Compression

smokeblack · 07-06-2008, 09:56 PM

I have a 95 12 valve and I am about to do a compression test on it but i cant find the specifications anywhere. What should the compression be new and with almost 200k on her?

__________________
95 blue standard cab long bed cummins 5" exhaust with aero turbine no fuel plate HTT pro street 66 custom intake sbc laser cut dvs ddp4 140 horse nozzles 16* timing 4k gsk 60 lb. valve springs ATS built nv 4500 with 1 3/8 input shaft

cursedtofirst45 · 07-07-2008, 12:09 AM

new should be about 17.5:1 i believe

__________________
1997 Dodge 2500 Cummins/Nv4500
Lots of Fuel, Less Air.

smokeblack · 07-07-2008, 02:49 PM

I was actually wondering the psi value sorry i didnt clarify

__________________
95 blue standard cab long bed cummins 5" exhaust with aero turbine no fuel plate HTT pro street 66 custom intake sbc laser cut dvs ddp4 140 horse nozzles 16* timing 4k gsk 60 lb. valve springs ATS built nv 4500 with 1 3/8 input shaft

ykdave · 07-08-2008, 12:07 AM

Compression ratio is 17.9:1, but like you know, thats not going to do you any good.

Your looking for 350psi on a new rebuild, around 300psi on a good used engine and oddly enough you are allowed up to a 100psi variance between cylinders.

Best bet is a blowby test though...

__________________
97 Ram 2500 / 5.9ctd / 5spd / nv4500 / 4x4 / np241
Starwheel cranked, no plate, autometer pyro and boost gauges, Single 4" stack, 33x10.5 Mud terrains, tons more to come

Charlie.Smith · 07-10-2008, 07:19 AM

By "blowby test" you probably mean a leakdown test.
[ OOPS! ykdave corrected me. ]

A leakdown test will detect and pinpoint problems you'll never notice with a compression test.

As a humerous note, my leakdown tester is so old, it's got a plate on the body that says "Caution - stand clear of the prop" :-)

__________________
Charlie Smith - Columbus, Ohio
'97 2500 4x4 auto, Suncoast TC/VB, #5 16.5*, Arrowcraft DRW, Aerotanks D60, KDP
'96 3500 2x4 auto, Goerend TC/VB, #5 16* DDP2 355hp/970tq, D60 tank, KDP

Last edited by Charlie.Smith : 07-10-2008 at 08:29 AM. Reason: Correction

ykdave · 07-10-2008, 08:06 AM

No, blowby test. Measuring the ammount of gasses that pass by the rings while its running.

Though a leakdown test is another alternative to diagnosing the problem area if you have low compression.

I can get you some more info on the blowby test if you need it, search on here and you can find info on how to build a cheap test tool instead of buying the one from cummins.

9 in/hg for new/rebuild (.221 orifice)
34 in/hg is max allowable (.221 orifice)

__________________
97 Ram 2500 / 5.9ctd / 5spd / nv4500 / 4x4 / np241
Starwheel cranked, no plate, autometer pyro and boost gauges, Single 4" stack, 33x10.5 Mud terrains, tons more to come

Last edited by ykdave : 07-10-2008 at 08:11 AM.

07-06-2008, 09:56 PM	#1 (permalink)
smokeblack Cummins Fan Join Date: Oct 2006 Location: Fort Collins, Colorado Posts: 46 smokeblack's Truck Pics	Compression I have a 95 12 valve and I am about to do a compression test on it but i cant find the specifications anywhere. What should the compression be new and with almost 200k on her? __________________ 95 blue standard cab long bed cummins 5" exhaust with aero turbine no fuel plate HTT pro street 66 custom intake sbc laser cut dvs ddp4 140 horse nozzles 16* timing 4k gsk 60 lb. valve springs ATS built nv 4500 with 1 3/8 input shaft

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07-07-2008, 12:09 AM	#2 (permalink)
cursedtofirst45 Cummins Enthusiast Join Date: Mar 2008 Location: gilbert, az Posts: 204 cursedtofirst45's Truck Pics	new should be about 17.5:1 i believe __________________ 1997 Dodge 2500 Cummins/Nv4500 Lots of Fuel, Less Air.

07-07-2008, 02:49 PM	#3 (permalink)
smokeblack Cummins Fan Join Date: Oct 2006 Location: Fort Collins, Colorado Posts: 46 smokeblack's Truck Pics	I was actually wondering the psi value sorry i didnt clarify __________________ 95 blue standard cab long bed cummins 5" exhaust with aero turbine no fuel plate HTT pro street 66 custom intake sbc laser cut dvs ddp4 140 horse nozzles 16* timing 4k gsk 60 lb. valve springs ATS built nv 4500 with 1 3/8 input shaft

07-08-2008, 12:07 AM	#4 (permalink)
ykdave Diesel Freak Join Date: Feb 2008 Posts: 980 ykdave's Truck Pics	Compression ratio is 17.9:1, but like you know, thats not going to do you any good. Your looking for 350psi on a new rebuild, around 300psi on a good used engine and oddly enough you are allowed up to a 100psi variance between cylinders. Best bet is a blowby test though... __________________ 97 Ram 2500 / 5.9ctd / 5spd / nv4500 / 4x4 / np241 Starwheel cranked, no plate, autometer pyro and boost gauges, Single 4" stack, 33x10.5 Mud terrains, tons more to come

07-10-2008, 07:19 AM	#5 (permalink)
Charlie.Smith Cummins Fan Join Date: Feb 2008 Location: Columbus, Ohio Posts: 34 Charlie.Smith's Truck Pics	By "blowby test" you probably mean a leakdown test. [ OOPS! ykdave corrected me. ] A leakdown test will detect and pinpoint problems you'll never notice with a compression test. As a humerous note, my leakdown tester is so old, it's got a plate on the body that says "Caution - stand clear of the prop" :-) __________________ Charlie Smith - Columbus, Ohio '97 2500 4x4 auto, Suncoast TC/VB, #5 16.5, Arrowcraft DRW, Aerotanks D60, KDP '96 3500 2x4 auto, Goerend TC/VB, #5 16 DDP2 355hp/970tq, D60 tank, KDP Last edited by Charlie.Smith : 07-10-2008 at 08:29 AM. Reason: Correction

07-10-2008, 08:06 AM	#6 (permalink)
ykdave Diesel Freak Join Date: Feb 2008 Posts: 980 ykdave's Truck Pics	No, blowby test. Measuring the ammount of gasses that pass by the rings while its running. Though a leakdown test is another alternative to diagnosing the problem area if you have low compression. I can get you some more info on the blowby test if you need it, search on here and you can find info on how to build a cheap test tool instead of buying the one from cummins. 9 in/hg for new/rebuild (.221 orifice) 34 in/hg is max allowable (.221 orifice) __________________ 97 Ram 2500 / 5.9ctd / 5spd / nv4500 / 4x4 / np241 Starwheel cranked, no plate, autometer pyro and boost gauges, Single 4" stack, 33x10.5 Mud terrains, tons more to come Last edited by ykdave : 07-10-2008 at 08:11 AM.