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Violent Idle When PCV Connected
https://slantsix.org/forum/viewtopic.php?t=68306		 Page 6 of 6
Author:  SlantSixDan [ Tue Apr 21, 2026 11:38 am ]
Post subject:  Re: Violent Idle When PCV Connected
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here's a vid
There should be oil all over the place. Everything should have a glossy film of oil on it. There should be oil in that recessed square-headed plug. The spark plug tubes should be oily.

Instead, everything's bone-dry. There's no oil getting to the top end – maybe a clogged passage, maybe the rearmost cam bearing out of position, maybe the rocker shaft installed wrong way round and/or clogged with baked sludge – and whichever valve guides were marginal-to-wonky before ate the replacements for the same valves.

Head's coming off again, for a complete valve job this time. New valves as required, hard exhaust seat inserts, all twelve guides, all twelve valve seats properly ground and lapped, appropriate valve stem seals, springs checked and replaced as necessary, rocker assembly disassembled, thoroughly cleaned and reassembled. All twelve pushrods checked for straightness and replaced as necessary.

Be aware that putting a nice, fresh head atop a tired/worn/high miles engine will often finish off the rings and/or bearings; you can wind up with an oil burner de luxe.
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Perhaps some gunk in the intake manifold that's consistently making its way in?
Nope.
Author:  Dart270 [ Tue Apr 21, 2026 1:26 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Some passage is blocked from the block to the head/rocker shaft, probably. Dan has got the possibilities there. I assume you have an oil pressure gauge and the oil pump is making pressure and the main/rod bearings are getting oil?

Lou
Author:  Rick Covalt [ Tue Apr 21, 2026 5:09 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Could he just pull the rearmost rocker arm bolt out and spin the engine over and see if oil is coming up from the cam? It could have spun the rear cam bearing and be blocking the oil passage coming up through.
Author:  morsim [ Tue Apr 21, 2026 6:02 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
Be aware that putting a nice, fresh head atop a tired/worn/high miles engine will often finish off the rings and/or bearings; you can wind up with an oil burner de luxe.
As it appears based on the previous vids, that it's already burning oil (even in the 3 running cylinders). And this isn't a new issue.
It must be bad/stuck rings, eh? Engine has around 75k miles on it; if that means much in conjunction with its sitting time.
I'll have to do another compression/leakdown test to confirm (& adding oil to see if compression improves). I don't remember the last numbers.
Do you think it's worth the head repairs considering the wear/age of the block? Also consider, the oil burning + lack of flow. If it takes any work to the block, I certainly do not have the tools or equipment/shop to arrange that, unfortunately. :(

Here's a theory:
Oil getting past rings; engine burns it; leaves behind nasty buildup; buildup gets stuck behind intake valves and accumulates (here's where I'm skeptical - wouldn't the exhaust valves be most affected?); because of tight guides, the valves get stuck from buildup + when warm, they thermally seize up from metal expansion (indicated by the fact that I could press them a bit after some time, albeit sticky).

This theory kills two birds with one stone. It's either that, or the oil burning and sticky valves are two separate issues.
But the third chirper is still: why is there no oil on top-end...
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Some passage is blocked from the block to the head/rocker shaft, probably. Dan has got the possibilities there. I assume you have an oil pressure gauge and the oil pump is making pressure and the main/rod bearings are getting oil?
I don't understand why that'd happen again after flow was restored following the "valve job". I remember now that he did send a video showing nice dribbling out the rockers. When I did the oil change, it wasn't particularly sludgy (but actually, the fuel pump was replaced because of leaky diaphragm)...

I never hooked up an oil gauge, just have the stock idiot light - ironically.
I don't know how to test if the main bearings are getting oil, but I do know that it's burning oil.

I'm so determined to get back on the road because she's just so beautiful.
Author:  SlantSixDan [ Tue Apr 21, 2026 6:41 pm ]
Post subject:  Re: Violent Idle When PCV Connected
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it appears that it's already burning oil (even in the 3 running cylinders). And this isn't a new issue.
It must be bad/stuck rings, eh?
Probably.
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Engine has around 75k miles on it; if that means much in conjunction with its sitting time.
Cars and their parts deteriorate from prolonged non-use and from prolonged use.
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Do you think it's worth the head repairs
They've got to be done…but given the oil burning, they've got to be done as part of a whole-engine overhaul.
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If it takes any work to the block, I certainly do not have the tools or equipment/shop
Most of us don't; we have to farm it out.
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Oil getting past rings; engine burns it; leaves behind nasty buildup; buildup gets stuck behind intake valves and accumulates
No, that's not it.
Author:  morsim [ Tue Apr 21, 2026 7:34 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
Quote:
Do you think it's worth the head repairs
They've got to be done…but given the oil burning, they've got to be done as part of a whole-engine overhaul.
Well I got that, but the question is really whether just repairing the head would be enough for occasional light-leisure use (assuming we can restore oil flow without block work) and let it burn oil until perhaps the rings un-stuck themselves after some driving.

As for the head repairs, how much $$$ would you guess it'd land me, all said and done (machining, etc.). Even just a ball-park estimate from your experience
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Most of us don't; we have to farm it out.
In my case, as much as I'd love to, it'd be too impractical given the money and accessibility constraints.
If not under already, I'd like to at the least stay overwater with this now-medium-sized project.
Author:  SlantSixDan [ Wed Apr 22, 2026 5:03 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
the question is really whether just repairing the head would be enough for occasional light-leisure use (assuming we can restore oil flow without block work) and let it burn oil until perhaps the rings un-stuck themselves after some driving.
That (rings unsticking) is not very likely, but also not out of the question. How long did this engine sit before it was put back into use, and how many miles has it done since then?
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As for the head repairs, how much $$$ would you guess it'd land me, all said and done (machining, etc.). Even just a ball-park estimate from your experience
Oof. I'm too many years out of the market to give even a decent guess.
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If not under already, I'd like to at the least stay overwater with this now-medium-sized project.
That is a tall order. Old cars eat money! The days when a Dart or Valiant was cheap and easy to fix and keep in parts are pretty much in the past. :(
Author:  Rick Covalt [ Wed Apr 22, 2026 8:12 pm ]
Post subject:  Re: Violent Idle When PCV Connected
The last head I had done (1year ago) I had the valves and seats ground. Reamed out the guides and installed bronze liners and sized them properly. Lapped all valves and re-assembled with new positive valve seals. $250 total. I did not need any new valves.
Author:  morsim [ Thu Apr 23, 2026 12:39 am ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
That (rings unsticking) is not very likely, but also not out of the question. How long did this engine sit before it was put back into use, and how many miles has it done since then?
It was sitting around 35 years in a garage on the east coast, up until around a year or two ago when I started working on it. It hasn't been driven more than a couple miles since then due to all the discoveries and the desire to avoid further damage. Plus, it's difficult getting around the block with 3 cylinders - even slant six and all!
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That is a tall order. Old cars eat money! The days when a Dart or Valiant was cheap and easy to fix and keep in parts are pretty much in the past.
I hear ya. I'd be curious how much value my Dart is worth as-is, at the moment vs. if fixed. As seen, the interior is in near-mint condition and I did much work. It's "just" the engine that needs attention at the moment.
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The last head I had done (1year ago) I had the valves and seats ground. Reamed out the guides and installed bronze liners and sized them properly. Lapped all valves and re-assembled with new positive valve seals. $250 total. I did not need any new valves.
That's comforting. What work did you do vs. what did the machinist do?
Author:  Rick Covalt [ Thu Apr 23, 2026 3:36 am ]
Post subject:  Re: Violent Idle When PCV Connected
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what did the machinist do?
He did it all. I did a little bowl porting before I took it to him.
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