Ford 2N Low Compression

Randy K. Crump · Dec 3, 2018

Ford 2N engine rebuilt with new pistons, rings, sleeves and valves. I think the compression is too low. Here are my compression test results. I cranked it 5 strokes which is the first number and last number, then placed oil in cylinder which is the last number.
Cylinder 1 - 80 - 105 - 135
Cylinder 2 - 60 - 80 - 100
Cylinder 3 - 60 - 90 - 115
Cylinder 4 - 90 - 115 - 125

Mechanic that did the overhaul no longer available. I have the head off. How do I remove valves and do they need to be ground?
THANKS!

Dollar Bill · Dec 3, 2018

The two middle cylinders may be due to improper head gasket seal. Adding oil during compression test improved 1&4 which points to rings vice valves.

How many hours on the rebuild?

Mike Groom · Dec 3, 2018

As Dollar Bill said,could be a head gasket,also if low hours since the rebuild the rings may not be seated on the two low cylinders,they did increase with oil.

Randy K. Crump · Dec 3, 2018

Under 50 hours on rebuild.

Dollar Bill · Dec 3, 2018

Rings should have seated in 50 hours. Am wondering if excess ring gap or not staggered properly?

How confident are you regarding test gauge accuracy? If is true, exploratory surgery may be your next move.

souNdguy · Dec 3, 2018

Not valves, you can get increasing pressure with oil. Ring issue would be my first thought. I forget, did you say that liners were replaced or not? If not.. Possible measurement issue with rings and liners.

Randy K. Crump · Dec 3, 2018

Yes, new pistons and sleeves were installed, all purchased from nnalert.

TheOldHokie · Dec 4, 2018

(quoted from post at 22:44:17 12/03/18) Yes, new pistons and sleeves were installed, all purchased from just 8n's.

My bet is the problem lies with workmanship not parts and materials. New sleeves, pistons with rings, and head gasket should be producing far better compression than you are reporting. And the leakage does not appear to be going through the valves. Hobo's favorite, a leakdown test, would be informative.....

TOH

Den N Ms · Dec 4, 2018

Randy,It could possibly have broken compression rings on cylinders #2 and #3,broken at installation maybe from a (bad ring compressor). Now that you have the head off that kind of puts a stop to a leak down test.You might try and get #2 and #3 to TDC and try and shake them side to side and see if you can feel/see any difference between them and #1 and #4 at TGC.Looser pistons on #2 and #3 would indicate broken rings.

Randy K. Crump · Dec 4, 2018

When I performed the compression test I waited a little bit before releasing the pressure on the gauge and the gauge needle did not move while I waited. For example, if the top number was 100, it maintained that. Is that a good sign?

Den N Ms · Dec 4, 2018

Randy,that is your compression gauge holding the pressure,and nothing to do with the condition of your engine.
Randy,did you check the pistons as I stated in my previous post?

Randy K. Crump · Dec 4, 2018

Not yet but I plan to.
One mechanic with many years of experience said that when the compression is low with the two middle cylinders (2,3) many times it is the head gasket. I used a metal gasket. There was black carbon around the middle of the gasket between cylinder 2 & 3. Do you think that has any significance?

R Geiger · Dec 4, 2018

Could be, did you have the head checked for warpage? When I overhauled one 7 years ago, the head was warped and had to have it milled. You could take it to a machine shop and have it checked and if you do have to have it milled, make sure the valves do not hit the head afterward.

Hobo,NC · Dec 5, 2018

Head off check valve seal
Make sure valve to seat is clean
bring piston up to TDC
Valves closed
pour gas are varsoil (mineral sprites) around valve

If valves seal no leakage
If leakage check again they are clean
If clean valves are leaking
Check adjustment if OK valve needs to come out

You can remove manifold and see which valve is leaking.

To late now are maybe not do you remember the first hit on the gauge reading while checking compression. The fist hit is the ability of the valves to seal all the rest are the ability of the cylinder to build compression. You gauge should have a check valve in it, it stores each compression event that's why it will keep building up till you manually bleed it off...

You should not have seen any signs of leakage across the head gasket cylinder to cylinder

Bob · Dec 5, 2018

(quoted from post at 11:35:27 12/03/18) Rings should have seated in 50 hours. Am wondering if excess ring gap or not staggered properly?

How confident are you regarding test gauge accuracy? If is true, exploratory surgery may be your next move.

"Am wondering if excess ring gap or not staggered properly? "

If you are talking about ring end gap (unless DRAMATICALLY large), along with staggering the rings, both those are more or less "old mechanics' wives tales, IMHO.

Ring groove wear is another (BAD) matter.

Note what piston ring GURU Dave Reed has to say about the subject...

http://www.ringspacers.com/tips.htm

Dean · Dec 5, 2018

Throttle open and air cleaner disconnected during compression test?

Good, fully charged battery and good cranking system?

Dean

Randy K. Crump · Dec 5, 2018

Yes, good fully charged battery, throttle and choke open. Air cleaner was NOT disconnected.

David G · Dec 5, 2018

Did you break it in and seat the rings?

Randy K. Crump · Dec 5, 2018

I ran it for about 50 hours.

Ford 2N Low Compression

Randy K. Crump

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Dollar Bill

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Mike Groom

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Randy K. Crump

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Dollar Bill

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souNdguy

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Randy K. Crump

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TheOldHokie

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Den N Ms

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Randy K. Crump

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Den N Ms

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Hobo,NC

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Bob

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