Hello all;
I recently brought a Jetliner from Georgia to California. The seller had indicated the compression was low. I tested
yesterday w/ reliable gage. Cold, (front to rear, psi), with all plugs out:
57,62,54,55,72,25
I repeated the test after adding 1 oz of motor oil in the plug holes. Still cold,
100+, 100+, 96, 71, 78, 42
The car does run, but I can't drive it until the brakes are done.
It seems to me the gas is old, plugs are beat, and the oil hasn't been changed in awhile, judging by color. I wonder, if I do an oil change, and add fresh gas with some kind of lead substitute additive, could I resurrect these readings closer to 100 psi ?
I've read that running unleaded gas can cause sticky valves/low compression.
Thank you in advance,
Andrew Pejack
PS: Is there a Jet category on the forums? I couldn't find one.
Greetings Andrew and welcome to the forum. there is only one reliable way to do a compression test and that is with the engine thoroughly warmed up, all plugs out, and throttle held wide open. You compressions should then be around 90 to 100, and all even. I suggest you do a oil change and give the car a good run, then check the tappets with the engine hot to .010 inlet and .010" exhaust. run the motor up to temperature again and then do your compression test. If any one cylinder is down it could be a burnt valve, or worn or broken piston ring. Good luck, and enjoy your Jet. I have had mine for 46 years, wonderful car.
Geoff
I'm no engine expert, but those readings would indicate to me that the rings were worn in all cylinders and that, in addition, the valves are burned or stuck open in cylinders 4 through 6. Possibly the headgasket is blown somewhere.
For starters, you could pull the head to check the valve and headgasket situation. If a few valves and the headgasket will dramatically improve the situation, you could leave the rings alone and just enjoy the car, for the time being.
(Now someone who actually KNOWS what he'd doing can jump in here and give you the real answer, LOL!) [oops, I see that Geoff jumped in before me, while I was still writing this reply!]
There is no Jet category on this forum, but there is one on the Open Hudson Forum.
Thank you guys !
I changed the oil and oil filter, and am also doing the trans fluid tomorrow.
The oil was pitch black and runny. Trans fluid didn't look to good either, very dark.
I'm trying to figure out how to drain and refill the torque converter,; the manual is kind of cryptic.
Do you guys use lead additives in your fuel when driving your Jets ?
-Andrew
I re-did the Jet compression test with engine warmed up, fresh oil/filter, and new gas with a lead type additive
to lubricate valve stems. The readings, (1 - 6 , psi ), were 80, 83, 84, 74, 80, 43 .
Here's a summary; as we all know, the factory spec. is 100psi minimum.
Cylinder , 1 , 2 , 3 , 4 , 5 , 6
cold crank , 57 , 62 , 54 , 55 , 72 , 25 . (psi)
cold w/1 oz oil , 100+,100+, 96 , 71 , 78 , 42. (psi)
hot engine w/ , 80 , 83 , 84 , 74 , 80 , 43. (psi)
leaded gas,
I remember my old Hornet had a #6 cylinder that was in the 40's, and it ran fine, just
used some oil. I guess I'll see how much oil the Jet uses.
-A
Andrew, I would suggest you at least check the tappet clearance of No. 6 exhaust valve. If that is correct, then you have a burnt valve. if it is closed up then you may have valve seat recession, but I doubt that.
Geoff
[quote=
Andrew Pejack
PS: Is there a Jet category on the forums? I couldn't find one.
For things related to Jets check out Sara Youngs excellent Jet website @ http://hudsonjet.net/
There are some manuals in the online library.
Hudsonly,
Alex B
Thanks Geoff; I will do that when it stops raining !
I remember adjusting the valves on my Hornet 302 engine, and I believe the procedure is similar.
-A
Leave a reply
