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Old 11-25-2012, 07:55 AM
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Ford 460 low compression and rough idle

I just got a F350 with a 460 with 160,000 miles. I'm told by the PO that it has low compression in two cylinders (# 1 and #5). It's not drivable, but it starts. I let it idle for about 10 minutes and I saw lots of gray smoke from the tail pipe and none from the oil fill hole.
This makes me think that the piston rings are bad, but the heads are good, is this a correct assumption?

Second; the rough idle could be a stretched timing chain, correct???

Also, can the timing chain be the cause and cure for low compression?

Thanks

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Old 11-25-2012, 08:21 AM
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do a cylinder leak down test. The rough idle is from running on 6 cylinders
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Old 11-25-2012, 08:27 AM
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timing chain.

A bad timing chain would cause all the cylinders to be about equally low. there is some other problem also, You can check the timing chain by pulling the dist cap, watching the rotor and turning the crank pully with a wrench, then seeing how much rotation in the opposite direction before the rotor moves. and you get a few more ponies by using a double roller chain and setting the gears dead on , the smog 460's ran retard on the cam as a cheap way of emission reduction.
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Old 11-25-2012, 09:03 AM
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Time to buy a leak down tester......

I've rebuilt one engine before, an air cooled VW, worked out well, but I don't think I want to mess with this one. Ill probably buy a crate engine. They're in the range of about $1700. Not too bad.

I'm hoping it won't have to come to that and maybe I can get by with spending a few hundred instead of a couple grand.
So for now, a leak down and a compression test. I'll repost with results.

The other issue is probably really worn out piston rings???
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Old 11-25-2012, 09:26 AM
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spark plug fitting.

You can knock out the center of an old spark plug and weld an air fitting to it for a quick and dirty test.
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Old 11-25-2012, 10:06 AM
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Quote:
Originally Posted by timothale View Post
You can knock out the center of an old spark plug and weld an air fitting to it for a quick and dirty test.
That sounds good. The one's I've been looking at have gages, is that important? without a gage, I guess I would be able to go only with what I can hear?

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Old 11-25-2012, 10:32 AM
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just rent/borrow a guage and you need a low pressure compressed air source
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Old 11-25-2012, 11:40 AM
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Quote:
Originally Posted by vinniekq2 View Post
just rent/borrow a guage and you need a low pressure compressed air source
Just checked with Autozone. They have them in the "rent a tool".
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