Valve seat and counterbore dimensions

6

68FB

New member
Hi, I'm working on a 1942 V8 that is installed in a Universal Carrier. It's a military armoured vehicle that was built by Ford Canada for WWII. The exhaust valves and seats are rough. Looks like corrosion from moisture getting in.

From searching, I found that original seats are 1 3/8 x 1 5/8 x 7/32".

I pulled the worst 2 seats by MIG welding a washer to the seat. I measured the seat counterbores in the block as 1.625-1.630" ID, so not round. The seat OD's are around 1.630". This was after the welding so they may have shrunk in a bit.

Since the press fit would have been around 0.005", I'm guessing the seat OD was originally 1.630" and the counterbore ID was 1.625".

The new seats I got from Macs, the only place I found that supplied them, were listed as 1.638" OD but are actually 1.640". The thickness is 0.250" rather than the spec 7/32".
So it looks like these nominally 0.010" oversize seats, which is a bummer because I was hoping that the counterbores would be round and the new seats would be standard size so this would be a DIY fix. Do I have this right?

And is it a problem the new seats being 1/32" thicker? Does the seat grinding process remove this extra meat?

Malcolm
 
I'm not a book writter but I don't think this is do it your self. You will need a precision
pilot that goes into the lifter bore and valve guide bore. Now you have a straight line
to measure the seat bore. You have to get the seat bore round then go from there.
Important thing with whatever new seat you buy is the ID of the seat that must match
the valve, don't worry about the seat thickness that will be cut flat then grind the seat
angle. Murphys law says you found two bad ones, so there is probably more. So I say
do them all so you can sleep well. Sorry I think you will need a milling machine and
a valve seat grinder just remember every thing and measurement comes off that pilot.

sam
 
Try goodson for the seats, I,m doing some A blocks at the moment and also have an old seat that came out of the 8ba in our old dragster engine,they are the same ones.
I think the part no is VS 1625 -A
lawrie
 
It is reasonably simple to machine a seat ring to coordinate with the diameter you want/need.
 
A lot of valve seats are made to similar specs so it would be easier just to match up an aftermarket seat to the engine you are working on. Just like fitting pistons, machine work has to be done in most cases to get the proper fit. These old engines have likely gone through a lot of heat cycles and you never know what size the counter bore will be. Thickness of a new seat can be adjusted easily on a surface grinder. A lathe can turn the OD of a seat either with hard bits or tool post grinder. Sometimes the counter bore in the block needs to be trued up and that would take special milling equipment.

You might get lucky and find a seat out of the box that will work but it's not always something you can count on. At least these are flatheads so you don't have to worry as much if a seat comes loose but it can do a lot of damage to the counter bore if it does. It doesn't do the valve much good either. When it happens in an aircraft cylinder with an aluminum head, it can drop a valve but it usually ends up with no compression due to all the abnormal wear in the counter bore and the valve wallowing around in the guide.
 
The seat is 1625-1 from the major suppliers.
Comes in +5 and +10 OS.
Should be available at you local machine shop...it´s a common size.
Machining a valve seat takes an expanding arbor or they have a bad habbit of not being round when done.
 
We have just bought all the proper stuff for removing and counter boring for the seats ,mainly for the A engines but also V8.s
Not cheap but nice stuff.
Lawrie
 
You want to do valve seat on a budget and time isn´t an issue get an old kwik way model M they work fine and you can even do them in car.
 
Wow, lot of good information here. I've got new seats from Macs that say 1.638" on the package label but are actually 1.640" OD. Weird. Since spec seat OD is is 1.625" +0/-0.001" according to flatheadmurre, these are 0.015" o/s. Macs don't say this on their website. Seems like they found something close and figured out the machine shop would figure it out.
This is a one time rebuild for me and I don't have the equipment to get these counterbores bored true for oversize seats so I need to find a machine shop who can.
I agree with flatheadmurre seat rings are a bit too flexible to chuck and should be held on an expanding mandrel to take material off the OD. So I'll see if the shop can deal without the seats I have.
Living in Canada is a bummer for this stuff; lack of machine shops, 2 week delivery from the US, and brokers taking their pound of flesh. But we're good at winter sports.
Malcolm
 
Seats are numbered by bore size a 1625-1 is actually about +5 bigger for pressfit so your seat are probably +10 OS.
The machine shop probably have an adjustable cutter and can make what you have fit.
 
flatheadmurre said:
Seats are numbered by bore size a 1625-1 is actually about +5 bigger for pressfit so your seat are probably +10 OS.
The machine shop probably have an adjustable cutter and can make what you have fit.
Click to expand...

That makes sense.

rotorwrench said:
One of these would work with the right tooling as was mentioned. https://www.ebay.com/i/263489868309?chn=ps (Kwik Way model M)
Click to expand...

I found a fairly local shop that will cut the bores and install my seats for $25 a seat. I'll go with them.

Just have to braze repair a cracked oil cooler boss on the integral bell housing now. I've brazed cast iron before but I'm a bit nervous about this. Photo shows partially ground-out crack, caused by over tightening the taper pipe fitting. I think I'll install an adapter fitting in the boss to open the crack up before I braze it. I can locally preheat the bell housing to 350F with a rosebud. I'm just not sure how to slow cool this big lump after welding. Its too big for my oven!

DSC00598.JPG


Malcolm
 
I repaired the same crake in an engine I did,BUT I used an arc welder,,I used a cast craft rod.no dramas,let me know if you want the number of the rod.
Lawrie
 
The hotter you get it the slower it needs to cool down but brazing only gets up to about 900*F where it is just turning red. Just brazing the boss area there is localized enough that it shouldn't have problems but the bell area is pretty thin. Cast iron cools slowly anyway but it won't hurt to take the heat source away slowly. If you have a way to blanket it with something that can take the heat, it will keep surrounding air draft to a minimum and aid in keep the cool down as slow as possible.
 
I vote for cold welding it...heating it up enough to braze it will take some serious heat into the rear of the block.
Welding in the middle of a block is difficult with the tension, but at that boss it will be able to contract a little with no issues.
So either cold or semi preheated and stick or tig weld it.
 
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