Originally Posted by andybyrd
my soninlaw has a pure proform 650 on a 302 and it has a bad off idle stumble we need help with that if anyone has fixed yours maybe you can tell us what you did.
Andy
Well, a few things to check for here;
1. float levels, engine running on level ground, yeah I know everybody does it!!! but on a Proform carb the fuel should be right at the bottom of the plug window or see thru plug if you have them, if not, get a set they work great for monitoring your float levels.
2. You may have to play around with the cam on the throttle linkage and slow down the 2ndarys a little bit.
3. Does this carb have jet extensions in the rear bowl? if not, better get a set of those too! Does it have the notched float in the rear bowl? it should!, if not send it back to Proform and tell them to fix it right :x
4. Fuel pressure, you should have no more than 7psi on a gauge past the reg. and before the carb.
5. IF, your carb has the secondary throttle shaft adjustment on it, this needs to be almost identical to the front shaft setting as this is a very touchy carb if not set right. Loosen both screws up after recording on some paper where they are now before you change them, and at least you can go back to that setting if all else fails. But, close both sets of butterflys, and then turn each one in, 1-1.5 turns in or clockwise on both shafts, fire it up and adjust them to get the highest vacuum reading you can obtain, it does have a vacuum port on the front or rear of the bottom plate right? my 950 did!! and then just play around with the idle until you can get a good idle and put into gear and it should not drop in rpm by more than a couple hundred rpm's and stay running, then pop it back into nuetral and if it sounds to high in the rpm's, well adjust the 4 corner idle screws again and then go back and readjust the throttle shaft screws until it likes your screw driver
I tell yea, the Proform 950 I had, was the BEST 4150 carb I ever had and my engine wanted more carb after that size too!!! big block 454 12:5:1 comp. with oval port heads put my 3600lb Elky at a best of 11:02 @ 123 mph with a 4.56 gear. I never did a jet test on it and I should have as I could have broke the 10's for sure, and I had an air cleaner on it too, big 14 inch x 4 incher.
6. idle screws, give them a full turn out from all the way in, and if it won't stay running turn all of them another 1/2 turn until it starts and runs by itself then adj. as needed. Great carbs if you can tune them right :wink:
John