Idle issues times 3

[notagn]

Hey Guys, working on a 64 Pontiac GTO 389 with tri power. Having idle issues set the timing at 6 initial any more and it has run on. The book says it should idle at 600 with the engine at 600 RPM it has 6 or 7 inches of vacuum. Using a propane torch looking for vacuum around manifold and all lines nothing found. Set all the lifters to no movement then 1 turn. (hydraulic cam)With the exception of #3 Intake and 7 exhaust all went well. 3 and 7 felt like I just hit a stop with the last 1/4 turn. The outboard carbs are not on the manifold at the time of trying to get the engine to idle. So I am looking for suggestions on what the next step is. Thanks for any suggestions.

[Firedome8]

Readjust valves to zero +1/8 turn for now,,,advance timming to around 16* no vacuum adv for now. Throttle 1.5 turn mixture screws 1.5 turns then try again. Maybe your valve adjustment did not go as planned.

[Tuner]

The original '64 Pontiac rocker adjustment was torque the rocker nut to 15-25 ft. lbs. The Pontiac rocker stud and nut (until '68..?) are not like the more familiar Chevy that uses a self-locking nut. The Pontiac stud has a shoulder below the threads and the nut is not self-locking, it is made to be torqued against the shoulder.

[ProPower engines]

Just curious are you using the oil through the rocker stud set up from back in the day??
When you mentioned the 3-7 rockers stopped short so to speak is the tip installed heights shorter thus allowing the not to bottom on the shoulder??

I would reset the lash as suggested to be sure you are not bottoming a lifter and holding a valve open. With just the center carb it should idle fine and have more vacuum so you may have a valve off the seat

[notagn]

I understand relashing the valve suggestions. If we gained vacuum after the work still think it's the direction to go? Any other thoughts on what might be going on?

[ProPower engines]

If you gain but don't fully fix the issue that just says your headed in the right direction.
valve lash is the 1st step since there is no positive answer to correct the problem.

[shiftbyear]

I don't know who did the carbs, but this place seems to have all the answers. I bought their dvd, it was very informative. Believe it or not, there is a special coating for the throttle blades to help them seat in the bores to help idle. Good luck

http://www.pontiactripower.com/

[jmarkaudio]

I don't know who did the carbs, but this place seems to have all the answers. I bought their dvd, it was very informative. Believe it or not, there is a special coating for the throttle blades to help them seat in the bores to help idle. Good luck

http://www.pontiactripower.com/

Say what???

[PackardV8]

I don't know who did the carbs, but this place seems to have all the answers. I bought their dvd, it was very informative. Believe it or not, there is a special coating for the throttle blades to help them seat in the bores to help idle. Good luck

http://www.pontiactripower.com/

Say what???

Been around forever. I have this vague recollection of a 1960s Hot Rod how-to-fix-your-3-carb-Stromberg-97-idle article touting a product with a name something like DAG213.

[jmarkaudio]

If the blades and bores are correct and the blades set right with the bore when you screw them down there should be no issue. The blades should not be completely seated at idle or no air gets in.

[MadBill]

During assembly, the DAG material was painted around the secondary blades of progressive linkage carbs (e.g. Quadrajet) by Rochester Products and likely others, to eliminate erratic leakage while adjusting the primary side mixture and airflow. During operation, the blades would soon 'bed-in' and minimize any leakage. Often you can see a 1/4" wide band of it around the periphery of such back butterflies.

[notagn]

Going to look at bottom of carb see how the throttle blade is oriented to the bore. right now I am sure its set well past the transition slot. Will also try backing of the lifters half a turn to see how the engine responds.

[Speedbump]

Am I the only one who thinks 6-7 inches of vacuum at idle for this engine is WAY low? probably a valve adjustment situation or am I missing something here?

[Tuner]

Am I the only one who thinks 6-7 inches of vacuum at idle for this engine is WAY low? probably a valve adjustment situation or am I missing something here?

I doubt you are the only. Something is amiss, timing retarded or a bunch of valves are too tight, crazy camshaft, etc??? Doubtful the original engine is still in the car and still in original condition.

The Pontiac engines of that era suffered from severe timing chain wear such that the chain would get so loose if the engine dieseled and kicked back on shutoff the chain could hop a tooth, saw that several times back in those days. One, I recall it was a '62 389 Catalina, chain so loose you could pass a piece of paper between the chain and crank sprocket. It ran OK until the last time it dieseled.

The Pontiac method of locking the adjusting nut by tightening it to the shoulder on the stud confuses most younger guys who have only experienced the Chevy with self-locking nuts.

Pontiac engines require a different Poly Lock than the Chevy because the original stud has the shoulder.

I'll bet very few know why Poly Locks are called Poly Locks, how they got the name Poly Lock.

[notagn]

I have to ask if I back of the valve adjustment and gain vacuum but not enough (guessing 18'' with a stock cam) what is the engine telling me?