About a month ago, I started a thead titled "Oil Pump Questions". I got a lot of responses, some much more useful than others. I have since changed out the oil pump in my car ('67 L79 Coupe), and now have some definitive answers to some of the questions I asked. At the risk of repeating myself, my problems were a constantly pegged oil pressure (60 lb.) gauge, excessive oil consumption, oil fouled plugs, and a large puff of blue smoke out of the exhaust at startup.
Here is what I found :
1. The pump in the engine was Melling "M55HV" which is their hi-volume pump.
2 The spring in the pump was their high pressure spring.
3. I replaced the pump with a Melling "10553" standard volume pump.
4. I did not go to my Chevrolet dealer ship for a pump, because a pump from them would probably have been the new design light weight pump (which is also made by Melling, but to GM specs); these have a reputation of breaking in service.
5. The "10553" pump came with a hi-pressure spring installed, and an intermediate spring in a plastic bag.
6. I called Melling and told them I needed a standard pressure "green" spring (part # 55049); it was sent to me no charge and showed up in my mailbox 2 days later.
7. I did not got to my chevrolet dealer for a spring as I did not want to spend the time and money and possibly end up with an incompatible spring.
8. I put a light coasting of grease on the oil pump gears to facilitate priming.
9. After installation, I cranked the car three time for 10 seconds with the coil wire out; half way through the third crank, I had 30 LBS. on the gauge,
10. The car started immediately and ran great and idled at 45 LBS. of oil pressure.
11. It now idles at 45 LBS. cold, 40 LBS. hot, and shows 50 LBS running down the road.
12. After the first couple of starts, the car no longer puffs out a blue cloud of smoke at start-up.
I have solved two of my 4 problems with this change. I am going to install a new set of plugs next week; I probably won't be able to tell if I solved the other two problems until sometime next year; it took several months for a new set of plugs to foul and start misfiring last time.
I beleieve the hi-volume, hi-pressure oil pump was putting more oil into the rocker area than the return drains and valve seals would take.
Stay tuned for the next installment to see if I have actually solved this problem, Everything looks good now from where I sit.
Here is what I found :
1. The pump in the engine was Melling "M55HV" which is their hi-volume pump.
2 The spring in the pump was their high pressure spring.
3. I replaced the pump with a Melling "10553" standard volume pump.
4. I did not go to my Chevrolet dealer ship for a pump, because a pump from them would probably have been the new design light weight pump (which is also made by Melling, but to GM specs); these have a reputation of breaking in service.
5. The "10553" pump came with a hi-pressure spring installed, and an intermediate spring in a plastic bag.
6. I called Melling and told them I needed a standard pressure "green" spring (part # 55049); it was sent to me no charge and showed up in my mailbox 2 days later.
7. I did not got to my chevrolet dealer for a spring as I did not want to spend the time and money and possibly end up with an incompatible spring.
8. I put a light coasting of grease on the oil pump gears to facilitate priming.
9. After installation, I cranked the car three time for 10 seconds with the coil wire out; half way through the third crank, I had 30 LBS. on the gauge,
10. The car started immediately and ran great and idled at 45 LBS. of oil pressure.
11. It now idles at 45 LBS. cold, 40 LBS. hot, and shows 50 LBS running down the road.
12. After the first couple of starts, the car no longer puffs out a blue cloud of smoke at start-up.
I have solved two of my 4 problems with this change. I am going to install a new set of plugs next week; I probably won't be able to tell if I solved the other two problems until sometime next year; it took several months for a new set of plugs to foul and start misfiring last time.
I beleieve the hi-volume, hi-pressure oil pump was putting more oil into the rocker area than the return drains and valve seals would take.
Stay tuned for the next installment to see if I have actually solved this problem, Everything looks good now from where I sit.
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