Carter Thermoquads ~ 'More General Information'

[70GS455]

I see a lot less TQs here than you do in your country. I have only seen 3 sizes of sec high speed bleeds: 0.027", 0.029", 0.039". Local Ford TQs, there are only 5 models, all 9000 series. These are 029. Majority of early Mopar TQs I have seen are 039. I convert all of them to 039.

We played around with the sec high speed bleeds. Went from 36 to 38 then 42. It went too lean, the biggest jets we had were .156, which made most power after re-sizing HSB back to .036. Found out we needed the air door open as much as practical, which pulled less fuel into the engine. We have more selection of smaller sec jets than larger, so for us keeping the HSB smaller is convenient. I plan to change it to 35 or 34 so I can go to a smaller jet if needed. I would like to open the air door to around .900 like in the Moparts SS article but I'm not sure that will work in our case

 

[70GS455]

Do you have any info you can share on the anti-siphon feature of the CS? We had an issue with fuel being pulled out of the squirters. Would like to replicate that.

Also, can you share tuning details of any high HP setups you have been involved with? Jets, rods, bleeds, door opening etc? Thank you

 

[Bewy]

The acc pump nozzle type that is used on the CS Is also used on Carter AVS carbs used on Chry V8s. I do not think it is an anti-siphon feature [ could be wrong ], but rather a way of atomising the fuel discharging from the pump nozzles. I have only seen this type of nozzle on these Carter carbs. Edel carbs & many Carter models do not use them.

I always use a 0.039-0.040" sec HSB, if it is not already. My reasoning is that because the sec jets are so big, the more air that is pre-mixed with the fuel will improve atomisation. When you see these carbs on a dyno, or a video of one, the AV opens very quickly, maybe a second from closed to fully open. So I think the sec HSB size is not a big player in rich/lean. Rich/lean at WOT can be adjusted by the sec jet size.
Not done any experimenting with AV door opening on a dyno, but it would obviously affect distribution. This is one of the great things about the TQ: all the things that can be varied/adjusted. On a low perf engine I set them at 750-800 against the black body; 850 on a HP engine.

If you go to Fuel Systems on this forum, I started a thread recently on TQ mods. There are pics there of the sec mods. Doing that mod on a 455 Pontiac, a 143 sec jet gave perfect A/F ratio on the dyno [ 6000 production series TQ ] . On that particular carb, I straightened the bent section [ front ] of the AV; the CS AV does not have this bend, that is where I got the idea from. But no back-to-back testing done on that.

 

[Bewy]

Should have added: I have collected a large number of TQ jets over the years, & drill them as reqd.