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Engine Compression
http://www.international2cvfriends.com/forum/viewtopic.php?f=7&t=3266		 Page 1 of 5
Author:  james2cv [ August 23rd, 2011, 9:56 pm ]
Post subject:  Engine Compression
Ok did a compression test earlier, one side was reading 165 and the other just under 140. Engine was warm and there's nowt wrong with the battery or starter. I know that 140 it abit low but not very very low... It's the big difference that's a bit more worrying? Time for new pistons and barrells in the not too distant future or should I not worry until it blows up or something?
Cheers,
J
Author:  Sean [ August 23rd, 2011, 10:02 pm ]
Post subject:  Re: Engine Compression
adjust the tappets first

then start worrying

or carry on worrying...whatever

Sean
Author:  twofifty AZU [ August 24th, 2011, 1:03 am ]
Post subject:  Re: Engine Compression
After you've adjusted the tappets if the readings are still uneven do a "wet" compression test. Put a bit of oil down the bore and test. If there is no change you have a leaky valve. If the compression goes up it was getting past a piston.
Author:  Devils Advocate [ August 24th, 2011, 12:57 pm ]
Post subject:  Re: Engine Compression
'They' do say that having a large difference is more significant that just, say, both being low. I don't actually know why that is...

But, my tuppenth worth is that 140 psi ain't that low at all, and 165 is pretty damn hot. I bet your car is running just fine?

It ain't going to blow up, and I'd suggest that no new barrels and stuff is needed for a goodly long time.
Author:  Sean [ August 24th, 2011, 1:41 pm ]
Post subject:  Re: Engine Compression
you want all the cylinders in a multi cylinder engine working the same - a high reading on one may indicate a wet bore or incorrect valve gaps and would need investigating,- low indicates wear, leaks or burnt valves - again worth investigating.

on a 2 cylinder there is no mean which to compare the readings, but there is a "healthy range", and its nicer to have a well balanced engine.

simplest and most probable is tappet clearance first to see if the high side drops or the low side comes up. Then leak down or oily test ( not as reliable on a horizontal engine)to see where the low side is loosing out.

good side is good poor side is at low end of what id be happy with but as long as its not blowing all its oil id not loose sleep over it

Sean
Keep on worrying those toads
Quote:
'They' do say that having a large difference is more significant that just, say, both being low. I don't actually know why that is...
Author:  ken [ August 24th, 2011, 3:17 pm ]
Post subject:  Re: Engine Compression
On the other hand,
if everything else with the engine was OK, those figures could suggest that there was an 8.5:1 piston in one side and a 9.0:1 in the other.
It does sound crazy, however it has been known to happen.

No, it wasn't at all hot and it did not run well... :lol:

ken

Devils Advocate wrote:
'They' do say that having a large difference is more significant that just, say, both being low. I don't actually know why that is...

But, my tuppenth worth is that 140 psi ain't that low at all, and 165 is pretty damn hot. I bet your car is running just fine?

It ain't going to blow up, and I'd suggest that no new barrels and stuff is needed for a goodly long time.
Author:  Sean [ August 24th, 2011, 3:37 pm ]
Post subject:  Re: Engine Compression
ken wrote:
On the other hand,
if everything else with the engine was OK, those figures could suggest that there was an 8.5:1 piston in one side and a 9.0:1 in the other.
It does sound crazy, however it has been known to happen.

No, it wasn't at all hot and it did not run well... :lol:

ken

:lol: :lol:
one of Norrys engines had that set up Harper took great delight in pointing out why it "ran a bit lumpy"
Author:  james2cv [ August 24th, 2011, 3:54 pm ]
Post subject:  Re: Engine Compression
Yes, the engine pulls fine really considering its the original 8:5:1 set up as far as I know. It doesn't use huge amounts of oil and will sit at 70 (ok 55 up hills) all day when it isn't pinking :roll: Will do tappets after Snetterton, having 123 put on today so hopefully I can floor it everywhere again :D Hopefully nowt to worry about immediately then.
Author:  Sean [ August 24th, 2011, 4:05 pm ]
Post subject:  Re: Engine Compression
james2cv wrote:
Yes, the engine pulls fine really considering its the original 8:5:1 set up as far as I know. It doesn't use huge amounts of oil and will sit at 70 (ok 55 up hills) all day when it isn't pinking :roll: Will do tappets after Snetterton, having 123 put on today so hopefully I can floor it everywhere again :D Hopefully nowt to worry about immediately then.


Ah see thats the sort of info we need

could well be a scuffed barrel or nipped ring now

when will you lot learn the importance of proper timing :roll:

why not get someone to do them properly DURING Snet?
there will be lots of time for that sort of crap fri and sat morning
and there will be enough people around who know how to use proper tools to set the ignition up tip top.

Sean
Author:  james2cv [ August 24th, 2011, 4:17 pm ]
Post subject:  Re: Engine Compression
Sean wrote:
james2cv wrote:
Yes, the engine pulls fine really considering its the original 8:5:1 set up as far as I know. It doesn't use huge amounts of oil and will sit at 70 (ok 55 up hills) all day when it isn't pinking :roll: Will do tappets after Snetterton, having 123 put on today so hopefully I can floor it everywhere again :D Hopefully nowt to worry about immediately then.


Ah see thats the sort of info we need

could well be a scuffed barrel or nipped ring now

when will you lot learn the importance of proper timing :roll:

why not get someone to do them properly DURING Snet?
there will be lots of time for that sort of crap fri and sat morning
and there will be enough people around who know how to use proper tools to set the ignition up tip top.

Sean



Oops. :oops: Ok yeah thinking about it I've probably knackered a head or something? If that's what pinking does? I'm guessing it does? I'm not getting 123 in a hope of solving the pinking, or because I think its better than points, cos as soon as it starts I try and sort it out asap, its just this engine seems to eat points. Literally. Going to reg day... timing perfect before I set off... On the way there 200 miles later... tinkle tinkle tinkle.
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