Who Has tried installing valve seats?

[rustybutterknife]

Looking to discuss installing valve seats with someone who has done it before. Successful or not. Type 1 or 4 doesn't matter.

[Amskeptic]

Looking to discuss installing valve seats with someone who has done it before. Successful or not. Type 1 or 4 doesn't matter.

I don't think we have any machinists here. We do have a lot of "information" that has been shared with us over the years, and with the serious consequences that come with dropped seats, there have been some heated exchanges regarding the *causes* of valve seat drops.

The factory had a two-stage process of chilling the actual seat, heating the aluminum head casting and installing with an interference fit of .003-.005" ? ( seems to be a proprietary secret). As the two subsequently arrived at the same temperature, the seat would expand while the aluminum shrank around it and this would give you seats that were locked in place. With later VWs under the additional stress of emissions-mandated hot operating temperatures, the factory added another step of sweging the aluminum around the seat, you can see punched arcs embedded in the aluminum surrounding the seat.

I trust factory seats implicitly. I have never had a seat failure in any Volkswagen engine under my care, and I drive my engines all across the country on interstates and into Death Valley in July with confidence.

With the understanding that there is no real world occasion where you could possibly match the initial installation temperature differential (of chilled seat insert and hot head casting), why do these cars have reputations of dropping seats?
A) overheat a VW engine waaay past normal operating temps and you deserve what's coming
B) cracks in the head from overheating and rapid overcooling that reach the seat circle
C) aftermarket experts are often selling bigger valve sizes that require "field-installed" new seats that are not installed with correct interference at correct temperature differential, or, there is inadequate head material remaining to prevent distortion that unclamps the insert.

I personally have not run a VW engine with anything less than factory seats in heads that have not shown overheating (except the Road Warrior which had so many cracks through exhaust ports, seats, spark plug holes, unbelievable, it was an embarrassment, but those heads wanted to live! so they did)

Soon, however, I will be putting some field-installed seat heads back into my 1600 Type 1 bus, and some day I will likely need seat work on the 2000 Type 4 bus but don't hold your breath. The used original single port heads I put in the 1600 seem awfully happy, and the 2000 engine is a baby at 85,000 miles.

Did anything get answered here?
Colin

[Bleyseng]

Its seems the type 4 1700 heads were robust and had extra metal to help hold them in. 2.0 L are thinner under the seats and prone to cracks as I had cut away pics showing this. The two gurus of heads now use a different seat material that matches the expansion better than the VW scintered seats. That is what makes the difference besides installing them with the proper heating and cooling.

[72Hardtop]

Its seems the type 4 1700 heads were robust and had extra metal to help hold them in. 2.0 L are thinner under the seats and prone to cracks as I had cut away pics showing this. The two gurus of heads now use a different seat material that matches the expansion better than the VW scintered seats. That is what makes the difference besides installing them with the proper heating and cooling.

Lenn Hoffman has also confirmed that the AMC castings have more material (comapared to the OE VW heads) in critical areas of the head which offer better resistance to cracking. The seats also hold much better with this added material.