74u

iTrader: (9)

I have been running a Holley 750HP and the car runs great. This weekend i decided to try my dads spare Pro Form 850 and see whether it runs any better MPH. Right out of the gate I start having problems...found a stripped float bowl thread (and 7 more that were about stripped) so I picked up a heli-coil kit and fixed. Now I finally get the carbs swapped and for some reason I can't get the primary throttle blades to close all the way and the idle is sitting at 1500.

What I've done so far...

1) verify no vacuum leaks
2) adjust 4 corner screws by eye, ear, nose to obtain proper mixture
3) back primary side idle stop screw all the way off

At this point the idle is still at 2000rpm...so...

4) verify t-cable freeplay
5) back the secondary stop screw out all the way

Now idling a 1500rpm...

6) shut it down and look down the holes with flashlight. Secondary blades are closed 100%...primary blades show a large (maybe .015 - .020") gap with the curb idle screw completely out.

7) noticed if I force the linkage closed (harder than the springs are capable of) the idle will drop a touch lower until I take pressure off.

What is holding the primary blades open? I examined my Holley (removed) and if I back the idle stop out the blades close tightly.

Thanks for the help!!

Doug G

Sounds an awful lot like a vacuum leak.

74u

iTrader: (9)

Why does my known good working Holley throttle blades close all the way when the idle screw is backed out, but primary blades on this carb still have a large gap? What keeps them from shutting all the way?

Doug G

there should be a screw that acts as a stop on the secondary's that you can only get to from the underside.

If its the primaries...maybe linkage bind ??

OutlawDrifter

iTrader: (9)

that's what i was thinking....or you don't have enough slack in your setup.

fast89stang

iTrader: (2)

progressive linkage on the driver side of carb may be holding the primaries open?