| Author | Topic |
|---|
Location:
Brisbane
Registered:
February 2005
|
|
compression test results on secondhand engines
|
Thu, 02 June 2005 06:16
|
 |
Hi everyone,
I found a blacktop 20v 4age at this imported engines place (not in a front cut) and asked for the compression test results.
They said they were 160, 165, 165, 165
The guy also said that they would be low figures, because the engine has been sitting for a long time, and that these figures could come up to 180 or 190 psi once the engine is run and put under load for a while. Does this sound beleivable to you guys? anyone observed this phenomenon? Or are they just making excuses for relatively low compression.
The documented compressions test specs for these engines is 153 minimum and 193 maximum psi, so the results are within spec, but I think my own silvertop had similar results last I tested it and its burning a bit of oil.
BTW, anyone know what the minimum and maximum compression specs are meant to be for the silvertop? (I used to know but I lost the information)
Cheers,
Adam.
|
|
|
Location:
sunny coast, qld
Registered:
October 2002
|
|
Re: compression test results on secondhand engines
|
Thu, 02 June 2005 06:32
|
|
I am not sure what the relevant range of that engine is but the results looks pretty good. I would have thought the main thing is that all the cylinders are even and there is minimal difference. There was talk about wet and dry comp tests just a couple of days ago.
It also matters how many times the engine is cranked as the readings will be lower with less cranks.
|
|
|
Location:
brisbane
Registered:
October 2004
|
|
|
I Supported Toymods
Location:
Sydney
Registered:
December 2002
|
|
Re: compression test results on secondhand engines
|
Thu, 02 June 2005 09:29
|
|
Test it with the engine cold and then again once the engine is at operating temp, the compression will be a bit higher when the engine is at full operating temp.
The acceptable compression ranges you list, are they cold or op temp measurements?
|
|
|
Location:
Brisbane
Registered:
February 2005
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 01:00
|
|
According to the service manual for this engine, those acceptable ranges are for operating temperature. and its actually 156 minimum, and 193 maximum
So would their be a big jump in compression between testing a cold engine and testing it at operating temperature?
I guess an engine importing place would only be able to test them cold unless they had some way of running the engine which isn't very likely I guess (engine by itself - not in front cut)
|
|
|
I supported Toymods
Location:
Australia
Registered:
November 2003
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 01:23
|
|
Compression tests pre thrashing are useless.
100% useless. (except for bargaining power if they seem low)
The test we conducted on Franks 1GGTE resulted in the following
From 6 to 1:
110 60 85 120 95 25
Now after running the motor for a bit, they are now all 150 stone cold.
Valves obviously were jammed open with carbon.
|
|
|
I Supported Toymods
Location:
Nthn Beaches, Sydney
Registered:
October 2004
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 01:31
|
|
|
I did a comp test on my silvertop recently (it's burning oil) and got 1200, 1200, 1100 & 1000 (kPa). Was told this wasn't too bad as the variation wasn't too big, but converting gives 174, 174, 160 & 145, and that looks pretty shit now. The test was done at operating temp, so cold would be even worse?
|
|
|
I supported Toymods
Location:
Australia
Registered:
November 2003
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 01:35
|
|
|
You should have no more than 15psi/100kpa from max to min.
|
|
|
I Supported Toymods
Location:
Nthn Beaches, Sydney
Registered:
October 2004
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 02:35
|
|
Aw, fuck it. Engine was only rebuilt 8 months ago, and it's used oil from the start. I think the aquaintance that put the bottom end together didn't put much effort into sizing the rings, just said standard would be fine, but the block's been honed twice that i know of.
Is this serious enough to pull it down again?
|
|
|
I supported Toymods
Location:
Australia
Registered:
November 2003
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 02:40
|
|
|
Just buy another silvertop bottom end for a couple of hunj and rebuild that.
|
|
|
Location:
Brisbane
Registered:
February 2005
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 02:51
|
|
Thanks for that info cruzsida.
I guess that does mean its reasonable to expect a big jump in comp test results after having an engine running under load for a while (if it was first tested after being sitting for ages)
for interests sake, what are the recommended compression ranges for the 1ggte?
|
|
|
I supported Toymods
Location:
Australia
Registered:
November 2003
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 02:59
|
|
NFI.
But most motors say 160-200 warm.
|
|
|
Location:
Montrose, VIC
Registered:
May 2002
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 12:38
|
|
Import Engine Blues - usually, when you buy an engine like that, it's pretty lazy for the first few minutes you run it - rings and valves are gummed up, as well as the injectors. When it starts, it usually coughs a bit, farts out some smoke, then picks up on all cylinders.
Change the oil before you start it, drive it for a week, then check the compression, and if it's not running smoothly, get the injectors cleaned. It's usually wise to throw in a new set of plugs as well.
|
|
|
I supported Toymods
Location:
Australia
Registered:
November 2003
|
|
Re: compression test results on secondhand engines
|
Fri, 03 June 2005 14:23
|
|
|
In my experience you should always clean injectors before you start the motor.
|
|
|
