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Old 12-28-1999, 05:49 PM
Michael Zrust Michael Zrust is offline
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Location: Scottsdale, AZ. USA
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I have a 440 with the MP 272/.455" cam. The carb is a Carter 625 CFM. To obtain a better idle, should I drill small holes in the primary butterflies? What size of holes?
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Old 12-29-1999, 01:43 AM
PRO PRO is offline
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Michael I've done this with limited success,what the real problem is your transfer tubes are supplying all the fuel the can,and its not enough,by drilling holes in the butterflies your allowing more air past the venturi's which pulls more gas into the intake and solves your idle problem,1st have you tried a different rate of spring,the metering rod plunger spring?You can buy a strip kit for your carter and it will come with 4 sets of springs.If you do drill start out very small like .094 and work up,when it works good dont drill more thinking you might gain something,you wont,also I'd have a spare set of butterflies around to swap in just in case(we are drilling only the primary side right?)Good Luck as you might need it.A bigger carb is probably in order....PRO...
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Old 12-29-1999, 01:51 AM
Michael Zrust Michael Zrust is offline
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I went with .092" and it did help slightly. I think I will stop there. One item I did leave out on the other post was the fact that I have a 4 hole phenolic 1" spacer beneath the Carter. All metal carburetors have problems out here in AZ in the summer time (115 ambient temp). The alcohol in the gas for oxygenation doen't help with the percolation issues.
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