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djkeev
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Joined: September 30, 2007
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Location: Reading Pennsylvania
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 Posted: Mon Dec 28, 2020 5:31 pm Post subject: AMC head, question & can this be reused? |
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I'm building up one good 2.1 from three 2.1’s of Unknown history and quality.
I've torn two of them apart.
One engine has original VW heads, one has a valve seat crack that extends far into the intake port,
No question, this VW head is garbage.....
That brings me to my question,
The other engine has two AMC heads of unknown age and mileage.
Judging from the layer of grease on top, it's been awhile.
The mating surfaces on both heads for the black rubber seal is like new! No corrosion what-so-ever.
No cracks between the valves either.
But....... one head has suffered a catastrophic failure!
Cylinder #1 had the intake valve break off just below the stem keeper area.
Once freed, the intake valve slid down into the combustion chamber and met the piston, when they collided the intake valve bent in multiple directions.
The bent valve was pushed up by the piston but because the valve could not slide in the guide, it pushed the valve guide up to the rocker arm.
Deeper inside the case, the hydraulic lifter has come apart. I haven't pulled the lifter yet to fully examine what happened. I suspect a bent pushrod too?
Anyway, my interest is in reusing this AMC head.
The intake valve guide is pushed up,
The valve spring area is oddly discolored and worn.
My guess is that it was driven for awhile after the stem broke and a lot of hit gasses were pushed up into the intake port and super heated the guide area.
Here are some photos,,,,,
Dave
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Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473
Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537
Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert
Last edited by djkeev on Mon Jan 04, 2021 10:18 am; edited 2 times in total |
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DanHoug
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Joined: December 05, 2016
Posts: 4798
Location: Bemidji, MN
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| Posted: Mon Dec 28, 2020 5:42 pm Post subject: Re: AMC head, can this be reused? |
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i do not like the color of that seat, tho i'm not sure what changed it. but that with the pushed up guide sends all sorts of red flags. what's the other AMC like? what's the valve guide wear like... how much shake to the valves?
you may recall this thread..
https://www.thesamba.com/vw/forum/viewtopic.php?t=711454&highlight=
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60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
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djkeev
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DanHoug
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Location: Bemidji, MN
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| Posted: Mon Dec 28, 2020 5:52 pm Post subject: Re: AMC head, can this be reused? |
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what i don't get about that color is there is no oil darkening like when you get hot spots. it's more of a hammered aluminum look than heat.
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-dan
60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
Past projects can be found at--
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djkeev
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Joined: September 30, 2007
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Location: Reading Pennsylvania
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| Posted: Tue Dec 29, 2020 6:27 am Post subject: Re: AMC head, can this be reused? |
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Things I don't like about that #1 intake.
The more I think about it, the less I think this head can be salvaged.
1) the discoloration of the Aluminum under the valve springs (inner and outer)
2) the wear pattern where the springs sit on the aluminum
3) the valve guides boss that serves as a locator for the internal spring has been beat by that spring moving around without the valve holding the top in alignment.
You can see how the edges are curled up with the wear
4) the machined area that surrounds the outer spring has been mangled as well by unrestrained spring movement
5) the guide pushed up about 1/2”
6) I slipped in one of the VW valves, that guide is no longer centered with the valve seat. One edge of the intake head has a good 1/32” gap between it and the seat.
I should probably look closer at the seat, maybe that was dislocated by the bent valve head?
The other original VW head looks really good. Very minor guide wear but no crack that I've yet seen. I'll clean it up better and will be able to see better.
If I run one AMC head and one VW head, are they similar enough in port sizes to not cause a power imbalance left to right?
Dave
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Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473
Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537
Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert |
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hdenter
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| Posted: Tue Dec 29, 2020 8:29 am Post subject: Re: AMC head, can this be reused? |
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If you are thinking of running mismatched heads, compare the volume of the compression chambers, too. I thought I remembered reading somewhere that the AMC heads have a bit more volume than VW heads.
Hans
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djkeev
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DanHoug
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| Posted: Tue Dec 29, 2020 2:43 pm Post subject: Re: AMC head, can this be reused? |
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very odd. i swear i can see that the seat is worn non-concentric.
you'd PROBABLY be ok pressing a new guide and and some serious seat cutting. the valve stem top would sit higher after that cutting and the valve should be ground down to be the same ht as the other.
or you could simplify your life and get a Corkins head all done and shiny.
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-dan
60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
Past projects can be found at--
www.thefixitworkshop.com |
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puchfinnland
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| Posted: Tue Dec 29, 2020 5:08 pm Post subject: Re: AMC head, can this be reused? |
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AMC heads that have bad seats or guides can be rebuilt into Mansi big valve heads, so do not throw them away
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Steve M.
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| Posted: Wed Dec 30, 2020 9:47 pm Post subject: Re: AMC head, can this be reused? |
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I've seen the cracks between the valve seats numerous times on good running heads, but never seen a crack going down into the intake plenum.
I myself would replace it.
https://intrepidoverland.com/shop/waterboxer-rebuilt-cylinder-head-single/
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djkeev
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IdahoDoug
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| Posted: Thu Dec 31, 2020 7:12 am Post subject: Re: AMC head, can this be reused? |
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I'd take it to a machine shop for an opinion. The guide may merely be skewed/distorted and all you'll need is a new guide and then to hand lap the valves and a new valve to replace the bent one. So no real machining, just the valve guide pressed out and back in. I can provide guidance on the valve lapping as I'm on #7 of 24 valves at the moment on another project.
Or, you may just have a full head service done to both AMCs and the guides would be part of that.
edit - I don't see an issue with the valve spring seats and the color is likely as stated - a different surface to the aluminum as its spring moved around a lot and created a polishing/resurfaced effect that's not harmful to supporting a spring and being back in service. The inner spring boss does not look unserviceable either.
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djkeev
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djkeev
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?Waldo?
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| Posted: Mon Jan 04, 2021 10:54 am Post subject: Re: AMC head, question & can this be reused? |
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Are you trying to have a properly rebuilt engine or just trying to cobble together a runner on the cheap?
If the former, then you should be replacing guides and valves anyway. If the latter, then replace the one guide and valve. I'm not sure why the rest of the wear shown would be of issue. Maybe I'm just not seeing it.
My understanding is that it is typical to have the stem rotate within the keepers which do not tightly clamp the stem. In that case, the keepers, upper spring seat, and spring will not rotate. Someone might have had the keepers clamp the stem, though, and in that case could account for the wear in the lower spring seat areas. |
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MarkWard
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| Posted: Mon Jan 04, 2021 11:36 am Post subject: Re: AMC head, question & can this be reused? |
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I don't have the WBX experience to say definitively, but most aluminum heads have some sort of metal spring seat between the head and the spring.
Also, a performance build can utilize shims under the springs to set the installed spring height. This ensures equal seat pressure on all the valves.
Worth doing a little reading about.
Everything spins in the valve train or should. It's unavoidable. I've seen some pretty cool slowed down videos of a valve train in action at high rpm.
Link
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djkeev
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DanHoug
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| Posted: Mon Jan 04, 2021 3:13 pm Post subject: Re: AMC head, question & can this be reused? |
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what does the end of the tappet adjuster look like on this valve? is it all beat up compared to the others?
the spring seat has been hammered but i don't see evidence of overheating. if the spring stayed in place after the valve stem broke, it would have gotten pushed around all kitty wampus and caused that burnished look and wear on the inner seat. i don't think that's a fatal thing, you just want to clean up the edges so they don't fatigue off.
see if you can see any marking on the other valves as to brand. since one broke, i'd be suspect of the other. most of the early AMC valve issues were with the exhausts but who knows. a new TRW intake valve is $9.
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-dan
60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
Past projects can be found at--
www.thefixitworkshop.com |
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djkeev
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dabaron
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| Posted: Mon Jan 04, 2021 3:34 pm Post subject: Re: AMC head, question & can this be reused? |
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how long was the Vanagon designed for? we've long passed that figure and any wear just needed to make it to that design requirement.
it's not being cheap, it's being cheap in the right places.
the new Subaru FB engine has a plastic intake manifold. how many years do you think that is designed to last?
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