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I'm deciding whether or not to rebuild my engine completely, or just down to the valves.
Facts:
Late model engine, serial number 199700's.
1. Cold, in-shop compression check prior to tear down was excellent, 115psi in #1, and 118psi in #2, 3 & 4.
2. Engine made strong pinging sound, with loss of power/RPM after running for a length of time. Probably due to leak in either head or manifold gasket, or head or manifold studs, or both. Noticed VERY slow reduction in antifreeze level in plastic overflow container.
3. I will count on this engine for the next 10 years at least.
With the engine out of the boat to resolve the pinging issue, I have taken the engine down to the point of removing all valves and tappets and scraping all gasket material off the block and head. Findings so far are:
1. Valves, valve chamber between block and head, and piston tops are all pretty heavily caked in carbon. Although compression was good, valve seats look pretty rough.
2. Cooling jackets have lots of debris build-up (but engine ran at 140 degrees consistently). Have only had a couple of 200+ degree overheatings since I bought the boat, and that was due to scaling clogging the manifold exit port.
3. There seems to be a leak in the accessory drive oil seal (will implement oil level fix) or water pump seal because lots of oil residue on engine underneath those housings.
4. I will have to replace some castings (water jacket side plate, maybe the manifold).
I'm at that crossroads where I have to decide whether to tear down the engine completely, or just down to the valves. My delimna is based primarily in my (conservative) concern over the condition of my crank and bearings. There is no reason to suspect they are ready to fail, but I know pinging is hard on bearings and this engine has pinged for at least a year of regular use. Since the engine is on the floor of my shop and it is already torn down to the valves, I see this as an opportunity to go ahead and insure it will be in as reliable condition as possible for the long term, and learn a thing or two if I ever have to do this again. To my knowledge, this engine has never been rebuilt.
I would check the crankshaft for any cracks and have it rejournaled, have head, block and manifold serviced and machine the valve seats. I'll let a machine shop tell me if pistons, valves, and bearings should be replaced and whether the cylinders should be rebored/resleeved.
What can I expect costs to be for machining and other 'service' costs I may incur? Are there any compelling reasons NOT to rebuild, or other compelling reasons TO rebuild?
Thanks for any feedback.
John
Facts:
Late model engine, serial number 199700's.
1. Cold, in-shop compression check prior to tear down was excellent, 115psi in #1, and 118psi in #2, 3 & 4.
2. Engine made strong pinging sound, with loss of power/RPM after running for a length of time. Probably due to leak in either head or manifold gasket, or head or manifold studs, or both. Noticed VERY slow reduction in antifreeze level in plastic overflow container.
3. I will count on this engine for the next 10 years at least.
With the engine out of the boat to resolve the pinging issue, I have taken the engine down to the point of removing all valves and tappets and scraping all gasket material off the block and head. Findings so far are:
1. Valves, valve chamber between block and head, and piston tops are all pretty heavily caked in carbon. Although compression was good, valve seats look pretty rough.
2. Cooling jackets have lots of debris build-up (but engine ran at 140 degrees consistently). Have only had a couple of 200+ degree overheatings since I bought the boat, and that was due to scaling clogging the manifold exit port.
3. There seems to be a leak in the accessory drive oil seal (will implement oil level fix) or water pump seal because lots of oil residue on engine underneath those housings.
4. I will have to replace some castings (water jacket side plate, maybe the manifold).
I'm at that crossroads where I have to decide whether to tear down the engine completely, or just down to the valves. My delimna is based primarily in my (conservative) concern over the condition of my crank and bearings. There is no reason to suspect they are ready to fail, but I know pinging is hard on bearings and this engine has pinged for at least a year of regular use. Since the engine is on the floor of my shop and it is already torn down to the valves, I see this as an opportunity to go ahead and insure it will be in as reliable condition as possible for the long term, and learn a thing or two if I ever have to do this again. To my knowledge, this engine has never been rebuilt.
I would check the crankshaft for any cracks and have it rejournaled, have head, block and manifold serviced and machine the valve seats. I'll let a machine shop tell me if pistons, valves, and bearings should be replaced and whether the cylinders should be rebored/resleeved.
What can I expect costs to be for machining and other 'service' costs I may incur? Are there any compelling reasons NOT to rebuild, or other compelling reasons TO rebuild?
Thanks for any feedback.
John
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