Q-jet with dual capacity accelerator pump
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| + | ==Overview== | ||
The question came up on what- if anything- is required to use a late model NON CCC/NON electronic Q-jet carb that has the dual capacity accelerator pump. Because these carbs are often mistaken for being full electronic/CCC-type feedback carbs, many who have them either don't know what they have, or if they do they don't know whether they can be used as-is or not. | The question came up on what- if anything- is required to use a late model NON CCC/NON electronic Q-jet carb that has the dual capacity accelerator pump. Because these carbs are often mistaken for being full electronic/CCC-type feedback carbs, many who have them either don't know what they have, or if they do they don't know whether they can be used as-is or not. | ||
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[[File:Qjet with CCC.jpg|300px|thumb|left|1981-up Q-jet with CCC emissions/computer control]] | [[File:Qjet with CCC.jpg|300px|thumb|left|1981-up Q-jet with CCC emissions/computer control]] | ||
| − | The dual capacity accelerator pump carbs can be ID'd by their solenoid plug mounted on the passenger side top front of the airhorn/carb top, along w/the LACK of a plug for the TPS (throttle position sensor) that's present on electronic feedback-type Q-jets used during the same years on vehicles using the "CCC" system | + | ==How to ID a dual capacity accelerator pump Q-jet== |
| + | The dual capacity accelerator pump carbs can be ID'd by their solenoid plug mounted on the passenger side top front of the airhorn/carb top, along w/the LACK of a plug for the TPS (throttle position sensor) that's present on electronic feedback-type Q-jets used during the same years on vehicles using the "CCC" system. | ||
These NON CCC/NON electronic dual capacity accelerator pump Q-jet carbs are found on 1985-'86 GM trucks and vans, and have desirable features- adjustable top-accessed APT, electric choke, correct linkage geometry for OD transmission TV cable, large 800 cfm casting, and generally less use/abuse/rebuilds on them than carbs from the '60s and '70s. | These NON CCC/NON electronic dual capacity accelerator pump Q-jet carbs are found on 1985-'86 GM trucks and vans, and have desirable features- adjustable top-accessed APT, electric choke, correct linkage geometry for OD transmission TV cable, large 800 cfm casting, and generally less use/abuse/rebuilds on them than carbs from the '60s and '70s. | ||
| − | + | ==How to make it work== | |
| + | Cliff Ruggles verified that basically nothing needs to be done to have the carb perform just like the earlier single capacity accelerator pump carbs. The plug and solenoid can be left intact, the default setting (with '''no''' external wiring or electrical source supplied to the plug) is such that the accelerator pump will deliver a normal pump shot. Or if desired the cavity under the solenoid can be filled with molten lead to prevent any chance of a leak. | ||
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| − | In cases where a large pump shot is needed, like with big cams, single plane intakes and/or heavy or high geared vehicles, an interesting idea would be to set the accelerator pump up with the larger pump shot volume needed for best acceleration when in the default mode. Then with the solenoid activated have a reduced shot volume for the street. The accelerator pump position could be selected using a simple toggle switch. | + | ==Possible use for dual capacity pump== |
| + | In cases where a large pump shot is needed, like with big cams, single plane intakes and/or heavy or high geared vehicles, an interesting idea would be to set the accelerator pump up with the larger pump shot volume needed for best acceleration when in the default mode. Then with the dual capacity accelerator pump solenoid ''activated'', have a reduced shot volume for the street. The accelerator pump position could be selected using a simple toggle switch. | ||
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| + | ==Carb numbers== | ||
| + | The carb number will be '''17085''' or '''17086'''. The 6th number will be 1, 2, 4, or 5. The 7th number will ''usually'' be 0, 1, or 2- but there are carbs made 1981 and later that do not follow the traditional numbering system. For that reason, there are Chevy/GMC carbs with 4 and 5 in the 7th position. If the 8th (final) digit is an even number it sometimes denote an automatic transmission application, odd for manual. This is not an absolute. | ||
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| + | ===Some numbers to look for:=== | ||
| + | *17085210 | ||
| + | *17085206 | ||
| + | *17085215 | ||
| + | *17085226 | ||
| + | *17085227 | ||
| + | *17086046 (ALT, AT, dual acc. pump) | ||
| + | *17086048 (ALT, AT, dual acc. pump) | ||
| + | *17085227 (AT, dual acc. pump) | ||
| + | *17086054 (AT, dual acc. pump) | ||
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[[Category:Engine]] | [[Category:Engine]] | ||
[[Category:Carburetors]] | [[Category:Carburetors]] | ||
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