427 IDA 48 Weber Modification Update

priobe · #1 (**permalink**) 08-28-2007, 01:30 PM

Hello All,

I figured since there was so many people that love tuning Webers and was undecided about the 3rd progression hole I would post some feed back.

Well I sent my carbs to PierceManifold to have the 3rd progession hole add to my setup. While the carbs were there, I had them do a look over the entire setup. The only thing that they found wrong was my mixture screws were questionable.

Since then I have installed them with the phoenolic spacers which I made. I took the car out for a drive and what a difference. The transition is perfect!!!!
My current setup is :

60 idle jet
60 holders (3/4 turn out)
40 mm chokes
210 air corrector
165 main jets
bypass 55

I am noticing that the car runs alittle rich at idle but a hell of lot better than before. I am also noticing when at idle and taking off hard the car bogs down but them picks back up. I am planning on changing out the bypass to a 75 or 80 to hope correct this problem.

Now I know what ElJaro was speaking about the true Weber experience.

Rick Parker · #2 (**permalink**) 08-28-2007, 03:45 PM

How does the jetting package differ from what you were previously using?

priobe · #3 (**permalink**) 08-29-2007, 08:36 AM

The jetting is not perfect. At idle I am experiencing a rich mixture but it is a lot better than what is was before. I also noticed when accelerating hard from a stand still the car will bog with the .55 bypass at the bottom of the bowl. This confirms exactly what Eljaro was speaking of in his thread "interesting weber jetting".

The only thing that I dont understand is that he mentioned in his thread that he will replace the .50 bypass with a 00 bypass (closed) to correct the boging problem. I would think you would have to go to a larger hole in the bypass to allow the pump jets to release less fuel.

Or is the purpose of the bypass valve in the bottom of the bowl to supply the fuel to the pump jet. If this is the case it would then make sense .Then less fuel will be drawn in to the pump jets.

Could you explain or possibly someone else?

Also, I am noticing a slight popping thru the exhaust with the 3 hole, but very easy to clear up with the mixture screw.

I have not hookup the wideband but I am sure I am on the a slight rich side. As soon as I have more time, hopefully the long weekend. I will tune some more

Brent Mills · #4 (**permalink**) 08-29-2007, 09:38 AM

I don't have the answers to all of your questions, but...Rich at idle is likely the mixture screws. When you adjust out the popping, you're actually making the mixture even more rich. I haven't heard of many folks getting rid of the popping (as long as we're talking about letting off the gas and letting the compression slow yo down sort of popping). If you're talking about popping on acceleration, you're lean.

priobe · #5 (**permalink**) 08-29-2007, 10:06 AM

Brent,

With the current setup I am running rich, which is why I need to change out my jet possibly the air holders. The popping that I am getting on deceleration is really not that bad.

One of my main concerns is the bypass valve in the bottom of the bowl. I would like to find out if a higher number bypass valve decreases or increases fuel flow to the pumps jets. When I accelerate hard from a stand still the motor will bog down for a second then it is fine. I am thinking if I was to change the bypass valve would I go up in number or down. If you could explain how this bypass valve work I would appriciate it.

Rick Parker · #6 (**permalink**) 08-29-2007, 11:22 AM

If you increase either number you get more fuel expelled at "that" location, hence larger number in the bypass valve lets more fuel be expelled back into the bowl and less is forced out the squirters. A larger # on the squirters or lower # on the bypass would put a larger volume of fuel into the throttle bore.

ENTDOC · #7 (**permalink**) 08-29-2007, 02:35 PM

I think on the squirters that they all feed the same total volume ,but bigger ones feed it over a shorter period of time

Eljaro · #8 (**permalink**) 08-29-2007, 05:11 PM

the bog on acceleration in my car was a lean one. so shutting off any bypass cured it. But I think a 0.35mm bypass hole would get rid of the black smoke shooting out the sidepipes when hitting the gas.But black smoke is still preferably to a bog. A larger bypass would definitely make things worse.
In Priobes case I see to large an air corrector there, so you need a large main jet to make up for that. Maybe going down with the air corr. you could take a smaller main jet too . In my case when revving up under load with the 210 air the mixture would lean out. Not a good thing. With a 115 air I got that sorted out and could go with a smaller main for a stable mixture ratio up to 6500rpm.

priobe · #9 (**permalink**) 09-05-2007, 01:01 PM

I installed the 00 bleeds and still looking good. I took the car for a ride and with a sudden acceleration the car just goes

There is alittle too much fuel at first but still good. I also tired it from a dead stop and a hard acceleration and my bogging problem is gone.

I will continue mimic Eljaro setup to see if it puts me in the right setup.

Next I will try 120 Idle air holders and 65 jets. If no success, then I will begin to modify the air holder from 60 -100 and work my way up to see if 100 is the magic number.