Staked Valve Seats

[lalkie]

I have a 65 corsa 140 and am considering a valve job. Does anyone have any experience with staked valve seats. It appears as if the sharp points produced around the seat would create hot spots. Is this a concern? With deep cut seats do valve springs need to be shimmed? Do 140 engines have a problem with dropping valve seats? Any help would be appreciate. Thanks Larry

['stitch']

http://www.americanflat6.com/
http://www.americanflat6.com/products/t ... heads.html

Tom does Excellent work!

[bbodie52]

Here are some opinions from a brief Corvair Forum search...

» Fri May 05, 2017 12:48 pm

I don't have my seats staked. It doesn't work. I have had seats replaced on a pair by Michael Leveque and on another pair by Tom Knoblauch. The heads that are on my stock turbo engine were done by a shop out in LA that the name is slipping my memory. The heads on my new turbo engine that I am putting together were done by Tom along with some custom welding of the chambers to adjust the quench without having the issues you have when milling them down to the step...

» Wed May 03, 2017 10:50 pm

You will get mixed reviews on Starr Cooke by a lot of the racers. He is known for staking stock seats which will still fall out.

» Thu May 04, 2017 7:53 pm

Just because the last ones lasted 150k does not mean the current set will. Some dropped seats when they were still relatively new or lower miles. Most 140 heads are now 48-53 years. You don't know the history such as whether they were overheated. I have lost several seats over the years. Any Corvair engines I build that will be driven long distances get new high press deep seats done by someone reputable. Just saying....

» Wed Dec 11, 2013 1:16 pm

...But to repeat what the others stated, staking the stock seats is a waste and doesn't guarantee a seat wont fall out.......regardless of what people will tell you. Nothing beats a properly installed deep seat.

» Wed Dec 11, 2013 2:11 am

staked valve seats wont help much - if at all.

» Tue Dec 03, 2013 10:05 am

Of all the 140's I've had over the years I can say I've never dropped a valve seat. Only one set of 140 heads I own were staked and that is because the shop that did my valve job insisted that it be done. There are a LOT of people in this area that have run the 140's in dune buggies and sand rails for 35-40 years and his shop specialized in VW and Corvair head work. If he said to do it, then I did it. I could not afford deep seats at the time and I don't regret the decision to have him stake the seats. His experience level with 140 heads was far greater than mine. I don't believe that the staking process produces hot spots of any significance. The electrode tip of a spark plug hanging out in the cylinder will have far more residual heat than a small ridge of aluminum that is heat sinked to a massive aluminum head.

If you want to learn more there is also a process where each valve is retained with set screws but that is not an easy fix either. Here is one such post. There are probably a dozen more about the set screw process.
http://corvaircenter.com/phorum/read.php?1,519403

I often heard that people who dropped seats were often just completing a long hot run up a hill or on the freeway and then used engine braking coasting down a hill or coming to a stop on an exit ramp. This makes sense if you have a hot head and the valve seat is suddenly cooled by massive amounts of incoming air from engine braking. A hot head has expanded so the cool seat shrinks and comes loose. I adjust my driving accordingly and use the wheel brakes instead of downshifting and engine braking if the engine has just gone through a workout. Who knows if it actually helps or not but I've never dropped a seat and I mostly have owned and driven 140's more than any other engine.

» Fri May 21, 2010 1:47 pm

Ronnie -- I always wondered if staking might cause hot spots and preignition

If you wanna stake them you can do it with a small punch and a hammer...

I did it years ago on my old blue 67 after I dropped one seat . I had the seat replaced and then staked them all. Never had another fall out after that.

[davemotohead]

IMO staking the seats does create hot spots that carbon can hide in and glow, also IMO staking actually loosens the seats in the head by destroying the integrity of the aluminum surrounding the seats, I have found numerous heads with dropped valve seats that were staked, the only sure way to keep them from dropping is to have a High press deep seat installed properly by a good reputable shop.

[66vairguy]

As already mentioned "staked seats" has been discredited as a proper fix after years of experience. The staked seats can come loose and hot spots are an issue.

Some of the confusion comes from attempting to make the seats fit tighter. No matter how "tight" the seats are installed (or later staked) as soon as the aluminum around the seats goes through a few thermal cycles of expansion and contraction the aluminum "grip" on the seat normalizes. The only fix that has proven reliable is a deeper seat that provides MORE contact area of contact between the seat and aluminum head.

Of course if you overheat a head even a deep seat can come loose.

The question about seat depth and valve height is valid and this is why you want to find a shop that has experience with Corvair heads.

[lalkie]

Thanks for the help. Looks like staked seats are out. I will talk to the shop I am planning on using to discuss deep seats and valve height. Thanks again. Larry