Exhaust Valve Seat

[DJ S]

I have a damaged hardened valve seat (1.625”).. It will need to be increased to the next size. Is there enough “meat” in the block to accept a 1.750” valve seat on #4 exhaust?

[Kurt in NJ]

40-6057-D, 1.6330/1.6335. For V8,
Some people adjust the outside diameter to fit the hole too

[Pete]

Originally Posted by DJ S

I have a damaged hardened valve seat (1.625”).. It will need to be increased to the next size. Is there enough “meat” in the block to accept a 1.750” valve seat on #4 exhaust?

The OD of a new seat ring does NOT necessarily have to be that big.
A simple sonic test should show how much meat is left in the area.
If the shop you are dealing with can not figure that out, you need a different shop.
That is a simple fix.

[DJ S]

This is the problem. The machine shop that originally did the work didn’t cut the seat concentric to the the guide. The guide was loose enough that it allow the valve to seal enough for a few thousand miles. It eventually bent the valve.

It an attempt to grind the seat gently, it sunk the seat way quicker than expected. I then tried to follow with a relief cut of 30 deg but i obviously got way above my head.

I stopped.

But the damage I did is already beyond the 1.625” seat. See pic. I didn’t go deep but there will be a very shallow pocket with a replacement seat unless enlarged to 1.750”.

Leason learned. Sometimes it’s best to leave it to the professionals… even when it involves pulling the motor.

[BRENT in 10-uh-C]

Adding to the number Kurt gave you, I also show that a SBi # ASB1640E-1 has an OD of 1.6395" and should be a pretty popular insert. None-the-less, you will need to find a machine shop that has an adjustable seat cutter along with the correct guide pilot.

[Marshall V. Daut]

Sponsored Links (Register now to hide all advertisements)

Failing a machine shop fix, try Sleeve Locker around the circumference of the seat. It used to be called Loctite 640, I believe. Whatever its new name and manufacturer is (Permatex?), once it sets up, it takes a torch to loosen the grip, far hotter than the engine temperatures will ever reach. It has saved me at least once on a cross country trip when a loose hardened valve seat kept coming out of its bore. The "glued" seat stayed in place for years afterwards until I upgraded to a stronger engine.
Because your seat was not cut properly in the block, you will have some wiggle room with the new seat. Coat the outside circumference of the new seat with the Sleeve Locker and set it in place. Install the valve with spring and keeper to apply downward pressure. The valve in its guide should center the new seat in its bore. Allow to cure for at least 24 hours, longer would be better.
This is a recommendation only if no machine shop can repair the error properly and it looks as if the block will have to be discarded. Naturally, a machining operation would be preferable. But if that is not practical, try the sleeve locker route. It just might save the engine and you a ton of money and hassle replacing it.
Marshall

[BRENT in 10-uh-C]

Originally Posted by Marshall V. Daut

Failing a machine shop fix, try Sleeve Locker around the circumference of the seat. It used to be called Loctite 640, I believe. Whatever its new name and manufacturer is (Permatex?), once it sets up, it takes a torch to loosen the grip, far hotter than the engine temperatures will ever reach.

This is a recommendation only if no machine shop can repair the error properly and it looks as if the block will have to be discarded. Naturally, a machining operation would be preferable. But if that is not practical, try the sleeve locker route. It just might save the engine and you a ton of money and hassle replacing it.
Marshall

Umm Marshall, are you sure this is the product to use?

I vaguely remember you having engine issues with your Cabriolet some years ago but I gotta tell you that Sleeve Retainer is only good to about 400°, ...and combustion cylinder temps will easily be 3 to 4 times that amount on a Model-A engine, -especially around an exhaust valve.

I use a product called Fluid Weld for valve seat sealing that is supposed to be good for temps up in the 3000° range, but even then it would be dicey on one that does not have a consistent pressure surrounding the interference fit of the seat.

[Marshall V. Daut]

Brent -
I'd have to look up the number of that sleeve locker (which has changed names and manufacturers) and its spec's, but the hot rod auto machine shop that recommended it said they used it all the time to save damaged cylinder heads and engine blocks and that it would hold even in the highest engine temperatures. And it did, for years. It saved my long-distance trip 20+ years ago by keeping the loose exhaust valve seat in place and I have used it since a couple times with good success. Admittedly, it's been a while since I last used it, though. Maybe the properties have changed with the new owner? As I stated in my previous post, a machine shop repair done properly would be best. But in lieu of tossing an otherwise good engine, why not at least try the sleeve locker or whatever it's called these days? The worst that can happen is the engine has to be torn down again or replaced, which it looks like it's heading for anyway. I think avoiding that might be worth $10 for the adhesive and equal parts of time and elbow grease spent assembling the engine and installing it. Of course, it's up to the owner. I'd be interested in hearing how he ends up solving the problem. We ALL would! I hope he comes back later and tells us.
Marshall

[johnneilson]

The other option is to get hands on a custom OD seat
I do this as I don’t want to machine out any more material than necessary
Tucker valve seats can make any size
Located in Odessa Texas
J

[Pete]

So far most of the suggested fixes are good.
Some are gooder than others....lol

With the new info, I would first sonic check for how much meat you have to work with. Assuming there is enough, then set the block in a mill and dial in on the guide bore, Then bore the hole to the minimum size to clean. Make sure the bottom face of the hole cleans square also. Then make a steel seat ring. Coat the ring OD and the sides and bottom of the hole with the stuff Brent uses and put the ring in with .006 press. Use the knee on the mill for a press so the ring goes in straight.
This fix is well within the capability of any machine shop with a mill and lathe.

Now, if after sonic check there is not enough meat to start with, all is not lost but the next fix starts to get pricey because it involves a welding shop that specializes in cast iron repair.
I will stop here because FEW will go this far....lol

[Randall]

I just replaced one today same situation someone had already put oversized seats in, I ran a tig torch around it to get it out and drove a new seat in and ground

[Randall]

If you were close I have a Kwik Way portable valve seat cutter I could use to install a larger new seat and not have to remove engine from car. If you didn't grind into the block just remove old one and install a new seat, if it goes in to easy then have someone cut the block for the seat number in my picture.
From what I am seeing I don't think what you did will hurt anything as long as seat goes in tight.
I have never had a problem using the seats in my picture.

Would also install a new guide.

[Randall]

If the guide is wore out that’s probably why it ground off center

[DJ S]

Update. Machine shop installed a replacement seat. Not thrilled about how they removed the old seat… chiseled out.

Is this missing chunk underneath the seat cause for concern? Seems like a great place for a crack to form.

[nkaminar]

I would also not be thrilled with the way the shop removed the old seat, and left the damage divot. At this point, there is not much you can do about it except to start over again and do some cast iron welding, that may cause other problems. Assemble the engine and run it. It will probably be OK depending on how you use your car. Meanwhile, if you put many miles on your car, save up for a Burtz block.

Cracks form when there is a sharp V in the metal. One option would be to take a diamond burr for a Dremel and smooth out that area. But that may make the problem worse, so your choice.

[Richard Knight]

Interesting thread. especially some suggestions are good did some are goober. It appears original shop used an old valve guide for there seat cutting tool because they did not have the 19/32 pilot that all old time seat cutter sets had. That was a huge mistake and created the rabbit hole. First find a shop with the proper tooling. The srd. O.D. for A sears was 1 5/8s, 1.625. The next seat size is 1 11/16 and then 1 3/4. Seats also come in plus sizes of .005, .010. It is a shame this turned into such a cluster. This was everyday work at my shop, no big deal. Somewhere there is mention o blocks cracking which is very true for the B blocks cast in 32 as the deck thickness changed to about .250 from .375. After 32 the deck thickness went back to .375 and when the diamond blocks became available they all had 4 stellite exhaust seats. These are facts learned the hard way. Naysayers can keep your thoughts to yourself.