Thermoquad on 340 (plug photos)
So I rebuilt a '73 Industrial TQ with 1-1/2" primaries. Walker kit from O'Reilly's, choke pull-off from Mikes. Sitting on a TQ adapter on LD340. (Cc'd 9:1 compression 340, headers, Lunati solid lifter cam, MSD ignition, etc.)
I modified a set of rods to 67/52/42. Replaced .098 stock jets with Carter .101's. Drilled pump nozzles to .031" and put a slightly heavier, longer spring rod spring in. I am running no choke (tied open.) Rods are adjusted 4 turns up and air door is set at 2-1/2 turns. Idle mix at 13.5 on the A/F meter.
I get very good fuel/air #'s on the meter. Around 13.5 part throttle, 14 at cruise. WOT at 11-11.5 or so. So I should be rich enough for street driving, I'd think. But I am often told to go by the plugs, not the meter. I was running BPR8ES NGK's, and was advised here to try a hotter plug so switched to BPR6ES plugs. After 40 miles or so I'm getting no color to speak of anywhere. This includes a fair number of WOT pulls, some from a stop to over an eight mile.
Also, the base of the porcelain is pure white.
Here are the plugs:
So I rebuilt a '73 Industrial TQ with 1-1/2" primaries. Walker kit from O'Reilly's, choke pull-off from Mikes. Sitting on a TQ adapter on LD340. (Cc'd 9:1 compression 340, headers, Lunati solid lifter cam, MSD ignition, etc.)
I modified a set of rods to 67/52/42. Replaced .098 stock jets with Carter .101's. Drilled pump nozzles to .031" and put a slightly heavier, longer spring rod spring in. I am running no choke (tied open.) Rods are adjusted 4 turns up and air door is set at 2-1/2 turns. Idle mix at 13.5 on the A/F meter.
I get very good fuel/air #'s on the meter. Around 13.5 part throttle, 14 at cruise. WOT at 11-11.5 or so. So I should be rich enough for street driving, I'd think. But I am often told to go by the plugs, not the meter. I was running BPR8ES NGK's, and was advised here to try a hotter plug so switched to BPR6ES plugs. After 40 miles or so I'm getting no color to speak of anywhere. This includes a fair number of WOT pulls, some from a stop to over an eight mile.
Also, the base of the porcelain is pure white.
Here are the plugs:
