? about cylinder compression
04-06-2007, 09:41 PM
#1
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? about cylinder compression Just got done checking my cylinder compression on my 95 firehawk with 94,000 miles on her. My compression range was from 190 to 178. So my question is have any of you checked yours and if so what did you guys get?I'm just trying to get what the normal range or average is, especialy something with higher miles.
Thanks in advance
Rick
Thanks in advance
Rick
04-07-2007, 10:08 AM
#3
Originally Posted by 396D1SS
thats pretty damn good compression for a lt1 with 94k
My stock wagon with 180K miles cranked higher and more consistently. Cams are a little different but it is 10.0 instead of 10.4 static so I would expect a good condition CLEAN f-body LT1 to crank 200psi easily. That said consistency is the most important thing because gauges can be inaccurate but even then are usually consistent.
You did this warm right?
You did it with the throttle blocked wide open?
Screwin gauge not hold over the hole?
It is pretty rare for an LT1 to have ring sealing issues if you do find the compression is a little low or inconsistent try a product like AutoRX which is an ester based cleaner. NOT solvent crap that can damage engines, it actually has lubrication properties of it's own. I ran it in my wagon and went from about 190-195 to 200-205psi at 180K miles. I attribute the gain to cleaning out the ring package so it can more efficiently do it's thing.
04-07-2007, 02:12 PM
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Originally Posted by 96capricemgr
Based on what?
My stock wagon with 180K miles cranked higher and more consistently. Cams are a little different but it is 10.0 instead of 10.4 static so I would expect a good condition CLEAN f-body LT1 to crank 200psi easily. That said consistency is the most important thing because gauges can be inaccurate but even then are usually consistent.
You did this warm right?
You did it with the throttle blocked wide open?
Screwin gauge not hold over the hole?
It is pretty rare for an LT1 to have ring sealing issues if you do find the compression is a little low or inconsistent try a product like AutoRX which is an ester based cleaner. NOT solvent crap that can damage engines, it actually has lubrication properties of it's own. I ran it in my wagon and went from about 190-195 to 200-205psi at 180K miles. I attribute the gain to cleaning out the ring package so it can more efficiently do it's thing.
My stock wagon with 180K miles cranked higher and more consistently. Cams are a little different but it is 10.0 instead of 10.4 static so I would expect a good condition CLEAN f-body LT1 to crank 200psi easily. That said consistency is the most important thing because gauges can be inaccurate but even then are usually consistent.
You did this warm right?
You did it with the throttle blocked wide open?
Screwin gauge not hold over the hole?
It is pretty rare for an LT1 to have ring sealing issues if you do find the compression is a little low or inconsistent try a product like AutoRX which is an ester based cleaner. NOT solvent crap that can damage engines, it actually has lubrication properties of it's own. I ran it in my wagon and went from about 190-195 to 200-205psi at 180K miles. I attribute the gain to cleaning out the ring package so it can more efficiently do it's thing.
96capricemgr,
Hey thanks for the feed back. I did do it with it warm, throttle blocked wide open, and a screw in type gauge.
I'm hoping a few more people reply. I would like to see what a low mile LT1 would have.
In my GM service manual it says.. The lowest reading should not be less than 70% of the highest and no cylinder reading should be less than 100psi.
Going from this I thought my numbers sounded pretty good. Well hope more will respond and we can see what the avg. is.
04-07-2007, 03:51 PM
#5
Last summer with almost 100K on the shortblock my Caprice cranked 225-230psi, but the 11.5:1 static compression might have something to do with that.
The GM number of 70% is BS you want them all to be within 10% so the lowest should be 90% or better. Like I said AutoRX would be the first thing I would do if the test was done right and comes up uneven or low. When you buy a single bottle it is a little pricey at about $25 I think but genuinely works and if the compression problems are from dirty rings it will fix it.
The GM number of 70% is BS you want them all to be within 10% so the lowest should be 90% or better. Like I said AutoRX would be the first thing I would do if the test was done right and comes up uneven or low. When you buy a single bottle it is a little pricey at about $25 I think but genuinely works and if the compression problems are from dirty rings it will fix it.
04-07-2007, 04:05 PM
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Mine were all with in 10% the highest being 190 the lowest 178. I had 2cylinders check 190, 5 Of them checked 180, and one of them 178. The 178 was the last one I checked so the motor had cooled some I don't no if that would effect it any. The 190's was the first ones that I checked.
