| FAQ |
| Members List |
| Social Groups |
| Calendar |
| Search |
| Today's Posts |
|
#1
07-25-2011, 02:39 PM
|
|||
|
|||
engine shudder/shake
engine has a shudder/shake to it.it seems like when it gets to a certain cylinder it moves the block on the mounts.
i dont think its a miss.i verified all cylinders are firing with a timing light.i checked the plugs and they all look textbook good accept #4 cylinder.it looks leaner than the rest.im thinking the valves of #4 are too tight.Am i on the right track???if i am how do i adjust only #4?? 78 400 standard bore 2801/1.52 rkrs holley650 dp,4777 16 steady vac guage runs good/strong 18initial/36 total....msd6...msd dist no vac adv. black 18 bushing/medium silver springs thank you |
|
#2
07-25-2011, 08:09 PM
|
||||
|
||||
|
If its not back firing thru the carb, then if its due to a too tight valve it will be the exh on #4.
Try this, idle the motor as low as you can. Pull off the valve cover on that side and tare off an long and tall enough strip of card board to slip down in between the valve springs and the valve cover ridge on the exh side of the head so that when the motor runs you get oil on the exh and have a fire. Next back off on the stock jam nut for #4 exh, you will hear a clicking and at that point if the valve was too tight your shudder should be gone. If so torque down the nut to 20 ft lbs and call it a day!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
|
#3
07-25-2011, 08:40 PM
|
||||
|
||||
|
You can also hook up a vacuum gauge and disconnect the coil wire and crank the engine. If you have a big sweep of the needle when the engine comes around full circle instead of steady vacuum, you have a dead cylinder (compression). You can also do this test by ear if you're experienced. The engine will crank over with an uneven sound as it speeds up when the low compression/no compression cylinder comes up on compression stroke. If it's a tight valve, as posted above, it's an easy fix, usually.
__________________
Jeff 
|
|
#4
07-25-2011, 09:18 PM
|
||||
|
||||
|
I had an issue like yours a few weeks back. It turned out to be a broken rocker stud. Hope that's not your issue.
|
|
#5
07-25-2011, 10:10 PM
|
|||
|
|||
|
i have poly locks ...is it the same deal...tighten till the tap goes away...also i have the bbc rocker studs. maybe its loose???the motor doesnt tap at all.#4 triggers the timing light.and i can shift at 5250 youd think it would come apart if something was loose or broken
|
|
#6
07-25-2011, 10:41 PM
|
||||
|
||||
|
My big block rocker broke because they were installed incorrectly. It broke idling in the driveway and had a serious miss. I shut it off & pulled the valve cover & discovered the broken rocker.
|
| Reply |
|
|
The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.
Linear Mode
