460 check-up
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Junior User
Joined: Apr 2004
Posts: 60
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From: Newark Delaware
460 check-up
I have lucked into a 79f250 w/460cid! 127k on engine. I don't have the cash to do a rebuild soon, I want to do some simple checks (compression etc..) to get an idea of what I am dealing with! What checks do you recommend. Also, If compression looks bad how do I know if its rings or valves? If truck idles rough how can I tell if its vacuum, timing, carb, or heads. Any info would be appreciated.
Posting Guru
Joined: Mar 2003
Posts: 1,349
Likes: 3
From: Cloud USA
Well, Do a basic compression test, record all the #'s, Then put a table spoon of oil in the cylinders and retest. If the compression goes up, then your rings are bad, if it stays about the same then your valves a bad. I would do a basic tunup with plugs and wires, plus cap and rotor. 127K isnt all that many miles, even abused they will last 200K plus
Elder User
Joined: Dec 2002
Posts: 738
Likes: 2
From: McChord AFB
when you go to pick the truck up you can kinda cheat. Get it running and if its rough just move the dizzy around a bit and if it smooths out your golden. I woldnt realy bo too worried about the millage. Old V-8s are tanks. 
Elder User
Joined: Sep 2003
Posts: 908
Likes: 4
dizzy = distributor. Thank our Aussie friends for that one. 
It the truck runs good, doesn't smoke excessively, doesn't have a noticable miss, then don't worry.
If you do a compression check, look for readings within 15% on all cylinders, and in the low to mid 100 PSI.
IF you find one or more cylinders low, THEN do the oil injection to determine if it's valves or rings. It also could be a blown head gasket, especially if two adjacent cylinders are low.
It the truck runs good, doesn't smoke excessively, doesn't have a noticable miss, then don't worry.
If you do a compression check, look for readings within 15% on all cylinders, and in the low to mid 100 PSI.
IF you find one or more cylinders low, THEN do the oil injection to determine if it's valves or rings. It also could be a blown head gasket, especially if two adjacent cylinders are low.
