Qjet on a nailhead

[Marx3]

Hi, I am dialing in an old Qjet that sits on a ´66 425 nailhead completely stock.
Id is 7027242 ( not sure about the last digit )

What jets and rods should I put in that carb?
MAB´s where .045, but they have been opened up to .060
jets/rod: 70/44
how about the idle system?
tubes are stock, DCR is .042, bypass is opened up to about .080

secondary rods are .057 tips.

Unfortuneately the cigarettelighter is not working at the moment, so I havent been able to measure AFR´s ( yet )

But all in all, do you think this carb should run good? or is it way off for a nailhead?

[omaha]

should be alright BUT, the early carbs did have their issues (as you may already know). Metering should be fairly close but may need help with main jets/rods.  I think maybe 72/ 44.  Nailhead should make plenty-o-vacuum if it is in good shape. I like nailhead motors. First car was a 63 Riviera.

[Marx3]

Great. as far as I remember the unit has the regular style seat, not that weird one. But the old weak type float setup.

I will report back on afr's when car gets up and running.

Nailheads are great engines and this one is in great condition. Its in a '66 Riviera :-) I really like them.

There should be a sort of register in here on what afr's which jet/rod combo gives in different STOCK carbs on STOCK engines...

[Rhett]

I've got a 7041304 (66 425) Service Replacement Q-Jet on my 65 Gran Sport - it's freakin awesome. it has a conventional seat, but the float arrangement has never been an issue. Only issue I ever had on it was I opened up the lower idle bleed too much and it caused an off idle stumble. Closed it up and it runs great, car does 14.7 - 14.8 stock all day long.

Current set up is:
Fuel Inlet   0.145
Float Level   0.250
Idle Tube   0.035
Idle Channel Restriction   0.046
Accel Pump Discharge   0.030
Main Air Bleed (upper)   0.070
Main Air Bleed (lower)   0.070
Idle Air Bleed (upper)   0.052
Idle Air Bleed (lower)   0.060
Mixture Hole   0.094
Primary Jets   0.074
Primary Rods   0.042
Secondary Well restriction   0.032
Secondary POE Restriction   0.052
Secondary Tube Restriction   0.036
Secondary Rods   CK .0527 L
Secondary Valve Opening   1.130
Secondary Hanger   K


I like the 74 jets, I am going back to a 43 rod next time it's open. The 44s ran great, but had a real lean AF at cruise. The 42s just feel too fat.

I also have a hybrid carb I built for racing a 67 base with a 73 body and airhorn. It has no choke, but runs great on everything (its my "try-on" carb). It's set up like this:
Fuel Inlet   0.135
Float Level   0.250
Idle Tube   0.036
Idle Channel Restriction   0.046
Accel Pump Discharge   0.028
Main Air Bleed (upper)   0.070
Main Air Bleed (lower)   0.070
Idle Air Bleed (air horn)   epoxy
Idle Air Bleed (upper)   0.055
Idle Air Bleed (lower)   0.081
Mixture Hole   0.090
Primary Jets   0.073
Primary Rods   0.044
Secondary Well restriction   0.035
Secondary POE Restriction   0.052
Secondary Tube Restriction   0.035
Secondary Rods   CK-CC
Secondary Valve Opening   1.250
Secondary Hanger   M

I think you'll be good with either jet rod combination....

Rhett

[Marx3]

great man! I haven't been able to measure afr on the car in question just yet, but will report back as soon as I have the numbers !

I have since come across another late 60's Qjet also in a 66 Riviera, this one ran a little lean, 16.5-17:1 at cruise ( although 12.6:1 at wot ), I will use your recipe! thanks