I am trying to install inner springs on a new set of heads after breaking in the cam on a rebuilt motor. The problem is I am putting 60lbs pressure through spark plug hole to keep valve from falling when I remove keepers and cap but air is shooting out. What am I doing wrong? Thanks for the help! Bob
if each cyl you are working on is at TDC on the compression stroke, it should not shoot air out anywhere. you have to turn the engine for each cylinder you work on. in addition to changing springs, you are doing a leakdown test, which is useful for diagnosis of the condition of each cylinder.
The air was coming out the carb...how do you know when the cyl you are working on is at TDC on the compression stroke? Really a novice! Thanks for the quick replys. Bob
i often tend to think in terms of non pushrod engines. i was assuming the rockers were still on the car. if air is coming out of the carb, it is coming thru or around the intake valve.
i am not familiar with pushrod engines as to whether the rockers can be removed all in one shot or not. someone else can tell you tho', i'm sure. you're going to have to remove the rockers anyway to get to the springs. you may be able to just remove all the rocker arms, and the valves should all be closed, in which case there is no need to determine TDC.
sorry, sometimes my brain works in circles. (and sometimes it doesn't work)
you can determine TDC compression with the rockers on, by putting your finger in the plug hole and turning the engine until the pressure pushes your finger out. you should also be able to watch the rockers pivot up and down to see the valves open and close. when both valves are closed, you should have very little leakage. it is best to keep a renewable air source hooked up in case you lose some pressure while changing springs.
an alternate method to air pressure is nylon rope fed into the cylindar when it is near TDC, and then turning the engine to TDC. the rope will hold the valves shut. be sure there is a few inches of rope sticking out of the plug hole. (this method can also be used to help loosen a crank pulley when all else fails).
On a push rod engine, you CAN remove all the rocker arms at the same time. Once you have all the rocker arms removed, you can put 60 PSI air pressure in to ANY cylinder through its spark plug hole and it should keep the valves closed and NOT blow up through the carb, regardelss of which piston is at TDC.
If you still get air coming up through the carb in any cylinder, then you may have a problem with a valve, a seat or binding somewhere between the stem and the guide. Of course, the car would probably run like sh*t if this is the case.
If you do need to locate TDC, do that first - before removing the rocker arms. Line up the timing mark on the balancer with the 0* mark on the timing plate. At this point, either #1 or #6 will be at TDC. You can easilly "spin" both pushrods of the TDC cylinder.
From that point, you rotate the balancer in 90* increments (CLOCKWISE while facing the engine) to go through the rest of the firing order. 1-8-4-3-6-5-7-2. You can guesstimate the 90* increment - it need not be exact.
Thanks for all the help...I added the inner springs today and I picked up a $7 attachment for my air hose, removed all plugs on one side and proceeded to put the air to each cyl. The valves closed and it worked well!
Does anybody know what the rule of thumb is on tightening the rockers down...I put them to where they seemed to be before adding inner springs and I have hyd. lifters but not sure if there is a formula. Thank you, Bob
To set the rockers, start out by turning the engine over with a large ratchet and socket that fits on the bolt that holds the balancer on the crank. I leave the spark plugs out and all the rockers off when I do this. Watch the pushrods as you turn the engine, making sure that they go up and down on the cylinder that you are working on. If they don't, they aren't located in the lifter. Correct that. The two pushrods will move one after the other as you have the exhaust, then the intake lobe on the cam go by. After the second (intake) pushrod comes back down, go a bit farther (not enough to start moving the exhaust pushrod again) and stop. Now you can install the rocker arms and torque them to the 20 ft.lbs for stock locking nuts. If you have the poly-locks, tighten the nut as you turn the pushrod with your other hand. When you feel the pushrod stop turning freely, give the nut an additional 1/2 turn and lock it down. This will give you enough preload in the lifter to get things going. Continue to do each cylinder. When you are done, double-check each rocker nut to make sure it is locked and replace the valve covers. If you want to readjust the rockers after starting and warming up the engine, buy a set of "piddle clips" to clip on the pushrod end of the rockers to avoid spraying oil around, remove the valve covers and install the clips. Restart the engine and, one at a time, go down the row of rockers, slowly loosening off the adjusting nut until you hear the clicking of excess lash. Tighten until the sounds just stops, then add 1/8 to 1/4 turn and lock. This will give the least amount of lifter pumpup at high revs.
Thanks for the detailed responses...I am going to try setting the rockers tomorrow. They look like regular nuts with roller TIP rockers by Comp Cam. I'm startin to think this is a job more suited for warm weather!
