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Discussion Starter · #1 ·
having rebuilt the engine some 16k miles ago, im some what suprised at the compression test result i just go today.

after 1200 mile after the rebuild, i tested is

cyl 1
184psi

cyl2
186psi

cyl3
185psi

cyl4
187psi

now today after 16k miles, and hard use with phase 2 etc.. i got this

cyl 1
161psi

cyl2
185psi

cyl3
180psi

cyl4
177psi

:confused:

Why has cylinder 1 lost 23psi? im sure its a worn ring/bore issue, i did a we test and gained 10psi, it jumped to 170..

I was told last time prior to my rebulid that cyl1 closest to the water pump would wear quickly due to the bore being the coolest? what has this got to do with it? :confused:
 

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Discussion Starter · #3 ·
well id say upto about 190 psi is achievable on a good let... some have even seen 200psi...

but i dunno why just cyl 1 is down, and the rest seem fine
 

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I was told last time prior to my rebulid that cyl1 closest to the water pump would wear quickly due to the bore being the coolest? what has this got to do with it?
Could cause looser fit if piston not at operating temp. being forged,

Was engine "fully" hot and thermostat open, (I always test once at least top third of rad hot or fan comes on)

Rings may not of bedded yet, keep testing they may well be Ok after another 1K, (or a good thrashing).

Or mearly the lack of heat being picked up by the air compared to the other cylinders :rolleyes:

DOUGAL
 

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Dougal, have you bumped your head ? I understood that ;)

It does sound like the rings have worn prematurely - I rebuilt my xe once and had a similar problem - new set of rings and a glazebreak, then it was fine.

I did have a couple of problems though which interrupted the run-in - not least of which was the oil cooler hose popping off and dumping all the oil, so pressure was lost for about 30secs.

the other thing is a faulty rebuild - perhaps the block was bored incorrectly or the rings gapped wrongly ?
 

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Discussion Starter · #6 ·
well gary i did a test after 1200 miles and it all appeared fine, then also verified it at 6k miles its was more of less the same as my first test ...now today its not to bad on cyl 2 and 3 but 1 is 23 psi down and 4 is 10psi down

Would it be a worn bore? or worn rings?

im already at 86.5mm bore so i only have another step to 87mm before its time to junk it...
 

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the end gap in the rings needs to be a certain size to allow for heat expansion - if it's too small the ring can't expand properly and will either crack or wear excessively.

I would've thought that would've shown up sooner though, if it was that.
 

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badly lapped in valves lead to drop in compression testing. could be a valve need sreseting. however, i'm still used to the A series, it would appear this is far less on the XE/LET heads. Just for your interest though, I have just put an 86000 mile LET in davey boys mk3 astra, only mod is a slightly thicker headgasket and an XE inlet cam, it came out with this:

1. 165
2. 164
3. 165
4. 164

however, although its in the 160,s the thciker headgasket and XE inlet cam lead to that, AND that was cold, with forged pistons, results would have been higher if it was warm. however, my main point is that engine/head have done 86000 miles and never had new rings, or valves reseating so there is something to check. You SURE the valves we reseated properly?.

Rich
 

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depends how it was buit, ideally they would all wear togther in a nice even pattern, getting worse and worse as time goes on.

Rich
 

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does it smoke?

do a leak down test find out where its going. more than 10 % please remove and repair :)

My no idea how many miles XE with no idea how many miles headgasket comped liek this, warm reading:

190
190
191
189

and leak down was

8%
9%
7%
7%

leak down test never lies....

Rich
 

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Discussion Starter · #16 · (Edited)
yup head was rebuilt, the bottom end was rebuilt..the valve seats were cut and i lapped the valves in...dave andrews did the head, i doubt it its the head at all or the wet test would not have given me a raise in pressure.

and as u say the wet test does suggest its a ring problem.

but, some thing has happend to cyl 1...very confusing....
 

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Discussion Starter · #20 ·
I used std mahle rings

the bedding in process as follows

15/40 vx mineral oil for 100 miles, rev up to 2.5 k with light accleration

oil change vx mineral oil, 100miles to 500 miles revs to 3k about 3.5k at 350 miles

oil change vx mineral oil 500- 1000, revs to 4.5k

1000 miles changed to vx 10/40 semi and changed to fully synthetic at 1500 miles

i did vary the speeds the engine load etc during the running in stage..

can u give me detail on how to do the leak down test correctly?
 
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