Type 4 engine forensics

[furgo]

[curtp07]

This thread is sort of like Clash of the Titans!

All the Greek VW Engine Gods were dragged out of hiding for this one!

Furgo love your posts!

IMHO this did kind of morph to more of engine rebuilding performance..agree with Steve.

Thanks all! This kept me reading for a while.
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Subaru

[SGKent]

Furgo is a great guy and this is a great thread - just probably should have gone to the engine and performance section since it is about discovery and theory. I appreciate Furgo's curiosity.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[furgo]

I'm happy for the thread to be moved wherever it's most appropriate. I've double-checked and I can't do it myself, so perhaps one of the moderators can (TCash, Glenn?).

Should we ever meet, I'd be equally happy to buy a round for all the fine gentlemen in this thread.
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'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)

Decode your M-Plate

[curtp07]

If I have a break while I'm in Hahn I'll take you up on that.
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Subaru

[Xevin]

[Clatter]

Med cart comes by,
Nurse hangs a fresh colostomy bag,
Hugs all around..
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Bus Motor Build

What’s That Noise?!?

[SGKent]

[orwell84]

[Xevin]

^^^^That’s some pretty funny shit right there
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Keep on Busin'

[dawie]

Alan Brase wrote...(On page 5):

"I have always thought it surprising that a factory new air cooled Vanagon could usually make it 100-150k miles, then even after a quality rebuild, would be having head problems within the next 40k miles."

Could it be that typically, at the time, heads got new guides and valves. Seats that seemed tight (when cold), only got cut. But in the meantime, unknown to the rebuider, severe thermal cycling has taken it's toll.
Doing the thermal test i found that seats which still seems tight even at 320F could be loose at max operating temp. Especially the intakes. (400F, using "circlip pliers meant for outer circlips", trying to turn seat in circular direction).

Maybe if seats were replaced each time as default, (to re-establish proper interference fit), things would have been different.

Severe thermal cycling over long time, especially while near upper limits of cht.
Heavy loaded bus doing mountain-driving, full throttle in third uphill, max cht, then steep downhill, foot off the throttle, engine braking in gear. Cooing fan blowing huge quantities of cold air over hot heads. Repeating at next hill.

A prominent rebuilder of type 4 heads once advised on a 914 forum: "Never let the engine idle between races. After each race, put in neutral and switch off immediately, coast to a stop."

[Wildthings]

[Abscate]

[Xevin]

[Abscate]

I'm still waiting for one of those hot 50-something women to come by and woo my tardy spring....
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.ssS!

[furgo]

[Clatter]

Hot 50-somethings?
That's an oxymoron!


Parting lines made during the casting process;
Pay no mind.
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Bus Motor Build

What’s That Noise?!?

[furgo]

[raygreenwood]

Yes.....the lines you are seeing are mold parting lines. In some places in some castings it is good to smooth these lines as they can help propagate cracks with age. I have never seen that the lines you are mentioning cause a problem.

Yes.....the tips of the valves "mushroom" from wear a very small amount so they catch or get tight when pulled through the guides. The harder the tips the less of this you get....but even stellite tips and/or hardened welded insert tips (most factory valves were this way) eventually get a small amount of expansion at the tip.

Using Porsche swivel feet virtually eliminates this expansion. Typically if valves are being reused a quick facing grind to the tip taking off just a few thousandths will remove this swelled part.

As to the longevity of the heads being less after rebuilds.....as Wildthings and Al Brase were pointing out....it is due to heat cycling. Any casting only has so much lifespan. Just rebuilding the parts attached to it only refurbishes the machined surfaces.

This is some of the same issues with reusing pistons with high miles even though they measure perfect at skirts and ring lands. They will be fine for now.....but realize that in heat cycles....they may be halfway or more to "skirt collapse"...so do not expect as-new mileage.

You CAN totally reset the heat cycling of an aluminum head to like-new condition.....but the process is not as common to find as it once was.....and is likely expensive enough that it would be cheaper to just get new castings.

It is still a common process in high end racing machine shops where a pair of specialty raw aluminum castings for a V-8 can run several thousand of dollars each and then had massive amounts of labor invested for porting work.

This process is also used when aluminum heads are heavily reworked with welding. Those heads have to be re-annealed.
They are placed in an oven ....after all ferrous metal has been removed....and brought up to temperature. Aluminum can be cooled down quickly but it can change surface planarity on machined surfaces......so the head seating area and sometimes the intake and exhaust manifold mating areas needs to be re-machined.

When they are worried about this for aluminum heads....and for all cast iron heads.....after the oven heating process.....the heads are submerged in a box of vermiculite (not used as much now because its carcenogenic)....or mica.....and allowed to cool slowly over 24 hours

I got to see this process on a pair of Brodix heads over Christmas. Very cool.

The only way this would be affordable....or practical.... to do on a VW head is if you say....needed to have an actual 2.0L 914 head for a concors restoration. If you have the budget.....after you weld up the cracks that these heads have and them remove all studs and seats......its the only way to make the head perform "as new".

The oven heating cycle is not the expense. They cook at 750°-780°F for 3 hours, then cool down at 50° per hour until they hit 500°F....then just let them air cool. Its not like they take any labor to do this. Just set the oven and the timer.

It's the much added cost of installing all new studs and seats and machining the head sealing surface.
If you have a special head you want to save and make like new.....and you strip it snd pull seats and studs yourself.....and take it to a racing machine shop that has the tools.....you can probably get the annealing done for about $200 or less. Then take it to your regular VW shop and have a normal valve job with new seats installed.
Then do all of the studs yourself.

In that case....you may get away with only a couple hundred more than a full valve job. As usual it depends on how much you can do yourself. Ray

[SGKent]

you spin the valve with your fingers while you hold a mill file against it. That will remove any burrs formed on it from the rocker screws or keepers. Failure to do that and forcing the valves thru the guides will damage the guides. You hold a valve open about 3/8" to 1/2", if you feel any wiggle then the guides need replacement. Because each guide is slightly different the valve seats must be reground if the guides are replaced.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin