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 1955 Traction Avant 11cv 
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Firing on two.
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Joined: December 17th, 2012, 10:03 pm
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Location: Luscan, Pyrenees, FRANCE
Post Re: 1955 Traction Avant 11cv
So I have done the compression test working from left to right 1, 2, 3, 4

Published ratio is 6.2/1 and compression circa 7.7bar or 111 psi with flat top pistons (I have domed pistons so this should lift the ratio slightly)

Cylinder 1 - 8.8 bar (127.6psi)
Cylinder 2 - 9.2 bar (133.4psi)
Cylinder 3 - 9.0 bar (130.5psi)
Cylinder 4 - 8.0 bar (116.0psi)

So I am a bit low on number 4 - why could this be.

I am super worried about the seal on the base of the cylinder sleeve, not that I have done it wrong, just because I have never done this before. But then that should not have an effect on the compression. Maybe the piston rings are lined up with the gaps?? Just guessing here so any advice would be appreciated.

Otherwise the figures seem OK to me.


March 24th, 2015, 2:04 pm
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Joined: March 5th, 2009, 6:23 pm
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Post Re: 1955 Traction Avant 11cv
Does the engine need "Running In"?


March 24th, 2015, 2:22 pm
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Joined: December 17th, 2012, 10:03 pm
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Location: Luscan, Pyrenees, FRANCE
Post Re: 1955 Traction Avant 11cv
Yes, it will do - done 100km so far.

I am just paranoid - I have ordered a CO2 detector to check any combustable gases in the coolant and also a leak down tester :(


March 24th, 2015, 2:33 pm
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Joined: June 19th, 2010, 8:40 pm
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Location: Kingswood, S.Glos.
Post Re: 1955 Traction Avant 11cv
Could be a slightly leaking valve on no.4. Did you lap the valves in?

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March 24th, 2015, 3:30 pm
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Joined: December 17th, 2012, 10:03 pm
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Post Re: 1955 Traction Avant 11cv
New valves and valve seats done by the machine shop - I would hope they would have done that but no I did not do it as they were fitted when I got the head back.


March 24th, 2015, 3:57 pm
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Joined: February 21st, 2012, 9:01 pm
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Location: Avranches, Sud Manche, France
Post Re: 1955 Traction Avant 11cv
Must admit that I always checked the heads I did on racing Mini's and the Dyane by turning the head upside down and filling the valve area with WD40 leaving over night and checking the next day by looking into the exhaust/inlet port for WD40


March 24th, 2015, 9:10 pm
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Post Re: 1955 Traction Avant 11cv
You got a point there ChrisW
WD40 is very thin and is a good valve seal checker.


March 24th, 2015, 11:50 pm
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Joined: November 8th, 2009, 5:42 pm
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Post Re: 1955 Traction Avant 11cv
I wouldn't worry much... It needs to run in and also the numbers you mentioned are higher then original, so nothing to worry about... as long as there is no coolant in the oil of the engine everything is fine.. Let it use some water.... they always did and always will do.. Your talking about a 60/65 years old engine (still) and no 2015 hightec magic piece of shit....

:lol: :lol: :lol: :lol: :lol:

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March 24th, 2015, 11:59 pm
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Joined: March 6th, 2009, 1:40 am
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Post Re: 1955 Traction Avant 11cv
Vasil,
diesel fuel is cheaper, also seems to be of similar viscosity to WD40... ;)

@ Chris, did you check the valve clearances prior to the compression test?
Whenever I've rebuilt an engine, I usually do the 'initial break-in' runs plus some more mileage, then check and adjust the clearances before a compression test

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March 25th, 2015, 12:41 am
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Post Re: 1955 Traction Avant 11cv
Just a quick compression test first.

I will take off the rocker cover and re-tighten the head bolts (loosen and torque back up) and I will also re-adjust the valve clearances now it has run a while.

As I mentioned - I am just being paranoid as it is my first full engine rebuild.


March 25th, 2015, 8:55 am
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