#21  
Old 09-18-2020, 02:56 AM
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When I pulled my 400 apart for the first time with about 90,000 miles on it, it had one lifter (forget which one) that had worn down to the point it had a pin hole in the center, cam lobe was also correspondingly worn ... I thought it still ran pretty good. Ran WAY better with a new cam and lifters in it , put another 30,000 miles on it.

Could be any of the things you mention, non of which are very serious ... I'd think if the rings are that bad in that cylinder it would have been smoking very noticeably for a long time.

If it's got kind of relatively low mileage on the original engine I'd just fix what needs fixing and nothing more, disturb as little of the rest of the engine as possible.

  #22  
Old 09-18-2020, 10:00 AM
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If it’s accurate and I think it is the miles are just under 68,000.
I’m pretty nervous about it but hoping something relatively minor.

  #23  
Old 09-18-2020, 10:13 AM
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If no sticky valve from bad gas, bent push rod, bad lifter....what’s next?

What would determine if the heads need valve jobs etc?

If the valves are functioning, does that mean the ring is bad in just one cylinder or is the head seat worn out?

My head is everywhere with what if this morning. I won’t k ow until the end of the day what step one of the fix is.

  #24  
Old 09-18-2020, 12:03 PM
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A leak down test would give you and overall idea of the condition of the rings and valve seats in combination.

I think there is little chance of bad rings in just one cylinder. A bad seat, bent valve, burned valve etc. will require the head being removed to fix it, in which case a valve job on both heads would make sense.

Bad lifter/lobe of course would mean replacing the cam and lifters.

Bent push rod, loose rocker, broken spring .... fairly easy fix (although I would want to know WHY the push rod was bent)

Anything to do with the valve train would typically not be that expensive or too much trouble and could most likely be done with the engine in the car if you wanted.

With just the valve cover off you can check the springs, rockers, pushrods and valve lift. With a tad more work, removing the spring retainers you could check for a sticky valve, worn valve guide.

To check the lobe/lifter condition you'd have to remove the intake ... but most likely a lobe/lifter bad enough to cause that kind of drop in compression is going to be reflected in reduced lift at the valve.

If you are worrying about the engine having to come out and be completely rebuilt ... I think that possibility is pretty slim.

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Old 09-18-2020, 04:01 PM
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“Slim” gives me some hope.

  #26  
Old 09-18-2020, 10:30 PM
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You guys won’t believe this but a screw in stud somehow backed itself out and made the rocker loose!

Retightened it and cinched the nut. Then just turned it over with cover off to see the rocker moving properly.

He didn’t get a chance yet to put the compression gauge back on it but he said he was 99% sure it’d have compression now. I’m hoping it’s around 150 like the other that was checked next to it yesterday.

He thinks that may have been causing the smoking but can’t recall why. On a side note he said he’s used to seeing hunk on the head and it looked really clean.

I’m excited to hear it run tomorrow now!

  #27  
Old 09-19-2020, 12:25 AM
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It might be moot now but I forgot to mention the exhaust pipe was spitting oil out the same side as the cylinder not functioning properly.

Maybe that will fix the smoking completely now.

  #28  
Old 09-19-2020, 04:19 AM
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Don't think I've ever heard of that. But yeah, that would explain the lack of compression.

  #29  
Old 09-19-2020, 10:41 AM
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Me neither and mechanic has been at it a long time without ever seeing that.

I put new valve covers on it two years ago when I first got it because the originals were shot but I never even looked at the rockers.

The car was unregistered for the road from 1972-2017 so it couldn’t have traveled far during that time. The chrome valve covers were rusty and engine itself was just about Paint-less.

Assembly line error? The timing chain had been changed by someone who knows when so somebody has messed with it...not sure why that would happen though.

  #30  
Old 09-20-2020, 02:48 PM
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For what its worth, I assembled an engine years ago that had crappy valve stem seals. It smoked bad, but only on start up, and would go away after a relatively short run time. pulled the springs & installed positive seals & never smokes now. So in my case, bad valve seals caused heavier smoke right at start up & went away.

Many years before that, I had an engine that didn't smoke much at start up, but if I would hold it in first gear & rev it to 4-5K, let off the gas while still in 1st, let the engine slow the car back down a bit, then hit the gas again it would put a blue cloud behind me. When I tore than engine down it had very worn cylinders & a few cracked rings.

I wouldn't think sitting would cause damage unless it was fairly caboned up and an oil ring is stuck, or maybe the valve stems have oil on them & it just needs a good run down the highway?

Is the engine quiet, or do you some valve train noise? A cam lobe can go pretty fast, but that would be super fast. maybe a rocker nut backed off, but you should have heard that I would think. usually a wiped lobe is pretty obvious, the push rod will get a bit loose & the rocker will not move much while cranking.

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  #31  
Old 09-20-2020, 03:19 PM
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I did hear noise on that side weeks ago but wrote it off as an exhaust leak because I was missing a bolt on manifold.
He retested the cylinder compression yesterday and it was 110 but he’s not sure his gauge is completely accurate. Friday it read 75, then 30 and 35 when it wasn’t even working.
After tightening up the stud and rocker nut on the cylinder not working it was 100 then 110. The cylinder in front of it was 150 and another on passenger side was 170.
He thinks his gauge is off but that cylinder is still lower. Will any compression come back after it’s actually started and I drive it some or is that permanent?
On a side note I was thinking of putting one of those Pertronix 1 lobe sensor units in because my points didn’t look great. Anyone try those?

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Old 09-21-2020, 09:12 AM
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Was it an intake or exhaust valve?

  #33  
Old 09-21-2020, 10:00 AM
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I don’t know. I’ll ask him tomorrow when I head over there.
Will that tell me anything about compression?

  #34  
Old 09-22-2020, 04:50 AM
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Smaller lift on the intake due to the loose stud would probably show less compression than it would if it were the exhaust valve.

I wouldn't think either valve would be damaged in any way by the reduced lift. Exhaust valve faces/seats can be damaged from not seating well and exhaust burning a groove in them ... but your issues is the opposite of that, it was seating too much

Basically if the intake valve lost lift then the cylinder would not draw in as much air and the compression would be less. How much less I don't know since the cranking rpm is so slow on a compression test.

  #35  
Old 09-22-2020, 10:10 AM
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Will any compression come back after started?

  #36  
Old 09-22-2020, 01:03 PM
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Hard to say, specially considering a possibly sketchy compression tester. Apparently the cylinder wasn't firing much ... hence the "miss". I'm not knowledgeable enough to know what kind of conditions that might create in a cylinder. Unburned fuel can wash the cylinder walls, which isn't great for them. Carbon on the valves and combustion chamber could have softened up and moved around, possibly holding a valve open a bit.

Hopefully someone else with chime in, but if you didn't notice that you had a miss to begin with, I can only assume it will run better than it did before. Hard to imagine any serious damage was done.

  #37  
Old 09-22-2020, 08:18 PM
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I talked to the mechanic and it was the intake valve. It’s not missing now, timing was set and points readjusted.
He said my timing was too retarded too so adjusted that.
I’m hoping the compression number was off and improves still but it’s a lot better than it could have been.
If it runs good I’m leaving well enough alone but should I be adding lead to the fuel since those 16 heads are original?

  #38  
Old 09-23-2020, 08:18 AM
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Lead additive probably wouldn't hurt ... I "think" 69s had induction hardened seats from the factory, but I could be wrong.

Lots of debate on this issue. Some people say if you don't do lots of long highway drives it's not an issue. Might want to post the question to the "street" section.

If it was mine, as long as it wasn't leaving a trail of smoke I'd just drive it. With 65K miles on the original engine you probably have 20,000 more miles to drive before anything serious needs to be addressed. Or more if the engine is a good one and well cared for. At that point it will probably need fairly complete "freshening" up to run like it should. Seems like you have a fundamentally sound engine that should be fine if it's not getting beat on or raced.


Last edited by dataway; 09-23-2020 at 08:24 AM.
  #39  
Old 09-23-2020, 10:16 AM
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I haven’t had a chance to drive it much. The mechanic said the head was clean and looked good. He told me last night it’s running good and not smoking at this point (knock on wood).

If it can’t hurt I think I’ll just run a reputable lead additive brand anyway with 91, octane and Lucas booster.

While there he discovered my master cylinder was leaking so he was trying to find a replacement for power 4 wheel drum unit. Rear brakes were just done with those larger wheel cylinders so not sure if connected.

  #40  
Old 09-25-2020, 10:27 PM
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I haven’t tested compression but it’s running fine and not smoking now after getting that cylinder working.
Drove it about 45 minutes with no issues.

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