340 compression I

[smileykeith]

340 utility gas what should the compression be on a cold engine

 

[Jim Becker]

The published number is 180#. That is with the engine warmed up, battery fully charged, throttle wide open and all spark plugs removed. You need to judge that down for a cold engine and down some more for dry cylinders (before you squirt some oil into each spark plug hole. This is also at sea level, take off 3-1/2% each 1,000' your altitude increases. This would also require an engine in excellent condition.

What will it start and run with? probably half that.

 

[used red MN]

If it was mine 85 to 130 would be accepta ble. However, those in the 85 to 95 range are getting into the unsatisfactory area. The main thing is that they are all in the same range say within 10-15 psi.

 

[Fritz Maurer]

180 seems like a lot . 80s MX 2-strokes were around 190, and they were running 11:1 C.R.

350 Chevy w/ 8:1 was 150.

Not disputing anyone, just thinking out loud.

 

[560Dennis]

The published number is 180#. That is with the engine warmed up, battery fully charged, throttle wide open and all spark plugs removed. You need to judge that down for a cold engine and down some more for dry cylinders (before you squirt some oil into each spark plug hole. This is also at sea level, take off 3-1/2% each 1,000' your altitude increases. This would also require an engine in excellent condition.

What will it start and run with? probably half that

interesting
Tell me how to (they) get 180 cause I want it . If get a stock Farmall engine to do that , I want to go back to NATPA with the Tractor .
Stock Engine in Tractor data is 7.6 to 1 120
any way I like to know ?

 

[Janicholson]

120 is pretty much new. each within 5% of each other is a solid indication. Compression gauges are not all calibrated. Jim

 

[Jim Becker]

interesting
Tell me how to (they) get 180 cause I want it . If get a stock Farmall engine to do that , I want to go back to NATPA with the Tractor .
Stock Engine in Tractor data is 7.6 to 1 120
any way I like to know ?

Seems high to me too. That is why I made a point of mentioning most of the qualifiers (It also spec'ed 150 RPM and use of a motorite tester). I don't think I have ever done a compression test on a warmed up engine and certainly have never used a tach to make sure I was testing at enough speed. But as I said, that is the published figure. If you want to know how they got it, you need to check with the people that wrote the book.