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MG TD TF 1500 - compression in pounds
|1954 mgtf 1250 engine|
Just rebuilt engine and installed it.
Ran Compression check from front of car going to rear and got the following results: 120-111-111-120. Is there an acceptable range and am I in it?
|The 120 readings are roughly appropriate, but the two 111 readings are low. Who did the final assembly and how much running time is on the engine? Could be a ring gap issue.|
the 120 readings are OK but the 111 readings are in my opinion on the low side at 93% of the other two.
Ideally they should all be within about 3% on newly rebuilt engine but personally unless you really want to pull the thing apart again and can live with a difference of 7% I would leave as it is.
My opinion and your engine so obviously your call.
Cheers , Pete.
|I was under the impression that 10% was the accepted variation in compression? Ed. That is just about what I am getting in my newly rebuilt TD engine, I just did the breakin and need to retorque the head and reset the valves. Then I will check the compression again.|
I would not accept any variation in compression greater than 3% on any engine I have personally built but I should point out these engines are at the "blueprint" end of the market.
I would rerun the compression test. Run it with the engine warm and the throttles locked open and the carb pistons held up.
|T. L. Manion Thomas|
|You need at least 500 preferably 1000 miles on a new engine to allow it bed in properly before taking any compression readings. If after running this distance your readings are still the same then this is perfectly acceptable.|
|You could try a "wet" compression test. Put some engine oil in each cylinder, through the spark plug hole, leave it for a short time, then test again. the oil will act as a temporary seal around the rings. If you still have these figures then it is not the rings it could be either the valves or the head gasket.|
This thread was discussed between 09/06/2007 and 11/06/2007
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