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Old 03-11-2019, 08:21 AM   #1
Railcarmover
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Default Against compression



My friend wanted to find the source of his light knock,so we fired his engine and put a stethoscope to it,isolated it to the center main area. He had a blowby issue as well,and I noticed it cranked over easy.The next weekend we went to work,pulled the pan off the '28 special coupe to take a look. to make life easy pulling the center cap I wanted to turn the crankshaft and move the crank throws level..I grabbed the throws and turned the engine,by hand,one full revolution,against compression..Now mind you,she fired cold on three turns.Its amazing how worn these engines can be and still run.Pistons so loose you could move them is a circle in the bore,number 3 ex valve fried..the rest of them done.But she ran smooth on all four.Weak,but smooth.
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Old 03-11-2019, 08:59 AM   #2
Ray in La Mesa
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Brings back memories of an engine we tore down 35 years ago. Could hear it knocking two blocks away as he drove it into the garage. We pulled the head and discovered the reason for the knock, you could stick a standard screwdriver about I" down between the piston & cylinder!! It is amazing how our old toys keep running under adverse conditions!
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Old 03-11-2019, 04:49 PM   #3
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Default Re: Against compression

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Originally Posted by Ray in La Mesa View Post
Brings back memories of an engine we tore down 35 years ago. Could hear it knocking two blocks away as he drove it into the garage. We pulled the head and discovered the reason for the knock, you could stick a standard screwdriver about I" down between the piston & cylinder!! It is amazing how our old toys keep running under adverse conditions!
With that amount of wear, that motor would have been so down on power that it might not have been running - walking, maybe!
I'm sure that in the day, when these were just another old car, a motor like that wouldn't be rebuilt or replaced. The car would have been scrapped and so millions of them were wrecked. That's not really much different today - what happens to a car "at the end of its life" when it is traded in on a new one? Scrapped and recycled! I'm sure our microwave oven has some metal from a 1970's car in it.
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Old 03-12-2019, 08:17 AM   #4
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Its one of the reasons the car endured through the decades in my opinion.The engine wears gradually and evenly,degrading slowly.The cars were run on penny a quart drain oil and sold for 5 bucks in the late forties instead of pitching a rod through the block and grenading like modern engines do,essentially avoiding the scrapyard because they still had value.
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Old 03-12-2019, 09:38 AM   #5
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Railcar,

You have hit on a subject that many do not realise.
Even the driving habits can affect the life of the high mileage motor, thus unbalancing the wear.
How many times have you heard a valve job done on a high-mileage motor only to have the bottom of the motor fail in a short time?

I'll bet that old motor once rebuilt will last a long time if machined straight and true.

J
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Old 03-12-2019, 09:54 AM   #6
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I agree John,its why its important to look at every aspect of the engine when modifying or doing general repair. A bearing adjustment done at the right time can save you alot of money.
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Old 03-12-2019, 06:08 PM   #7
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I agree John,its why its important to look at every aspect of the engine when modifying or doing general repair. A bearing adjustment done at the right time can save you alot of money.
Agreed here, too.
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Old 03-12-2019, 08:36 PM   #8
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Default Re: Against compression

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Originally Posted by Railcarmover View Post


My friend wanted to find the source of his light knock,so we fired his engine and put a stethoscope to it,isolated it to the center main area. He had a blowby issue as well,and I noticed it cranked over easy.The next weekend we went to work,pulled the pan off the '28 special coupe to take a look. to make life easy pulling the center cap I wanted to turn the crankshaft and move the crank throws level..I grabbed the throws and turned the engine,by hand,one full revolution,against compression..Now mind you,she fired cold on three turns.Its amazing how worn these engines can be and still run.Pistons so loose you could move them is a circle in the bore,number 3 ex valve fried..the rest of them done.But she ran smooth on all four.Weak,but smooth.
Iím guessing your installing a new gasket and head bolts on re-assembly?
Those look ready for retirement.
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Old 03-12-2019, 10:06 PM   #9
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He had a decent used engine,It measured out, .040 over,model a style valves,no shims on good babbit so we might be fitting some main caps..basic hone and re ring,lap valves and fit bearings.Ill donate a good A cam to the process,an old time overhaul for a friend.
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