little large and the gauge returns to zero differently each time, haha.

 

[messix]

what size is the carb?

a 450cfm might work.

for the secondarys the wot vacuum needs be more than the secondary spring is rated at.

the richness is prolly the idle isn't set up right. check the float level too. you can roughly adjust the adjust the over all mixture with the fuel pressure and the float level. high fuel level in the fuel bowl will richen the set up and lower levels will lean it out.

and rotory's are a different breed. you need to get a a rotory forum to get better advise.

good luck.

 

[84Toyota4x4]

what size is the carb?

a 450cfm might work.

for the secondarys the wot vacuum needs be more than the secondary spring is rated at.

the richness is prolly the idle isn't set up right. check the float level too. you can roughly adjust the adjust the over all mixture with the fuel pressure and the float level. high fuel level in the fuel bowl will richen the set up and lower levels will lean it out.

and rotory's are a different breed. you need to get a a rotory forum to get better advise.

good luck.

Supposedly its a 465. I reset the idle (four corner) and got it up to 18-19 in mg. I had guessed before and set it without the gauge hooked up.

I will try lowering the floats a little and seeing if that helps at all. I did try pulling the spring completely (I know, I know)
but it still didn't seem to want to open, the bastard.

I'm on a couple rotary forums, have been for about 10 years. I was running a Weber side draft 2 bbl, which I'm ok with. I got this about a year ago because my car was stolen and stripped and I got a good deal on it. I'm just trying to make it work out since I just got the car running recently.

Again, thanks for the tips!

~T.J.

 

[Binder]

Sounds like the engine just doesn't need the CFM required to open the secondaries. I would beware of trying to adjust the mixture too much by screwing with the float level. Use the idle mixture screws that's what they're for.

 

[Binder]

What's the dispacement of the engine and max RPMs?

 

[messix]

Sounds like the engine just doesn't need the CFM required to open the secondaries. I would beware of trying to adjust the mixture too much by screwing with the float level. Use the idle mixture screws that's what they're for.

if you do readjust the fuel presure it will affect the float level. 6psi is kinda high for a holley. 3-5 psi is good. remember thats how much pressure the float is going to need to work against to close the fuel inlet needle.

and the idle "screws" will only adjust the idle mixture, it will not do anything for the part throttle or wot mixture. you would have to change the main jets on the primary and secondary to adjust that. to get really deep for part throttle you would also change the air bleeds and emulsion tubes to dial in the mixture.... but your dealing with a holley and close enough is... close enough.

 

[Binder]

if you do readjust the fuel presure it will affect the float level. 6psi is kinda high for a holley. 3-5 psi is good. remember thats how much pressure the float is going to need to work against to close the fuel inlet needle..

Correct. You need to set the fuel pressure before setting the float level but this has little to do with mixture so long as the fuel level is within it's correct level "range".

and the idle "screws" will only adjust the idle mixture, it will not do anything for the part throttle or wot mixture. you would have to change the main jets on the primary and secondary to adjust that. to get really deep for part throttle you would also change the air bleeds and emulsion tubes to dial in the mixture.... but your dealing with a holley and close enough is... close enough.

This is why you have to change these things to adjust mixture. Don't forget the power valve, accelerator cam and nozles too.......If you were to say lean out the mixture at idle by lowering the float level you're effectively starving the carb of fuel supply. Fine and dandy at idle but now what happens when you increase the load but the supply is barely enough to supply idle demands?.....Anyways my point is I wouldn't cheat on this with float level.

 

[messix]

Correct. You need to set the fuel pressure before setting the float level but this has little to do with mixture so long as the fuel level is within it's correct level "range".




This is why you have to change these things to adjust mixture. Don't forget the power valve, accelerator cam and nozles too.......If you were to say lean out the mixture at idle by lowering the float level you're effectively starving the carb of fuel supply. Fine and dandy at idle but now what happens when you increase the load but the supply is barely enough to supply idle demands?.....Anyways my point is I wouldn't cheat on this with float level.

i agree with you binder that cheatinbg is not for the permenant fix. just that he could get a rough idea if his jetting was way off. and i use the fuel pressure "cheat " when running my rig at higher altitudes to lean it out some so it's not running so stinky rich. a lb or two is all thats needed.

 

[Binder]

i agree with you binder that cheatinbg is not for the permenant fix. just that he could get a rough idea if his jetting was way off. and i use the fuel pressure "cheat " when running my rig at higher altitudes to lean it out some so it's not running so stinky rich. a lb or two is all thats needed.

When I used to run a Holley on my wheeler I would cheat the float level down a bit and run a dial-adjustable FP regulator. Turn the pressure down when I hit the trail and turn it back up for the drive home.:awesomework:

 

[messix]

When I used to run a Holley on my wheeler I would cheat the float level down a bit and run a dial-adjustable FP regulator. Turn the pressure down when I hit the trail and turn it back up for the drive home.:awesomework:

yep thats what i got!

 

[84Toyota4x4]

Thanks guys. I'm leaning towards it just being too big. A little more research shows its a 550 CFM not a 465, so someone has done some customizing/main body swapping, but it came off a motor more ported than mine (think bigger cam for a piston motor).

I tried dropping the fuel pressure 1 PSI and didn't notice a change so its back. Also, the accelerator pump is squirting a ton of fuel, it practically puddles on the butterflies when blipping the throttle or free revving. It runs good in the upper RPMs under load though, lol.

I was going to address the jetting, pump cams/diaphragms/squirters after I got it all working, but I'm not sure what I'm going to do now that I know the carb is basically almost 100 CFM too big.

Thanks for all the help guys, I wish I had thought to just check the carb number from the beginning. Again, too simple I guess. I bought the thing about a year ago and just got it running. I hardly remember anything about it, haha.

FWIW, its a 1.1 liter, and 8K is redline. 5 speed car, 2000 LBS if it matters. I'm on my phone or I would convert that to cubic inches for you, lol.

~T.J.

 

[Binder]

1.1 liter is about 67 cubic inches. A Wankel has a intake stroke on each revolution so at 8000 RPM works out to be about 310 CFM if I did my math right. :redneck:
Sounds like the carb is too big for it.

 

[03 CON]

1.1 liter is about 67 cubic inches. A Wankel has a intake stroke on each revolution so at 8000 RPM works out to be about 310 CFM if I did my math right. :redneck:
Sounds like the carb is too big for it.

You math geek

:haha:

 

[Binder]

You math geek

:haha:

I just make **** up. It's up to you smart people to call me out on it.:redneck:

 

[03 CON]

I just make **** up. It's up to you smart people to call me out on it.:redneck:

I am not taking you out!! You might ask Karl.....


:fawkdancesmiley:

 

[84Toyota4x4]

Just as an update, I read about someone successfully using a 500 carb on a motor similar to mine using an open spacer under the carb so I thought I would give that a shot. $20 later and a 0.5" phenolic open spacer and the secondaries are working.

Its semi complicated to explain why its working if youre not familiar with rotary engine intakes, but basically the carb was bolted to an individual runner intake with no plenum area, which was causing the carb to miss out on a lot of air flow since it was only seeing air flow from half of the intake ports for both rotors.

...Or in other words, each rotor has two intake ports and with no plenum area, only two were being used until the secondaries opened - which obviously wasnt happening. Now with the spacer, all 4 are used regardless of if its the primaries or secondaries that are opened, the mixture can "mix" in the open area and be taken in to all 4 ports.

Time to start dialing it in! Thanks for the tips though everyone!

~T.J.