What should Compression Be
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Freshman User
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What should Compression Be
I have a 50 ford F-1 and am in the process of restoring it,
It runs But it did not sound right(how should it sound without a muffler
)So I shecked the Compression and they were all at
75-90 lbs. Is that what it should be?
Thanks
Colter
It runs But it did not sound right(how should it sound without a muffler
)So I shecked the Compression and they were all at 75-90 lbs. Is that what it should be?
Thanks
Colter
Lead Driver
Joined: Oct 1999
Posts: 6,777
Likes: 553
From: Kalispell, MT
The shop manual says 110. From experience it's more important that they be as close as possible. Flatheads will run with a lot less compression than you have there.
They do sound pretty ragged without mufflers - Every time I change my exhaust I fire it up before putting it back together
just to listen to it!
If the engine has been sitting awhile you might try a wet compression test - squirt a tablespoon of oil into each spark plug hole and then check comp. If it changes much you probably have some sticky rings - normal if sitting any length of time. You might get and use some Marvel Mystery Oil and see if it improves. It goes in the crankcase, gas tank and even directly in the plug holes to loosen things up. That's why it's a 'marvel'.
They do sound pretty ragged without mufflers - Every time I change my exhaust I fire it up before putting it back together
just to listen to it!If the engine has been sitting awhile you might try a wet compression test - squirt a tablespoon of oil into each spark plug hole and then check comp. If it changes much you probably have some sticky rings - normal if sitting any length of time. You might get and use some Marvel Mystery Oil and see if it improves. It goes in the crankcase, gas tank and even directly in the plug holes to loosen things up. That's why it's a 'marvel'.
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Yes it is a 239 V-8 That was my next thing to try was the oil. If it does not improve do you think I should rebuild the engine or is this good enough, I am not going to supe it up with a new carb and manifold or anything just leave it original.
thanks
Colter
thanks
Colter
Fleet Owner
Joined: Jul 2004
Posts: 27,299
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From: NM
A cylinder leakdown test would be worth trying first. A lot of these old flatties have carboned-up valve seats, or sticking lifters. Then again, a lot of them have worn out rings, too, but it's smart to figure out which it is first.
Mine has numbers about like yours, but I am at 5300'. As MT says, if they are all about even, say within 5 lbs, that's a better indication. As slow as these crank with the stock starter, a low battery/low cranking speed can throw the numbers off too.
Mine has numbers about like yours, but I am at 5300'. As MT says, if they are all about even, say within 5 lbs, that's a better indication. As slow as these crank with the stock starter, a low battery/low cranking speed can throw the numbers off too.
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Well I went and oiled up all the cylinder's real good and then checked the compression and it came out to 125 lbs except for one cylinder was 100 lbs. I Also did a valve test on #1 cylinder and and I did not hear any leaks, I stuck an air hose in the spark plug hole when the cylinder was closed and listened for air hissing out of the carb. and muffler and heard nothing.
Colter
Colter
