Compression Test
05-31-2004, 01:54 PM
#1
Registered User
Thread Starter
Join Date: Apr 2001
Location: Surrey, B.C., Canada
Posts: 670
Compression Test
Trying to chase down the cause of my new stroker motor smoking.
Anyone know what 11:1 compression would give you in PSI?
I've been testing and I got an approximate average of 200 dry and 210 wet.
Does that sound right? I was thinking that it should be more into the 220 range.
Anyone know what 11:1 compression would give you in PSI?
I've been testing and I got an approximate average of 200 dry and 210 wet.
Does that sound right? I was thinking that it should be more into the 220 range.
05-31-2004, 03:13 PM
#2
Registered User
Join Date: Feb 2004
Location: Abbeville , LA
Posts: 291
200 to 210 with 11:1 CR is a lot
unless you have very short camshaft duration and/or over advanced
i would need to know
1-intake centerline cam was degreed on
2- intake valve lash setting
3- intake duration @ .050"
then i could calculate the Cranking psi
and see if 200 to 210 correlates
unless you have very short camshaft duration and/or over advanced
i would need to know
1-intake centerline cam was degreed on
2- intake valve lash setting
3- intake duration @ .050"
then i could calculate the Cranking psi
and see if 200 to 210 correlates
05-31-2004, 03:14 PM
#3
Registered User
Join Date: Sep 2002
Posts: 655
I'm getting an avg. of 235 PSI
Deck Height = 9.025"
Felpro FPP-1094 steel gasket = 0.015" compressed thickness
Wiesco Hyper-Eutetic Piston = 7 cc relief
Sportsman II heads 72 cc = ~ 70.3 cc ( ~ 1.7 c.c., decked - 0.010" )
The pistons are chamfered and have large reliefs.
I don't know the top compression ring depth. It's
probably a STD height. Nothing fancy about the
pistons.
Felpro claims 0.015" compressed thickness, but I mic'd mine at 60 ft.lbs which yielded 0.017".
I meausred my quench to be 0.021" with a depth guage from the deck to piston face. Add gasket
thickness of 0.017 for total quench height.
My heads were shaved by 0.010" which is about 2 cc
off the 72 cc head chamber (4.1 bore x 0.017 high).
4.03 x 3.48 bore and stroke
That's my math. The compression tests range from
232 - 237 psi across all cylinders.
I figure about 11:1 mechanical compression
Deck Height = 9.025"
Felpro FPP-1094 steel gasket = 0.015" compressed thickness
Wiesco Hyper-Eutetic Piston = 7 cc relief
Sportsman II heads 72 cc = ~ 70.3 cc ( ~ 1.7 c.c., decked - 0.010" )
The pistons are chamfered and have large reliefs.
I don't know the top compression ring depth. It's
probably a STD height. Nothing fancy about the
pistons.
Felpro claims 0.015" compressed thickness, but I mic'd mine at 60 ft.lbs which yielded 0.017".
I meausred my quench to be 0.021" with a depth guage from the deck to piston face. Add gasket
thickness of 0.017 for total quench height.
My heads were shaved by 0.010" which is about 2 cc
off the 72 cc head chamber (4.1 bore x 0.017 high).
4.03 x 3.48 bore and stroke
That's my math. The compression tests range from
232 - 237 psi across all cylinders.
I figure about 11:1 mechanical compression
05-31-2004, 03:43 PM
#5
Registered User
Join Date: Sep 2002
Posts: 655
Larry,
The current camshaft is a 292H by Comp Cams.
I dialed the camshaft at 110 degrees intake centerline.
The duration at 0.050" is 244 degrees.
I used a zero lash and 0.010" preload (dial)
Here are the MFG's spec:
292H
292/292 AD
244/244 @ 0.050
.518/.518 LIFT
110 LSA
2500-6500 RPM RANGE
The current camshaft is a 292H by Comp Cams.
I dialed the camshaft at 110 degrees intake centerline.
The duration at 0.050" is 244 degrees.
I used a zero lash and 0.010" preload (dial)
Here are the MFG's spec:
292H
292/292 AD
244/244 @ 0.050
.518/.518 LIFT
110 LSA
2500-6500 RPM RANGE
05-31-2004, 04:15 PM
#6
Registered User
Thread Starter
Join Date: Apr 2001
Location: Surrey, B.C., Canada
Posts: 670
I didn't put the motor together. Since it was in the shop for all the machining I juts let them build it. I dont have a copy of my cam card right now. The 306 cam is pretty close. I know mine is 113 LSA and I think it has a couple more degrees on the intake.
by the sounds of Zero_to_69 my compression could be on the low side of things.
Judging by the wet and dry testing, would it be a safe assumption that the rings haven't set properly yet? The dry test actually increased by about 10 PSI since the last time I tested. (about 5-600km ago)
by the sounds of Zero_to_69 my compression could be on the low side of things.
Judging by the wet and dry testing, would it be a safe assumption that the rings haven't set properly yet? The dry test actually increased by about 10 PSI since the last time I tested. (about 5-600km ago)
Last edited by irocz383; 05-31-2004 at 06:30 PM.
06-07-2004, 01:31 AM
#7
Registered User
Join Date: Mar 2002
Posts: 54
Originally posted by MaxRaceSoftware
200 to 210 with 11:1 CR is a lot
unless you have very short camshaft duration and/or over advanced
i would need to know
1-intake centerline cam was degreed on
2- intake valve lash setting
3- intake duration @ .050"
then i could calculate the Cranking psi
and see if 200 to 210 correlates
200 to 210 with 11:1 CR is a lot
unless you have very short camshaft duration and/or over advanced
i would need to know
1-intake centerline cam was degreed on
2- intake valve lash setting
3- intake duration @ .050"
then i could calculate the Cranking psi
and see if 200 to 210 correlates
I buy a 93 Z M6 and have 40.000 Miles and have a K&N CAI, I change the plugs and made a comp test wit 2 diff gauges because the comp were too high all the cly were in the 300 Psi 305 to 298 psi.
I dont think the car have a diff cam and I only use 95 Oct Gas all the time and dont have any Know.
Could you tell me what CR my Z have. Thanks
06-07-2004, 10:14 AM
#8
Registered User
Join Date: Feb 2004
Location: Abbeville , LA
Posts: 291
Originally posted by Zero_to_69
Larry,
The current camshaft is a 292H by Comp Cams.
I dialed the camshaft at 110 degrees intake centerline.
The duration at 0.050" is 244 degrees.
I used a zero lash and 0.010" preload (dial)
Here are the MFG's spec:
292H
292/292 AD
244/244 @ 0.050
.518/.518 LIFT
110 LSA
2500-6500 RPM RANGE
Larry,
The current camshaft is a 292H by Comp Cams.
I dialed the camshaft at 110 degrees intake centerline.
The duration at 0.050" is 244 degrees.
I used a zero lash and 0.010" preload (dial)
Here are the MFG's spec:
292H
292/292 AD
244/244 @ 0.050
.518/.518 LIFT
110 LSA
2500-6500 RPM RANGE
you might have a little more than 11:1 cr w/235 psi
06-07-2004, 10:18 AM
#9
Registered User
Join Date: Feb 2004
Location: Abbeville , LA
Posts: 291
Farc , i need the following Info;
Originally posted by MaxRaceSoftware
i would need to know
1-intake centerline cam was degreed on
2- intake valve lash setting
3- intake duration @ .050"
then i could calculate the Cranking psi
i would need to know
1-intake centerline cam was degreed on
2- intake valve lash setting
3- intake duration @ .050"
then i could calculate the Cranking psi
06-07-2004, 11:04 AM
#10
Registered User
Thread Starter
Join Date: Apr 2001
Location: Surrey, B.C., Canada
Posts: 670
Heres the specs on my cam....
Intake Exhaust
Gross Valve Lift .510 .540
Duration @ .006 Tappet Lift 281 283
Valve Timing @ .050 (Open) 2 BTDC 54 ABDC
Valve Timing @ .050 (Close) 48 BBDC 8 ATDC
Cam specs installed at 113 intake centre line
Duration at .050” 230 242
Lobe Lift .3400 .3600
Lobe Seperation 113
Intake Exhaust
Gross Valve Lift .510 .540
Duration @ .006 Tappet Lift 281 283
Valve Timing @ .050 (Open) 2 BTDC 54 ABDC
Valve Timing @ .050 (Close) 48 BBDC 8 ATDC
Cam specs installed at 113 intake centre line
Duration at .050” 230 242
Lobe Lift .3400 .3600
Lobe Seperation 113
06-07-2004, 11:36 AM
#11
Registered User
Join Date: Feb 2004
Location: Abbeville , LA
Posts: 291
Originally posted by irocz383
Heres the specs on my cam....
Intake Exhaust
Gross Valve Lift .510 .540
Duration @ .006 Tappet Lift 281 283
Valve Timing @ .050 (Open) 2 BTDC 54 ABDC
Valve Timing @ .050 (Close) 48 BBDC 8 ATDC
Cam specs installed at 113 intake centre line
Duration at .050” 230 242
Lobe Lift .3400 .3600
Lobe Seperation 113
Heres the specs on my cam....
Intake Exhaust
Gross Valve Lift .510 .540
Duration @ .006 Tappet Lift 281 283
Valve Timing @ .050 (Open) 2 BTDC 54 ABDC
Valve Timing @ .050 (Close) 48 BBDC 8 ATDC
Cam specs installed at 113 intake centre line
Duration at .050” 230 242
Lobe Lift .3400 .3600
Lobe Seperation 113
11:1 CR = 203.92 psi with your cam specs (very accurate gauge)
after 7 to 10 needle pulses on tester
your engine's compression test looks OK to me.
i'm a little surprised you can run that much psi with pump gas,
176 cranking psi and 92 prem seems to be about the most i can use in Suburban towing Dragster trailer
06-07-2004, 11:45 AM
#12
Registered User
Thread Starter
Join Date: Apr 2001
Location: Surrey, B.C., Canada
Posts: 670
Rumour has it that Canadian gas is a little richer... some how, I dont know.
The highest on pump we have here is 94 and that all I ever use. That is for normal driving. If I'm headed out to the track I'll be putting in a couple bottles of octaine boost. Maybe just go buy some racing fuel.
Thanx for the help. My mind is at easy knowing that its pretty close to spec.
Too follow up on my burning oil... my machinist says that he used double moly rings with a 400 grit finish on the cylinder walls. In the early stages of the motor I had an over fueling problem and more idle time than either of us were comfortable with. Hes telling me that a cpombination of these two made the rings not set in properly. Being double molly rings he says that they still may not have set and to get some hard milage on it and the smoke should go away.
Does this sound reasonable? Or should I go get another opinion?
The highest on pump we have here is 94 and that all I ever use. That is for normal driving. If I'm headed out to the track I'll be putting in a couple bottles of octaine boost. Maybe just go buy some racing fuel.
Thanx for the help. My mind is at easy knowing that its pretty close to spec.
Too follow up on my burning oil... my machinist says that he used double moly rings with a 400 grit finish on the cylinder walls. In the early stages of the motor I had an over fueling problem and more idle time than either of us were comfortable with. Hes telling me that a cpombination of these two made the rings not set in properly. Being double molly rings he says that they still may not have set and to get some hard milage on it and the smoke should go away.
Does this sound reasonable? Or should I go get another opinion?
06-07-2004, 11:48 AM
#13
Registered User
Join Date: Feb 2004
Location: Abbeville , LA
Posts: 291
just for reference;
dynoed an NHRA A/ND 393 cid SBC with 16:1 CR + Methanol injection
that engine cranked 285 psi with 16 volt system and 16:1 CR
...program calculated 287.83 cranking psi (large Roller Cam)
403.76 cranking psi "if it would have" a 180 deg @ .050" duration extremely small cam..and you could find a starter to turn the engine over fast enough to get a reading?
dynoed an NHRA A/ND 393 cid SBC with 16:1 CR + Methanol injection
that engine cranked 285 psi with 16 volt system and 16:1 CR
...program calculated 287.83 cranking psi (large Roller Cam)
403.76 cranking psi "if it would have" a 180 deg @ .050" duration extremely small cam..and you could find a starter to turn the engine over fast enough to get a reading?
06-07-2004, 12:27 PM
#14
Registered User
Join Date: Feb 2004
Location: Abbeville , LA
Posts: 291
Originally posted by irocz383
Too follow up on my burning oil... my machinist says that he used double moly rings with a 400 grit finish on the cylinder walls. In the early stages of the motor I had an over fueling problem and more idle time than either of us were comfortable with. Hes telling me that a cpombination of these two made the rings not set in properly. Being double molly rings he says that they still may not have set and to get some hard milage on it and the smoke should go away.
Does this sound reasonable? Or should I go get another opinion?
Too follow up on my burning oil... my machinist says that he used double moly rings with a 400 grit finish on the cylinder walls. In the early stages of the motor I had an over fueling problem and more idle time than either of us were comfortable with. Hes telling me that a cpombination of these two made the rings not set in properly. Being double molly rings he says that they still may not have set and to get some hard milage on it and the smoke should go away.
Does this sound reasonable? Or should I go get another opinion?
Racer7088
Erik Koenig
Erik's Web Page
Horsepower Engineering
Houston, TX
can give you good advice on honing your engine !!
http://www.horsepowerengineering.com...s/P0002481.jpg
your cyl bores should reflect back white light..take a look at pics on Erik's website.
400 to 600 grit is tricky to accomplish correctly, without folding peaks over and shinning back dark light.
i'd use 400 grit if the block's cylinder bores wasn't distorted more than .001" after torque plates were installed...and hone the block with 2 to 3 new packs of 400 grit stones .
if you see more than .001" + with torque plates, i'd use 280 to 320 grit...even then, i use at least 2 new packs of stones, one for each side on final hone..i don't file the hone guides like Sunnen says you could do.
there are a lot of things to look..it might not even be your hone job...you want to use an oil ring design like SealedPower/SpeedPro or the new Hastings oil ring design or similiar.
you should have an "S" shaped oil ring in either a vertical (Hastings) or horizontal (SpeedPro)
Valve guides ?? seals?? intake gasket sealing ?
06-07-2004, 12:37 PM
#15
Registered User
Thread Starter
Join Date: Apr 2001
Location: Surrey, B.C., Canada
Posts: 670
wow! I think if its still smoking by the end of the summer I'm going to just pull it out and do a refresh on it.
I replaced the intake gasket for ease of mind... nothing changed. The guides were replaced when the motor was being build and they said the valve seals looked good still. Just be going on what hes telling me its only possibility is the rings. With the compresion ratio's looking good it doesn't sound logical that it would be the rings.
I know he used a torque plate on the block too. I specifically made sure he did that after decking the block also. I wanted this thing to be perfect!
Going with a courser finish like the 320 or 280, that obviously would make the rings seat a lot faster. That should in time smoothen out and be just as good as a finer finish right?
I replaced the intake gasket for ease of mind... nothing changed. The guides were replaced when the motor was being build and they said the valve seals looked good still. Just be going on what hes telling me its only possibility is the rings. With the compresion ratio's looking good it doesn't sound logical that it would be the rings.
I know he used a torque plate on the block too. I specifically made sure he did that after decking the block also. I wanted this thing to be perfect!
Going with a courser finish like the 320 or 280, that obviously would make the rings seat a lot faster. That should in time smoothen out and be just as good as a finer finish right?