[kenneth77]

if you have a power valve that dont function,( open all the time),how will i know?
will it affect the idle?
i think i may have problems with my 66 tripower. engine has black dry spark plugs,and likes to suck false air.it idles better if i disconnect a vacuum hose on the carb(not vac ign),engine also almost dies if i pinch the pcv hose.plugs are autolite 85,and initial timing are 12,and 32 total.fuel pressure 4psi,idle mixture screws out 1,5 turn( engine dies if i turn to far inn)
engine idles like **** when cold,and a little better when warm.(choke disconnected)
manifolds vacuum reads 16 at idle,its not steady,but vibrates from 15-16 .
could it be the power valve giving extra fuel,or should i look at something else?




thx

[kenneth77]

engine is a 389 with summit 2802 camshaft,stock compression,roller 1,5 rocker arms, rohads lifters.

[Tom Vaught]

Lots of the older Rochester Tri-Powers had poor gas mileage and other drive complaints because the "Power Piston" was stuck in the air horn cavity of the carb. Usually you could work the flat "nail like" plunger (with the spring on it) in and out a bunch of times and use a bit of light oil and free it up so it worked fine again. Other times you could easily remove it by pushing the plunger in and letting the spring push the plunger back so that it hit the retaining washer. Many times doing this and you would see the retaining washer come out of the airhorn. Then you would lightly sand the piston with some fine sand paper, clean the grit off, and then reinstall it in the airhorn. A light staking would hold it in place and the piston would work fine again.

Tom Vaught

[kenneth77]

is there something i am missing.is there suppose to be a retaining washer in the hole in the airhorn,where the power piston should go inn?

yesterday i took off the airhorn,turned it upside dowm,and tried with a rubber hose to make vacuum,to see if the power piston activated.it did not happen.
the power piston goes up and down fine,if i use my fingers.its very easy to mount in the airhorn.

[kenneth77]

shouldt there be something to hold the power valve retaining spring in place in the airhorn/or make sure it does seal for vacuum. if i have the airhorn upside down with the power valve in place,and turn the airhorn around,most of the time the power valve falls out.the power valve retaing spring go very easy inside the mounting hole in the airhorn.i cant see that the airhiorn gasket will hold it it place,since the hole in the gasket is bigger than the retaining spring on the power valve. im confused or stupid (both?) pls help me out

see the pics

[carbking]

The washer is in place.

Push the piston into its cavity, and the washer will slide down into a slight recess in the airhorn. When in place, the washer will be very slightly below the surface of the airhorn. Now, using a pin punch, punch the airhorn area around the washer in three equidistant spots to "peen" a wee bit of the casting over the washer, thus holding it in place. You can see the areas where punch marks were previously made.

Jon.