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  View original topic: Question about sandblasting the heads on my 1966 Type 3
lakedawgs Sat Feb 13, 2016 4:40 pm

Hello,

Have not worked on my 1966 Squareback in a long time. Hopefully that is now changing with some work on the heads.

I have lightly cleaned with degreaser and rinsed w/ high pressure water at the carwash. They look pretty good to me so far.

I had a machinist buddy measure the valve guides and they are within tolerance on the ID. I have purchased new exhaust valves.

I want to sandblast the heads. My plan was to reassemble the head rockers and springs with valves, to protect valve seats and guides, and blast away. I plan to reuse the intake valves. Will blasting hurt them? I plan to use 80 grit glass bead.

Thanks
Lakedawgs






Thanks
Lakedawgs

VWCOOL Sat Feb 13, 2016 4:59 pm

What makes you think they 'Look pretty good'?

Who told you sandblasting was a suitable process?

They have been loose and will need a slice to clean-up

lakedawgs Sat Feb 13, 2016 5:17 pm

I don't see any cracks, at this point. Compared to pics in a couple of manuals I have and online. The valves are really shiny and barely discolored on the shafts after only a wipedown. The valve seat and edges of the valves look very smooth with not pitting or burn marks. The valves also do not seem 'sunken' in the seats. Keeper grooves are nice and sharp. Valve ends are nice and flat, not mushroomed or showing a divot from the rockers.

I have also read, in multiple sources, that blasting is one of the best ways to look for cracks (with a torch). IF, this is bad info I have, that is the reason for this post, educate me.

THANKS
Lakedawgs

lakedawgs Sat Feb 13, 2016 5:19 pm

As far as 'they have been loose'. I have read that if they have been loose, the area where the barrel sits in the head will be shiny. If they have not been loose, it should be a dull grey. This area is a dull grey.

Is that bad info I have?
I don't mind getting the heads cut at all, just want to understand correctly.

Thanks much,
Lakedawgs

raygreenwood Sat Feb 13, 2016 7:17 pm

1. No sandblasting. That will destroy a head. GLASS BEAD BLASTING....is what you want.

2. Keeping valve guides with a zillion miles nust because they are in spec...is false economy. This is not a watercooled, cast iron V-8 head. They may not be worn....but at this age...thdy also may not be tight in the head....or may have cracks starting them. Just replace them.

This is also important because the guide is used for a pilot for the valve seat grinding stones. By being still in spec....but maybe toward the high side....you get a less accurate or cencentric grind on the valve seats.

3. Saving valves....especially exhaust valves is just false economy. Just replace them. Every valve has a lifespan. A lot of yours is used up.
Doing work on the heads. ..just to lose a valve at 50k miles....because it really has 135K miles on it......andchaving it beat a hole in a piston....is not a money saver. Also.....I hop you dont really mean that the valve keeper grooves are really "sharp". They are not supposed to be. They get that way from wear and fretting in the keepers.

Ray

lakedawgs Sat Feb 13, 2016 8:12 pm

Thanks for the reply
I might not have been clear.

As far as sandblasting, I mentioned the media will be 80 grit glass bead, not sand, but I did say 'sandblasting' as a generic term

The valve guide 'rock', ranges from .014-.020 on the 8 guides. Acceptable spec, as I understand is less than .030. But your logic is sound as far as guide acting as the seat for pilot stones.

I plan to replace the exhaust valves, which I have read is a must, but have read the intake valves are ok to reuse if they look good. I am guessing that is bad advice.

I have read and believe, the keeper grooves in the valve should be sharp. If rounded over, they have become worn down. Is that not right? Seems crazy, if they should not be sharp, but I am here to learn.

I know the motor was rebuilt within the last 3000-5000 miles according to the previous owner. And there are signs of a rebuild for sure. I simply tore down the motor as a matter for wanting to perform an overall recondition of the suspension, brake system, fuel line, motor, etc.

I am not at all adverse to having machine work done if needed, but if the measurements or parts are well within spec, that does not seem logical, am I wrong? Don't get me wrong, I am not here to fight with folks with a ton more knowledge about this stuff than me. It just seems odd to replace parts that are good, just because the motor is apart.

This car is a toy for me, it will never be a daily driver. If it gets 5000 miles I year, I would be shocked. While I look forward to tooling around with the wife and kid. The 'build' of the motor/car is a major part of the experience for me, and I can very likely see pulling the motor again in 2-3 years and going through it again for a few months.

I really appreciate any input I get here, this is an invaluable resource for sure.

THANKS
Lakedawgs

raygreenwood Sat Feb 13, 2016 10:59 pm

Really as cheap as valves are.....I dont ever reuse valves unless they are under 30K miles....and I installed them. ...and have had them out for something very minor and not related ro head issues.

Most valves are two piece. The heads are fusion welded to the stems. They stretch over ther life span and they fatigue. They run very high temps. Even if they are perfectly in spec.....they have a lifespan. How soon do you want to be redoing this work?

ACVW heads and valves are not known for especially high miles between complete rebuilds....compared to modern water cooled engines. At 100k miles at best.....many items are heat cycled to death. How many miles does it have on the valves?

You do realize that if a valve head pops off at highway speed the engine is junk? Vrading and measuring the condition of valves was old school economy.....balanced against the fact that reusing valves at the half life point was no big deal.....because in another 50k miles or so you are going to rebuild the engine anyway. And.....back then.....all parts needed for a rebuild even up to a new case were relatively inexpensive and available over most parts counters. Not the case anymore. Why take the risk for less tjan $100 in parts.

Examine the grooves in the valve stem carefully. They are a square cut to fit the collets.

Don't just feel them.....examine the shape and fit with the collets. As they wear...they can wear rounded. ...or they can wear thin with sharp feeling edges like little knife blades....which being thin....can easily shear off and pull through.

Also each time you regrind the valves the sit,deeper onto the seats and the higher the stems sit. You sill have do most probably do shim work on the rockers to re-establish proper valve geometry. ....at best. At worst.....you may need to get new pushrods cut to length to get valve geometry perfect.

And.....not having excellent valve geometry. ...puts side loading on the valve guides.....which wears them faster....and easily exploits any cracks that may be starting unseen.....which can commonly cause exposed guide material in the ports ro crack off and get sucked into the engine.

Its not just if parts are in spec......its how old they are and how many miles.

Pistons in spec.....I would reuse. In a stock build....a piston is not liable to fail catastrophically with age. It may have skirt collapse and start scuffing and burn oil....but thats just a teardown and rebuild. You snap a valve off and its 50/50 whether the whole engine is toast....or just need a new head, bearings, one piston and cylinder and a new oil cooler.

Just have the heads completely redone. Ray

lakedawgs Sun Feb 14, 2016 10:58 am

OK, blasted the heads, happy with the outcome. Torched the areas where cracks can appear, between the valves and plug holes, everything seems solid.
I am, however, going to go ahead and have the valve guides replaced and valve seats checked out. Valves were a bit 'cruchy' when I pulled them out due to glass bead. I have only used a blaster for general rust removal and as told, that stuff gets everywhere!! I forgot what a nasty job that is.
Will drop the heads at my machinist hopefully in the next couple of weeks.

Thanks
Lakedawgs



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