another oil pressure question and more

[f_inscreenname]

All right long story short. Last fall I had a good motor (360ci mopar) with no problems. This year before I even started it this year I did a total rebuild. Since then I have burned up a set of roller rockers, bent a valve, and a number of push rods over three different test runs. Between each test run I did a top end rebuild (chasing ideas). The last time out I had good oil pressure (40lbs idle, 60lbs when running). The problem I have now is after running at a plane for a minute or two then coming to a stop the lifters start tapping for a about 90 seconds then will go away. A couple things I noticed when this happens is, when I come to a stop the oil pressure drops to 20 to 15psi from 60psi and will slowly build back (over 90secs at idle) to 40psi and the tapping goes away. When it builds the oil pressure gage needle bounces by 5psi up and down while getting higher overall. The motor is very clean inside (like new). New oil pump and lifters and all the oil passages look clean (what I can see). With the heads off I can shoot oil out of the passage (from the block ) across the deck of the boat just by cranking the motor with the starter. Now I don't know what to do. During each rebuild I used different oils (10w-40, HD30) and filters. I also use a Melling high volume oil pump but if all the oil was pumped to the top of the motor I don't think I would have burned up rockers would I? <br /> I know this question is like one I posted before but this time I thought I would leave out the things that didn't matter or that I all ready solved. That and my PC crashed last week so this is my first time back in a week. <br /> Thanks again.

 

[LubeDude]

Re: another oil pressure question and more

Lets be a little more specific on "burned up rockers" for one thing.<br /><br />I still think you are foaming your oil. Next time it does this, stop the boat and quickly pull the dipstick and see if there are air bubbles in the oil. It may not show much, but there shouldnt be like any.<br /><br />Like I posted in the last post, it could be that you are pumping your oil to the top and it doesnt have enough time to get back down. This will cause you to suck air also causing the foaming. I wish I knew more about those engines, as to where the oil comes in. Does it come up through the push rods like a chevy, or does it have a rocker shaft like a big block ford, or what? If you are sure you are not overfilling the crankcase, you might try adding one more quart of oil and see if you still have the problem. One extra quart will not cause any problem, but do not go any farther. I know that back in the seventies, Ford had some problems with some of there 351 Cleavland engines doing what you are describing and recomended adding another quart.

 

[f_inscreenname]

Re: another oil pressure question and more

Rockers are on shafts. When I “burned up” the rockers. I mean the rockers shafts burred up (from lack of oil) and froze the rocker to the shaft holding the exhaust valve open to long and the piston hit it (bent valve). Did the top end and took it out again and within 30 seconds after on a plane all the valves were not closing soon enough and you could here the pistons helping them close (no valve damage but three bent push rods). Took it apart when I got home and found most of the rockers welded to the shaft. $250.00 set of rockers trashed. Installed old stamp rockers and took it out again and that is when I found it would keep good oil pressure all the time with no problems except when I would came to a stop like I said before. I have it apart again installing a new intake gasket and I broke a rocker shaft bolt off in the head so they are off also. During the down time and with the motor half apart I thought this would be the best time to pull it out and take it apart if I have to.

 

[LubeDude]

Re: another oil pressure question and more

Not being familiar with this engine, did you have the shafts and the oil holes and the rockers lined up correctly, and the right rocker stands in the right place so the oil could get to the shaft and out to the rockers? These all have to be lined up or the oil cant get to the rockers. Thats the only way you could have welded the rockers to the shaft. Its very easy to miss aline the oil holes. Or the head gasket not positioned correctly so the oil can get through the heads to the rocker shafts. Something to follow up on when you assemble again.

 

[f_inscreenname]

Re: another oil pressure question and more

That us just it everything was lined up perfectly . There is no reason for the motor to do this but there must be. Before the rockers froze to the shafts (second test drive) when on the water (under load) I ran it in the driveway (at different rpm’s) with no problems for awhile (45 mins). I have put that behind me and now like I said I have great oil pressure at all rpm’s. I did a run at about 3200rpms for about a 1/2 hour and the oil pressure was fine (60psi) till I came to a stop and that is when the tapping started for 90sec’s and then went away. I have tried long and short runs with the same results. Like I said before I have one head on and one off and just by cranking the starter the oil flows out the shafts and rockers good and the flow out of the block will shoot across the deck. I am at a total loss.