Need feedback on My 86 6.9 Compression test??????????
#1
Need feedback on My 86 6.9 Compression test??????????
I have a 86 f250 6.9 with 360kms. all the glow plugs were faulty so I decided to do a compression test as I was pulling all the glow plugs out. IM hoping some of the experts here could let know what they think of my engine compression.
Cyl 1: 440psi Cyl 5: 400psi
Cyl 2: 420psi Cyl 6: 400psi
Cyl 3: 420psi Cyl 7: 460psi
Cyl 4: 400psi Cyl 8: 420psi
As I didnt have a remote starter i could watch the compression build up I just recorded the compression after turning the engine over 10times for each cylinder.
Let me know what you think.
Thanks
Cyl 1: 440psi Cyl 5: 400psi
Cyl 2: 420psi Cyl 6: 400psi
Cyl 3: 420psi Cyl 7: 460psi
Cyl 4: 400psi Cyl 8: 420psi
As I didnt have a remote starter i could watch the compression build up I just recorded the compression after turning the engine over 10times for each cylinder.
Let me know what you think.
Thanks
#3
#4
Join Date: Nov 2003
Location: Campbell River, B.C.
Posts: 6,900
Likes: 0
Received 2 Likes
on
2 Posts
Some 6.9s have tested at over 500 PSI, but those are rare. 400 is still fine, but what about cylinders 1,2,3 and 4?
Was the engine hot or cold?
Adding a turbo on an older engine will not ruin it, but if you're really concerned, keep below 7 PSI (even 5 psi makes a big difference that you will notice). Generally 10 PSI is still safe and some push higher, but with older head gaskets, there is a risk to start a leak. Blowing a head gasket is rare and if it does fail, there will generally be plenty of warnings signs.
Doing a head gasket job is a great time to put ARP head studs in (over twice the tensile strength of the stock bolts), but it is a pain and takes a lot of time and cuss words to get it done right.
Was the engine hot or cold?
Adding a turbo on an older engine will not ruin it, but if you're really concerned, keep below 7 PSI (even 5 psi makes a big difference that you will notice). Generally 10 PSI is still safe and some push higher, but with older head gaskets, there is a risk to start a leak. Blowing a head gasket is rare and if it does fail, there will generally be plenty of warnings signs.
Doing a head gasket job is a great time to put ARP head studs in (over twice the tensile strength of the stock bolts), but it is a pain and takes a lot of time and cuss words to get it done right.
#5
the engine was cold. hasnt been running in a few days.
should I have done it warm? my manual says some ford engines should be warmed up where other engines will be tested cool.
#6
Join Date: Nov 2003
Location: Campbell River, B.C.
Posts: 6,900
Likes: 0
Received 2 Likes
on
2 Posts
But even if not, a compression test after a good long run would probably get slightly better results. Its not unusual for these trucks to get a little soft if they aren't run hard for a long time. Its one of the reason they shouldn't be used as daily drivers. Or if you do drive them lightly, 'excercise' them on the weekend to prevent glazing.
But even if nothing changes, thats more or less right where my engine was when I put my turbocharger on. The only reason I rebuilt mine was due to a glow plug incident that left a few pistons with signature marks on them.
#7
Looks decent to me. The important thing isn't so much the raw numbers as consistency. One or 2 cylinders 100 psi lower than the rest is bad. With all in the 4-500 range you should be fine.
Now, the correct way to check is it with a hot engine and all 8 glow plugs out. That way you get the fastest cranking speed and everything is warmed up.
Now, the correct way to check is it with a hot engine and all 8 glow plugs out. That way you get the fastest cranking speed and everything is warmed up.
Trending Topics
#8
Thread
Thread Starter
Forum
Replies
Last Post
truck crazy man
1987 - 1996 F150 & Larger F-Series Trucks
17
02-06-2014 07:50 PM
econoshorty
Ford Inline Six, 200, 250, 4.9L / 300
7
09-06-2010 11:24 PM
gwp36530
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
7
04-25-2004 01:02 AM
quads
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
4
04-11-2002 10:15 PM