Compression Test Information / Problem Solving
05-12-2009, 10:18 PM
#1
12 Second Club
Thread Starter
iTrader: (35)
Join Date: Jan 2006
Location: Danville PA
Posts: 1,550
Likes: 0
Received 0 Likes
on
0 Posts
Compression Test Information / Problem Solving Alright guys. I need alittle help and im stumped at what it could be. It just doesnt make sense to me. To make a long story short, my Trans Am now has the motor out of my Camaro. The engine sat on a stand all winter. The only thing that has been changed since then are the following.
Ported Intake
LPE 58mm TB
Melling Select M155 oil Pump w/ GM white spring (High Pressure)
E-Waterpump
Bigger Injectors
LPP Longtubes
The car runs real strong. However everytime I get on it, it produces a major blue cloud of smoke. Only when im into the throttle though. My questions are, could the PCV system not be keeping up? Is there anyway that sand from sand blasting and porting the intake be blocking/clogging the pcv system? (I know would suck, put possible and dont want to rule it out.) I did however check for that and blew the intake out with air when I received it back. Im also running a breather on my valve cover, but is it possible that I have to much crank case pressure? Im going to look into the intake manifold itself to see if there is oil in the intake and pull it as a last resort. But first im going to do a leak down test on the car. Now here is the info I need from you all. I know how to do a leak down, but what do you all consider acceptable measurements when performing?
I have 11:1 compression ratio. What should the compression guage read in PSI? How long is an acceptable time frame for the leak down? What is an acceptable range of measurement for compression in PSI if it doesnt reach the desired "perfect measurement?"
Also any ideas or input would greatly be appreciated.
Ported Intake
LPE 58mm TB
Melling Select M155 oil Pump w/ GM white spring (High Pressure)
E-Waterpump
Bigger Injectors
LPP Longtubes
The car runs real strong. However everytime I get on it, it produces a major blue cloud of smoke. Only when im into the throttle though. My questions are, could the PCV system not be keeping up? Is there anyway that sand from sand blasting and porting the intake be blocking/clogging the pcv system? (I know would suck, put possible and dont want to rule it out.) I did however check for that and blew the intake out with air when I received it back. Im also running a breather on my valve cover, but is it possible that I have to much crank case pressure? Im going to look into the intake manifold itself to see if there is oil in the intake and pull it as a last resort. But first im going to do a leak down test on the car. Now here is the info I need from you all. I know how to do a leak down, but what do you all consider acceptable measurements when performing?
I have 11:1 compression ratio. What should the compression guage read in PSI? How long is an acceptable time frame for the leak down? What is an acceptable range of measurement for compression in PSI if it doesnt reach the desired "perfect measurement?"
Also any ideas or input would greatly be appreciated.
05-13-2009, 09:45 PM
#3
TECH Regular
iTrader: (4)
Join Date: Nov 2004
Location: Wilmington, NC
Posts: 427
Likes: 0
Received 0 Likes
on
0 Posts
If you have a leak down tester and compressor that will give you more info on each particular cylinder, otherwise scroll down until you see "compresion test" : http://shbox.com/1/4th_gen_tech2.html
05-13-2009, 11:08 PM
#6
TECH Regular
iTrader: (4)
Join Date: Nov 2004
Location: Wilmington, NC
Posts: 427
Likes: 0
Received 0 Likes
on
0 Posts
A leak down test is simply for assesment. Its been awhile, but I believe a Cheap half *** assesment can be determined by whether it creates smoke when down shifting with no/little throttle, if so then valve seals. If only during WOT then likely rings. Also if the car sits for awhile and puffs blue smoke on initial start up-->valve seals.
**this is only info I remember from my own endeavors a fews years ago...memory is a bit hazy. I do remember the leak down testing provided me with the best info tho...
**this is only info I remember from my own endeavors a fews years ago...memory is a bit hazy. I do remember the leak down testing provided me with the best info tho...
Last edited by Chevyguy358; 05-13-2009 at 11:16 PM.
05-13-2009, 11:31 PM
#7
12 Second Club
Thread Starter
iTrader: (35)
Join Date: Jan 2006
Location: Danville PA
Posts: 1,550
Likes: 0
Received 0 Likes
on
0 Posts
Its under heavy acceleration. Also if im in it hard then let off and let the engine do the braking, it does it as well. Im going to pull the plugs, inspect them and go from there. Compression test, pcv system, then pulling the intake to see if it didnt seal correctly.
Trending Topics
05-14-2009, 12:30 AM
#8
TECH Regular
iTrader: (4)
Join Date: Nov 2004
Location: Wilmington, NC
Posts: 427
Likes: 0
Received 0 Likes
on
0 Posts
Its under heavy acceleration. Also if im in it hard then let off and let the engine do the braking, it does it as well. Im going to pull the plugs, inspect them and go from there. Compression test, pcv system, then pulling the intake to see if it didnt seal correctly.
05-17-2009, 07:52 PM
#11
12 Second Club
Thread Starter
iTrader: (35)
Join Date: Jan 2006
Location: Danville PA
Posts: 1,550
Likes: 0
Received 0 Likes
on
0 Posts
1 - 170 2 - 160
3 - 170 4 - 175
5 - 180 6 - 185
7 - 162 8 - 180
Well there are the compression numbers. From the data gathered, that seems to be fine. However, there is oil on the inside of the intake. The PCV lines are clear and have no oil residue in them. But the entire inside of the intake is coated? The only thing that was changed was the intake is now Ported. Any ideas?
3 - 170 4 - 175
5 - 180 6 - 185
7 - 162 8 - 180
Well there are the compression numbers. From the data gathered, that seems to be fine. However, there is oil on the inside of the intake. The PCV lines are clear and have no oil residue in them. But the entire inside of the intake is coated? The only thing that was changed was the intake is now Ported. Any ideas?
05-17-2009, 08:26 PM
#12
I would eliminate the pcv. Especially if you are beating on it. Nothing like sucking oil into your intake for no good reason because you are running stock emissons pcv system
05-17-2009, 08:52 PM
#15
12 Second Club
Thread Starter
iTrader: (35)
Join Date: Jan 2006
Location: Danville PA
Posts: 1,550
Likes: 0
Received 0 Likes
on
0 Posts
Ive been looking into getting one, however what doesnt make sense is that the car is sucking in oil now that the intake is ported and it didnt before. I shouldnt have this issue IMO. Im going to pull the intake next and see if I can see if the gaskets are not sealing. Ill keep everyone up to date.
05-17-2009, 08:53 PM
#16
TECH Regular
iTrader: (4)
Join Date: Nov 2004
Location: Wilmington, NC
Posts: 427
Likes: 0
Received 0 Likes
on
0 Posts
Well I would think you may be sucking oil from the lifter valley into the heads. Your compression test wouldn't attribute to anything of the intake charge prior to the intake valve; just the combustion chamber. Are you sure you correctly installed the intake after the port job? Torque and sequence? Also, make sure the intake ports that were opened matched up good to the heads. Just some thoughts.
05-17-2009, 08:57 PM
#17
Bad valve stem seals, worn valve guides, intake manifold gaskets not sealing, pcv system, fresh air hose. All those will cause oil to get into the intake. As far as compression tests mine were 235-237 on the 3 cylinders I could get the tester on just for comparison.
05-17-2009, 09:02 PM
#18
12 Second Club
Thread Starter
iTrader: (35)
Join Date: Jan 2006
Location: Danville PA
Posts: 1,550
Likes: 0
Received 0 Likes
on
0 Posts
Well I would think you may be sucking oil from the lifter valley into the heads. Your compression test wouldn't attribute to anything of the intake charge prior to the intake valve; just the combustion chamber. Are you sure you correctly installed the intake after the port job? Torque and sequence? Also, make sure the intake ports that were opened matched up good to the heads. Just some thoughts.
Thanks for all your input. Big help. 
05-17-2009, 09:05 PM
#19
12 Second Club
Thread Starter
iTrader: (35)
Join Date: Jan 2006
Location: Danville PA
Posts: 1,550
Likes: 0
Received 0 Likes
on
0 Posts
Bad valve stem seals, worn valve guides, intake manifold gaskets not sealing, pcv system, fresh air hose. All those will cause oil to get into the intake. As far as compression tests mine were 235-237 on the 3 cylinders I could get the tester on just for comparison.