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Violent Idle When PCV Connected
https://www.slantsix.org/forum/viewtopic.php?t=68306		 Page 5 of 6
Author:  SlantSixDan [ Thu Apr 16, 2026 4:25 pm ]
Post subject:  Re: Violent Idle When PCV Connected
No, it's leaking past the threads. The threads are not the seal; the flare and its seat are. Piece of crud preventing a full seal? Faulty flare? Find/fix.
Author:  morsim [ Thu Apr 16, 2026 6:02 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
No, it's leaking past the threads. The threads are not the seal; the flare and its seat are. Piece of crud preventing a full seal? Faulty flare? Find/fix.
Thanks for the info, did not understand that mechanism till now.
No crud or build up. Might be faulty but I wouldn't know the difference... Old stock flare was no problem
Author:  Rick Covalt [ Thu Apr 16, 2026 6:52 pm ]
Post subject:  Re: Violent Idle When PCV Connected
So your barb fitting is inverted flare on the inside? If yes, then with both fittings being brass they should seal up with no problem. Check for any burrs or dings at the sealing surface. If that is Ok then I would use two wrenches, tighten, then loosen, tighten then loosen multiple times and try and get the two surfaces to seat better to each other.
Author:  morsim [ Fri Apr 17, 2026 1:17 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
So your barb fitting is inverted flare on the inside? If yes, then with both fittings being brass they should seal up with no problem. Check for any burrs or dings at the sealing surface. If that is Ok then I would use two wrenches, tighten, then loosen, tighten then loosen multiple times and try and get the two surfaces to seat better to each other.
No dings, looks clean... Tried but it's just not making a good seal.
For now, I've hooked up the old short flared metal line - which kinda defeats the purpose - till I can go out and figure it out.
Otherwise, I've been able to start er up but it's QUITE shaky at warm idle (~750rpm). I haven't yet adjusted the mixture screw properly since the carb rebuild, and that's likely contributing or is the issue. BUT it's just TOO ROCKY! I can't get the flathead to stay in the mixture screw!

I don't believe I hear any misfiring, but could be wrong. This guy (heat control valve?) is also shaking around and banging against the stop pin making a racket. Should something be connected to that? I don't remember
UPDATE: Looking at the other end, seems like the anti-rattle spring might be missing - could that intense rattle cause intense rough idle?
Author:  morsim [ Fri Apr 17, 2026 3:37 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Let me take a step back here a sec.

Looking back in our pre-hiatus thread history, I had posted clips of the exhaust smoke and engine view. Being that there isn't much change in it's current running state, I'm going to do as Rick & Dan suggested here (adjust valve lash) and here (testing which cylinder is possibly misfiring by pulling plugs & pics of plugs).

Sounds like a plan? Or has anything I posted thus far since then indicated that different diagnostic steps should be taken?
Author:  Dart270 [ Sat Apr 18, 2026 4:27 am ]
Post subject:  Re: Violent Idle When PCV Connected
Yes, definitely do the "pull a plug wire" test and definitely adjust the valve lash. Tight valve lash is a very common cause of rough idle and stalling.

Lou
Author:  SlantSixDan [ Sat Apr 18, 2026 1:53 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
No dings, looks clean... Tried but it's just not making a good seal.
Reminds me: about 25 years ago when I bought a box of ten of those fittings, there were two in it that failed to seal exactly the way you describe. They looked fine but didn't seal. The other 8 sealed just fine.

Parts quality has declined very badly since then, across the board.
Quote:
This guy (heat control valve?)
Yes.
Quote:
is also shaking around and banging against the stop pin making a racket. Should something be connected to that?
No.
Quote:
Looking at the other end, seems like the anti-rattle spring might be missing
Yes, it is.
Quote:
could that intense rattle cause intense rough idle?
No.

Valve adjustment should be your first next step.
Author:  morsim [ Mon Apr 20, 2026 2:03 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Oh man, here's the development.

I removed the valve cover to adjust lash, and you wouldn't believe it; the pushrods for intake valves 1,5,&6 are off the rockers (and 5 is bent). The valves feel stuck as well. They don't move. Engine is only running on 3 cylinders!

Now this is shocking because I've done a decent amount of work on the head thus far.
See exactly what was done here)
Including, all new intake valves, seals, cleanup, etc.

What's strange: these were the same valves that got stuck and bent BEFORE the head work (that prompted the job in the first place).
I'm utterly stumped!

My buddy had done most of the valve work, and he reported that after the job, there was a nice flow of oil from the rocker arms... Here's a picture of what it looks like now: https://i.imgur.com/ddYozea.jpeg - does it appear lacking? Is it seizing due to lack of oil? Old gas clogged it from before I swapped tank? I had new fuel filter...
What can I do to unstuck them, permanently...

I would love to understand what's going on :|
Author:  SlantSixDan [ Mon Apr 20, 2026 2:37 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
I removed the valve cover to adjust lash, and you wouldn't believe it; the pushrods for intake valves 1,5,&6 are off the rockers (and 5 is bent). The valves feel stuck as well. They don't move. Engine is only running on 3 cylinders!
Oh, no! Well, at least you've found the cause of the crummy running, and that's a start.

[quoteNow this is shocking because I've (replaced all intake valves and 2 exhaust valves)[/quote]

Okeh, but I don't see where you paid attention to the valve guides. And since we're on the subject:

• How did you mate the new valves to the head? Did you…have a valve grind done? Lap them in? Neither?

• What attention has been paid to the valve seats? Assuming you're working with the car's original head, it was made before induction-hardened exhaust valve seats entered production. Slant-6s with soft valve seats are more tolerant than some other engines of a steady diet of unleaded fuel, but they're not immune to its effects.
Quote:
What's strange: these were the same valves that got stuck and bent BEFORE the head work
Points at guides and/or inadequate oil.
Quote:
My buddy had done most of the valve work, and he reported that after the job, there was a nice flow of oil from the rocker arms... Here's a picture of what it looks like now
Where is all this nice-flow-of-oil your buddy talks about? I sure don't see it; that top end looks dry. Even after engine shutdown and it's been sitting awhile, there ought to be much more oil up here than we see. (Also, what's with the weird removal of all colour from the pic except in a blotch in the middle? Regular full-colour photos make it easier to spot problems.)
Author:  Rick Covalt [ Mon Apr 20, 2026 3:47 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
does it appear lacking? Is it seizing due to lack of oil?
Did you oil the valve stems when they were installed in the guides? Yes the top end looks non oiled???
Author:  morsim [ Mon Apr 20, 2026 4:12 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Unsure about how the valves were seated, and my buddy doesn't remember. I'd assume he lapped them in, but unsure.

Yeah, not sure what happened in that pic, here's a vid: https://imgur.com/a/5Sirzoo

Even if bad oil flow, isn't it quite the coincidence that the same exact valves failed?
I managed to get them a bit loose to the point where I can press down (hard) to move a little, but they feel sticky and when I press, only the pressed side goes down. I noticed when pressing the other working valves, the whole valve-spring-metal-surface moves down evenly...
Perhaps some gunk in the intake manifold that's consistently making its way in?
Author:  Rick Covalt [ Mon Apr 20, 2026 4:21 pm ]
Post subject:  Re: Violent Idle When PCV Connected
It sounds as though you did not have the valve guides checked or replaced. If they were tight / seized before and they were not replaced or had liners put in then they may be seized again.
Author:  morsim [ Mon Apr 20, 2026 5:00 pm ]
Post subject:  Re: Violent Idle When PCV Connected
Quote:
It sounds as though you did not have the valve guides checked or replaced. If they were tight / seized before and they were not replaced or had liners put in then they may be seized again.
Can I confirm this without having to remove the head yet again? I'm getting tired, but really do not want to give up.

I have in my notes from the valve work that the "guides were cleaned".

I will be away now again for a couple months, and I'd love to compile a solid task list for when I get back - but within a mediocre budget :shock:
Author:  Rick Covalt [ Mon Apr 20, 2026 7:08 pm ]
Post subject:  Re: Violent Idle When PCV Connected
I hate to say it but I but think the head is going to have to come back off. If it has seized 2 times then something is wrong with the guides or the valves. I think you are fighting a loosing battle. When I have a valve job done it does not cost that much to have bronze liners pushed in and sized properly for the valves. Then you are all set. But you have to have the head off again to do it. Sorry.
Author:  morsim [ Mon Apr 20, 2026 8:27 pm ]
Post subject:  Re: Violent Idle When PCV Connected
I really do appreciate your advice, there's no need for the apology - this is on me for not doing it right the first time 'round.
I'll only be back when it's sticky and hot out, so not the most fun for a job like this. But I'm determined to get her back on the road. I've done so much and can't give up now.

Now, can you please elaborate on the process for the guide work? Explain-like-I'm-5, please.
Will it need machining? (The last shop I went to didn't have me feeling confident in their work, thankfully it was just a cleaning. Will need to find a different shop if so).

And perhaps, anything else I should keep my eyes open for once the head is off.
I'm a visual learner, so if you've got any resources of your own/on the Internet, then, well, a picture is a thousand words; and a video is 60 pictures, per second - so kindly share.
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