Valve Adjustment/initial setting
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Joined: Oct 2020
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Valve Adjustment/initial setting
I have a 1981 302 and It’s been difficult for me to find info on it about valves. What type of valves would be in it, adjustable, non-adjustable, hydraulic, solid, etc? And how do I set or adjust them?
Just performed a compression test, here are the numbers
#1 155
#2 165
#3 165
#4 175
#5 65
#6 165
#7 70
#8 160
Thanks in advance
Just performed a compression test, here are the numbers
#1 155
#2 165
#3 165
#4 175
#5 65
#6 165
#7 70
#8 160
Thanks in advance
Lead Driver
Joined: Sep 2003
Posts: 7,013
Likes: 205
From: SoCal
Most likely 1.78 intake / 1.45 exhaust, non-adjustable rockers bolted down through pedestals, hydraulic flat tappet cam followers. You can decrease lifter preload using shims under the pedestals or get shorter pushrods. The only way to increase lifter preload is to get longer pushrods.
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
Yep that is a non adjustable hydraulic valvetrain. The low compression you have on 2 cylinders is not going to be a valve adjustment issue, it could be a broken valve spring, a chipped valve or really dirty valve seats that don't seal very well, or worn or broken piston rings. Add some oil to those cylinders and test again, if compression comes up the piston rings are the issue, if there is no change it's something to do with the valves.
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New User
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Yep that is a non adjustable hydraulic valvetrain. The low compression you have on 2 cylinders is not going to be a valve adjustment issue, it could be a broken valve spring, a chipped valve or really dirty valve seats that don't seal very well, or worn or broken piston rings. Add some oil to those cylinders and test again, if compression comes up the piston rings are the issue, if there is no change it's something to do with the valves.
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
Is it possible or very likely that just two out of eight cylinders would have excessively worn bores or piston rings, while the other six are reasonably good? Did the truck sit in a field for a long time or anything like that?
Logistics Pro
Joined: Dec 2003
Posts: 3,776
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From: Foothills of NC
Those cylinders could have been washed down by gas also. Get it running, then check the compression again. Even running it just a few minutes with the valve covers off will be enough.
I have seen washed cylinders drop compression to basically zero a couple of times.
I have seen washed cylinders drop compression to basically zero a couple of times.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Ah. I wondered about that.
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