Strange Compression Test Results

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Model T Ford Forum: Forum 2015: Strange Compression Test Results
Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Wednesday, July 01, 2015 - 06:14 pm:

A recent compression test produced these results:

1 - 65 psi, 2 - 35 psi, 3 - 45 psi, and 4 - 45 psi.

How can the high number on cylinder 1 be explained with a stock engine and head?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Georgetown TX on Wednesday, July 01, 2015 - 06:36 pm:

Worn out.cam shaft.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Wednesday, July 01, 2015 - 07:26 pm:

You need to go further. Give each cyl. a shot of oil just before testing and re-take the cylinders. There may be a difference in the 2-3 & 4 readings. If it goes up it's usually rings. No change possibly indicates leaking valves. I've seen 1 engine with 65 Lbs across the board but it did have some work done. It could be a cam as suggested but you really should do the oil thing first.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charles whitehouse on Wednesday, July 01, 2015 - 07:37 pm:

Carbon build up in no.1?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Henry Petrino in Modesto, CA on Wednesday, July 01, 2015 - 08:26 pm:

Also, be sure the throttle is wide open and the choke is also fully open.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Wednesday, July 01, 2015 - 08:38 pm:

What kind of head and pistons do you have? 65 seems kind of high, but if it is correct, the others are too low. 35 seems low. I would suggest that you check again with a different compression gauge before you pull everything apart. Your gauge might have some problems.

If you get the same compression, tear things down and inspect.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Aaron Griffey, Hayward Ca. on Wednesday, July 01, 2015 - 10:08 pm:

Screw the plugs back in part way, start the engine & run it a minute, shut it down and recheck.
I have been beaten by that one before.
Maybe they are al 65 but when you broke the spark plugs loose some fine carbon broke loose and got under 2 or three of the valves.
It happens, but usually only one valve traps some carbon under it as it is going out the exhaust port.


Top of pagePrevious messageNext messageBottom of page Link to this message  By paul iverson freeport ill. on Wednesday, July 01, 2015 - 10:19 pm:

dont be to quick to take it apart run it a while test again and try a diff. gauge is it running?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Wednesday, July 01, 2015 - 11:30 pm:

Another thought. That 65 pounder is bothering me. Especially when compaired to the others. How well do you know this car/engine? Is it possible some half a**ed job was done where just one piston & rings were replaced and the other 3 are original?


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Thursday, July 02, 2015 - 07:44 am:

An excellent possibility!

A little more research will be done, before the head is removed.

This vehicle was recently purchased, so anything is possible.

All the tar was leaking out of the #3 coil and the wires could have been totally crossed to put #1 coil on the drivers side and make that coil run cylinder #1.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Georgetown TX on Thursday, July 02, 2015 - 07:59 am:

The worn out cam shaft is opening and closing the valve late / early respectively. Thus the cylinder pressure is higher.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Thursday, July 02, 2015 - 09:13 am:

James,for the #3 coil boiling all the tar out you have a short in the wire to the timer and the coil keep buzzing till it died.
Have seen this last sunday in France, not easy to clean out.

Andre
Belgium


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthonie Boer---- Klaaswaal NL on Thursday, July 02, 2015 - 09:23 am:

Andre' gebruikte hij 12 volt of liep de motor op magneet ??
Toon


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Friday, July 03, 2015 - 12:49 am:

Weet ik niet Toon maar volgens zijn uitleg is het s'nachts gebeurd. Het contact was nog al los en kon zonder weerstand van links naar rechts worden bewogen. Het contact zou weleens de ganse nacht hebben opgestaan.

Andre
Belgium

Translation:
Toon asked me if the car was running on 12V battery or Magneto?
My answer:
I don't know Toon. As the driver told It happened over night. His contact switch was loose and can be moved from left to right without any resistant.
It could be contact was on the all night.

Andre
Belgium


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