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235 Questions sticky / stuck valves #605635 Thu Dec 31 2009 12:41 AM
Joined: Jan 2009
Posts: 252
F
Ferndale53 Offline OP
Shop Shark
I picked up a late model 235 with the 848 head for a good price, but its been sitting a few years.

I did a cold compression test and got these results:

1: 55 psi
2: 110
3: 110
4: 130
5: 0
6: 40

I did a redneck leakdown test by blowing compressed air in the cylinders, and found 3 valves were stuck partially open. I didn't feel any air coming from the dipstick tube.

I pulled the head, and confirmed that the 3 valves I suspected wern't closing all the way. The #1,#6 intake wern't open all that much, but the #5 exhaust was open quite a bit, explaining the 0 reading.

Now, this is my first project, so I don't know a whole lot about this sorta stuff. Before I send it off to a machine shop I want some opinions.

I worked both stuck intake valves and soaked them in seafoam, and they seem to work fine with the head sitting on a bench. I put a puddle of seamfoam on all the intake valves, and it took about an hour for the seamfoam to leak from all of them. Should it be a perfect seal or is this acceptable?

Sorry for the long ramble, any help would be great. Heres a few pictures of the patient.

http://i50.tinypic.com/209j4o4.jpg
http://i50.tinypic.com/33vnnuc.jpg

Re: 235 Questions sticky / stuck valves [Re: Ferndale53] #605642 Thu Dec 31 2009 01:07 AM
Joined: Oct 2005
Posts: 95
T
Truckasaurus Offline
Shop Shark
Judging by the carbon deposits that are visible, you may have more carbon build up in the exhaust ports as well as on the valve seats.

Clean it off and put it back together, it might run fine.
Just be careful about where the carbon chips go.
Ray

Re: 235 Questions sticky / stuck valves [Re: Truckasaurus] #605650 Thu Dec 31 2009 01:26 AM
Joined: Mar 2002
Posts: 8,864
truckernix Offline
Master Gabster
Those are nice photos. I really like looking inside these old sixes!

I think you need to get rid of the carbon on the Head. I would do the rings and rear main while it is on the shop floor.


1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed


My Chevy Master 4 Door is on the Road!
Re: 235 Questions sticky / stuck valves [Re: truckernix] #605680 Thu Dec 31 2009 03:33 AM
Joined: Apr 2009
Posts: 29
C
chevymgb Offline
New Guy
Mine looked about the same as yours. I cleaned the carbon off ran some old wore out emery paper thru the guides (I just rolled it up and ran it thru, but not too much to make them sloppy - just not sticky)and then lapped all the valves with compound and the old fashion suction cup type tool. New head gasket and everything was fine with 110# to 118# on all six. I had bad compression On two cyl. before I started.

Last edited by chevymgb; Thu Dec 31 2009 03:34 AM.
Re: 235 Questions sticky / stuck valves [Re: chevymgb] #605689 Thu Dec 31 2009 04:16 AM
Joined: Aug 2007
Posts: 1,891
S
Scott Danforth Offline
Shop Shark
oven cleaner works like magic to remove carbon


The problems we face today can not be addressed at the same level of intelligence we were at when we created them - Albert Einstein Or with the same level of $ - Me
Re: 235 Questions sticky / stuck valves [Re: Scott Danforth] #605789 Thu Dec 31 2009 03:36 PM
Joined: Apr 2005
Posts: 1,944
B
Builder Offline
Shop Shark
Look for marks on the pistons and valves to determine if they made contact with each other. Make sure the valves didn't get bent.

You might as well pull the valves out and at least lap the seats like chevymgb suggests. That way you can clean them up real good and replace aparts as needed.

Re: 235 Questions sticky / stuck valves [Re: Builder] #605824 Thu Dec 31 2009 05:32 PM
Joined: Feb 2000
Posts: 3,963
J
Joe H Offline
Shop Shark
While the head is apart, soak it for a hour or so in your favorite degreaser, I like Castrol Super Clean, and then hit the car wash for a hot soapy wash. It will come very clean and be a lot easer to handle for the overhaul. Oven cleaner works great for this. You can do this after lapping the valves, that way you clean all the compound out at the same time.

Joe


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