TheSamba.com :: View topic - Valve

Tue Nov 18, 2008 9:37 am

73, great shape. Type IV engine. Owned for 1 1/2 years - 8k miles by me. PO says it was rebuilt prior to his purchasing, so it would have about 15k-20k miles on engine.

It runs great - perhaps slightly hot lately, which is why I adjusted the valves this morning.

While adjusting, I noticed that one of the valves? on #2 was sunken in a bit (#4 has been that way since I bought it) - what I mean is that there is a dip so that the feeler guage bends a bit toward the engine.

I have read the posts and although I can assume this is a problem, I am trying to figure out the problem and the scope of the problem. From what I have read, it seems like a "sunken valve" is one that sticks up?

Mainly, is this something to get repaired immediately or in the intermediate term?

Tue Nov 18, 2008 10:03 am

Classic case of a "dropped" valve - or sunken valve. Yes you need to get this fixed imediately --- but aside from that you need to treat the cause more than ever once this is fixed.

Type IV engines run HOT compared to the Type I. It is imperative that you get the temps down no matter what. Propper induction, timing, cooling systems are critical. HOT is anything over 400. Average temp on a stock engine should be around 380 at 65-70.

Bascly the heads need to come off (BOTH) - and send them to Adrien at Headflowmasters - or order some new heads from Jake Raby since your bottom end is relatively new.

Do NOT drive until this is fixed - the valve could snap off and "grenade" the engine.

Tue Nov 18, 2008 11:15 am

Thanks. Any idea of cost? Maybe more importantly, how involved this is? I have replaced drag link, added guages, added SVDA, electronic points, etc., but have never done any "real" engine work. Does the engine need to come out?

On the heat side, I don't think heat is an issue - at least anymore (other than caused by the valve). Damage was probably cause prior to my purchase. Although the engine was rebuilt, the PO didn't have any guages (not even oil pressure). I have added oil pressure, oil temp and CHT on #1 (#3 threads are bad), replaced seals, etc. and although CHT sensor is on #1, I never see 400 degrees unless going up mountains. Usual cruising (55-60mph) temp is 340-350 (VDO) although lately more like 350-360.

Tue Nov 18, 2008 11:29 am

If the seats are sinking into the head, or if the valves are stretching then that valve would be losing clearance very quickly. The valve adjustment screws do wear and that will cause a feeler gauge to seemed cocked.

Tue Nov 18, 2008 4:14 pm

Not sure what you are talking about from you description. Are you meaning that the end of the valve stem is cupped? If so this is very different from a recessing valve. What do you mean when you say the feeler gauge bends towards the engine?

The head of the valve stem should wear flat, but sometimes they don't and will wear badly concave.

Tue Nov 18, 2008 9:46 pm

Wildthings wrote: Not sure what you are talking about from you description. Are you meaning that the end of the valve stem is cupped? If so this is very different from a recessing valve. What do you mean when you say the feeler gauge bends towards the engine?

The head of the valve stem should wear flat, but sometimes they don't and will wear badly concave.

you describe what i thought he meant also: if he concurs, what difference would that make to the valve wear? Cupping instead of flat? Any?

dp

Wed Nov 19, 2008 12:06 am

dweller wrote: Wildthings wrote: Not sure what you are talking about from you description. Are you meaning that the end of the valve stem is cupped? If so this is very different from a recessing valve. What do you mean when you say the feeler gauge bends towards the engine?

The head of the valve stem should wear flat, but sometimes they don't and will wear badly concave.

you describe what i thought he meant also: if he concurs, what difference would that make to the valve wear? Cupping instead of flat? Any?

dp

If they are cupped you can not adjust them with any level of accuracy. You must remove the rockers, and use a die grinder to reface them smooth. You also probably will need to replace the adjusting screws.

They will wear to a cup if there is not sufficient offset in where the adjusting screw contacts the head.

Wed Nov 19, 2008 8:56 am

Wildthings wrote:

If they are cupped you can not adjust them with any level of accuracy. You must remove the rockers, and use a die grinder to reface them smooth. You also probably will need to replace the adjusting screws.

They will wear to a cup if there is not sufficient offset in where the adjusting screw contacts the head.

okay, that i can see, but if the OP is experiencing a cupped valve stem end, this is or is not any relation to a 'dropped' or 'sunken' valve, which is being diagnosed in responses above.

was looking in the gallery for a pic of what he's describing and can't find one, perhaps someone has a pic. I found this schematic of the offset:

now this offset should produce a pattern running around the stem end, correct? at least mine has them on the ends and have believed it to be normal.

perhaps the OP will chime in and clarify.
dp

Wed Nov 19, 2008 9:24 am

Thanks guys. Let me make another stab at this. Bear with me - this just reminds me how much I don't know.

The surface where the adjusting screw meets the valve (stem, I would think) is lower than the surrounding "dish" which sits on the valve spring. Basically, the "stem" is getting shorter so when the feeler gauge is inserted between the screw and the stem, it doesn't lay flat, but bends in the direction of the valve stem.

This is the case with both valves on #4 and one valve on #2.

Wed Nov 19, 2008 9:29 am

Tooster wrote: Thanks guys. Let me make another stab at this. Bear with me - this just reminds me how much I don't know.

The surface where the adjusting screw meets the valve (stem, I would think) is lower than the surrounding "dish" which sits on the valve spring. Basically, the "stem" is getting shorter so when the feeler gauge is inserted between the screw and the stem, it doesn't lay flat, but bends in the direction of the valve stem.

This is the case with both valves on #4 and one valve on #2.

Your keepers and/or the valve stems themselves are failing. Do not drive it another mile as a dropped valve is imminent.

Wed Nov 19, 2008 9:32 am

That's not good, a keeper is slipping, the spring cap is wearing or the valve itself is wearing. All of the above can lead to the valve coming loose and getting sucked into the cylinder, believe me it's not pretty.

You can remove a valve spring in place with the head on, it's worth having a look to see what's going on. You may get away with just some new caps and keepers.

Wed Nov 19, 2008 9:58 am

I will pop the covers tonight and try and take a picture. I didn't say this before, but I don't think it is the case in which the stem has been hammered down and is flatened out creating the gap, but that the stem is simply "shrinking" - or sinking.

What would be the cause of this since I have this in 3 valves? Doesn't sound like this is typical.

I need to read up on the keepers and figure out what I can and can't do myself. Any advice on the skill level of that work?

Do I start there and see what I can do or do I start thinking about replacing the heads. While I am asking, can the heads be replaced without pulling the engine?

Wed Nov 19, 2008 10:11 am

only a good vw shop will have the spring compressor tool you would need to be able to do this with the head still in place.

take some good pics and get them posted, im sure others will be able to help you decide if you can do this yourself or not, but based on the possible downside of one small detail for this job, id leave it up to professionals or you'll be shopping for a rebuild sooner than you want.

Wed Nov 19, 2008 11:28 am

AMC heads use cheap components. Especially if you have the stronger valve springs that are designed for use with hydraulic lifters the keepers, retainers, and the valves themselves are all of cheap material that will fail early and often. Getting the heads rebuilt with better components is the way to go.

Thu Nov 20, 2008 6:04 am

Quote: Getting the heads rebuilt with better components is the way to go.
The ONLY way to go with the AMCs.

I threw away a 55 gallon drum of valves, seats, springs, retainers and valve guides that came from AMC heads last year alone... I NEVER use these components, not for any level of engine preparation- not even bone stock.

Thu Nov 20, 2008 7:50 am

After you get this fixed, consider installing a good cylinder head temp gauge to avoid it happening again.

Thu Nov 20, 2008 8:07 am

I don't know what heads I have or if they are AMC's. However, since the pan is to keep the 1DER BUS forever (hopefully), it doesn't look like a band-aide approach makes any sense and is too risky.

The problem is I really don't know what shape the engine is in (compression check tonight) to find out. It seriously looks new and supposedly only has 15-20k on it. I just don't know what the PO did?

As fearful as I am in taking the engine out since I have never done it (I read about it and it doesn't look too hard) at a minimum, it seems like I need to drop the engine and take off the heads and have them replaced.

So the $1000 question is - for someone still trying to make sense of all of this - exactly what heads do I buy (assuming everything else piston, etc. are fine) Exactly the same?, what type of valves, sodium filled? That is all greek to me. I have read the threads and it sounds like I should buy from Len at HAM or Headflowmasters. I am in NC, so HAM may be easier/quicker.

You guys are amazing. Jake, I read your website last night for at least 2 hours and definately want to go that direction eventually (it's a when, not an if).

Thu Nov 20, 2008 8:24 am

Randy, on the CHT guage, that was the first thing I put in after buying the bus last year. The sender is on #1, since the #3 plug was difficult, but since that time, it has only approached 400 a couple of times (blue ridge mountains) and runs at about 350 at 55-60 mph.

That being said, I am concerned about why this happened. I could blame it on the PO - who told me he drove it at 65 all the time - with no working oil pressure light (red flag yes, but the rest of the bus is pristine and I know a lot more now than I did then) - I actually fixed that 1st and put in a VDO pressure gauge too.

Basically, I have been a freak about heat since I bought it. Tin is perfect, but I plugged all the holes, shifted to an SVDA from an 009 that wasn't advancing correctly, heater tubes loose and leaking, plugged pre-heater tube (on a 73), religious about adjusting the vales. 2 of the 3 problem vales were there when I bought it, the 3rd one seems new, but maybe more noticeable, since I know more now.

Can I blame the PO, or is it simply a case of the heads may not have been that great to begin with?

Thu Nov 20, 2008 8:34 am

Quote: So the $1000 question is - for someone still trying to make sense of all of this - exactly what heads do I buy (assuming everything else piston, etc. are fine) Exactly the same?, what type of valves, sodium filled? That is all greek to me. I have read the threads and it sounds like I should buy from Len at HAM or Headflowmasters. I am in NC, so HAM may be easier/quicker.

www.aircooledtechnology.com/cylinderheads.htm

The 7416, 7424 and LE 160 heads are the only units listed that are designed for a Bay Window Bus application.

Not even our race engines see as much heat and load as the heads installed onto an engine pushing a sub 5K pound Bay Window Bus.

Thu Nov 20, 2008 8:35 am

do not drive the car until a professional VW mechanic looks at this. If you can see the valve moving deeper into the retainer or mushroomed then something is about to happen.

Either the keepers are failing and this is causing the retainer to get ready to pop off resulting into the valve dropping into the cyl and destroying the engine, OR you have some kind of piston to valve interference going on which is hammering the valves. Either way what you are describing is a catastrophic failure about ready to happen.