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Author Topic:   drilling primaries on quadrajet 750
avila
Member
posted July 09, 2003 10:54 PM
I'm in the evolving process of drilling the holes in the butterflies so that I can close down the butterflies using the curb idle s_c_rew. I'm trying to get down to the recommened exposer of .020" of the idle transfer slot.

Currently I'm at hole diameters of .125" and expsoer is at .035". I idle at 900rpm with this setting.

Is is safe to keep drilling larger to get to the recommended
.020" exposer setting? How would I know if I drilled out too much?


KPLugnut
Member
posted July 10, 2003 10:58 PM
I would never go more than about .140" but the more important rule of thumb is to measure the actuall WIDTH of the idle transfer slot and use that as the measurement for how much of the slot you want to expose vertically under the butterflies. So, if the slot width is about .030", then you're pretty darn close to optimum right now.

Hope that helps,
KP


o5racer
Member
posted July 13, 2003 01:56 PM
I must be doing something wrong. just about all of the engines I have built in the last 5 years wont idle high enough. The q-jet that I hsve on now I had to drill another idle air passage in addition to opening the original up to about .875 just to get the plates even clost to the bottom of the transfer slot. I have had 5 or 6 different Q-jets on 4 engines. The cam I am running is a midwest #1 .504 lift with big duration. I think it was 255 and 265 @.050 plus Im running 1.6 rockers on top os its a .537 lift. Any ideas? Its on a flat top 358, 11 to 1, ported cammelbacks with an edlebrock 2101 intake. At idle it only pulls about 7 inches of vaccuum, none of them have ever been higher i just figured it was because of the cam.


KPLugnut
Member
posted July 13, 2003 08:43 PM
Yep, it's the cam....

KP

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