Webers leaking

[Zs-ondabrain]

My only experience is with EFI cars which always have a return line and yes the FPR should be on the return line. A good FPR for EFI will always have a return port. How it works (IMHO):

Picture a garden hose on at full flow with an open end. The water flows out the end of the hose at whatever pressure water lines have. Now if you cap the end, pressure builds up in the line. Now poke 6 small holes in the hose (those are your injectors). It starts spraying water out of those holes because of the high pressure. Now say it is just spraying WAY too much but, you know if you turn off the water that it wont spray anything thing. If this is the case (as with a fuel pump) the only way to regulate it is to make a small opening in the end of the hose (this is your FPR) to relieve SOME but not all of the pressure. All you do is keep making the hole in the end of the hose larger until the pressure in the hose is regulated to what you want.

I guess the same would apply for carbs. I don't have a return line though :disappoin

Awesome explanation Mike. I totally get it and can actually visualize what your saying. Thanks.

Found out that my Bleed backs are 50's and should probably 0's

My Idle jets are 45's

Dave

[yetterben]

So many people have so many problems with triples if they would just buy a wideband for 200 bucks there would be no guessing. You would be like oh i am lean at 2 grand better up the idles or oh i am lean at the top but the mid is good,better drop corrector down etc etc.

[yetterben]

The weber books are all wrong on jetting for the L-gata. 50 or 55's should be in order for a L

[Zs-ondabrain]

So I plugged the bleed back holes as suggested. (Set Screws w/ thread lock)

Moved the FPR and gauge to the return line (near the man. pump.

Backed off on the throttle screws (a smidge)

The rich screws are at about 1.25 out from seated.

Runs like crap again. So I got the throttle screws just barely pushing the throttle. Turned the rich screws in to 1 turn out. Idles better again but have a flat spot like there's no fuel when I hit or lightly press the pedal.

Gonna widen the 45's to 50 on the idle jets, as I'm a light footer around town and run a lot of the time on the idle jets.

Dave

[yetterben]

dave are you sure you took the bleedback out and not something else? look at a parts explosion.

its id# 43.

Pull your accel jet out and make sure its clean. its assessable outside the carb behind the progression port screws.

Edited May 19, 2010 by yetterben

[Zs-ondabrain]

Acceleration Jets are Clean, pulled each one, cleaned, blew them out and reinstalled. Move the butterfly's and they all squirt fuel out above the open butterfly's.

#43 is a "Pump Spill" also known (by you) as a Bleed back. The part number is 79701.050 Ending in .050, I pulled mine and they are 50's as well. Plugged them off as instructed. There doesn't appear to be any other option than 50. So maybe plugging is a bad option???

Located at the bottom of the Float bowl, between the mains and the spring loaded Accel. Pump. Nothing else there so it must be the right part.

I'll know more tomorrow after I mess with the idle. If I can't get it to run better, I'll yank the plugs and reinstal the Pump Spill / Bleed backs and see if that helps.

My $700 worth of suspension parts show up tomorrow so I'll see what I can do before having to tear the car apart for a full 2 day rebuild (struts, springs, cleaning, etc. (front and rear)

Dave

Edited May 19, 2010 by Zs-ondabrain

[yetterben]

you dont want any bleed back. Something is a amiss in those carbs. a good boiling would be nice.

[Zs-ondabrain]

Maybe pull everything out and give it a good fuel douching or higher pressure Brake cleaner douche? Some of the screws feel gritty like sandy or something.

Dave

[yetterben]

indeed. Pull all the jets and throttle shaft and boil them for a hour or so.

[70 Cam Guy]

Just want to put in my 2 cents. It is my understanding the Spectre dial FPR is not a back pressure regulator. Is that what you've put on your return and have you verified the correct pressure at the carbs? I have tried mine on the return side and it did not work to regulate pressure. It's possible I missed where it was replaced. When I simply blocked the return on my car equipped with the mechanical fuel pump, pressure held steady at 4 psi or slightly less, not too high

This is not to say the carbs couldn't use a proper cleaning but just some food for thought.

[Zs-ondabrain]

I ended up putting the items in this order.........

Fuel tank, Electric Fuel Pump, Fuel filter before the Mechanical Pump, all 3 webers, fuel pressure Gauge, fuel Pressure Regulator, return hardline to tank....

The FPR is dialed in a *3* and the gauge shows about 4 pounds of pressure.

So fuel pressure is no longer an issue.

I'm half tempted to rip each carb off, one at a time, and completely tear each one down, boil the parts, scrub everything down and reassemble them when I'm positive that each and every part is exact, clean and dialed in to the truest sense of the phrase.

But first I gotta get the new struts and springs in. ANYONE GOT A SET OF REAR BRAKE CYLINDERS FOR AN EARLY 72'???? Just need a set that the bleeders aren't broken off. The P.O. tightened the bleeders so damn hard that the aluminum block has stress cracks from being overtightened.

ANYONE?? PLEASE!!

Dave

[Mikez73]

Threadjack...I feel so at home now

70 Cam Guy...if it acts as an obstruction downstream I guess it can be sort of a backpressure FPR . Technically tho I think you're right.

I would toss the Spectre and at least go for a Holley 12-804...altho having just returned one of those to Summit, I think it's pretty lame too as far as FPR's go. I guess I got spoiled using Aeromotive with my z31. But hey if you have steady 4psi and enough volume then why mess with a good thing.

Dave, if you do tear the carbs down, take pics please

There are probably guys here with buckets of brake cylinders lying around but if worse comes to worst I have a friend who has a 72 parts car. I can check to see if it has the brake cylinders.

yetterben...thanks for the parts ID. A wideband o2 is great for efi with turbo using a standalone ecu where it would be used on a regular basis. For carbs it would be great to just borrow or rent one. Some of us either don't have the money for it or just can't justify spending $200+ on something you might need to use just once. On the other hand, when I sold my shiro I sold my wideband too and got almost what I paid for it.