Suggestions for "pullover"

[cspeier]

I found some old threads, but looking for more help..

I'm fighting pullover on my 4 cylinder. I have a Comp Cams vibration spacer. I've tried several things. Anyone tried the washer under the diaphram? Anyone know someone who makes them already modified? Getting ready to try a anti-pullover nozzle..

Any other suggestions or ideas??

PS Bill Jones in a email, over a year ago, you sent me a link for a fix. In the email you said. "sooner or later your going to need to know about this" My question, how did you know that??

[bill jones]

-Here's that same info incase you want to reread thru it.

http://www.stockcarracing.com/techarticles/scrp_0508_carburetor_cures/ -fix for nozzle pullover for Holley 4412's
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-another discussion of nozzle pullover on dominator carburetors and some discussion on fixing it.

http://speedtalk.com/forum/viewtopic.php?t=5583&start=15

-Ok fixed the problem,,first it was a vibration induced agitation of the squirter circuit in this case.

-After trying several other fixes including, flush grinding the nozzels, springs on top of lead balls under the squirter, drilling a .028 hole in the channel to help vent off any signal, (didn't work here), two things in combination fixed it.

-Changing the bowls over to the older style with the ball valve in the pump cavity, and machining up new squirter needles from brass needles with a viton tip on the bottom.

-These were made both longer and larger in diameter to try and increase the weight.

-These two have all but cured the problem, a vibration present in some engine combinations.
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-here's a link to Ryan Browns dyno videos of the problem.
http://ryanbrownracing.com/Video.html

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-I first read about a guy in NY--Richie Zuhl I think--who was dynoing a tunnel ram with 660's (if I remember the story right)---was going rich on top end----so he got up on top of the engine and watched what was happening--found it to be nozzle pullover.

-Then dealing with 350 & 500 Holley two barrel carburetors on oval track cars----and dealing with the Pinto 4 cylinder at Bonneville begets you experience with this problem.

[Troy Patterson]

I'm not clear if the issue is the result of vibration or high velocity.

I've never had an issue with vibration causing this kind of issue - perhaps I'm just lucky. If it is velocity related, - can't say this is a problem for my large cfm carbs either - I have this that might help your problem.

Troy Patterson TMPCarbs.net TMP Carbs

[Hendrens Racing Engines]

Troy
On the 4 cylinder engines with the carb mounted off to the side its mainly a vibration problem.the umbrella ck valve is so good that the carb vibration up and down at high frequency actually pumps a steady stream out the nozzles,thats why anti pull over nozzles or vacuum breakers don't work. the solution has been old style bowls with the ball check and heavy ck valves. the other problem is agitating the fuel in the bowl.that problem can be helped a lot by installing front wheel drive damper shocks from the roll cage front hoop to the engine and the use of rubber engine mounts with limiters on them instead of solid mounts. Bill

[cspeier]

I'm not 100% this is totally vibration. I've made some runs with the converter flash at 5300. The problem, it would go to 5300 pause then climb to 7200+. I played with plenum spacers, squirters, cams, etc and have now actually made it worse. It reacts exactly like the first paragraph of the article Bill linked. It gets to 5000, bangs and pops. It reminds me of a stall being on a rev chip. Never had it this bad.

This thing is remarkably smooth. Here is a photo of the arm I have on the manifold. Like I said, this seems to be a new problem. This is a dominator. The fast guys in this /EA class all run this same size and builder.

[Troy Patterson]

How much horsepower are you making out of that motor?

Troy Patterson TMPCarbs.net TMP Carbs

[cspeier]

It made 460@9500.

[shawn]

Looks good Chad. I see you tried a plenum spacer, but was it a rubber one?
shawn

[JBV-HEADS]

Email sent with #

Joe

[Troy Patterson]

It made 460@9500.

Are you allowed to run a 650 2 barrel? At that horsepower level, the engine could certainly use it.

I realize the 500 cfm 2 barrel carb will flow 750 cfm @ 5" lbs of vaccum - if memory serves me.

This 650 cfm 2 barrel set up with a Weber Power Plate could net you some serious mid range torque and probably a little horsepower - if not a sizeable percentage gain.

Troy Patterson TMPCarbs.net TMP Carbs

[MaxFlow]

460 @ 9500 is more 4cyl than a 4412 could handle. Did you say "Dominator" carb? I hope that's what you said. Cause I'm gonna fall off my chair if this engine is making 460 with a 4412 carb.

[bill jones]

-does this Dominator have the nozzle pullover out of BOTH nozzles?

-Have you actually witnessed and observed the pullover?

-If you have observed and verified it is indeed pullover-----have you watched it thruout the entire rpm range to see if the pullover comes and goes?

-If you did watch it thruout the entire range---what did you observe?

-If you did watch it thruout the entire range did you happen to video tape the pullover?

-If you haven't observed the carburetor thruout the entire rpm range---why not?

[cspeier]

Are you allowed to run a 650 2 barrel

I can run any size carb(s) as long as they are within spec. Throttle size, etc must be within a spec. I can also run Webers up to a certain size.

Did you say "Dominator" carb?

Yes, this has a 2.00 bore dominator on it.

I see you tried a plenum spacer, but was it a rubber one?

My spacer was solid rubber.

Joe, I'll give you a call, thanks.

Bill, I've witnessed exactly what the video showed with the fuel pulling over the boosters. When I put a load on it with the trans brake, at 5000 rpm the boosters will shoot up a mist of fuel around 6 inches. It wasn't an issue on the dyno, as far as I know. So no, I haven't observed it throughout the entire rpm range. I do know the thing sounds unreal and it's very responsive when I just nail the throttle. Under load, on the brake, it has issues..

[bill jones]

-I thought you were concerned about NOZZLE pullover--never heard any previous mention about fuel shooting a 6" mist up out of the BOOSTERS----which is an entire different issue.

-Fuel shooting mist 6" up out of the BOOSTERS sounds like "standoff" or classic reversion to me.
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-How do you set the float level?

-how much fuel pressure do you have at 5000rpm when on the trans brake?

-Are you using a rev limiter/stutter box when on the trans brake?

-Is the throttles WFO when the transbrake is applied at 5000rpm?

-What specific steps have been taken to TRY to reduce reversion?

-Have you ever thought about installing windows into that manifold?

[cspeier]

Yes, I guess I have all sorts of issues. The windows have been discussed and the supplies are on the way. I actually installed 1/2 plenum spacer, made it worse. With that 1/2 I also added 1.5 inches of carb spacer, made it worse. To be honest, I was told it was your classic case of standoff. Then I noticed the fuel being pulled over the boosters, re-read your article, and it seemed exactly what I had.

I have 6.5 lbs on the brake. I have a digtal 7 box with no starting line rpm, the value is set at 12500. The float level was set how I was told. However, it IS on jack stands??? It's not level.. Issue??

What kind of pressure, float level would you run?


FYI. The carb sits on the manifold sideways.

I sound crazy don't I