I have a pro systems 4150 with a 6.5 power valve in the front, motor is BBC 454 w/ 254/263 @50 solid cam. Timing is locked out at 36*, most vacuum at idle has been 10 inches, should I get a high flow 4.5 power valve? Try to load a picture,also where is the secondary idle screw?

I don't see a secondary idle speed screw on that carb. I would try the 4.5 power valve also.

Dave

In your picture, look directly to the right of the right edge on the centerline of the carb and you will see a small spring. This is the spring that the secondary throttle opening screw resides in.

In your picture, look directly to the right of the right edge on the centerline of the carb and you will see a small spring. This is the spring that the secondary throttle opening screw resides in.

I must be looking at it backwards or something, standing on my head :D
It looks to me the secondary screw is on the bottom left of the picture and on the side (as in the up side of the carb)

I must be looking at it backwards or something, standing on my head :D
It looks to me the secondary screw is on the bottom left of the picture and on the side (as in the up side of the carb)

You're absolutely right. I was looking at the primary throttle blades. The secondary adjustment is on the other side as you described. Sorry about the focus.

https://publish.comcast.net/rpath/4MAXmQL4QhF39kmjBm-7a-vWMLhOd4p3Kci-V-205aV5w3Ejts_lvVFWxja954y_02NAufQzxln2pcKGivrqRM9P zUhM7He28wpIoKQBE_A/

Is that 10" idle vac in gear if running autotrans?

If your running autotrans and the 10" idle vac is in neutral then its more like 6" maybe 7" in gear .

If thats the case the 6.5 p/valve in the prim side is not good at all,its to close the avtivation of the p/valve ,you would need more like a 3.5 if 6" idle vac or 4.0 if 7" idle vacuum in gear.

If the idle vac is 10" in gear with auto trans or in neutral with man trans then if you suspect the p/valve is commijg on a little too early then try a 5.0 but a 4.5 may be going too consrvative/lean when it comes to being under load fuel enrichment.

Scott

In your picture, look directly to the right of the right edge on the centerline of the carb and you will see a small spring. This is the spring that the secondary throttle opening screw resides in. Is this it?

Is that 10" idle vac in gear if running autotrans?

If your running autotrans and the 10" idle vac is in neutral then its more like 6" maybe 7" in gear .

If thats the case the 6.5 p/valve in the prim side is not good at all,its to close the avtivation of the p/valve ,you would need more like a 3.5 if 6" idle vac or 4.0 if 7" idle vacuum in gear.

If the idle vac is 10" in gear with auto trans or in neutral with man trans then if you suspect the p/valve is commijg on a little too early then try a 5.0 but a 4.5 may be going too consrvative/lean when it comes to being under load fuel enrichment.

Scott As I was loading pics some replies came in looks like I've got the right screw for secondary idle now. Your right about the vacuum I'll chock my wheels and check vacuum in gear its probably around 7 inches, man I hope I can solve the richness. Might be the source of my stalling I've been fighting all season too?