Dual Quad Tunnel Ram

[50 F1]

Yes it is plumbed into the area that is open to both carbs.

Thanks Mike

[wayne petty]

Sorry for a slight hi-jack, but re-reading this brought a question to mind:

Wayne - Do I read correctly that an O2 sensor is safe at a full 12 volts?  Can it run 12 v full time or is that just for set-up/testing?

3 wire oxygen sensors for narrow band air fuel ratio displays can run full 12 volts to the heater circuit..  94/95 chevy truck with 5.7L engines is one application..

1995 Chevrolet Truck C2500 3/4ton P/U 2WD 5.7L TBI 8cyl any of the below.   or punch in the numbers at various parts sites to check the various applications..

Denso/Oxygen Sensor Part Number: 234-3011


NGK O2s/Oxygen Sensor Part Number: 21004


Bosch/Oxygen Sensor Part Number: 15700


Bosch/Oxygen Sensor Part Number: 15726
Application: Cab and Pickup
Up-stream sensor (located before catalytic converter)
Notes: Universal fit. 3 wire sensor.

[wayne petty]

Finally got it running Friday night. It runs just OK Right now I have two problems. One is eratic idle. I checked for vacuam leaks and could not find any. The other problem is when I rev it up a little off idle it takes a long time to come back down to idle.

What I have done so far. Adjust the idle screws, just by ear. I have taken them down tell the motor starts to slow down then back them out a half turn. Also have tried taking them out tell the motor starts to slow down and then take them in a half turn.  I can get it to run real good and have it idling around 600 rpms and it will sit there for a couple minutes then it will start to idle higher then it will go back down.

I have run fuel pressure from 2psi to 6psi with no difference.

I put the accelerator pumps linkage on the lowest setting to give it less of a shot off idle

I have taken the carbs apart and adjusted the float levels and  float drops.

I made sure the slot in the base of the carbs was barely showing with the butterflys shut.

Both carbs have the stock (base is what Edelbrock calls them) metering rods and jets.

Mike

take the carbs back off..    turn them upside down..

take the base plates off..    back off the primary and secondary idle speed screw.. so all the throttle plates are fully closed.. hold them up to the light.. so you are looking for ANY tiny gaps around the edges.

if you see uneven gaps...  loosen throttle blade screws no more than 1/8 of a turn.. hold fingers on plates to center them in the hole.. snug screws back down... hold to light again..  

when they are perfectly centered in the bores of the base plate..

set the secondary idle stop screw.. the short one in from the bottom side.. so the secondary just does not hang up in the bore...

set the primary so the lower side is just barely exposing the idle transition slot.. refer to the images way up...

why go thru all this.. because the levers crack the throttle open when you set the carb down..  it knocks the blades slightly off center.  this is why some people use 2" bolts with pairs of nuts to make legs for carbs that are being worked on or in storage on the shelf.. so the throttle blades don't get knocked out of center..

how did you hook the PCV into the plenum..

would you like to talk about these adjustments on the phone.. ?

[50 F1]

Thanks for the reply Wayne.

I bought this intake and carbs used and when I got it had two npt drilled and tapped holes in it one on each side of the plenum. I plugged one side and plumbed the pcv
into the other side.

With work I can only work on this on the weekend.  I will work on your suggestions in a couple days and post my results.

Thanks Mike

[50 F1]

Wayne I have been working on the carbs.  All the butterflys needed tweaking to get centered in the bores. And  the barbed fitting in the back of the front carb that I am using for the power brakes was loose not even finger tight.

Also there is a small slot about 1/2" from the transfer slot. I hope you can see the pictures. On one of the carbs the slot is way bigger than the other carb.

I also have a new carb (never used) and the slot in that one is smaller than the one I am wondering about.

Does this mean anything?

Thanks Mike

[wayne petty]

Wayne I have been working on the carbs.  All the butterflys needed tweaking to get centered in the bores. And  the barbed fitting in the back of the front carb that I am using for the power brakes was loose not even finger tight.

Also there is a small slot about 1/2" from the transfer slot. I hope you can see the pictures. On one of the carbs the slot is way bigger than the other carb.

I also have a new carb (never used) and the slot in that one is smaller than the one I am wondering about.

Does this mean anything?

Thanks Mike

different sizes of slots might be an issue in setting them up for a dual quad set up.. where both primaries open at the same time.


now you also have me wondering.. about secondary opening rates.

are these vacuum secondary.. you might want to order 2 of the quick change secondary housings and with 2 sets of springs.. so you can fine tune the secondary opening.

lets start with your carb numbers...

on all 3 carbs...

check the diameter of the base plate openings also..
are they all matching...  

how about some  examination of the venturi's do the boosters match.

are the venturi diameters match also...

i have a holley master parts catalog.. but it does not include engineering data...

see if you can find the stamping numbers on the primary metering blocks also..

[wayne petty]

are you talking about the idle transition slots in the middle..

or the vacuum port on the right???
i pasted your pictures together..

http://i1207.photobucket.com/albums/bb476/waynep712/waynep712%20carb%20album/holleyidletransitionslots_zps6a6ff870.jpg~original

[50 F1]

These are Edelbrock carbs.

I worked on it about half the day Sunday.

I was able to get idle to come down after it is revved up by moving distributor a little.

Made new base gaskets.

I have ballest resistor problems now or maybe since I started on this.

I have to get a new one.

Going to try to get a buddy over to give me a hand.

I am real close to putting a single 4 barrel intake bake on it.

I am talking about the slot next to the transfer slot.

Thanks Mike

[wayne petty]

the slot next to the idle transition slot does NOT effect idle.. it goes to the vacuum fitting either on the front of the carb or the side of the carb...

are the idle transition slots the same width...

how about carb numbers..

can you see the primary boosters with the carb  top off?? do the stamped in letters and numbers that denote the calibration of the primary boosters match on both carbs???

its not like you live next door or even up the block.. i though you had holleys..


by the way.. here is a neat PCV catalog.. i does not give flow rates.. but it can be crossed to come up with conventional brand part numbers..

one of the things i want to do is buy a whole bunch of PCV valves and flow test them at various vacuum readings..

http://www.teamlucor.com/stores/generaldocuments/Novo 2006 Catalog.pdf

were you able to get the primary plates almost closed..

please.. while you the carbs off.. or even with them on..

remove the idle mixture screws..    spray in some carb cleaner..  follow that with a blast of compressed air..

this cleans out the idle air bleeds and the idle transition  restriction...

[wayne petty]

i chopped up an old primary booster i had...

so the primary circuit can be seen...

[wayne petty]

just a thought..

http://forums.chevyhiperformance.com/70/9552842/general-chevy-technical-discussion/pcv-valve/

[50 F1]

I was able to spend some time on this yesterday.

I have it running good now. At least good enough to drive when I get to that point.

This is what I did to get it running, with the help from you guys.

Adjusted the butterflys to fit in the bores good.

Made new base gaskets for boths carbs.

Took the idle air screws out and blew them out with compressed air.

Adjusted timing.

Found out I had the vacuum advance for the distributor on the wrong port on the carb.

Took the pcv out of the tunnel ram plenum and plugged that hole and put the pcv into the front of the back carb.  I have the power brake booster going into the back of the front carb.

Once it is warmed up and the choke is off it will idle at around 600rpms (no tach yet) idle does not go up and down and when rev'd up it will idle back down right away.

I am sure I will still have some problems once I can drive it but I am happy for now.  If I had a single four barrel intake sitting around last weekend I am sure the dual set up would of been sitting on my work bench right now.

What do you think made the biggest improvement. I really don't know because I did most of it at one time.  But I think my biggest problem was the timing and the vacuum advance in the wrong port.

Thanks for the help
Mike

[wayne petty]

you have just learned how to set up a carb properly..

using a vacuum gauge to set the idle mixture is next but you might have already done that..

these forum are for learning..   sharing knowledge..


i learned a lot from reading  C9's threads on carbs..

he was really great at setting up carbs..