Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
6 cyl draw threw turbo
hiy_po:
Where I am at
Idle Down tibes 0.064' #52 top 0.046' #56 bottom
Idle Down-Channel Restriction 0.067' #51
Idle Discharge tube 0.118' #32
Upper Idle Air-Bleed 0.18' (Air horn)
Upper Idle Air-Bleed 0.070' #50
Lower Idle Air-Bleed 0.087' #44
Idle Air By Pass throtle plate outlet 0.079' #47
Main Air Bleeds (In the main casting) - 0.026
Main Air-Bleed Airhorn 0.090" #43
Primary Jet 0.073
Primary Rod o.048
Custom: / (2-5) / 0.900' spring
ATP 2 turns up.
Secondary Metering Rods DA 0.044 inch tip
Secondary hanger bracket B
Needle seat 0.130
Float setting 0.240.
Cliff Ruggles:
Not sure why your LIAB's are .087". That is HUGE and will cause a pretty big leak-path and reduce "pull" on the DCRs's, idle tubes,etc. Then you have two pairs of upper IAB's?
That will require a big idle tubes and DCR's, and probably not the best set up for the little 6 cylinder engine.
You only need one pair of upper IAB's. I'd rather see the LIAB's reduced to .070", block off the UIAB's in the main casting, and open up the UIAB's in the airhorn to .040".
Then you can use small idle tubes, and much smaller DCR's and bring in PLENTY of fuel at idle and to the transfer slots for improved off idle transition.
A few Q-jets were used on smaller CID engines, specifically the Pontiac OHC in line 6's from the 1960's. Those carbs have very small idle tubes, DCR's, and tiny IAB's. They work quite well on those engines and I'm sure the factory used the smaller specs for a reason.......Cliff
hiy_po:
OK that will give me something to do tomorrow. Will try and make those changes.
My thinking was I have very low vacuum at Idle so need things open up big to get the fuel flowing.
I will try peen the LIAB closed a bit and redrill to 0.070 If I cant peen them maybe try to melt some lead into the holes and redrill.
I can lead fill the UIAB in the main body, blocking them and resmooth and drill the holes in the Air-horn to 0.040
I was just experimenting but can see why I joined because I do need some guidance.
And you are correct about it pulling hard. It looks like my AFRs are close but it just kept picking up speed evenly it is missing the hard pull. The push back in the seat is not there.
Once I have it to your specs will test it again and re think the Idle tubes and IDCRs
Thank you for taking the time to read and comment.
77cruiser:
Rather than trying to peen them smaller get some 6-32 brass setscrews for the lower bleeds 8-32 for the DCR.
hiy_po:
Well I tried to peen, was getting to awkward and difficult, so lead filled it, the lead fell out when I drilled it. so yes it is now fitted with a Brass bush. I have one in but looks like I am going to have to make it smaller as it looks like its blocking half the passage.
Those Brass grub screws are incredibly hard to get in Aus. Something so simple you can walk into a corner shop and buy are not available here. I have searched EBay and online, I have found suppliers in USA but this is the message I get when I try to order them
Cancelling Your McMaster-Carr Order on 10/06
Contact photo
From McMaster-Carr
To hiy_po@hiy-po.com
Date 2019-10-07 21:26
Message Body
Hi Adam,
Thank you for considering McMaster-Carr for your purchase. However, we will not accept orders from your location due to the cost of complying with US export regulations.
Andrew
Have found another place as well with branches in US and Canada, I cant even get an account because I am in Aus.
And our dollar is incredibly weak, what costs $US10 costs me $AU60 delivered.
I have one other Question is my carb an 800 CFM casting?? Looks like it has the lumps.
Tried to take a pic but turned out blury. Took some othe pics of progress.
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