A
Anonymous
Guest
Tested my 250 last night. I think they look ok.
1. 132
2. 140
3. 130
4. 137
5. 132
6. 132
I'm at around 4700ft elevation.
1. 132
2. 140
3. 130
4. 137
5. 132
6. 132
I'm at around 4700ft elevation.
I would be happy with that unless I had just spent a ton of money on a performance rebuild.
Was that cold and dry(no squirts of oil)? Or warmed up?
Either way they are all close to each other which is a good sign. Stock used motors usually seem to run fine as long as they are all close and over about 110. Its when you get below 100 or a 30+% drop between clys you start to have possible porblems.
Was that cold and dry(no squirts of oil)? Or warmed up?
Either way they are all close to each other which is a good sign. Stock used motors usually seem to run fine as long as they are all close and over about 110. Its when you get below 100 or a 30+% drop between clys you start to have possible porblems.
james singleton
Well-known member
While on the discussion of compression (and not trying to hijack this thread), but what would the following compression numbers tell someone on this 1965 200cid engine??????
#1 179psi
#2 180psi
#3 176psi
#4 135psi *went to 155psi after a tablespoon of oil added to cyl.
#5 118psi *went to 135psi after a tablespoon of oil added to cyl.
#6 203psi
The engine spec's on the 200cid say that the Compression Pressure should be 155-195psi @ Crankng Speed.
P.S. It seems strange to me that I would have such a low number on #5 (118psi) and 203psi on #6 cyclinder???? The engine has quite a few miles on it! Any explanations??? Anyone??
#1 179psi
#2 180psi
#3 176psi
#4 135psi *went to 155psi after a tablespoon of oil added to cyl.
#5 118psi *went to 135psi after a tablespoon of oil added to cyl.
#6 203psi
The engine spec's on the 200cid say that the Compression Pressure should be 155-195psi @ Crankng Speed.
P.S. It seems strange to me that I would have such a low number on #5 (118psi) and 203psi on #6 cyclinder???? The engine has quite a few miles on it! Any explanations??? Anyone??
james singleton
Well-known member
RBOHM, Thanks for your input. So the fact that I put a little oil in the #4 and #5 cylinders and they came up to where they did, is it still more than likely a bad head gasket??? What about the rings being bad; is that a possibility?? If it is just a bad head gasket, do my compression readings sound as if the engine probably still has some life in it??? Thanks again! Jim
James, my 2 cents......
If it runs ok and its not going through much more than 1 quart of oil in 1000 miles or loosing much (if any) coolant in the same time frame I would keep running it while keeping my eyes open for another motor to rebuild. I would not worry about a smooth idle or acceleration as long as it stays running. Everything but #6 seem like they could be 'normal' wear and tear. By normal I mean a combination of valve seats and rings. The oil helping points more to rings than valve seats. I wonder if #6 maybe has a differnt piston in it from a repair earlier in its life? Remember these engines are at the end of the period where it was common for a 'valve and ring job' every 25-50K miles so maybe they had it apart and found a problem with only that one piston and replaced it with something close they had on hand. It would take a lot of carbon to do that but a slightly differnt pin height could easily do that and I have seen motors with one odd piston in them before. Often times if you have a head gasket leak you will be blowing coolant out your overflow because of the extra air being introduced to the cooling system. When you shut it down the pressure in the cooling system will often push coolant into the cylinder, you may even be able to see steam if you pull the spark plug when its hot. The spark plugs may also be steam cleaned.
If it runs ok and its not going through much more than 1 quart of oil in 1000 miles or loosing much (if any) coolant in the same time frame I would keep running it while keeping my eyes open for another motor to rebuild. I would not worry about a smooth idle or acceleration as long as it stays running. Everything but #6 seem like they could be 'normal' wear and tear. By normal I mean a combination of valve seats and rings. The oil helping points more to rings than valve seats. I wonder if #6 maybe has a differnt piston in it from a repair earlier in its life? Remember these engines are at the end of the period where it was common for a 'valve and ring job' every 25-50K miles so maybe they had it apart and found a problem with only that one piston and replaced it with something close they had on hand. It would take a lot of carbon to do that but a slightly differnt pin height could easily do that and I have seen motors with one odd piston in them before. Often times if you have a head gasket leak you will be blowing coolant out your overflow because of the extra air being introduced to the cooling system. When you shut it down the pressure in the cooling system will often push coolant into the cylinder, you may even be able to see steam if you pull the spark plug when its hot. The spark plugs may also be steam cleaned.
A
Anonymous
Guest
fordconvert":1ofik0vx said:
I don't think the engine has been rebuilt recently. I warmed up the engine for 10 minutes, didn't add oil.
Madman, thats the way I do compression checks if the engine still runs. If you find something odd like James did thats when you add the oil. If the engine has been sitting for a while you usually need to add the oil also because the rings dont tend to seal well on cold dry pistons and bores especially at cranking speeds.
buy a leak down tester that plugs into the air compressor and do a check like that. if it leaks (air) from exhaust or inlet manifold its valves, if it leaks from the oil filler its rings, if it bubbles up the radiator (cap off) then its head gasket. if its all 3 rebuild time!
MM21,
Personally I think the numbers are too low. It VERY good that they are as even as the are. That tells me that the rings and valves are in the same condition. My engine had consistant low numbers too (before the rebuild). What I found out was that the PO had installed a composite head gasket with out milling the head. My 200 came stock with the metal head gasket that is thinner than the composite. I don't know if the 250 were the same way?
If the engine runs fine, doesn't burn oil (bad rings), the plugs don't foul (leak valve stem seals), leaks at every gasket (bad rings again), blue smoke doesn't come out the tail pipe or you can see smoke coming out of the breather cap (REALLY bad rings) then run the car until one of those symptoms occur!
James: The engine in my car had the same thing: one cylinder was WAY higher than the rest. I found out that the valve stem seal was leaking bady into that cylinder (it would foul the plug in 100 miles it was so bad). My guess is that somehow oil is getting into that cyliner and forming a nice seal witht the rings. Do you know the conditions of the valve stem seals?
Personally I think the numbers are too low. It VERY good that they are as even as the are. That tells me that the rings and valves are in the same condition. My engine had consistant low numbers too (before the rebuild). What I found out was that the PO had installed a composite head gasket with out milling the head. My 200 came stock with the metal head gasket that is thinner than the composite. I don't know if the 250 were the same way?
If the engine runs fine, doesn't burn oil (bad rings), the plugs don't foul (leak valve stem seals), leaks at every gasket (bad rings again), blue smoke doesn't come out the tail pipe or you can see smoke coming out of the breather cap (REALLY bad rings) then run the car until one of those symptoms occur!
James: The engine in my car had the same thing: one cylinder was WAY higher than the rest. I found out that the valve stem seal was leaking bady into that cylinder (it would foul the plug in 100 miles it was so bad). My guess is that somehow oil is getting into that cyliner and forming a nice seal witht the rings. Do you know the conditions of the valve stem seals?
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