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Discussion Starter #1
Combo: stock shortblock, custom cam (224/224, .574/ .534 110sla) ... not exactly a huuuge cam, TFS heads, Stealth intake, 650 carb.

The brakes work awesome but when coming to a stop the car dies. Doesn't die on the freeway under hard braking (when the revs are still high) and it starts and idles like a champ. 7.5psi fuel pressure on the Holley gauge, with the HiTech Motorsports cam I am seeing 14-16 Hg at idle which should be fine for power brakes no?

I figured it must be something to do with the carb? But I adjusted the floats ... primary bowl first, until trickles out of the sight plug hole, then the secondary bowl the same way. I also installed jet extensions in the secondary bowl ... didn't cure it.

The stock vacuum reservoir in the passenger side inner fender is hooked up ... should there be a check valve? I installed a cheap $5 Kragen check valve (tried both ways) and it didn't make a difference.

I'm not sure if it's a carb problem, or a vacuum problem.

FWIW, our old combo (GT40P's with a B-Cam) did the same thing, except I didn't have jet extensions installed in the carb yet. :confused:
 

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Try putting a piece of tubing bridging the vents stacks. Cut a notch at the top of the tubing to give you a new vent location. I had the same problem, it fixed me right up. I had fuel sloshing out the vents into the carb under hard deceleration.
 

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Try putting a piece of tubing bridging the vents stacks. Cut a notch at the top of the tubing to give you a new vent location. I had the same problem, it fixed me right up. I had fuel sloshing out the vents into the carb under hard deceleration.
X2...seen this done several times.
 

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Discussion Starter #5
Try putting a piece of tubing bridging the vents stacks. Cut a notch at the top of the tubing to give you a new vent location. I had the same problem, it fixed me right up. I had fuel sloshing out the vents into the carb under hard deceleration.
What sort of tubing did you use?
 

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Just a piece of fuel line or vacuum tubing. Pretty much anything that will fit. I used a piece of 1/4 inch pushlock hose.
 

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Discussion Starter #7
Just a piece of fuel line or vacuum tubing. Pretty much anything that will fit. I used a piece of 1/4 inch pushlock hose.
Won't rubber fuel hose deteriorate over time and throw rubber fragments into the carb?
 

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Yes, but you can change it from time to time. Maybe try changing the air/idle adjustment. I had that problem with an older holley carb once...rebuilt it and it was good to go. lol, still doesn't answer your question though. Good luck.
 

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Discussion Starter #9
I will try the tube thing after work ... I rebuilt the carb and the thing runs really nicely around town and like a raped ape at WOT but it's sketchy when getting hard brake coming to a stop.
 

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Discussion Starter #10
LOL ... the tube didn't seem to do the trick, I dunno. The car was noticeably harder to start, and when I got it running, it didn't idle very well. Then the tube birst on the freeway and sprayed gas everywhere... nothing bad happened but eeeek. That seems like a bandaid fix ...

A couple of guys on the Vette forums recommend using this which installs in the metering body to prevent fuel spillover during accelerating and braking:

http://www.summitracing.com/parts/HLY-26-89/

Any possibility it could be a bad needle? I rebuilt the carb and replaced everything that the Holley kit came with, including the new needles.

I also am thinking that the secondary transfer slots are adjusted incorrectly. I'm guessing I just use a dial indicator/ feeler gauge to measure how much they stick out past the throttle blade?

 

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Take the needles out and clean them real good and reinstall also make sure the idle mix is correct and does not move check last that vent tube should be on there already if not get them and put them on asap .
 

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Damn, that sucks about the tube. Glad nothing bad happened. Did you cut a vent hole at the top? Anyway, have you sprayed carb cleaner around to check for a vacuum leak? Sure seems like the carb should be ruled out by now...I mean after the rebuild. Good luck.
 

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LOL ... the tube didn't seem to do the trick, I dunno. The car was noticeably harder to start, and when I got it running, it didn't idle very well. Then the tube birst on the freeway and sprayed gas everywhere... nothing bad happened but eeeek. That seems like a bandaid fix ...

Just making sure! You did cut a hole in the top of the arc of the hose. You have to have a vent to atmosphere.
 

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Discussion Starter #15
Check the brake booster....
The brake booster is brand new from Autozone, I highly doubt it is bad. Plus, if I pump the brake pedal rapidly at idle, there is no fluctuation in idle speed... that is usually the tell tale sign that the booster is bad.

Just making sure! You did cut a hole in the top of the arc of the hose. You have to have a vent to atmosphere.
I appreciate the follow-up!!! I actually cut a "slit" at the top of the hose about two inches long ... is this correct? I am pretty firm on not putting that hose back on there though. A bunch of gas sprayed everywhere including on the headers and I don't care to repeat that lol.

Anyways, an update on my part. I pulled the carb apart last night to see if I could see any signs of something wrong. Pulled the needles out... they were fine (not stuck) and still looked brand new from when I rebuilt the carb a few months ago.

I adjusted the accelerator pump to linkage clearance to ~.010". I hadn't checked that in a while. I also adjusted the idle air mixture screws back to 1.5 turns instead of the 2 turns where they were at before. A lot of the carb manuals say to start at 1.5 turns and turn *inwards* until the idle speed/ vacuum reading begins to drop.

Lastly, I flipped the carb upside down and verified the secondary transfer slot for the primaries. I measured ~.040" which is in spec.



.......The interesting thing that I found was that I think there was too much preload on the secondary throttle plate? I turned the adjustment screw all the way out, then turned it in until it bottomed out and started opening the throttle plate, then turned it 1/8 turn more just to ensure that the throttle plate doesn't stick. I read about this in the Holley Tuning Handbook.

Overall results... a definite improvement. The idle speed still drops, but not nearly as much. I stood on the brakes from 130 and came to a stop. The idle dropped a bit, but there's a definite improvement. I'm thinking the problem is still in the carburetor, either in the idle mixture settings, or float settings, or possibly by adding this part:



"Control fuel slosh during hard acceleration and braking.

The vent baffle is used with the center-hung style fuel bowl. It extends the fuel bowl vent to near the wall of the fuel bowl and can effectively control fuel splash on the primary side when accelerating hard, or on the secondary side when braking hard."

http://www.summitracing.com/parts/HLY-26-89/?image=large
 

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The brake booster is brand new from Autozone, I highly doubt it is bad. Plus, if I pump the brake pedal rapidly at idle, there is no fluctuation in idle speed... that is usually the tell tale sign that the booster is bad.
Sorry, I didn't see where you mentioned anything about it.... I would still plug off the vacuum line going to it before I wasted anymore time trying to find it. Its not like Autozone is known for quality replacement parts. :D
 

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drop thr rear float level a bit, it will solve your problem
ding ding we have a winner. Talk about a bunch of non carb tunners giving advise lol. I was reading the whole thread wondering if anybody actualy new how to work on holleys. The rear float leval is to high just like mentioned just drop it about 1/8 to 1/4 below the plug. The car will run just fine.The rear sight plug on Holleys is actualy a little higher on the bowl than the front anyhow. Good luck.
 
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