I have a customer with a 66 389 and it has the 80 psi pump in it. Likely someone put a washer behind the spring in the relief valve as well. It will peg close to 100 psi when cold. It has started to cause a problem with the lifters . Seems with sae 40 when cold, at startup i will run rough untill the lifters start to finally bleed some pressure .i know the lifters are pumping up and holding the valves open a smidge casuing misfiring/rough running.
I have even put on poly locks and set the valve adjustement to 1/8 turn past zero lash to help alleviate the problem
He is coming in tommororw for a oil change .I am going to put in 5w 30
I hope it clears the problem up.
After it runs a few minutes and the oil warms up, the pressure drops some and the misfires quit occuring, everything is good. When it is cold , and misfiring , it is a challenge to keep it running long enough to warm up.
Of course we have had some 30 degree nights, and a few 20 ish degree nights.
Have anyone else had an issue that the lifters pump up and hold open the valves?
I have also changed the valve springs as well with new stock springs .
My original take on the problem was the springs were getting weak ( and they were) and it was allowing the lifter to pump up against the valve and hold it open until pressure dropped.
Comments?
|