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Original Message
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| RE: engine running REAL fat ,,WHY?? |
| By Gerry Proctor - 11/29/2001 8:09:14 AM; IP 208.217.67.247 |
Where is it running rich, Robbie? With 9"hg idle vacuum idle I suspect your using a fairly lumpy cam with an idle rpm is near 1k rpm. It commonly happens that in order to achieve a stable idle, you have to crack the throttle idle screw open far enough which exposes the idle transfer slots that causes a rich idle and unresponsive idle mixture adjustment. The solution here is delicate tuning such as more initial and less centrifugal and vacuum advance. This increases the idle rpm and vacuum which allows you to reduce the throttle opening. You may even have to drill bleed holes in the primary throttle blades to allow enough airflow and keep the transfer slot covered.
If you're fat on the main circuit, then you may be dealing with a restriction in the main air bleeds or a leak in the power valve circuit. A 66 jet in the primary is on the small side for most applications and, though you didn't make this clear, it appears you're running dual quads. Are you aware that Ford's dual quad set up was a lot more than a couple of Holley 1850 600 cfm carbs? You didn't write what carbs your using, but most folks commonly use this setup. The idle and main air bleeds are larger in the Ford dual setup to facilitate tuning these carbs. The tiny restrictions in the single quad-spec carbs are too small to run very well on a dual setup. Enlarging the bleeds may be beyond your tuning abilities as this proceedure requires tuning skills far beyond those of folks who rebuild carbs.
I can understand why you're suffering detonation with an 11.7:1 compression ratio. This level of compression requires more than booster additives can offer. These products generally don't raise the pump octane number more than a point which is nowhere near the detonation resistance you need with that much squeeze. You may have to visit your local drag strip and get some 100+ to eliminate the detonation variable from your tuning problems. |
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