Have you checked the compression on #7 cylinder? Almost certainly that
exhaust valve is leaking badly.
Ken H.
> Ok warmed the engine up, then pulled the valve cover.
>
>
> Yes it has adjustable lifters
>
> The #1 intake, closest to the front xould be pushed down easily, just a
> little spring pressure
>
> The #7 exhaust, closest to the back has a lot of carbon while the rest are
> clean, should I worry?
>
> I started the engine with the valve cover off and oil squirted out of #1
> so hard it hit the drivers seat! No video cause I shut it down ASAP!
>
> So what do you guys think?
>
> Obviously the lifter is bad? or is it something else?.
>
> here's a picture of the carboned rocker
>
>
[/url"]http://www.gmcmhphotos.com/photos/data/7358/20210327_133702.jpg]
[/url
> ]
>
> ________________________________
> From: Keith V
> Sent: Friday, March 26, 2021 10:45:22 AM
> To: gmclist
> Subject: [GMCnet] Re: Valve tick?
>
> Thanks!
> Firstly it does have an adjustable valve train that was put in on the
> rebuild.
> Ill pull the cover off this weekend and see what it looks like, maybe make
> a mess.
>
> I did sniff around for an exhaust leak, nothing obvious, but of course
> still possible (hopefull !)
> I run 10w30, let the engine warm up and it didnt change.
>
> The coach has sat all winter, and a lot of last summer, so who knows whats
> gone bad
> ________________________________
> From: John Wright
> Sent: Friday, March 26, 2021 9:59:05 AM
> To: gmclist
> Subject: [GMCnet] Re: Valve tick?
>
> How about an exhaust gasket leak? I had a ticking sound and it turned out
> to be a leaking exhaust gasket leak and they don’t go away, only get worse.
>
> J.R. Wright
> GMC Great Laker MHC
> GMCGL Tech Editor
> GMC Eastern States Charter Member
> GMCMI
> 78 GMC Buskirk 29.5’ Stretch
> 75 GMC Avion (Under Reconstruction)
> Michigan
>
> >
> >> So Ime hearing quite a bit of what sounds like valve tick on the
> drivers side.
> >> Just tick, tick, tick, tick...
> >> hopefully it's just an adjustment? ( yeah right )
> >>
> >> What should I look for?
> >> it's a 355 that was rebuild about 10 years ago and otherwise runs well.
> >> the last oil analysis (last spring) looked fine
> >>
> >>
> >> Keith Vasilakes
> >> Mounds View MN
> >> 76 exRoyale
> >> MicroLevel
> >
> > Keith,
> >
> > First, are you sure this is in the valve speed range. You know enough
> about engines that I think we can be sure you are good there.
> >
> > In a stock 455, there is no adjustment possible. Replacing a lash
> adjuster (lifter) is means removing the intake.
> >
> > Let's start looking at the positive side. If this developed recently, it
> could just be a single piece of micro-crud fouling one of the two valves in
> a
> > single hydraulic lash adjuster. If the coach has not had a highway pull
> recently, it could be carbon on an exhaust valve. Let hope for one of
> these.
> >
> >
> > This is actually a very common issue. Now I would ask what lube oil you
> are using. If like many of us, you are running a 15WXX, you might try going
> > to a 5WXX for a short test. I have seen cases where the less viscous
> lube oil get when the thicker did not. Given the conditions in Minnesota,
> it
> > may take a while to determine if this got it of not. The 5WXX oil will
> not have the anti-wear additives to protect the camshaft lobes, so idle it a
> > minimum with that oil fill.
> >
> > People always want to determine which lash adjuster is the issue, but it
> seldom matters. You can guess a side pretty easily, but to determine which
> > is the actual problem, you have to idle the engine with the valve gear
> cover removed. As the system lubricates the valve gear by pushing lube oil
> up
> > the push rods, this is really messy unless you get the little clips that
> go on the rockers.
> >
> > Let us know what you are doing and maybe we can provide more information.
> >
> > Matt
> > --
> > Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL,
> GMCES
> > Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum
> Brakes with Applied Control Arms
> > SE Michigan - Near DTW - Twixt A2 and Detroit
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